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Pavel Sumarokov
Asked:2020-11-23 02:44:55 +0000 UTC2020-11-23 02:44:55 +0000 UTC

拖放视图元素 LinearLayout - 如何更改视图元素的顺序

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我有一个带有 TextView 元素的 LinearLayout。每个 TextView 元素都分配有一个处理程序

    ... new View.OnTouchListener() {

            int initialX = 0;
            int initialY = 0;
            static final int MAX_CLICK_DURATION = 200;
            long startClickTime;

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                long clickDuration = Calendar.getInstance().getTimeInMillis() - startClickTime;
                switch (event.getAction()) {
                    case MotionEvent.ACTION_DOWN:
                        initialX = (int) event.getX();
                        initialY = (int) event.getY();
                        startClickTime = Calendar.getInstance().getTimeInMillis();
                        break;
                    case MotionEvent.ACTION_MOVE:
                        if (clickDuration > MAX_CLICK_DURATION) {
                            int currentX = (int) event.getX();
                            int currentY = (int) event.getY();
                            dcl.setText(String.format(Locale.getDefault(), "(%d,%d)", currentX, currentY));
                        }
                        break;
                    case MotionEvent.ACTION_UP:
                        if (clickDuration < MAX_CLICK_DURATION) v.performClick();
                        break;
                }
                return true;
            }
        });

理想情况下，当我松开手指时，我打算将开始拖放的元素放在它被拉伸到的元素之前，但现在我只显示坐标，检查监听器的工作。

问题是当手指离开原始元素时，包括移动到另一个 TextView 元素，处理程序停止工作（在这个“预调试”示例中，坐标停止更新），这开始滚动包含此 LinearLayout 元素的 ScrollView .

如何使其在离开原始元素时也可以拖动，并且仅当您将手指从 TextView 元素中捏在 ScrollView 的可用空间上时才进行滚动？即使短按，您也需要保存 TextView 的 OnClick，但我或多或少想通了，这行负责：

if (clickDuration < MAX_CLICK_DURATION) v.performClick();

PS。我知道使用 DragListView 更容易做到这一点，但在这种情况下这是不可能的。TextView所在的LinearLayout是继承在层次结构深处的组件的一部分，您不能将LinearLayout更改为ListView，因为 此层次结构的其他组件将崩溃。

android

1 个回答

  1. Best Answer

    我通过以下方式解决了它：

    @Override
protected void onAttachedToWindow() {
    super.onAttachedToWindow();
    scrollView = null;
    ViewParent parent = this;
    while (parent != null && !(parent instanceof ScrollView)) parent = parent.getParent();
    if (parent != null) scrollView = (ScrollView) parent;
}

private int displayHeight;
private ScrollView scrollView;
private boolean scrollDisabled = false;

private void disableScrolling() {
    if (scrollView != null) scrollView.requestDisallowInterceptTouchEvent(true);
    scrollDisabled = true;
}

private void enableScrolling() {
    if (scrollView != null) scrollView.requestDisallowInterceptTouchEvent(false);
    scrollDisabled = false;
}

private void scrollDynamically(int posY) {
    if (scrollView == null) return;
    int[] layoutOnScreen = new int[2];
    mLayout.getLocationOnScreen(layoutOnScreen);
    //здесь и в дальнейшем mLayout - LinearLayout, на котором размещены перетаскиваемые элементы
    if (layoutOnScreen[1] < 240 && posY < 300) scrollView.smoothScrollBy(0, posY < 200 ? -20 : -10);
    if (posY > displayHeight - 150) scrollView.smoothScrollBy(0, posY > displayHeight - 50 ? 20 : 10);
}


private void init() {
    //здесь определяется высота дисплея
    WindowManager windowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
    if (windowManager == null) return;
    Display display = windowManager.getDefaultDisplay();
    Point size = new Point();
    display.getSize(size);
    displayHeight = size.y;
    mLayout.setPadding(2, 4, 2, 20);
}

private final OnTouchListener DRAG_AND_DROP = new OnTouchListener() {

    long startClickTime;
    TextView target = null;
    TextView source = null;

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        long clickDuration = Calendar.getInstance().getTimeInMillis() - startClickTime;
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                source = (TextView) v;
                startClickTime = Calendar.getInstance().getTimeInMillis();
                break;
            case MotionEvent.ACTION_MOVE:
                if (clickDuration > MAX_CLICK_DURATION) {
                    if (!scrollDisabled) disableScrolling();
                    target = null;
                    for (int i = mLayout.getChildCount(); i >= 0; --i) {
                        View anyChild = mLayout.getChildAt(i);
                        if (anyChild instanceof TextView) {
                            TextView child = (TextView) anyChild;
                            Rect bounds = new Rect();
                            child.getHitRect(bounds);
                            if (bounds.contains(v.getLeft() + (int) event.getX(), v.getTop() + (int) event.getY())) target = child;
                            else if (child != source) child.setTextColor(0xFFFFFFFF);
                        }
                    }
                    if (target == null) {
                        source.setTextColor(0xFF660000);
                        source.setPaintFlags(source.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
                    } else {
                        source.setPaintFlags(source.getPaintFlags() & ~Paint.STRIKE_THRU_TEXT_FLAG);
                        if (target != source) {
                            target.setTextColor(0xFF77FF00);
                            source.setTextColor(0xFFFF7700);
                        }
                        else source.setTextColor(0xFF77FFFF);
                    }
                    scrollDynamically((int) event.getRawY());
                }
                break;
            case MotionEvent.ACTION_UP:
                if (clickDuration < MAX_CLICK_DURATION) v.performClick();
                else {
                    if (target == null) /*действия при удалении*/;
                    else {
                        target.setTextColor(0xFFFFFFFF);
                        if (target == source) /*действия при вставке*/;
                        else /*действия при перемещении*/;
                    }
                    source.setPaintFlags(source.getPaintFlags() & ~Paint.STRIKE_THRU_TEXT_FLAG);
                    source.setTextColor(0xFFFFFFFF);
                }
                enableScrolling();
                break;
        }
        return true;
    }
};

    因此，拖放提供了三个功能：删除元素、移动元素（如果目标不在屏幕上，则可以在拖动时滚动）和插入新元素。这保留了元素的 onClick 和 ScrollView 的滚动。

    • 1

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