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本文主要介绍Android Support v7提供的RecycleView和交错式布局（通常成为瀑布流布局）的使用和事件监听处理。
1. 涉及到开源库有：
Fresco :
Facebook开源的不是一般强大的图片加载组件库
Bufferknife :
Android View和事件绑定库，通过注解完成，在编译时APT处理注解文档。
2. 模块配置
Android Studio模块，build.gradle配置：
apply plugin: 'com.android.application'
android {
compileSdkVersion 21
buildToolsVersion '21.1.2'
defaultConfig {
applicationId 'secondriver.sdk'
minSdkVersion 16
targetSdkVersion 21
versionCode 1
versionName '1.0'
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
packagingOptions {
exclude 'META-INF/services/javax.annotation.processing.Processor'
}
lintOptions {
disable 'InvalidPackage'
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:21.0.3'
compile 'com.android.support:recyclerview-v7:21.0.3@aar'
compile 'com.android.support:cardview-v7:21.0.3@aar'
compile 'com.facebook.fresco:fresco:0.8.0'
compile 'com.jakewharton:butterknife:7.0.1'
testCompile 'junit:junit:4.12'
}3. 布局文件
主布局文件：activity_recycleview.xml 包含一个RecycleView，将作为主屏幕组件。
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout android:id="@+id/swipe_refresh_layout" xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content"> <android.support.v7.widget.RecyclerView android:id="@+id/recycler_view" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentTop="true" android:scrollbars="vertical" /> </RelativeLayout>
RecycleView 通过设置不同的布局管理器对象来实现不同的布局显示，如：
android.support.v7.widget.LinearLayoutManager 可以实现ListView的布局效果
android.support.v7.widget.GridLayoutManager 可以实现GridView的布局效果
android.support.v7.widget.StaggeredGridLayoutManager 可以实现交错式网格布局效果
次布局文件(RecycleView中显示的每一项视图的布局)：item_recycelview.xml 通过com.android.support:CardView包提供的CardView帧式容器布局包含一个ImageView和TextView作为RecycleView的每一项视图的布局。
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:card_view="http://schemas.android.com/apk/res-auto" xmlns:fresco="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center"> <android.support.v7.widget.CardView android:id="@+id/card_view" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" card_view:cardCornerRadius="4dp" card_view:cardUseCompatPadding="true"> <RelativeLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical"> <com.facebook.drawee.view.SimpleDraweeView android:id="@+id/info_p_w_picpath" android:layout_width="300dp" android:layout_height="420dp" fresco:actualImageScaleType="centerCrop" fresco:placeholderImage="@mipmap/ic_launcher" fresco:roundAsCircle="false" fresco:roundBottomLeft="true" fresco:roundBottomRight="true" fresco:roundTopLeft="true" fresco:roundTopRight="true" fresco:roundedCornerRadius="1dp" fresco:roundingBorderWidth="2dp" /> <TextView android:id="@+id/info_text" android:layout_width="200dp" android:layout_height="80dp" android:textSize="20sp" android:textColor="@android:color/holo_blue_dark" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_alignLeft="@id/info_p_w_picpath" android:layout_alignRight="@id/info_p_w_picpath" android:layout_below="@id/info_p_w_picpath" android:gravity="left|center_vertical"/> </RelativeLayout> </android.support.v7.widget.CardView> </LinearLayout>
ImageView组件使用的是Fresco库提供的视图组件。
4. Activity实现和数据填充
4.1 RecycleView中的每一项视图的数据组成
文本信息+ 图片地址（url,file,resId） 本示例中采用Url网络图片
/**
* View项的数据对象
*/
static class Pair {
public String text;
public String url;
public Pair(String text, String url) {
this.text = text;
this.url = url;
}
}
4.2 RecycleView中国的每一项视图的数据填充，即适配器
自定义适配器需要实现RecycleView.Adapter类。
static class RecycleViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
/**
* RecycleView的View项单击事件监听
*/
public interface OnRecycleViewItemClickListener {
void onRecycleViewItemClick(View view, int position);
}
private ArrayList<Pair> items = new ArrayList<>();
private OnRecycleViewItemClickListener mOnRecycleViewItemClickListener;
public RecycleViewAdapter(ArrayList<Pair> items) {
this.items = items;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recyclerview, parent, false);
return new RecycleViewItemHolder(view, mOnRecycleViewItemClickListener);
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
Pair pair = items.get(position);
((RecycleViewItemHolder) holder).setContent(pair);
}
@Override
public int getItemCount() {
return items.size();
}
public void setOnRecycleViewItemClickListener(OnRecycleViewItemClickListener onItemClickListener) {
if (null != onItemClickListener) {
this.mOnRecycleViewItemClickListener = onItemClickListener;
}
}
}主要实现onCreateViewHolder和onBindViewHolder方法。由于RecycleView并未提供为视图项添加监听事件，这里自定义个一个事件监听接口，在实例化适配器的时候可以选择设置事件监听。
4.3 创建ViewHolder需要通过自定义ViewHolder类继承RecycleView.ViewHolder。
static class RecycleViewItemHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
@Bind(R.id.info_text)
public TextView infoTextView;
@Bind(R.id.info_p_w_picpath)
public SimpleDraweeView draweeView;
private RecycleViewAdapter.OnRecycleViewItemClickListener onItemClickListener;
public RecycleViewItemHolder(View itemView, RecycleViewAdapter.OnRecycleViewItemClickListener onItemClickListener) {
super(itemView);
ButterKnife.bind(this, itemView);
this.onItemClickListener = onItemClickListener;
itemView.setOnClickListener(this);
}
public void setContent(Pair pair) {
infoTextView.setText(pair.text);
draweeView.setImageURI(Uri.parse(pair.url));
}
@Override
public void onClick(View v) {
if (null != onItemClickListener) {
onItemClickListener.onRecycleViewItemClick(v, getPosition());
}
}
}在构造方法中的传入OnRecycleViewItemClickListener对象，并且自定义ViewHolder实现OnClickListener接口，通过为itemView对象设置OnClickListener监听事件，在onClick方法中将点击事件的处理交由OnRecycleViewItemClickListener对象处理，从而达到为RecycleView中的itemView注册点击事件。
如果不采用这种方式添加事件监听，就不需要自定义监听接口和自定义ViewHolder实现事件监听接口以及事件处理。另外可以通过获得的itemView之后，通过组件I的获取组件来添加事件监听。还可以通过获得的自定义ViewHolder，来访问每个组件。
4.4 Activity的具体实现
package secondriver.sdk.activity;
import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
import com.facebook.drawee.view.SimpleDraweeView;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Random;
import butterknife.Bind;
import butterknife.ButterKnife;
import secondriver.sdk.R;
/**
* Author : secondriver
* Created : 2015/11/18
*/
public class RecycleViewActivity extends Activity {
private static final String TAG = RecyclerView.class.getName();
private static final String[] RES_URL = new String[]{
"http://p1.wmpic.me/article/2015/11/16/1447644849_hySANEEF.jpg",
//减少篇幅，此处省去14个图片Url
};
@Bind(R.id.recycler_view)
public RecyclerView mRecycleView;
private final int PRE_SCREEN_NUMBER = 6;
private final int SPAN_COUNT = 2;
private int previousLastIndex = 0;
private boolean isSlidingToLast = false;
private RecycleViewAdapter mAdapter;
private ArrayList<Pair> mItem = new ArrayList<>();
//交错式网格布局管理对象，即通常称的瀑布流布局
private StaggeredGridLayoutManager mLayoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recyclerview);
ButterKnife.bind(this);
Fresco.initialize(this); //重要，Fresco做一系列初始化工作
initRecycleView();
}
private void initRecycleView() {
mLayoutManager = new StaggeredGridLayoutManager(SPAN_COUNT, StaggeredGridLayoutManager.VERTICAL);
mRecycleView.setLayoutManager(mLayoutManager);
mAdapter = new RecycleViewAdapter(mItem);
loadData(false);
mRecycleView.setAdapter(mAdapter);
mRecycleView.setItemAnimator(new DefaultItemAnimator());
//RecycleView的View项单击事件监听
mAdapter.setOnRecycleViewItemClickListener(new RecycleViewAdapter.OnRecycleViewItemClickListener() {
@Override
public void onRecycleViewItemClick(View view, int position) {
long id = mRecycleView.getChildItemId(view);
Log.d(TAG, "View项的根视图:" + view.getClass().getName() + ",position=" + position + " ViewHolder_Id=" + id);
//通过findViewById查找View项中的元素
SimpleDraweeView draweeView = (SimpleDraweeView) view.findViewById(R.id.info_p_w_picpath);
if (null != draweeView) {
draweeView.setImageURI(Uri.parse(RES_URL[0]));
Toast.makeText(RecycleViewActivity.this, "通过findViewById查找View项中的元素", Toast.LENGTH_LONG).show();
}
RecycleViewItemHolder recycleViewItemHolder = (RecycleViewItemHolder) mRecycleView.findViewHolderForPosition(position);
if (null != recycleViewItemHolder) {
recycleViewItemHolder.infoTextView.setText("通过ViewHolder找到View项中的元素");
}
}
});
//下拉刷新，追加内容
mRecycleView.setOnScrollListener(
new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
if (isPullToBottom() && isSlidingToLast) {
if (mItem.size() > 36) { //最大数据量
Toast.makeText(RecycleViewActivity.this, "没有数据了", Toast.LENGTH_LONG).show();
return;
} else {
loadData(false);
Log.d(TAG, "notifyItemRangeInserted startPosition=" + previousLastIndex);
mAdapter.notifyItemRangeInserted(previousLastIndex, PRE_SCREEN_NUMBER);
}
}
}
if (newState == RecyclerView.SCROLL_STATE_SETTLING) {
Log.d(TAG, "settling");
}
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
isSlidingToLast = dy > 0; //上拉，下滑
Log.d(TAG, "dx = " + dx + " dy=" + dy + " isSlidingToLast=" + isSlidingToLast);
}
}
);
}
private boolean isPullToBottom() {
int[] lastIndexs = mLayoutManager.findLastCompletelyVisibleItemPositions(null);
Log.d(TAG, "last item =" + Arrays.toString(lastIndexs) + ", have item=" + mAdapter.getItemCount());
int maxIndex = mAdapter.getItemCount() - 1;
for (int i : lastIndexs) {
if (i == maxIndex) {
return true;
}
}
return false;
}
private void loadData(boolean isClear) {
if (isClear) {
mItem.clear();
}
previousLastIndex = mItem.size();
Random r = new Random();
for (int index = 0; index < PRE_SCREEN_NUMBER && index < RES_URL.length; index++) {
mItem.add(new Pair("Card " + (previousLastIndex + index), RES_URL[r.nextInt(RES_URL.length)]));
}
Log.d(TAG, "mItem count =" + mItem.size());
}
}说明：
RecycleView的ItemView的数据由Pair对象管理存储
Fresco库默认配置下的使用之前需要初始化调用Fresco.initialize(Context)
上述实现了2个事件监听，一个OnScrollerListener由RecycleView提供，实现下拉刷新；一个OnRecycleViewItemClickListener由自定义的RecycleViewAdpater提供，实现单击itemView来更换图片(SimpleDraweeView)和文字(TextView)。
Butterknife和Fresco库的具体使用参见其Github上的文档。
5. 效果图
比较遗憾ScreenRecord不支持模拟器和Android4.4一下的系统，只能附上截图。
![[Android学习笔记三] Support v7提供交错式网格布局开发示例](https://cache.yisu.com/upload/information/20200311/46/197013.jpg)
![[Android学习笔记三] Support v7提供交错式网格布局开发示例](https://cache.yisu.com/upload/information/20200311/46/197014.jpg)
![[Android学习笔记三] Support v7提供交错式网格布局开发示例](https://cache.yisu.com/upload/information/20200311/46/197015.jpg)
![[Android学习笔记三] Support v7提供交错式网格布局开发示例](https://cache.yisu.com/upload/information/20200311/46/197016.jpg)
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