Android应用开发中RecyclerView组件使用入门教程

2020-04-11 10:44:56

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RecyclerView是一种列表容器, 发布很久了, 才想起来写点什么.

RecyclerView相比于ListView, 在回收重用时更具有灵活性, 也就是低耦合, 并且提供了扩展. 加载多个视图时, 应该多用RecyclerView代替ListView.

那么我们来看看这东西应该怎么用? 比如生成一个瀑布流的视图.

2016224180636421.png (1080×1920)

首先我们从一个HelloWorld写起, 看看如何构建一个RecyclerView.

1. 依赖库
Gradle配置, 添加Recycler库

compile 'com.android.support:recyclerview-v7:+'

2. 资源文件
资源文件

 <android.support.v7.widget.RecyclerView  android:id="@+id/test_recycler_view"  android:layout_width="match_parent"  android:layout_height="match_parent"/>

3. 代码
LayoutManager: 管理RecyclerView的结构.
Adapter: 处理每个Item的显示.
ItemDecoration: 添加每个Item的装饰.
ItemAnimator: 负责添加/移除/重排序时的动画效果.

LayoutManager/Adapter是必须, ItemDecoration/ItemAnimator是可选. /**  * 初始化RecyclerView  *  * @param recyclerView 主控件  */ private void initRecyclerView(RecyclerView recyclerView) {  recyclerView.setHasFixedSize(true); // 设置固定大小  initRecyclerLayoutManager(recyclerView); // 初始化布局  initRecyclerAdapter(recyclerView); // 初始化适配器  initItemDecoration(recyclerView); // 初始化装饰  initItemAnimator(recyclerView); // 初始化动画效果 }

4. LayoutManager
管理RecyclerView的布局结构.

 private void initRecyclerLayoutManager(RecyclerView recyclerView) {  // 错列网格布局  recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,    StaggeredGridLayoutManager.VERTICAL)); }

提供了多种LayoutManager, 瀑布流使用错列网格布局.
5. Adapter
适配器, 处理RecyclerView的Item事务.

 private void initRecyclerAdapter(RecyclerView recyclerView) {  mAdapter = new MyAdapter(getData());  recyclerView.setAdapter(mAdapter); }

对于Adapter, 我们需要展开来说, 先看看类.

public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> { private List<DataModel> mDataModels; private List<Integer> mHeights; MyAdapter(List<DataModel> dataModels) {  if (dataModels == null) {   throw new IllegalArgumentException("DataModel must not be null");  }  mDataModels = dataModels;  mHeights = new ArrayList<>(); } @Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {  View itemView = LayoutInflater.from(parent.getContext())    .inflate(R.layout.item_recycler_view, parent, false);  return new MyViewHolder(itemView); } @Override public void onBindViewHolder(MyViewHolder holder, int position) {  DataModel dataModel = mDataModels.get(position);  // 随机高度, 模拟瀑布效果.  if (mHeights.size() <= position) {   mHeights.add((int) (100 + Math.random() * 300));  }  ViewGroup.LayoutParams lp = holder.getTvLabel().getLayoutParams();  lp.height = mHeights.get(position);  holder.getTvLabel().setLayoutParams(lp);  holder.getTvLabel().setText(dataModel.getLabel());  holder.getTvDateTime().setText(new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH)    .format(dataModel.getDateTime())); } @Override public int getItemCount() {  return mDataModels.size(); } public void addData(int position) {  DataModel model = new DataModel();  model.setDateTime(getBeforeDay(new Date(), position));  model.setLabel("No. " + (int) (new Random().nextDouble() * 20.0f));  mDataModels.add(position, model);  notifyItemInserted(position); } public void removeData(int position) {  mDataModels.remove(position);  notifyItemRemoved(position); } /**  * 获取日期的前一天  *  * @param date 日期  * @param i 偏离  * @return 新的日期  */ private static Date getBeforeDay(Date date, int i) {  Calendar calendar = Calendar.getInstance();  calendar.setTime(date);  calendar.add(Calendar.DAY_OF_YEAR, i * (-1));  return calendar.getTime(); }}

（1）onCreateViewHolder创建ViewHolder.

（2）onBindViewHolder绑定每一项数据.

（3）getItemCount返回列表长度.

（4）RecyclerView强制使用ViewHolder.

public class MyViewHolder extends RecyclerView.ViewHolder { private TextView mTvLabel; // 标签 private TextView mTvDateTime; // 日期 public MyViewHolder(View itemView) {  super(itemView);  mTvLabel = (TextView) itemView.findViewById(R.id.item_text);  mTvDateTime = (TextView) itemView.findViewById(R.id.item_date); } public TextView getTvLabel() {  return mTvLabel; } public TextView getTvDateTime() {  return mTvDateTime; }}

在onCreateViewHolder方法, 创建类; 在onBindViewHolder方法, 绑定数据.
DataModel

public class DataModel { private String mLabel; private Date mDateTime; public String getLabel() {  return mLabel; } public void setLabel(String label) {  mLabel = label; } public Date getDateTime() {  return mDateTime; } public void setDateTime(Date dateTime) {  mDateTime = dateTime; }}

6. ItemDecoration
项的装饰, 比如ListView中的分割线, 在本例中, 左右两条粉线.

 private void initItemDecoration(RecyclerView recyclerView) {  recyclerView.addItemDecoration(new MyItemDecoration(this)); }

ItemDecoration, 注意parent和child的使用方式.

public class MyItemDecoration extends RecyclerView.ItemDecoration { private static final int[] ATTRS = new int[]{android.R.attr.listDivider}; private Drawable mDivider; public MyItemDecoration(Context context) {  final TypedArray array = context.obtainStyledAttributes(ATTRS);  mDivider = array.getDrawable(0);  array.recycle(); } @Override public void onDraw(Canvas c, RecyclerView parent, State state) {  drawHorizontal(c, parent);  drawVertical(c, parent); } // 水平线 public void drawHorizontal(Canvas c, RecyclerView parent) {  final int childCount = parent.getChildCount();  // 在每一个子控件的底部画线  for (int i = 0; i < childCount; i++) {   final View child = parent.getChildAt(i);   final int left = child.getLeft() + child.getPaddingLeft();   final int right = child.getWidth() + child.getLeft() - child.getPaddingRight();   final int top = child.getBottom() - mDivider.getIntrinsicHeight() - child.getPaddingBottom();   final int bottom = top + mDivider.getIntrinsicHeight();   mDivider.setBounds(left, top, right, bottom);   mDivider.draw(c);  } } // 竖直线 public void drawVertical(Canvas c, RecyclerView parent) {  final int childCount = parent.getChildCount();  // 在每一个子控件的右侧画线  for (int i = 0; i < childCount; i++) {   final View child = parent.getChildAt(i);   int right = child.getRight() - child.getPaddingRight();   int left = right - mDivider.getIntrinsicWidth();   final int top = child.getTop() + child.getPaddingTop();   final int bottom = child.getTop() + child.getHeight() - child.getPaddingBottom();   mDivider.setBounds(left, top, right, bottom);   mDivider.draw(c);  } } // Item之间的留白 @Override public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {  outRect.set(0, 0, mDivider.getIntrinsicWidth(), mDivider.getIntrinsicHeight()); }}

本例重写了listDivider

 <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">  ...  <item name="android:listDivider">@drawable/divider_bg</item> </style><?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"  android:shape="rectangle"> <solid android:color="#ff00ff"/> <size android:height="4dp"/> <size android:width="4dp"/></shape>

7. ItemAnimator
动画效果比较复杂, 使用默认动画. 如要定制的话, 继承DefaultItemAnimator; 如设置null, 则不显示任何动画.

 private void initItemAnimator(RecyclerView recyclerView) {  recyclerView.setItemAnimator(new DefaultItemAnimator()); // 默认动画 }

8. 最终Activity

public class MainActivity extends AppCompatActivity { private MyAdapter mAdapter; @Override protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.activity_main);  Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);  setSupportActionBar(toolbar);  FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);  fab.setOnClickListener(new View.OnClickListener() {   @Override   public void onClick(View view) {    Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)      .setAction("Action", null).show();   }  });  // 初始化RecyclerView  initRecyclerView((RecyclerView) findViewById(R.id.test_recycler_view)); } /**  * 初始化RecyclerView  *  * @param recyclerView 主控件  */ private void initRecyclerView(RecyclerView recyclerView) {  recyclerView.setHasFixedSize(true); // 设置固定大小  initRecyclerLayoutManager(recyclerView); // 初始化LayoutManager  initRecyclerAdapter(recyclerView); // 初始化Adapter  initItemDecoration(recyclerView); // 初始化边界装饰  initItemAnimator(recyclerView); // 初始化动画效果 } /**  * 初始化RecyclerView的LayoutManager  *  * @param recyclerView 主控件  */ private void initRecyclerLayoutManager(RecyclerView recyclerView) {  // 错列网格布局  recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,    StaggeredGridLayoutManager.VERTICAL)); } /**  * 初始化RecyclerView的Adapter  *  * @param recyclerView 主控件  */ private void initRecyclerAdapter(RecyclerView recyclerView) {  mAdapter = new MyAdapter(getData());  recyclerView.setAdapter(mAdapter); } /**  * 初始化RecyclerView的(ItemDecoration)项目装饰  *  * @param recyclerView 主控件  */ private void initItemDecoration(RecyclerView recyclerView) {  recyclerView.addItemDecoration(new MyItemDecoration(this)); } /**  * 初始化RecyclerView的(ItemAnimator)项目动画  *  * @param recyclerView 主控件  */ private void initItemAnimator(RecyclerView recyclerView) {  recyclerView.setItemAnimator(new DefaultItemAnimator()); // 默认动画 } /**  * 模拟的数据  *  * @return 数据  */ private ArrayList<DataModel> getData() {  int count = 57;  ArrayList<DataModel> data = new ArrayList<>();  for (int i = 0; i < count; i++) {   DataModel model = new DataModel();   model.setDateTime(getBeforeDay(new Date(), i));   model.setLabel("No. " + i);   data.add(model);  }  return data; } /**  * 获取日期的前一天  *  * @param date 日期  * @param i 偏离  * @return 新的日期  */ private static Date getBeforeDay(Date date, int i) {  Calendar calendar = Calendar.getInstance();  calendar.setTime(date);  calendar.add(Calendar.DAY_OF_YEAR, i * (-1));  return calendar.getTime(); } @Override public boolean onCreateOptionsMenu(Menu menu) {  // Inflate the menu; this adds items to the action bar if it is present.  getMenuInflater().inflate(R.menu.menu_main, menu);  return true; } @Override public boolean onOptionsItemSelected(MenuItem item) {  // Handle action bar item clicks here. The action bar will  // automatically handle clicks on the Home/Up button, so long  // as you specify a parent activity in AndroidManifest.xml.  int id = item.getItemId();  switch (item.getItemId()) {   case R.id.id_action_add:    mAdapter.addData(1);    break;   case R.id.id_action_delete:    mAdapter.removeData(1);    break;  }  //noinspection SimplifiableIfStatement  if (id == R.id.action_settings) {   return true;  }  return super.onOptionsItemSelected(item); }}

为了测试动画, Menu额外添加两个按钮。

9.运行ReactNative示例
既然感觉ReactNative开发靠谱, 那么我们就来看看ReactNative都能做哪些好玩的东西, 和原生的有哪些区别?
示例图

2016224180350086.jpg (750×1334)

2016224180414706.jpg (1080×1920)

按照文档安装一些命令行工具, 再下载Git代码.
Github: https://github.com/facebook/react-native

内容很多, 包含一些依赖库和示例(Example), 下载的有点慢, 耐心等待.

下载完成后, 在react-native内, 执行npm install.

Android项目执行, 参考ReactAndroid的README.md.

在react-native目录, 新建local.properties

sdk.dir=/Users/wangchenlong/Installations/android-sdkndk.dir=/Users/wangchenlong/Installations/android-ndk-r10e

执行

cd react-native./gradlew :ReactAndroid:assembleDebug

再执行

./gradlew :ReactAndroid:installArchives

启动服务

./packager/packager.sh

安装项目

cd react-native./gradlew :Examples:UIExplorer:android:app:installDebug

一定要先启动服务, 再安装项目.
出现transforming 100%, 即导入成功.

2016224180504265.jpg (570×366)

在最新版本中, 我的红米note4无法运行项目.
报错: Upload package to device fails.
原因是编译的gradle版本太高, 默认1.5.0, 实际1.2.0~1.3.0都可以运行.
我的是1.2.3.
真机调试, 本人红米note(Android 4.2)
摇动手机, 选择Dev Settings->Debug sever host & port for device. 设置IP地址, 观察本机的IP, 填入即可. 我当前的是

192.168.2.202:8081
注意设置端口8081, 否则无法加载. 有些情况可以直接输入IP即可.
Android5.0以上, 直接设置端口即可.