Question

我想用ScrollView实现'Quick return header'。我的标题不是工具栏，它是FrameLayout ..

Answer 1

基本上您需要使用select new ParentRecord { ParentID = item.ParentID, Name = item.Name, Age = item.Age, MyNestedChildRecords = (from ns in item.MyNestChildRecords select ns).ToList(); }.ToList();（在API 21中添加）。此功能允许孩子（滚动的孩子）与他的父母（通常是Nested Scrolling）进行交流。但是，为了进行嵌套滚动，您需要：

父视图必须实现NestedScrollingParent interface
子视图必须实现NestedScrollingChild interface

CoordinatorLayout实现了CoordinatorLayout，但不幸的是，NestedScrollingParent没有实现ScrollView接口。

所以，你不能使用SCROLLVIEW进行嵌套滚动（在API 21之前：查看底部的EDIT部分）。但是，您可以使用基本为NestedScrollingChild的{{1}}来实现NestedScrollView接口。

之后，您需要创建自定义ScrollView并覆盖方法NestedScrollingChild，CoordinatorLayout.Behavior和onStartNestedScroll。您可以在下面看到符合您需求的代码（我从this example获取了一些更改）。

假设您查看的是onNestedPreScroll，您可以在布局中执行以下操作：

onNestedScroll

正如您所看到的，FramLayout附加了自定义行为。然后，您需要以这种方式修改上述QuickHideBehavior示例：

<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">
        </LinearLayout>
    </android.support.v4.widget.NestedScrollView>
    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="84dp"
        android:background="#FF0000"
        app:layout_behavior=".QuickHideBehavior">
    </FrameLayout>
</android.support.design.widget.CoordinatorLayout>

你已经完成了。

我建议您查看更多示例here或{em>戴夫史密斯

编辑：实际上，自API 21起，FrameLayout（或public class QuickHideBehavior extends CoordinatorLayout.Behavior<View> { private static final int DIRECTION_UP = 1; private static final int DIRECTION_DOWN = -1; /* Tracking direction of user motion */ private int mScrollingDirection; /* Tracking last threshold crossed */ private int mScrollTrigger; /* Accumulated scroll distance */ private int mScrollDistance; /* Distance threshold to trigger animation */ private int mScrollThreshold; private ObjectAnimator mAnimator; //Required to instantiate as a default behavior public QuickHideBehavior() { } //Required to attach behavior via XML public QuickHideBehavior(Context context, AttributeSet attrs) { super(context, attrs); TypedArray a = context.getTheme() .obtainStyledAttributes(new int[] {R.attr.actionBarSize}); //Use half the standard action bar height mScrollThreshold = a.getDimensionPixelSize(0, 0) / 2; a.recycle(); } //Called before a nested scroll event. Return true to declare interest @Override public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, View child, View directTargetChild, View target, int nestedScrollAxes) { //We have to declare interest in the scroll to receive further events return (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0; } //Called before the scrolling child consumes the event // We can steal all/part of the event by filling in the consumed array @Override public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dx, int dy, int[] consumed) { //Determine direction changes here if (dy > 0 && mScrollingDirection != DIRECTION_UP) { mScrollingDirection = DIRECTION_UP; mScrollDistance = 0; } else if (dy < 0 && mScrollingDirection != DIRECTION_DOWN) { mScrollingDirection = DIRECTION_DOWN; mScrollDistance = 0; } } //Called after the scrolling child consumes the event, with amount consumed @Override public void onNestedScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) { //Consumed distance is the actual distance traveled by the scrolling view mScrollDistance += dyConsumed; if (mScrollDistance > mScrollThreshold && mScrollTrigger != DIRECTION_UP) { //Hide the target view mScrollTrigger = DIRECTION_UP; restartAnimator(child, getTargetHideValue(coordinatorLayout, child)); } else if (mScrollDistance < -mScrollThreshold && mScrollTrigger != DIRECTION_DOWN) { //Return the target view mScrollTrigger = DIRECTION_DOWN; restartAnimator(child, 0f); } } //Called after the scrolling child handles the fling @Override public boolean onNestedFling(CoordinatorLayout coordinatorLayout, View child, View target, float velocityX, float velocityY, boolean consumed) { //We only care when the target view is already handling the fling if (consumed) { if (velocityY > 0 && mScrollTrigger != DIRECTION_UP) { mScrollTrigger = DIRECTION_UP; restartAnimator(child, getTargetHideValue(coordinatorLayout, child)); } else if (velocityY < 0 && mScrollTrigger != DIRECTION_DOWN) { mScrollTrigger = DIRECTION_DOWN; restartAnimator(child, 0f); } } return false; } /* Helper Methods */ //Helper to trigger hide/show animation private void restartAnimator(View target, float value) { if (mAnimator != null) { mAnimator.cancel(); mAnimator = null; } mAnimator = ObjectAnimator .ofFloat(target, View.TRANSLATION_Y, value) .setDuration(250); /*mAnimator = ObjectAnimator.ofFloat(target, "alpha", 0f, 1f).setDuration(250);*/ mAnimator.start(); } private float getTargetHideValue(ViewGroup parent, View target) { if(target instanceof FrameLayout) return -target.getHeight(); return 0f; } }）支持嵌套滚动，但您需要启用它：

ScrollView

当然，您需要设置

ListView

如何在android中使用scrollview实现“快速返回”

1 个答案: