Android BottomSheetBehavior，如何禁用快照？

Question

标准的 android BottomSheetBehavior 具有树状态:隐藏、折叠和展开。

我想让用户在折叠和展开之间“离开” Bottom Sheet 。现在，使用默认行为，它将捕捉到最接近的折叠或展开。我应该如何禁用此快照功能？

Answer 1

我将展示一种方法来为扩展BottomSheetDialogFragment 的View 实现此类功能。

扩展:

首先覆盖onResume:

@Override
public void onResume() {
    super.onResume();
    addGlobaLayoutListener(getView());
}

private void addGlobaLayoutListener(final View view) {
    view.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
        @Override
        public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
            setPeekHeight(v.getMeasuredHeight());
            v.removeOnLayoutChangeListener(this);
        }
    });
}

public void setPeekHeight(int peekHeight) {
    BottomSheetBehavior behavior = getBottomSheetBehaviour();
    if (behavior == null) {
        return;
    }
    behavior.setPeekHeight(peekHeight);
}

上面的代码应该做的只是将 BottomSheet peekHeight 设置为 View 的高度。这里的关键是函数 getBottomSheetBehaviour()。实现如下:

private BottomSheetBehavior getBottomSheetBehaviour() {
    CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) ((View) getView().getParent()).getLayoutParams();
    CoordinatorLayout.Behavior behavior = layoutParams.getBehavior();
    if (behavior != null && behavior instanceof BottomSheetBehavior) {
        ((BottomSheetBehavior) behavior).setBottomSheetCallback(mBottomSheetBehaviorCallback);
        return (BottomSheetBehavior) behavior;
    }
    return null;
}

这只是检查 View 的父级是否设置了“CoordinatorLayout.LayoutParams”。如果是，设置适当的 BottomSheetBehavior.BottomSheetCallback (下一部分需要)，更重要的是返回 CoordinatorLayout.Behavior，它应该是 BottomSheetBehavior。

折叠:

这里 [`BottomSheetBehavior.BottomSheetCallback.onSlide (View bottomSheet, float slideOffset)``]( https://developer.android.com/reference/android/support/design/widget/BottomSheetBehavior.BottomSheetCallback.html#onSlide(android.view.View , float)) 正是我们所需要的。来自[文档]( https://developer.android.com/reference/android/support/design/widget/BottomSheetBehavior.BottomSheetCallback.html#onSlide(android.view.View , float):

Offset increases as this bottom sheet is moving upward. From 0 to 1 the sheet is between collapsed and expanded states and from -1 to 0 it is between hidden and collapsed states.

这意味着，只需检查第二个参数即可进行崩溃检测:

在同一个类中定义 BottomSheetBehavior.BottomSheetCallback:

private BottomSheetBehavior.BottomSheetCallback mBottomSheetBehaviorCallback = new BottomSheetBehavior.BottomSheetCallback() {

    @Override
    public void onStateChanged(@NonNull View bottomSheet, int newState) {
        if (newState == BottomSheetBehavior.STATE_HIDDEN) {
            dismiss();
        }
    }

    @Override
    public void onSlide(@NonNull View bottomSheet, float slideOffset) {
        if (slideOffset < 0) {
            dismiss();
        }
    }
};