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实现onNestedPreFling，onNestedFling实现了快速滑动的连贯性，头部是NestScrollView，触摸头部也能滑动，之前其他教程很少看到写这些的 -
onNestedPreFling实现思路： 先调用ScrollCompat的fling计算头部滑动完时的加速度，传递给RecyclerView fling -
onNestedFling实现思路：先用ScrollCompat模拟Recyrview，计算RecyclerView滚动到边界时的加速度，再根据加速度，调用ScrollCompa的fling进行头部Scroll -
同样本例子只提供实现思路，不提供具体使用，因为不同项目要求不一样
xml
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/coordinate"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ProgressBar
android:layout_width="40dp"
android:layout_height="40dp"
android:indeterminate="true"
android:layout_gravity="center_horizontal"
android:layout_marginTop="-400px" />
<ImageView
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_gravity="center_horizontal"
android:layout_marginTop="-200px"
android:src="@mipmap/ic_launcher" />
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="bottom">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:background="@color/colorPrimary"
android:orientation="vertical">
<ImageView
android:id="@+id/ic1"
android:layout_width="match_parent"
android:layout_height="90dp"
android:scaleType="centerCrop"
android:src="@drawable/snap" />
<ImageView
android:id="@+id/ic2"
android:layout_width="match_parent"
android:layout_height="211dp"
android:layout_marginTop="90dp"
android:scaleType="centerCrop"
android:src="@drawable/grid" />
</FrameLayout>
</android.support.v4.widget.NestedScrollView>
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#f00"
android:fadingEdge="none"
android:overScrollMode="never"
app:layout_behavior="com.example.ck.nest.MyListenerBehavior"/>
</android.support.design.widget.CoordinatorLayout>
MyListenerBehavior behavior = MyListenerBehavior.getBehavior(recyclerView);
behavior.setCanOverScroll(500)
.setScrollListener(new MyListenerBehavior.OnScrollListener() {
@Override
public void onScroll(int scroll) {
Log.i(TAG, "onScroll: "+scroll);
}
@Override
public void overScroll(int overScroll) {
Log.i(TAG, "overScroll: "+overScroll);
}
});
@Override
public void onNestedScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
//下滑动 child滑动接着dependency 滑动，
if (dyUnconsumed < 0 && coordinatorLayout.getScrollY() > -overScroll) {
scrollBy(coordinatorLayout, dyUnconsumed);
}
}
@Override
public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dx, int dy, int[] consumed) {
//上滑动 dependency 先滑动，接着child滑动
if (dy > 0 && coordinatorLayout.getScrollY() < originalHeight) {
Log.i(TAG, "onNestedPreScroll: " + dy);
scrollBy(coordinatorLayout, dy);
if (scroll + dy > originalHeight) {
consumed[1] = originalHeight - scroll;
} else
consumed[1] = dy;
}
}
@Override
public boolean onNestedFling(CoordinatorLayout coordinatorLayout, View child, View target, float velocityX, float velocityY, boolean consumed) {
if (velocityY < 0 && coordinatorLayout.getScrollY() >0) {
Log.i(TAG, "onNestedFling: " + velocityY);
resetType(FlingRunnable.SCROLL_CCONTINUE);
scrollCompat.fling(0, 0, 0, (int) velocityY, 0, 0, Integer.MIN_VALUE, Integer.MAX_VALUE);
ViewCompat.postOnAnimation(dependencyView.get(), runnable);
return true;
}
return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
}
@Override
public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, View child, View target, float velocityX, float velocityY) {
// //上滑
if (velocityY > 0 && coordinatorLayout.getScrollY() != originalHeight) {
resetType(FlingRunnable.PRE_FLING);
scrollCompat.fling(0, coordinatorLayout.getScrollY(), 0, (int) velocityY, 0, 0, Integer.MIN_VALUE, Integer.MAX_VALUE);
ViewCompat.postOnAnimation(dependencyView.get(), runnable);
return true;
}
return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
}