Android RecyclerView的应用
一:RecyclerView是什么
从Android5.0开始，谷歌推出一个用于大量数据展现的新控件RecyclerView,能够代替传统的ListView,更加弱小和灵便。
在AndroidX我的项目中增加依赖：implementation 'androidx.recyclerview:recyclerview:1.1.0'
在非AndroidX我的项目中增加依赖：implementation 'com.android.support:recyclerview-v7:26.1.0'//对应的是compileSdkVersion的版本
//Android布局应用<android.support.v7.widget.RecyclerView android:layout_width="match_parent" android:layout_height="match_parent" /> //AndroidX布局应用 <androidx.recyclerview.widget.RecyclerView android:layout_width="match_parent" android:layout_height="match_parent"/>RecyclerView的长处
1.反对部分刷新
2.能够自定义Item增删时的动画
3.可能实现Item拖拽和侧滑删除等性能
二：RecyclerView应用
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <androidx.recyclerview.widget.RecyclerView android:id="@+id/tv_recycler" android:layout_width="match_parent" android:layout_height="match_parent"/></LinearLayout>1.创立布局管理器
LinearLayoutManager:线性布局，以垂直或程度滚动形式显示列表
GridLayoutManager:网格布局，在网格中显示我的项目
StaggeredGridLayoutManager：瀑布流布局，在扩散对齐网格中显示我的项目
LinearLayoutManager layoutManager=new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false);//线性布局管理器 GridLayoutManager gridLayoutManager=new GridLayoutManager(this,3);//网格布局管理器 StaggeredGridLayoutManager staggeredGridLayoutManager=new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL);//瀑布流布局 2.适配器应用
public class MyRecycleViewAdapter extends RecyclerView.Adapter<MyRecycleViewAdapter.MyHolder> { private List<String> mDatas;//数据源 private Context context; private OnItemClickListener onItemClickListener; /**向内部提供调用设置监听*/ public void setOnItemClickListener(OnItemClickListener onItemClickListener){ this.onItemClickListener=onItemClickListener; } public MyRecycleViewAdapter(Context context,List<String> mDatas) { this.context=context; this.mDatas = mDatas; } /** * 创立ViewHolder并返回，后续item布局里控件都是从ViewHolder中取出 */ @NonNull @Override public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) { //将咱们自定义的item布局转成View View view = LayoutInflater.from(context).inflate(R.layout.item_one, parent, false); //将View传递给咱们自定义ViewHolder return new MyHolder(view); } /**通过办法提供的ViewHolder,将数据绑定到的ViewHolder中*/ @Override public void onBindViewHolder(@NonNull MyHolder holder, int position) { holder.tv_content.setText(mDatas.get(position)); holder.tv_content.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if (onItemClickListener!=null){ onItemClickListener.onItemClick(v,holder.getAdapterPosition()+1); } } }); } /** * 获取数据源总的条目 */ @Override public int getItemCount() { return mDatas.size(); } static class MyHolder extends RecyclerView.ViewHolder { TextView tv_content; public MyHolder(@NonNull View itemView) { super(itemView); tv_content=itemView.findViewById(R.id.tv_content); } } /**自定义的接口*/ public interface OnItemClickListener{ void onItemClick(View view,int position); }}RecyclerView 封装了viewholder的回收复用，标准化了ViewHolder，编写Adapter面向的是ViewHolder而不是View,复用的逻辑封装了
创立适配器步骤：
1.创立Adapter：创立一个继承RecyclerView.Adapter<VH>的Adapter类（VH是ViewHolder的类名）
2.创立ViewHolder：在Adapter中创立一个继承RecyclerView.ViewHolder的动态外部类，记为VH。ViewHolder的实现和ListView的ViewHolder实现简直一样。
三个办法：
onCreateViewHolder： 创立ViewHolder并返回，后续item布局里控件都是从ViewHolder中取出。
onBindViewHolder：通过办法提供的ViewHolder，将数据绑定到ViewHolder中。
getItemCount：获取数据源总的条数。
下面2个适配器和布局管理器是必须设置的
3.Item Decoration(可选)设置分割线
//增加分割线 tv_recycler.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL));//默认的分割线 能够自定义距离款式须要继承RecyclerView.ItemDecoration类，该类是抽象类
public class MyItemDecoration extends RecyclerView.ItemDecoration { private final Drawable mLine; private final int orientation; public MyItemDecoration(Context context, int orientation) { this.orientation = orientation; int[] attrs = new int[]{android.R.attr.listDivider};//零碎的分割线色彩 TypedArray a = context.obtainStyledAttributes(attrs); mLine = a.getDrawable(0); a.recycle(); } /**在Item绘制之前被调用，用于绘制距离款式*/ @Override public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) { super.onDraw(c, parent, state); if (orientation==RecyclerView.HORIZONTAL){ drawVertical(c, parent, state); }else if (orientation==RecyclerView.VERTICAL){ drawHorizontal(c, parent, state); } } /**onDraw和onDrawOver2个其中一个就行*/ @Override public void onDrawOver(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) { super.onDrawOver(c, parent, state); } /**设置item的偏移量，偏移的局部用于填充距离款式，即设置分割线的宽、高；在RecyclerView的onMesure()中会调用该办法。*/ @Override public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) { super.getItemOffsets(outRect, view, parent, state); if (orientation == RecyclerView.HORIZONTAL) { //画垂直线 outRect.set(0, 0, mLine.getIntrinsicWidth(), 0); } else if (orientation == RecyclerView.VERTICAL) { //画水平线 outRect.set(0, 0, 0, mLine.getIntrinsicHeight()); } } /** * 画垂直分割线 */ private void drawVertical(Canvas c, RecyclerView parent, RecyclerView.State state) { int childCount = parent.getChildCount(); for (int i = 0; i < childCount; i++) { View child = parent.getChildAt(i); int left = child.getRight(); int top = child.getTop(); int right = left + mLine.getIntrinsicWidth(); int bottom = child.getBottom(); mLine.setBounds(left, top, right, bottom); mLine.draw(c); } } /** * 画程度分割线 */ private void drawHorizontal(Canvas c, RecyclerView parent, RecyclerView.State state) { int childCount = parent.getChildCount(); for (int i = 0; i < childCount; i++) { View child = parent.getChildAt(i); int left = child.getLeft(); int top = child.getBottom(); int right = child.getRight(); int bottom = top + mLine.getIntrinsicHeight(); mLine.setBounds(left, top, right, bottom); mLine.draw(c); } }}咱们能够批改零碎自定义分割线色彩
在res下values下theme主题中
<!--自定义零碎分割线色彩-->
<item name="android:listDivider">@drawable/customizelistdivider </item>
在res/drawable中设置customizelistdivider
<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"> <gradient android:endColor="#ff0000ff" android:startColor="#ffff0000" android:type="linear" /> <size android:height="4dp" android:width="4dp"/></shape>
应用设置自定义分割线
tv_recycler.addItemDecoration(new MyItemDecoration(this,RecyclerView.VERTICAL));
4.ItemAnimator动画（可选）
tv_recycler.setItemAnimator(new DefaultItemAnimator());//设置默认动画
默认动画继承DefaultItemAnimator来实现自定义动画
相干实现
public class SecondActivity extends AppCompatActivity { private RecyclerView tv_recycler; private MyRecycleViewAdapter myRecycleViewAdapter; private List<String> mDatas=new ArrayList<>(); @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_second); initData();//初始化数据 tv_recycler=findViewById(R.id.tv_recycler); //创立布局管理器 LinearLayoutManager layoutManager=new LinearLayoutManager(this);//默认垂直排列 //GridLayoutManager gridLayoutManager=new GridLayoutManager(this,3); //StaggeredGridLayoutManager staggeredGridLayoutManager=new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL); layoutManager.setOrientation(RecyclerView.HORIZONTAL);//设置程度排列 //LinearLayoutManager layoutManager1=new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false); //设置布局管理器 tv_recycler.setLayoutManager(layoutManager); //增加分割线 tv_recycler.addItemDecoration(new MyItemDecoration(this,RecyclerView.VERTICAL));//自定义分割线 tv_recycler.setItemAnimator(new DefaultItemAnimator()); //tv_recycler.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL));//默认的分割线 //创立数据适配器 myRecycleViewAdapter=new MyRecycleViewAdapter(this,mDatas); //设置数据适配器 tv_recycler.setAdapter(myRecycleViewAdapter); //内部适配器数据监听条目点击 myRecycleViewAdapter.setOnItemClickListener(new MyRecycleViewAdapter.OnItemClickListener() { @Override public void onItemClick(View view, int position) { Toast.makeText(SecondActivity.this, "第"+position+"条数据", Toast.LENGTH_SHORT).show(); } }); } private void initData() { for (int i=0;i<40;i++){ mDatas.add("我是item"+i); } }}5.Item条目监听，点击事件监听
/**向内部提供调用设置监听*/ public void setOnItemClickListener(OnItemClickListener onItemClickListener){ this.onItemClickListener=onItemClickListener; } public MyRecycleViewAdapter(Context context,List<String> mDatas) { this.context=context; this.mDatas = mDatas; } /**自定义的接口*/ public interface OnItemClickListener{ void onItemClick(View view,int position); } @Override public void onBindViewHolder(@NonNull MyHolder holder, int position) { holder.tv_content.setText(mDatas.get(position)); holder.tv_content.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if (onItemClickListener!=null){ onItemClickListener.onItemClick(v,holder.getAdapterPosition()+1);//在绑定数据的时候给内部传递得postion从1开始 } } }); } //内部调用开始 myRecycleViewAdapter.setOnItemClickListener(new MyRecycleViewAdapter.OnItemClickListener() { @Override public void onItemClick(View view, int position) { Toast.makeText(SecondActivity.this, "第"+position+"条数据", Toast.LENGTH_SHORT).show(); } });END:只愿年过半百，归来仍是少年