实现NestedScrollingChild问题

Question

我正在尝试一些用于为自定义视图实现NestedScrollingChild的示例。

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    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"
    android:fitsSystemWindows="true"
    tools:context=".MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            android:theme="@style/AppTheme.AppBarOverlay"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/AppTheme.PopupOverlay"/>

    </android.support.design.widget.AppBarLayout>

    <com.ayeauto.custom.NestedScrollingChildView
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="bottom">
        </com.ayeauto.custom.NestedScrollingChildView>

</android.support.design.widget.CoordinatorLayout>

这个例子工作正常，我可以看到ToolBar与 NestedScrollingChildView 上的滚动一起折叠。但是，如果我进行以下更改，那么 NestedScrollingChildView 上的滚动就没有效果了。如果我滚动它，工具栏不会折叠

<com.ayeauto.custom.NestedScrollingChildView
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/viewpager"
            android:layout_width="match_parent"
            android:layout_height="300dp"
            android:layout_gravity="bottom">
            </com.ayeauto.custom.NestedScrollingChildView>

即，如果我给出一个大小的高度，那么它就不起作用了。 我正在使用android支持库23.1.1

import android.content.Context;
import android.support.v4.view.GestureDetectorCompat;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;


public class NestedScrollingChildView extends View implements NestedScrollingChild, GestureDetector.OnGestureListener {
    private final NestedScrollingChildHelper mNestedScrollingChildHelper;
    private GestureDetectorCompat mDetector;

    public NestedScrollingChildView(Context context) {
        this(context, null);
    }

    public NestedScrollingChildView(Context context, AttributeSet attrs) {
        this(context, null, 0);
    }

    public NestedScrollingChildView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mNestedScrollingChildHelper = new NestedScrollingChildHelper(this);
        mDetector = new GestureDetectorCompat(context, this);
        setNestedScrollingEnabled(true);
    }

    @Override
    public void setNestedScrollingEnabled(boolean enabled) {
        mNestedScrollingChildHelper.setNestedScrollingEnabled(true);
    }

    @Override
    public boolean isNestedScrollingEnabled() {
        return mNestedScrollingChildHelper.isNestedScrollingEnabled();
    }

    @Override
    public boolean startNestedScroll(int axes) {
        return mNestedScrollingChildHelper.startNestedScroll(axes);
    }

    @Override
    public void stopNestedScroll() {
        mNestedScrollingChildHelper.stopNestedScroll();
    }

    @Override
    public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
        return mNestedScrollingChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
    }

    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
        return mNestedScrollingChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
    }

    @Override
    public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
        return mNestedScrollingChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
    }

    @Override
    public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
        return mNestedScrollingChildHelper.dispatchNestedPreFling(velocityX, velocityY);
    }

    @Override
    public void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        mNestedScrollingChildHelper.onDetachedFromWindow();
    }

    @Override
    public boolean hasNestedScrollingParent() {
        return mNestedScrollingChildHelper.hasNestedScrollingParent();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event){
        final boolean handled = mDetector.onTouchEvent(event);
        if (!handled && event.getAction() == MotionEvent.ACTION_UP) {
            stopNestedScroll();
        }
        return true;
    }

    @Override
    public boolean onDown(MotionEvent e) {
        startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
        return true;
    }

    @Override
    public void onShowPress(MotionEvent e) {
    }

    @Override
    public boolean onSingleTapUp(MotionEvent e) {
        return false;
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        dispatchNestedPreScroll(0, (int) distanceY, null, null);
        dispatchNestedScroll(0, 0, 0, 0, null);
        return true;
    }

    @Override
    public void onLongPress(MotionEvent e) {

    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        return true;
    }
}

I got the code from here它使用android支持库22.2.1，我改为23.1.1因为我面对这个问题我创建的自定义视图在22.2.1中工作但在23.1.1中停止工作