android - 如何通过从屏幕底部边缘拉动来显示 BottomSheet？

Question

我是 Android 的新手 BottomSheet并且我已经成功地尝试了有关如何使用它的示例，但大多数示例仅演示了通过查看点击事件显示/隐藏 BottomSheet。

现在我有以下代码:

BottomSheetBehavior mBottomSheetBehavior;

@Override
protected void onCreate() {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main);
   View bottomSheet = findViewById(R.id.bottom_sheet);
   mBottomSheetBehavior = BottomSheetBehavior.from(bottomSheet);
   mBottomSheetBehavior.setPeekHeight(0);
   mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN);
}

现在，我只想知道当状态为 BottomSheetBehavior.STATE_HIDDEN 时，是否可以通过从屏幕底部边缘拉/拖来显示 BottomSheet。 peekHeight 是 0 ？，类似于 DrawerLayout 的行为？

Answer 1

我认为 BottomSheetBehavior 不提供该功能，但您可以拦截包含 Activity 中的触摸事件，并在检测到底部拉动时展开 Bottom Sheet :

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    bottomPullDetector = new GestureDetectorCompat(this, new BottomPullListener());
}

@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
    return bottomPullDetector.onTouchEvent(ev) || super.dispatchTouchEvent(ev);
}


private class BottomPullListener extends GestureDetector.SimpleOnGestureListener {
    private static final int SWIPE_THRESHOLD = 20;
    private final int displayHeight;
    private boolean beginningOnBottom;

    BottomPullListener() {
        final Point displaySize = new Point();
        getWindowManager().getDefaultDisplay().getSize(displaySize);
        displayHeight = displaySize.y;
    }

    @Override
    public boolean onDown(MotionEvent event) {
        beginningOnBottom = displayHeight - event.getY() < SWIPE_THRESHOLD;
        return beginningOnBottom;
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        if (beginningOnBottom && e1.getY() > e2.getY()) {
            cameraFragment.expandBottomSheet();
            return true;
        }
        return false;
    }
}