Pages must fill the whole ViewPager2 (use match_parent)

从Viewpager2源码中找出抛出异常的代码

private RecyclerView.OnChildAttachStateChangeListener enforceChildFillListener() {
        return new RecyclerView.OnChildAttachStateChangeListener() {
            @Override
            public void onChildViewAttachedToWindow(@NonNull View view) {
                RecyclerView.LayoutParams layoutParams =
                        (RecyclerView.LayoutParams) view.getLayoutParams();
                if (layoutParams.width != LayoutParams.MATCH_PARENT
                        || layoutParams.height != LayoutParams.MATCH_PARENT) {
                    throw new IllegalStateException(
                            "Pages must fill the whole ViewPager2 (use match_parent)");
                }
            }

            @Override
            public void onChildViewDetachedFromWindow(@NonNull View view) {
                // nothing
            }
        };
    }

如果子view的宽和高不是Match_parent就会抛出异常 ，我们在看下enforceChildFillListener

mRecyclerView.addOnChildAttachStateChangeListener(enforceChildFillListener());

一个注册监听，我们在看下addOnChildAttachStateChangeListener方法

 public void addOnChildAttachStateChangeListener(
            @NonNull OnChildAttachStateChangeListener listener) {
        if (mOnChildAttachStateListeners == null) {
            mOnChildAttachStateListeners = new ArrayList<>();
        }
        mOnChildAttachStateListeners.add(listener);
    }

这个方法就是注册一个监听器，当子视图附加到RecyclerView或从RecyclerView分离时，该监听器就会收到通知， 问题的原因找到了，那么问题就好解决了。
归根结底就是子view的宽和高并没有起到效果，虽然在xml文件中设置了，类似这样

<?xml version="1.0" encoding="UTF-8"?>
<androidx.appcompat.widget.AppCompatImageView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/item_guide_img"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:srcCompat="@mipmap/audio_stop"
    tools:ignore="MissingDefaultResource" />

或者这样都是不行的

<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.appcompat.widget.AppCompatImageView xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/item_guide_img"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:srcCompat="@mipmap/audio_stop"
        tools:ignore="MissingDefaultResource" />

</LinearLayout>

解决方案有两种：
第一种就是

  View inflate = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.item_guide_img, parent,false)
  // 我们给view设置父布局

第二种：

  View inflate = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.item_guide_img, null);
            
            ViewGroup.LayoutParams layoutParams =
                    new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);

            inflate.setLayoutParams(layoutParams);
//动态设置宽和高