Android應用開發中RecyclerView組件使用入門教程

2020-04-11 10:44:56

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RecyclerView是一種列表容器, 發布很久了, 才想起來寫點什么.

RecyclerView相比于ListView, 在回收重用時更具有靈活性, 也就是低耦合, 并且提供了擴展. 加載多個視圖時, 應該多用RecyclerView代替ListView.

那么我們來看看這東西應該怎么用? 比如生成一個瀑布流的視圖.

2016224180636421.png (1080×1920)

首先我們從一個HelloWorld寫起, 看看如何構建一個RecyclerView.

1. 依賴庫
Gradle配置, 添加Recycler庫

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

2. 資源文件
資源文件

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

3. 代碼
LayoutManager: 管理RecyclerView的結構.
Adapter: 處理每個Item的顯示.
ItemDecoration: 添加每個Item的裝飾.
ItemAnimator: 負責添加/移除/重排序時的動畫效果.

LayoutManager/Adapter是必須, ItemDecoration/ItemAnimator是可選. /**  * 初始化RecyclerView  *  * @param recyclerView 主控件  */ private void initRecyclerView(RecyclerView recyclerView) {  recyclerView.setHasFixedSize(true); // 設置固定大小  initRecyclerLayoutManager(recyclerView); // 初始化布局  initRecyclerAdapter(recyclerView); // 初始化適配器  initItemDecoration(recyclerView); // 初始化裝飾  initItemAnimator(recyclerView); // 初始化動畫效果 }

4. LayoutManager
管理RecyclerView的布局結構.

 private void initRecyclerLayoutManager(RecyclerView recyclerView) {  // 錯列網格布局  recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,    StaggeredGridLayoutManager.VERTICAL)); }

提供了多種LayoutManager, 瀑布流使用錯列網格布局.
5. Adapter
適配器, 處理RecyclerView的Item事務.

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

對于Adapter, 我們需要展開來說, 先看看類.

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);  // 隨機高度, 模擬瀑布效果.  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); } /**  * 獲取日期的前一天  *  * @param date 日期  * @param i 偏離  * @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創建ViewHolder.

（2）onBindViewHolder綁定每一項數據.

（3）getItemCount返回列表長度.

（4）RecyclerView強制使用ViewHolder.

public class MyViewHolder extends RecyclerView.ViewHolder { private TextView mTvLabel; // 標簽 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, 創建類; 在onBindViewHolder方法, 綁定數據.
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
項的裝飾, 比如ListView中的分割線, 在本例中, 左右兩條粉線.

 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); } // 水平線 public void drawHorizontal(Canvas c, RecyclerView parent) {  final int childCount = parent.getChildCount();  // 在每一個子控件的底部畫線  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);  } } // 豎直線 public void drawVertical(Canvas c, RecyclerView parent) {  final int childCount = parent.getChildCount();  // 在每一個子控件的右側畫線  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之間的留白 @Override public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {  outRect.set(0, 0, mDivider.getIntrinsicWidth(), mDivider.getIntrinsicHeight()); }}

本例重寫了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
動畫效果比較復雜, 使用默認動畫. 如要定制的話, 繼承DefaultItemAnimator; 如設置null, 則不顯示任何動畫.

 private void initItemAnimator(RecyclerView recyclerView) {  recyclerView.setItemAnimator(new DefaultItemAnimator()); // 默認動畫 }

8. 最終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); // 設置固定大小  initRecyclerLayoutManager(recyclerView); // 初始化LayoutManager  initRecyclerAdapter(recyclerView); // 初始化Adapter  initItemDecoration(recyclerView); // 初始化邊界裝飾  initItemAnimator(recyclerView); // 初始化動畫效果 } /**  * 初始化RecyclerView的LayoutManager  *  * @param recyclerView 主控件  */ private void initRecyclerLayoutManager(RecyclerView recyclerView) {  // 錯列網格布局  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)項目裝飾  *  * @param recyclerView 主控件  */ private void initItemDecoration(RecyclerView recyclerView) {  recyclerView.addItemDecoration(new MyItemDecoration(this)); } /**  * 初始化RecyclerView的(ItemAnimator)項目動畫  *  * @param recyclerView 主控件  */ private void initItemAnimator(RecyclerView recyclerView) {  recyclerView.setItemAnimator(new DefaultItemAnimator()); // 默認動畫 } /**  * 模擬的數據  *  * @return 數據  */ 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; } /**  * 獲取日期的前一天  *  * @param date 日期  * @param i 偏離  * @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); }}

為了測試動畫, Menu額外添加兩個按鈕。

9.運行ReactNative示例
既然感覺ReactNative開發靠譜, 那么我們就來看看ReactNative都能做哪些好玩的東西, 和原生的有哪些區別?
示例圖

2016224180350086.jpg (750×1334)

2016224180414706.jpg (1080×1920)

按照文檔安裝一些命令行工具, 再下載Git代碼.
Github: https://github.com/facebook/react-native

內容很多, 包含一些依賴庫和示例(Example), 下載的有點慢, 耐心等待.

下載完成后, 在react-native內, 執行npm install.

Android項目執行, 參考ReactAndroid的README.md.

在react-native目錄, 新建local.properties

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

執行

cd react-native./gradlew :ReactAndroid:assembleDebug

再執行

./gradlew :ReactAndroid:installArchives

啟動服務

./packager/packager.sh

安裝項目

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

一定要先啟動服務, 再安裝項目.
出現transforming 100%, 即導入成功.

2016224180504265.jpg (570×366)

在最新版本中, 我的紅米note4無法運行項目.
報錯: Upload package to device fails.
原因是編譯的gradle版本太高, 默認1.5.0, 實際1.2.0~1.3.0都可以運行.
我的是1.2.3.
真機調試, 本人紅米note(Android 4.2)
搖動手機, 選擇Dev Settings->Debug sever host & port for device. 設置IP地址, 觀察本機的IP, 填入即可. 我當前的是

192.168.2.202:8081
注意設置端口8081, 否則無法加載. 有些情況可以直接輸入IP即可.
Android5.0以上, 直接設置端口即可.