• ViewPager和ViewPager2

    1.ViewPager简单使用：

       1）定义Layout

    1.   <androidx.viewpager.widget.ViewPager
    2.             android:id="@+id/viewpager"
    3.             android:layout_width="match_parent"
    4.             android:layout_height="match_parent"/>

          2）初始化View

    1.   private void initViews() {
    2.         viewPager = findViewById(R.id.viewpager);
    3.         List<String> list = new ArrayList<>();
    4.         for (int i = 0; i < 10; i++) {
    5.             list.add("pos: " + i);
    6.         }
    7.         views = new ArrayList<>();
    8.         for (int i = 0; i < list.size(); i++) {
    9.             View view = LayoutInflater.from(this).inflate(R.layout.layout_item, null);
    10.             TextView textView = view.findViewById(R.id.textview);
    11.             textView.setText(list.get(i));
    12.             views.add(view);
    13.         }
    14.         MyPageAdapter pageAdapter = new MyPageAdapter(this, views);
    15.         viewPager.setAdapter(pageAdapter);
    16.     }

        3）PageAdapter

      

    1. public class MyPageAdapter extends PagerAdapter {
    2.     private Context context;
    3.     private List<View> views;
    4.  
    5.     public MyPageAdapter(Context context, List<View> list) {
    6.         this.context = context;
    7.         this.views = list;
    8.     }
    9.  
    10.     @Override
    11.     public int getCount() {
    12.         if (views == null) {
    13.             return 0;
    14.         } else {
    15.             return Integer.MAX_VALUE;
    16.         }
    17.     }
    18.  
    19.     @Override
    20.     public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
    21.         return view == object;
    22.     }
    23.  
    24.     @NonNull
    25.     @Override
    26.     public Object instantiateItem(@NonNull ViewGroup container, int position) {
    27.         int index = position % views.size();
    28.         Log.e("nyz", "instantiateItem " + position);
    29.         Log.e("nyz", "childCount " + container.getChildCount());
    30.         container.addView(views.get(index));
    31.         return views.get(index);
    32.     }
    33.  
    34.     @Override
    35.     public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
    36.  
    37.         Log.e("nyz", "destroyItem " + position);
    38.         Log.e("nyz", "childCount " + container.getChildCount());
    39.         container.removeView((View) object);
    40.     }
    41.  
    42. }

    2.ViewPager2的简单使用

     1）layout引入ViewPager2

    1.  <androidx.viewpager2.widget.ViewPager2
    2.             android:id="@+id/viewpager2"
    3.             android:layout_width="match_parent"
    4.             android:layout_height="match_parent" />

       2）Activity中。

    1.   List<String> list = new ArrayList<>();
    2.         for (int i = 0; i < 10; i++) {
    3.             list.add("pos: " + i);
    4.         }
    5.  
    6.         viewPager2 = findViewById(R.id.viewpager2);
    7.         //设置ViewPager是纵向滚动，还是横向滚动
    8. //        viewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);
    9.         viewPager2.setOrientation(ViewPager2.ORIENTATION_HORIZONTAL);
    10.         viewPager2.setAdapter(new MyPageAdapter2(this, list));

     3）Adapter，定义Adapter和定义RecycleView的Adapter是一样的。因为在ViewPager2内部有一个RecycleView。

    1. public class MyPageAdapter2 extends RecyclerView.Adapter {
    2.     private Context context;
    3.     private List list;
    4.  
    5.     public MyPageAdapter2(Context context, List list) {
    6.         this.context = context;
    7.         this.list = list;
    8.     }
    9.  
    10.     @NonNull
    11.     @Override
    12.     public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    13.         View view = LayoutInflater.from(context).inflate(R.layout.layout_item, parent,false);
    14.         MyViewHolder viewHolder = new MyViewHolder(view);
    15.         return viewHolder;
    16.     }
    17.  
    18.     @Override
    19.     public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
    20.         ((MyViewHolder) holder).update(list.get(position));
    21.     }
    22.  
    23.     @Override
    24.     public int getItemCount() {
    25.         return list.size();
    26.     }
    27.  
    28.     class MyViewHolder extends RecyclerView.ViewHolder {
    29.         private TextView textView;
    30.  
    31.         public MyViewHolder(@NonNull View itemView) {
    32.             super(itemView);
    33.             textView = itemView.findViewById(R.id.textview);
    34.         }
    35.  
    36.         public void update(String str) {
    37.             textView.setText(str);
    38.         }
    39.     }
    40. }

    4）java.lang.IllegalStateException: Pages must fill the whole ViewPager2 (use match_parent)

    1.  Process: com.example.viewpager, PID: 8447
    2.     java.lang.IllegalStateException: Pages must fill the whole ViewPager2 (use match_parent)
    3.         at androidx.viewpager2.widget.ViewPager2$4.onChildViewAttachedToWindow(ViewPager2.java:270)
    4.         at androidx.recyclerview.widget.RecyclerView.dispatchChildAttached(RecyclerView.java:7561)
    5.         at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:860)
    6.         at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
    7.         at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8601)
    8.         at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8559)
    9.         at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8547)
    10.         at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1641)
    11.         at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
    12.         at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:665)
    13.         at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4134)
    14.         at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3851)
    15.         at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)
    16.         at android.view.View.layout(View.java:23750)
    17.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    18.         at androidx.viewpager2.widget.ViewPager2.onLayout(ViewPager2.java:527)
    19.         at android.view.View.layout(View.java:23750)
    20.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    21.         at androidx.swiperefreshlayout.widget.SwipeRefreshLayout.onLayout(SwipeRefreshLayout.java:689)
    22.         at android.view.View.layout(View.java:23750)
    23.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    24.         at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
    25.         at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
    26.         at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
    27.         at android.view.View.layout(View.java:23750)
    28.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    29.         at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
    30.         at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
    31.         at android.view.View.layout(View.java:23750)
    32.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    33.         at androidx.appcompat.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:536)
    34.         at android.view.View.layout(View.java:23750)
    35.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    36.         at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
    37.         at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
    38.         at android.view.View.layout(View.java:23750)
    39.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    40.         at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
    41.         at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
    42.         at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
    43.         at android.view.View.layout(View.java:23750)
    44.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    45.         at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
    46.         at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
    47.         at com.android.internal.policy.DecorView.onLayout(DecorView.java:880)
    48.         at android.view.View.layout(View.java:23750)
    49.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    50.         at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:4082)
    51.         at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:3501)
    52.         at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:2410)
    53.         at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:9402)
    54.         at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1193)
    55.         at android.view.Choreographer.doCallbacks(Choreographer.java:945)
    56.         at android.view.Choreographer.doFrame(Choreographer.java:851)
    57.         at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1175)
    58.         at android.os.Handler.handleCallback(Handler.java:938)

      出现上面的异常的解决方案：

    1）解决方案1 在onCreateViewHolder时不能使用下面的方式：

         View view = LayoutInflater.from(context).inflate(R.layout.layout_item,null);

         而应该使用下面的方式，就不会出现上面的异常：

        View view = LayoutInflater.from(context).inflate(R.layout.layout_item, parent,false);

    2）解决方案2 动态设置宽高

    1.   View view = LayoutInflater.from(context).inflate(R.layout.layout_item,null);
    2.  
    3.         ViewGroup.LayoutParams layoutParams =
    4.                 new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
    5.         view.setLayoutParams(layoutParams);

    通过上面的异常信息，可以看出来Choreographer的调用流程：

    FrameDisplayEventReceiver.run--doFrame---doCallbacks--CallbackRecord.run--TraversalRunnable.run--doTraversal--performTraversals--performLayout--layout--

    然后就是熟悉的onLayout onMeasure onDraw.

    可以参考另外一篇介绍编舞者的文章：

    Choreographer--编舞者源码分析_choreographer 源码分析-CSDN博客

    1.  at android.view.View.layout(View.java:23750)
    2.         at android.view.ViewGroup.layout(ViewGroup.java:6525)
    3.         at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:4082)
    4.         at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:3501)
    5.         at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:2410)
    6.         at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:9402)
    7.         at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1193)
    8.         at android.view.Choreographer.doCallbacks(Choreographer.java:945)
    9.         at android.view.Choreographer.doFrame(Choreographer.java:851)
    10.         at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1175)
    11.         at android.os.Handler.handleCallback(Handler.java:938)

    代码下载：

    https://download.csdn.net/download/niuyongzhi/88408862

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  • 原文地址：https://blog.csdn.net/niuyongzhi/article/details/133702302