RecyclerView 是一个非常强大的控件，他可以说是一个增强版的listView，不仅可以轻松实现listview的效果，而且还增加了很多的效果。通过设置不同的LayoutManager、ItemDecoration、ItemAnimator可以实现丰富的效果。
一、RecyclerView的简单使用
1，配置buid.gradle
dependencies { implementation fileTree(dir: 'libs', include: ['*.jar']) implementation 'com.android.support:appcompat-v7:28.0.0' implementation 'com.android.support.constraint:constraint-layout:1.1.3' implementation 'com.android.support:recyclerview-v7:28.0.0' testImplementation 'junit:junit:4.12' ...... }
2，在布局中加入RecyclerView控件，然后创建一个RecyclerView的布局文件item_recycler。
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <android.support.v7.widget.RecyclerView android:id="@+id/id_recyclerview" android:layout_width="match_parent" android:layout_height="match_parent"/> </LinearLayout>
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical"> <TextView android:id="@+id/tv_item" android:layout_width="match_parent" android:layout_height="50dp" android:gravity="center" android:text="moon"/> </LinearLayout>
3,使用RecyclerView。
public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); List<String> list = new ArrayList<>(); for (int i = 0; i < 20; i++) { list.add(String.valueOf(i)); } RecyclerView recyclerView = findViewById(R.id.id_recyclerview); //设置线性布局管理器 recyclerView.setLayoutManager(new LinearLayoutManager(this)); //设置item增加和删除时的动画 recyclerView.setItemAnimator(new DefaultItemAnimator()); HomeAdapter adapter = new HomeAdapter(list); recyclerView.setAdapter(adapter); } class HomeAdapter extends RecyclerView.Adapter<HomeAdapter.MyViewHolder> { List<String> list; public HomeAdapter(List<String> list) { this.list = list; } //移除元素 public void removeData(int position){ list.remove(position); notifyItemRemoved(position); } //加载条目布局 @Override public HomeAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { MyViewHolder holder = new MyViewHolder(LayoutInflater.from(MainActivity.this). inflate(R.layout.item_recycler,parent,false)); return holder; } //将条目和数据进行绑定 @Override public void onBindViewHolder(HomeAdapter.MyViewHolder holder, int position) { holder.tv.setText(list.get(position)); } //条目的总数量 @Override public int getItemCount() { return list.size(); } //内部类，构造函数接收一个View参数，这个参数通常就是条目 class MyViewHolder extends RecyclerView.ViewHolder { TextView tv; public MyViewHolder(View itemView) { super(itemView); tv = itemView.findViewById(R.id.tv_item); } } } }
需要说的就是上面的布局管理器，我们这里使用的是线性布局的方式，当然也可以使用其他的方式，比如：
//设置水平线性布局管理器 LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this); linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL); recyclerView.setLayoutManager(linearLayoutManager); //还有网格的方式 StaggeredGridLayoutManager manager = new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL); recyclerView.setLayoutManager(manager);
二、设置分割线，直接上代码
public class DividerItemDecoration extends RecyclerView.ItemDecoration { private static final int[] ATTRS = new int[]{ android.R.attr.listDivider }; public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL; public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL; private Drawable mDivider; private int mOrientation; public DividerItemDecoration(Context context ,int orientation){ final TypedArray a = context.obtainStyledAttributes(ATTRS); mDivider = a.getDrawable(0); setOrientation(orientation); } private void setOrientation(int orientation) { if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST){ throw new IllegalArgumentException("invaild orientation"); } mOrientation = orientation; } @Override public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) { if (mOrientation == VERTICAL_LIST){ drawVertical(c,parent); }else { drawHorizontal(c,parent); } } private void drawHorizontal(Canvas c, RecyclerView parent) { final int top = parent.getPaddingTop(); final int bottom = parent.getHeight()-parent.getPaddingBottom(); final int childCount = parent.getChildCount(); for (int i = 0; i < childCount; i++) { final View child = parent.getChildAt(i); final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams(); final int left = child.getRight()+params.rightMargin; final int right = left + mDivider.getIntrinsicWidth(); mDivider.setBounds(left ,top,right ,bottom); mDivider.draw(c); } } private void drawVertical(Canvas c, RecyclerView parent) { final int left = parent.getPaddingLeft(); int right = parent.getWidth()-parent.getPaddingRight(); final int childCound = parent.getChildCount(); for (int i = 0; i < childCound; i++) { final View child = parent.getChildAt(i); final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)child.getLayoutParams(); final int top= child.getBottom() + params.bottomMargin; final int bottom = top + mDivider.getIntrinsicHeight(); mDivider.setBounds(left,top,right,bottom); mDivider.draw(c); } } @Override public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) { if (mOrientation == VERTICAL_LIST){ outRect.set(0,0,0,mDivider.getIntrinsicHeight()); }else { outRect.set(0,0,mDivider.getIntrinsicWidth(),0); } } }
这里的核心方法是onDraw方法，他根据传进来的orientation来判断是绘制横向的item和分割线还是纵向的分割线。其中，drawHorizontal用于绘制横向的item的分割线，drawVerical用于绘制纵向的item的分割线，getItemOffsets方法则用于设置item的padding属性，虽然没有默认的分割线，但是好处也发现了，我们可以更灵活的自定义分割线，实现自定义的分割线。
我们只需要在setAdapter之前加入入下代码便可以加入分割线。
recyclerView.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL_LIST));
三，自定义点击事件
在适配器中定义接口并提供回调。这里我们定义了条目的点击事件和长按事件。
1，首先定义接口。
public class MainActivity extends AppCompatActivity { public interface OnItemClickListener { void onItemClick(View view, int position); void onItemLogClick(View view, int position); } .......
2,在适配器类中创建该接口的引用，并创建回调方法。
private OnItemClickListener onItemClickListener; //回调方法 public void setOnItemClickListener(OnItemClickListener onItemClickListener) { this.onItemClickListener = onItemClickListener; }
3，在适配器类中对每个item进行监听，并且将事件回调给我们的自定义监听。
class HomeAdapter extends RecyclerView.Adapter<HomeAdapter.MyViewHolder> implements View.OnClickListener, View.OnLongClickListener { private OnItemClickListener onItemClickListener; //回调方法 public void setOnItemClickListener(OnItemClickListener onItemClickListener) { this.onItemClickListener = onItemClickListener; } List<String> list; public HomeAdapter(List<String> list) { this.list = list; } //移除元素 public void removeData(int position) { list.remove(position); notifyItemRemoved(position); } @Override public HomeAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(MainActivity.this). inflate(R.layout.item_recycler, parent, false); MyViewHolder holder = new MyViewHolder(view); //实现监听 view.setOnClickListener(this); view.setOnLongClickListener(this); return holder; } @Override public void onBindViewHolder(HomeAdapter.MyViewHolder holder, int position) { //对每一个条目设置标记 holder.itemView.setTag(position); holder.tv.setText(list.get(position)); } @Override public int getItemCount() { return list.size(); } @Override public void onClick(View v) { //如果不为空则回调监听 if (onItemClickListener != null) { onItemClickListener.onItemClick(v, (int) v.getTag()); } } //如果回调使用长时间单击，则为true，否则为false。 @Override public boolean onLongClick(View v) { //如果不为空则回调监听 if (onItemClickListener != null) { onItemClickListener.onItemLogClick(v, (int) v.getTag()); return true; } return false; } //内部类，构造函数接收一个View参数，这个参数通常就是条目 class MyViewHolder extends RecyclerView.ViewHolder { TextView tv; public MyViewHolder(View itemView) { super(itemView); tv = itemView.findViewById(R.id.tv_item); } } }
4，最后我们在activity中实现我们的自定义监听
adapter.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(View view, int position) { Toast.makeText(MainActivity.this, "点击了"+position+"条", Toast.LENGTH_SHORT).show(); } @Override public void onItemLogClick(View view, final int position) { new AlertDialog.Builder(MainActivity.this) .setTitle("确定删除吗?") .setNeutralButton("取消",null) .setPositiveButton("确定", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { adapter.removeData(position); } }) .show(); } });
长按会弹出对话框，删除时会有消失的动画。如图所示：
最后贴出全部的代码。布局就不贴了哈。分割线的代码在上面有！
public class MainActivity extends AppCompatActivity { public interface OnItemClickListener { void onItemClick(View view, int position); void onItemLogClick(View view, int position); } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); List<String> list = new ArrayList<>(); for (int i = 0; i < 20; i++) { list.add(String.valueOf(i)); } RecyclerView recyclerView = findViewById(R.id.id_recyclerview); //设置线性布局管理器 recyclerView.setLayoutManager(new LinearLayoutManager(this)); //设置item增加和删除时的动画 recyclerView.setItemAnimator(new DefaultItemAnimator()); //添加分割线 recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL_LIST)); final HomeAdapter adapter = new HomeAdapter(list); recyclerView.setAdapter(adapter); adapter.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(View view, int position) { Toast.makeText(MainActivity.this, "点击了" + position + "条", Toast.LENGTH_SHORT).show(); } @Override public void onItemLogClick(View view, final int position) { new AlertDialog.Builder(MainActivity.this) .setTitle("确定删除吗?") .setNeutralButton("取消", null) .setPositiveButton("确定", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { adapter.removeData(position); } }) .show(); } }); } class HomeAdapter extends RecyclerView.Adapter<HomeAdapter.MyViewHolder> implements View.OnClickListener, View.OnLongClickListener { private OnItemClickListener onItemClickListener; //回调方法 public void setOnItemClickListener(OnItemClickListener onItemClickListener) { this.onItemClickListener = onItemClickListener; } List<String> list; public HomeAdapter(List<String> list) { this.list = list; } //移除元素 public void removeData(int position) { list.remove(position); notifyItemRemoved(position); } @Override public HomeAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(MainActivity.this). inflate(R.layout.item_recycler, parent, false); MyViewHolder holder = new MyViewHolder(view); //实现监听 view.setOnClickListener(this); view.setOnLongClickListener(this); return holder; } @Override public void onBindViewHolder(HomeAdapter.MyViewHolder holder, int position) { //对每一个条目设置标记 holder.itemView.setTag(position); holder.tv.setText(list.get(position)); } @Override public int getItemCount() { return list.size(); } @Override public void onClick(View v) { //如果不为空则回调监听 if (onItemClickListener != null) { onItemClickListener.onItemClick(v, (int) v.getTag()); } } //如果回调使用长时间单击，则为true，否则为false。 @Override public boolean onLongClick(View v) { //如果不为空则回调监听 if (onItemClickListener != null) { onItemClickListener.onItemLogClick(v, (int) v.getTag()); return true; } return false; } //内部类，构造函数接收一个View参数，这个参数通常就是条目 class MyViewHolder extends RecyclerView.ViewHolder { TextView tv; public MyViewHolder(View itemView) { super(itemView); tv = itemView.findViewById(R.id.tv_item); } } } }
