RecyclerView scale center item

Tuesday, 22/09/2020

Tram Ho

1) Place the problem

Suppose the customer has a list of images and requests that this list be displayed on the screen and the center item is scaled more than the next item in the following manner:

2) Solution

There are many ways to do the above, in this article I will guide you to use RecyclerView to solve this problem.

As we can see, the item in the middle will be the largest (the center) and away from the center the item will be smaller.

Thus the size of the items will be inversely proportional to the distance between that item and the recyclerView’s center

<span class="token keyword">class</span> <span class="token class-name">ZoomCenterLinearLayoutManager</span> <span class="token keyword">extends</span> <span class="token class-name">LinearLayoutManager</span> <span class="token punctuation">{</span>
    <span class="token keyword">public</span> <span class="token class-name">ZoomCenterLinearLayoutManager</span> <span class="token punctuation">(</span> <span class="token class-name">Context</span> context <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">super</span> <span class="token punctuation">(</span> context <span class="token punctuation">)</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token keyword">public</span> <span class="token class-name">ZoomCenterLinearLayoutManager</span> <span class="token punctuation">(</span> <span class="token class-name">Context</span> context <span class="token punctuation">,</span> <span class="token keyword">int</span> orientation <span class="token punctuation">,</span> <span class="token keyword">boolean</span> reverseLayout <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">super</span> <span class="token punctuation">(</span> context <span class="token punctuation">,</span> orientation <span class="token punctuation">,</span> reverseLayout <span class="token punctuation">)</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token keyword">public</span> <span class="token class-name">ZoomCenterLinearLayoutManager</span> <span class="token punctuation">(</span> <span class="token class-name">Context</span> context <span class="token punctuation">,</span> <span class="token class-name">AttributeSet</span> attrs <span class="token punctuation">,</span> <span class="token keyword">int</span> defStyleAttr <span class="token punctuation">,</span> <span class="token keyword">int</span> defStyleRes <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">super</span> <span class="token punctuation">(</span> context <span class="token punctuation">,</span> attrs <span class="token punctuation">,</span> defStyleAttr <span class="token punctuation">,</span> defStyleRes <span class="token punctuation">)</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">public</span> <span class="token keyword">boolean</span> <span class="token function">checkLayoutParams</span> <span class="token punctuation">(</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">.</span> <span class="token class-name">LayoutParams</span> lp <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        lp <span class="token punctuation">.</span> width <span class="token operator">=</span> <span class="token function">getWidth</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token operator">/</span> <span class="token number">3</span> <span class="token punctuation">;</span> <span class="token comment">//Độ rộng của mỗi item sẽ bằng 1/3 độ rộng của RecyclerView</span>
        <span class="token keyword">return</span> <span class="token boolean">true</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">onLayoutCompleted</span> <span class="token punctuation">(</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">.</span> <span class="token class-name">State</span> state <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">super</span> <span class="token punctuation">.</span> <span class="token function">onLayoutCompleted</span> <span class="token punctuation">(</span> state <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token function">scaleMiddle</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">scrollHorizontallyBy</span> <span class="token punctuation">(</span> <span class="token keyword">int</span> dx <span class="token punctuation">,</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">.</span> <span class="token class-name">Recycler</span> recycler <span class="token punctuation">,</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">.</span> <span class="token class-name">State</span> state <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token function">scaleMiddle</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token keyword">return</span> <span class="token keyword">super</span> <span class="token punctuation">.</span> <span class="token function">scrollHorizontallyBy</span> <span class="token punctuation">(</span> dx <span class="token punctuation">,</span> recycler <span class="token punctuation">,</span> state <span class="token punctuation">)</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">scaleMiddle</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">float</span> midpoint <span class="token operator">=</span> <span class="token function">getWidth</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token operator">/</span> <span class="token number">2.f</span> <span class="token punctuation">;</span>
        <span class="token keyword">for</span> <span class="token punctuation">(</span> <span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span> <span class="token punctuation">;</span> i <span class="token operator">&lt;</span> <span class="token function">getChildCount</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> i <span class="token operator">++</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token class-name">View</span> child <span class="token operator">=</span> <span class="token function">getChildAt</span> <span class="token punctuation">(</span> i <span class="token punctuation">)</span> <span class="token punctuation">;</span>
            <span class="token keyword">float</span> childMidpoint <span class="token operator">=</span> <span class="token punctuation">(</span> <span class="token function">getDecoratedRight</span> <span class="token punctuation">(</span> child <span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token function">getDecoratedLeft</span> <span class="token punctuation">(</span> child <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token operator">/</span> <span class="token number">2.f</span> <span class="token punctuation">;</span> <span class="token comment">// tính hoành độ của item</span>
            <span class="token keyword">float</span> d <span class="token operator">=</span> <span class="token class-name">Math</span> <span class="token punctuation">.</span> <span class="token function">abs</span> <span class="token punctuation">(</span> midpoint <span class="token operator">-</span> childMidpoint <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// khoảng cách giữa item và điểm trung tâm của recyclerView</span>
            <span class="token keyword">float</span> scale <span class="token operator">=</span> <span class="token number">1f</span> <span class="token operator">-</span> <span class="token number">0.35f</span> <span class="token operator">*</span> d <span class="token operator">/</span> midpoint <span class="token punctuation">;</span> <span class="token comment">//tính độ scale của item (0/35: Số này càng lớn thì các item 2 bên sẽ càng nhỏ</span>
            child <span class="token punctuation">.</span> <span class="token function">setScaleX</span> <span class="token punctuation">(</span> scale <span class="token punctuation">)</span> <span class="token punctuation">;</span>
            child <span class="token punctuation">.</span> <span class="token function">setScaleY</span> <span class="token punctuation">(</span> scale <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

class ZoomCenterLinearLayoutManager extends LinearLayoutManager {

super ( context ) ;

}

public ZoomCenterLinearLayoutManager ( Context context , int orientation , boolean reverseLayout ) {

super ( context , orientation , reverseLayout ) ;

}

public ZoomCenterLinearLayoutManager ( Context context , AttributeSet attrs , int defStyleAttr , int defStyleRes ) {

super ( context , attrs , defStyleAttr , defStyleRes ) ;

}

@Override

public boolean checkLayoutParams ( RecyclerView . LayoutParams lp ) {

lp . width = getWidth ( ) / 3 ; //Độ rộng của mỗi item sẽ bằng 1/3 độ rộng của RecyclerView

return true ;

}

@Override

public void onLayoutCompleted ( RecyclerView . State state ) {

super . onLayoutCompleted ( state ) ;

scaleMiddle ( ) ;

}

@Override

public int scrollHorizontallyBy ( int dx , RecyclerView . Recycler recycler , RecyclerView . State state ) {

scaleMiddle ( ) ;

return super . scrollHorizontallyBy ( dx , recycler , state ) ;

}

public void scaleMiddle ( ) {

float midpoint = getWidth ( ) / 2.f ;

for ( int i = 0 ; i < getChildCount ( ) ; i ++ ) {

View child = getChildAt ( i ) ;

float childMidpoint = ( getDecoratedRight ( child ) + getDecoratedLeft ( child ) ) / 2.f ; // tính hoành độ của item

float d = Math . abs ( midpoint - childMidpoint ) ; // khoảng cách giữa item và điểm trung tâm của recyclerView

float scale = 1f - 0.35f * d / midpoint ; //tính độ scale của item (0/35: Số này càng lớn thì các item 2 bên sẽ càng nhỏ

child . setScaleX ( scale ) ;

child . setScaleY ( scale ) ;

}

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<?xml version="1.0" encoding="utf-8"?>

< layout xmlns: android = " http://schemas.android.com/apk/res/android "

xmlns: app = " http://schemas.android.com/apk/res-auto "

xmlns: tools = " http://schemas.android.com/tools " >

< androidx.constraintlayout.widget.ConstraintLayout

android: layout_width = " match_parent "

android: layout_height = " wrap_content " >

< TextView

android: id = " @+id/text_name "

android: layout_height = " 0dp "

app: layout_constraintBottom_toBottomOf = " parent "

app: layout_constraintDimensionRatio = " 1:1 "

app: layout_constraintEnd_toEndOf = " parent "

app: layout_constraintHorizontal_bias = " 0.0 "

app: layout_constraintStart_toStartOf = " parent "

app: layout_constraintTop_toTopOf = " parent " />

</ androidx.constraintlayout.widget.ConstraintLayout >

</ layout >

item_empty.xml (Since we need a space at the beginning and end to display the first and last scale item)

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        <span class="token attr-name"><span class="token namespace">android:</span> layout_width</span> <span class="token attr-value"><span class="token punctuation">=</span> <span class="token punctuation">"</span> match_parent <span class="token punctuation">"</span></span>
        <span class="token attr-name"><span class="token namespace">android:</span> layout_height</span> <span class="token attr-value"><span class="token punctuation">=</span> <span class="token punctuation">"</span> wrap_content <span class="token punctuation">"</span></span> <span class="token punctuation">&gt;</span></span>

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<?xml version="1.0" encoding="utf-8"?>

< androidx.constraintlayout.widget.ConstraintLayout

< TextView

android: layout_height = " 0dp "

</ androidx.constraintlayout.widget.ConstraintLayout >

</ layout >

<span class="token keyword">package</span> <span class="token namespace">com <span class="token punctuation">.</span> example <span class="token punctuation">.</span> recyclerviewzoomcenter</span> <span class="token punctuation">;</span>

<span class="token keyword">import</span> <span class="token namespace">android <span class="token punctuation">.</span> view</span> <span class="token punctuation">.</span> <span class="token class-name">LayoutInflater</span> <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token namespace">android <span class="token punctuation">.</span> view</span> <span class="token punctuation">.</span> <span class="token class-name">View</span> <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token namespace">android <span class="token punctuation">.</span> view</span> <span class="token punctuation">.</span> <span class="token class-name">ViewGroup</span> <span class="token punctuation">;</span>

<span class="token keyword">import</span> <span class="token namespace">androidx <span class="token punctuation">.</span> annotation</span> <span class="token punctuation">.</span> <span class="token class-name">IntDef</span> <span class="token punctuation">;</span>
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<span class="token keyword">import</span> <span class="token keyword">static</span> <span class="token namespace">com <span class="token punctuation">.</span> example <span class="token punctuation">.</span> recyclerviewzoomcenter</span> <span class="token punctuation">.</span> <span class="token class-name">ItemAdapter</span> <span class="token punctuation">.</span> <span class="token class-name">ViewType</span> <span class="token punctuation">.</span> EMPTY <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token keyword">static</span> <span class="token namespace">com <span class="token punctuation">.</span> example <span class="token punctuation">.</span> recyclerviewzoomcenter</span> <span class="token punctuation">.</span> <span class="token class-name">ItemAdapter</span> <span class="token punctuation">.</span> <span class="token class-name">ViewType</span> <span class="token punctuation">.</span> NORMAL <span class="token punctuation">;</span>

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    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">getItemViewType</span> <span class="token punctuation">(</span> <span class="token keyword">int</span> position <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span> position <span class="token operator">==</span> <span class="token number">0</span> <span class="token operator">||</span> position <span class="token operator">==</span> dataList <span class="token punctuation">.</span> <span class="token function">size</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">1</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">return</span> EMPTY <span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
        <span class="token keyword">return</span> NORMAL <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token annotation punctuation">@NonNull</span>
    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">public</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">.</span> <span class="token class-name">ViewHolder</span> <span class="token function">onCreateViewHolder</span> <span class="token punctuation">(</span> <span class="token annotation punctuation">@NonNull</span> <span class="token class-name">ViewGroup</span> parent <span class="token punctuation">,</span> <span class="token keyword">int</span> viewType <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span> viewType <span class="token operator">==</span> EMPTY <span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token class-name">ItemEmptyBinding</span> binding <span class="token operator">=</span> <span class="token class-name">ItemEmptyBinding</span> <span class="token punctuation">.</span> <span class="token function">inflate</span> <span class="token punctuation">(</span> <span class="token class-name">LayoutInflater</span> <span class="token punctuation">.</span> <span class="token function">from</span> <span class="token punctuation">(</span> parent <span class="token punctuation">.</span> <span class="token function">getContext</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">,</span> parent <span class="token punctuation">,</span> <span class="token boolean">false</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
            <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">EmptyViewHolder</span> <span class="token punctuation">(</span> binding <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
        <span class="token class-name">ItemRecyclerBinding</span> binding <span class="token operator">=</span> <span class="token class-name">ItemRecyclerBinding</span> <span class="token punctuation">.</span> <span class="token function">inflate</span> <span class="token punctuation">(</span> <span class="token class-name">LayoutInflater</span> <span class="token punctuation">.</span> <span class="token function">from</span> <span class="token punctuation">(</span> parent <span class="token punctuation">.</span> <span class="token function">getContext</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">,</span> parent <span class="token punctuation">,</span> <span class="token boolean">false</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">ItemViewHolder</span> <span class="token punctuation">(</span> binding <span class="token punctuation">)</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">onBindViewHolder</span> <span class="token punctuation">(</span> <span class="token annotation punctuation">@NonNull</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">.</span> <span class="token class-name">ViewHolder</span> holder <span class="token punctuation">,</span> <span class="token keyword">int</span> position <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span> holder <span class="token keyword">instanceof</span> <span class="token class-name">ItemViewHolder</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token punctuation">(</span> <span class="token punctuation">(</span> <span class="token class-name">ItemViewHolder</span> <span class="token punctuation">)</span> holder <span class="token punctuation">)</span> <span class="token punctuation">.</span> <span class="token function">bindData</span> <span class="token punctuation">(</span> dataList <span class="token punctuation">.</span> <span class="token function">get</span> <span class="token punctuation">(</span> holder <span class="token punctuation">.</span> <span class="token function">getAdapterPosition</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>

    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">getItemCount</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">return</span> dataList <span class="token punctuation">.</span> <span class="token function">size</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token keyword">static</span> <span class="token keyword">class</span> <span class="token class-name">ItemViewHolder</span> <span class="token keyword">extends</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">.</span> <span class="token class-name">ViewHolder</span> <span class="token punctuation">{</span>
        <span class="token keyword">private</span> <span class="token class-name">ItemRecyclerBinding</span> binding <span class="token punctuation">;</span>

        <span class="token keyword">public</span> <span class="token class-name">ItemViewHolder</span> <span class="token punctuation">(</span> <span class="token annotation punctuation">@NonNull</span> <span class="token class-name">ItemRecyclerBinding</span> binding <span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">super</span> <span class="token punctuation">(</span> binding <span class="token punctuation">.</span> <span class="token function">getRoot</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
            <span class="token keyword">this</span> <span class="token punctuation">.</span> binding <span class="token operator">=</span> binding <span class="token punctuation">;</span>
        <span class="token punctuation">}</span>

        <span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">bindData</span> <span class="token punctuation">(</span> <span class="token class-name">Data</span> data <span class="token punctuation">)</span> <span class="token punctuation">{</span>
            binding <span class="token punctuation">.</span> imageView <span class="token punctuation">.</span> <span class="token function">setImageResource</span> <span class="token punctuation">(</span> data <span class="token punctuation">.</span> <span class="token function">getImageId</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
            binding <span class="token punctuation">.</span> textName <span class="token punctuation">.</span> <span class="token function">setText</span> <span class="token punctuation">(</span> data <span class="token punctuation">.</span> <span class="token function">getName</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>

    <span class="token keyword">static</span> <span class="token keyword">class</span> <span class="token class-name">EmptyViewHolder</span> <span class="token keyword">extends</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">.</span> <span class="token class-name">ViewHolder</span> <span class="token punctuation">{</span>

        <span class="token keyword">public</span> <span class="token class-name">EmptyViewHolder</span> <span class="token punctuation">(</span> <span class="token annotation punctuation">@NonNull</span> <span class="token class-name">ItemEmptyBinding</span> binding <span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">super</span> <span class="token punctuation">(</span> binding <span class="token punctuation">.</span> <span class="token function">getRoot</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>

    <span class="token annotation punctuation">@IntDef</span> <span class="token punctuation">(</span> <span class="token punctuation">{</span> EMPTY <span class="token punctuation">,</span> NORMAL <span class="token punctuation">}</span> <span class="token punctuation">)</span>
    <span class="token keyword">public</span> <span class="token annotation punctuation">@interface</span> <span class="token class-name">ViewType</span> <span class="token punctuation">{</span>
        <span class="token keyword">int</span> EMPTY <span class="token operator">=</span> <span class="token number">0</span> <span class="token punctuation">;</span>
        <span class="token keyword">int</span> NORMAL <span class="token operator">=</span> <span class="token number">1</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

package com . example . recyclerviewzoomcenter ;

import android . view . LayoutInflater ;

import android . view . View ;

import android . view . ViewGroup ;

import androidx . annotation . IntDef ;

import androidx . annotation . NonNull ;

import androidx . recyclerview . widget . RecyclerView ;

import com . example . recyclerviewzoomcenter . databinding . ItemEmptyBinding ;

import com . example . recyclerviewzoomcenter . databinding . ItemRecyclerBinding ;

import java . util . List ;

import static com . example . recyclerviewzoomcenter . ItemAdapter . ViewType . EMPTY ;

public class ItemAdapter extends RecyclerView . Adapter < RecyclerView . ViewHolder > {

public ItemAdapter ( List < Data > dataList ) {

this . dataList = dataList ;

}

@Override

public int getItemViewType ( int position ) {

if ( position == 0 || position == dataList . size ( ) - 1 ) {

return EMPTY ;

}

return NORMAL ;

}

@NonNull

@Override

public RecyclerView . ViewHolder onCreateViewHolder ( @NonNull ViewGroup parent , int viewType ) {

if ( viewType == EMPTY ) {

ItemEmptyBinding binding = ItemEmptyBinding . inflate ( LayoutInflater . from ( parent . getContext ( ) ) , parent , false ) ;

return new EmptyViewHolder ( binding ) ;

}

ItemRecyclerBinding binding = ItemRecyclerBinding . inflate ( LayoutInflater . from ( parent . getContext ( ) ) , parent , false ) ;

return new ItemViewHolder ( binding ) ;

}

@Override

public void onBindViewHolder ( @NonNull RecyclerView . ViewHolder holder , int position ) {

if ( holder instanceof ItemViewHolder ) {

( ( ItemViewHolder ) holder ) . bindData ( dataList . get ( holder . getAdapterPosition ( ) ) ) ;

}

@Override

public int getItemCount ( ) {

return dataList . size ( ) ;

}

static class ItemViewHolder extends RecyclerView . ViewHolder {

private ItemRecyclerBinding binding ;

public ItemViewHolder ( @NonNull ItemRecyclerBinding binding ) {

super ( binding . getRoot ( ) ) ;

this . binding = binding ;

}

private void bindData ( Data data ) {

binding . imageView . setImageResource ( data . getImageId ( ) ) ;

binding . textName . setText ( data . getName ( ) ) ;

}

static class EmptyViewHolder extends RecyclerView . ViewHolder {

public EmptyViewHolder ( @NonNull ItemEmptyBinding binding ) {

}

@IntDef ( { EMPTY , NORMAL } )

public @interface ViewType {

int EMPTY = 0 ;

int NORMAL = 1 ;

}

<span class="token keyword">package</span> <span class="token namespace">com <span class="token punctuation">.</span> example <span class="token punctuation">.</span> recyclerviewzoomcenter</span> <span class="token punctuation">;</span>

<span class="token keyword">import</span> <span class="token namespace">androidx <span class="token punctuation">.</span> appcompat <span class="token punctuation">.</span> app</span> <span class="token punctuation">.</span> <span class="token class-name">AppCompatActivity</span> <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token namespace">androidx <span class="token punctuation">.</span> recyclerview <span class="token punctuation">.</span> widget</span> <span class="token punctuation">.</span> <span class="token class-name">LinearLayoutManager</span> <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token namespace">androidx <span class="token punctuation">.</span> recyclerview <span class="token punctuation">.</span> widget</span> <span class="token punctuation">.</span> <span class="token class-name">LinearSnapHelper</span> <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token namespace">androidx <span class="token punctuation">.</span> recyclerview <span class="token punctuation">.</span> widget</span> <span class="token punctuation">.</span> <span class="token class-name">RecyclerView</span> <span class="token punctuation">;</span>

<span class="token keyword">import</span> <span class="token namespace">android <span class="token punctuation">.</span> os</span> <span class="token punctuation">.</span> <span class="token class-name">Bundle</span> <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token namespace">android <span class="token punctuation">.</span> view</span> <span class="token punctuation">.</span> <span class="token class-name">View</span> <span class="token punctuation">;</span>

<span class="token keyword">import</span> <span class="token namespace">java <span class="token punctuation">.</span> util</span> <span class="token punctuation">.</span> <span class="token class-name">ArrayList</span> <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token namespace">java <span class="token punctuation">.</span> util</span> <span class="token punctuation">.</span> <span class="token class-name">List</span> <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token namespace">java <span class="token punctuation">.</span> util</span> <span class="token punctuation">.</span> <span class="token class-name">Random</span> <span class="token punctuation">;</span>

<span class="token keyword">import</span> <span class="token keyword">static</span> <span class="token namespace">com <span class="token punctuation">.</span> example <span class="token punctuation">.</span> recyclerviewzoomcenter</span> <span class="token punctuation">.</span> <span class="token class-name">ItemAdapter</span> <span class="token punctuation">.</span> <span class="token class-name">ViewType</span> <span class="token punctuation">.</span> EMPTY <span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token keyword">static</span> <span class="token namespace">com <span class="token punctuation">.</span> example <span class="token punctuation">.</span> recyclerviewzoomcenter</span> <span class="token punctuation">.</span> <span class="token class-name">ItemAdapter</span> <span class="token punctuation">.</span> <span class="token class-name">ViewType</span> <span class="token punctuation">.</span> NORMAL <span class="token punctuation">;</span>

<span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MainActivity</span> <span class="token keyword">extends</span> <span class="token class-name">AppCompatActivity</span> <span class="token punctuation">{</span>
    <span class="token keyword">private</span> <span class="token class-name">String</span> <span class="token punctuation">[</span> <span class="token punctuation">]</span> names <span class="token operator">=</span> <span class="token punctuation">{</span> <span class="token string">"A"</span> <span class="token punctuation">,</span> <span class="token string">"B"</span> <span class="token punctuation">,</span> <span class="token string">"C"</span> <span class="token punctuation">}</span> <span class="token punctuation">;</span>
    <span class="token keyword">private</span> <span class="token class-name">List</span> <span class="token generics"><span class="token punctuation">&lt;</span> <span class="token class-name">Data</span> <span class="token punctuation">&gt;</span></span> dataList <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span> <span class="token generics"><span class="token punctuation">&lt;</span> <span class="token punctuation">&gt;</span></span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>

    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">protected</span> <span class="token keyword">void</span> <span class="token function">onCreate</span> <span class="token punctuation">(</span> <span class="token class-name">Bundle</span> savedInstanceState <span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">super</span> <span class="token punctuation">.</span> <span class="token function">onCreate</span> <span class="token punctuation">(</span> savedInstanceState <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token function">setContentView</span> <span class="token punctuation">(</span> <span class="token class-name">R</span> <span class="token punctuation">.</span> layout <span class="token punctuation">.</span> activity_main <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token class-name">RecyclerView</span> recyclerView <span class="token operator">=</span> <span class="token function">findViewById</span> <span class="token punctuation">(</span> <span class="token class-name">R</span> <span class="token punctuation">.</span> id <span class="token punctuation">.</span> recyclerView <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token keyword">for</span> <span class="token punctuation">(</span> <span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span> <span class="token punctuation">;</span> i <span class="token operator">&lt;</span> <span class="token number">10</span> <span class="token punctuation">;</span> i <span class="token operator">++</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token class-name">Random</span> random <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Random</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
            <span class="token class-name">Data</span> data <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Data</span> <span class="token punctuation">(</span> names <span class="token punctuation">[</span> random <span class="token punctuation">.</span> <span class="token function">nextInt</span> <span class="token punctuation">(</span> <span class="token number">3</span> <span class="token punctuation">)</span> <span class="token punctuation">]</span> <span class="token punctuation">,</span> <span class="token class-name">R</span> <span class="token punctuation">.</span> drawable <span class="token punctuation">.</span> image_1 <span class="token punctuation">,</span> NORMAL <span class="token punctuation">)</span> <span class="token punctuation">;</span>
            dataList <span class="token punctuation">.</span> <span class="token function">add</span> <span class="token punctuation">(</span> data <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
        dataList <span class="token punctuation">.</span> <span class="token function">add</span> <span class="token punctuation">(</span> <span class="token number">0</span> <span class="token punctuation">,</span> <span class="token keyword">new</span> <span class="token class-name">Data</span> <span class="token punctuation">(</span> <span class="token string">""</span> <span class="token punctuation">,</span> <span class="token number">0</span> <span class="token punctuation">,</span> EMPTY <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        dataList <span class="token punctuation">.</span> <span class="token function">add</span> <span class="token punctuation">(</span> <span class="token keyword">new</span> <span class="token class-name">Data</span> <span class="token punctuation">(</span> <span class="token string">""</span> <span class="token punctuation">,</span> <span class="token number">0</span> <span class="token punctuation">,</span> EMPTY <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token class-name">ItemAdapter</span> adapter <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ItemAdapter</span> <span class="token punctuation">(</span> dataList <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        recyclerView <span class="token punctuation">.</span> <span class="token function">setLayoutManager</span> <span class="token punctuation">(</span> <span class="token keyword">new</span> <span class="token class-name">ZoomCenterLinearLayoutManager</span> <span class="token punctuation">(</span> <span class="token keyword">this</span> <span class="token punctuation">,</span> <span class="token class-name">LinearLayoutManager</span> <span class="token punctuation">.</span> HORIZONTAL <span class="token punctuation">,</span> <span class="token boolean">false</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        recyclerView <span class="token punctuation">.</span> <span class="token function">setAdapter</span> <span class="token punctuation">(</span> adapter <span class="token punctuation">)</span> <span class="token punctuation">;</span>
        <span class="token class-name">LinearSnapHelper</span> snapHelper <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">LinearSnapHelper</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// Sử dụng SnapHelper để RecyclerView luôn focus vào 1 item (snap position)</span>
        snapHelper <span class="token punctuation">.</span> <span class="token function">attachToRecyclerView</span> <span class="token punctuation">(</span> recyclerView <span class="token punctuation">)</span> <span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

import androidx . appcompat . app . AppCompatActivity ;

import androidx . recyclerview . widget . LinearLayoutManager ;

import androidx . recyclerview . widget . LinearSnapHelper ;

import android . os . Bundle ;

import android . view . View ;

import java . util . ArrayList ;

import java . util . Random ;

public class MainActivity extends AppCompatActivity {

private String [ ] names = { "A" , "B" , "C" } ;

private List < Data > dataList = new ArrayList < > ( ) ;

@Override

protected void onCreate ( Bundle savedInstanceState ) {

super . onCreate ( savedInstanceState ) ;

setContentView ( R . layout . activity_main ) ;

RecyclerView recyclerView = findViewById ( R . id . recyclerView ) ;

for ( int i = 0 ; i < 10 ; i ++ ) {

Random random = new Random ( ) ;

Data data = new Data ( names [ random . nextInt ( 3 ) ] , R . drawable . image_1 , NORMAL ) ;

dataList . add ( data ) ;

}

dataList . add ( 0 , new Data ( "" , 0 , EMPTY ) ) ;

dataList . add ( new Data ( "" , 0 , EMPTY ) ) ;

ItemAdapter adapter = new ItemAdapter ( dataList ) ;

recyclerView . setLayoutManager ( new ZoomCenterLinearLayoutManager ( this , LinearLayoutManager . HORIZONTAL , false ) ) ;

recyclerView . setAdapter ( adapter ) ;

LinearSnapHelper snapHelper = new LinearSnapHelper ( ) ; // Sử dụng SnapHelper để RecyclerView luôn focus vào 1 item (snap position)

snapHelper . attachToRecyclerView ( recyclerView ) ;

}

So we have already solved the above problem ^^

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Source : Viblo

RecyclerView scale center item

1) Place the problem

2) Solution

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