Android:如何将 ScrollView(带有文本)放入 Gallery 中？

Question

我将在 Android 应用程序的图库中放置文本。文本在 ScrollView 中。一切正常，但在向右或向左拖动文本时，没有显示下一页/元素(屏幕保持静止)。如果我在 scrollView 之外有一些东西，它会在拖动时更改为下一个元素。

有人能帮忙吗？

Answer 1

您需要重写 onInterceptTouchEvent - 您可以使用它在 MotionEvent 传送到 ScrollView 之前获取它们，然后重定向如果您愿意，可以将它们添加到您的 ViewGroup(在本例中为 Gallery)。

如果用户将手指向左或向右移动得太远，则以下类会将 MotionEvent 重定向到您的 Gallery。此外，如果用户向上或向下移动他们的手指相当多，那么向左或向右移动他们的手指将不再有效果，因此您不必担心在进行大量滚动时图库会发生变化。

class ScrollViewGallery extends Gallery {

    /** 
     * The distance the user has to move their finger, in density independent
     * pixels, before we count the motion as A) intended for the ScrollView if
     * the motion is in the vertical direction or B) intended for ourselfs, if
     * the motion is in the horizontal direction - after the user has moved this
     * amount they are "locked" into this direction until the next ACTION_DOWN
     * event
     */
    private static final int DRAG_BOUNDS_IN_DP = 20;

    /**
     * A value representing the "unlocked" state - we test all MotionEvents
     * when in this state to see whether a lock should be make
     */
    private static final int SCROLL_LOCK_NONE = 0;

    /**
     * A value representing a lock in the vertical direction - once in this state
     * we will never redirect MotionEvents from the ScrollView to ourself
     */
    private static final int SCROLL_LOCK_VERTICAL = 1;

    /**
     * A value representing a lock in the horizontal direction - once in this
     * state we will not deliver any more MotionEvents to the ScrollView, and
     * will deliver them to ourselves instead.
     */
    private static final int SCROLL_LOCK_HORIZONTAL = 2;

    /**
     * The drag bounds in density independent pixels converted to actual pixels
     */
    private int mDragBoundsInPx = 0;

    /**
     * The coordinates of the intercepted ACTION_DOWN event
     */
    private float mTouchStartX;
    private float mTouchStartY;

    /**
     * The current scroll lock state
     */
    private int mScrollLock = SCROLL_LOCK_NONE;

    public ScrollViewGallery(Context context) {
        super(context);
        initCustomGallery(context);
    }

    public ScrollViewGallery(Context context, AttributeSet attrs) {
        super(context, attrs);
        initCustomGallery(context);
    }

    public ScrollViewGallery(Context context, AttributeSet attrs,
            int defStyle) {
        super(context, attrs, defStyle);
        initCustomGallery(context);
    }

    private void initCustomGallery(Context context) {
        final float scale = context.getResources().getDisplayMetrics().density;
        mDragBoundsInPx = (int) (scale*DRAG_BOUNDS_IN_DP + 0.5f);
    }

    /**
     * This will be called before the intercepted views onTouchEvent is called
     * Return false to keep intercepting and passing the event on to the target view
     * Return true and the target view will recieve ACTION_CANCEL, and the rest of the
     * events will be delivered to our onTouchEvent
     */
    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        final int action = ev.getAction();
        switch (action) {
        case MotionEvent.ACTION_DOWN:
            mTouchStartX = ev.getX();
            mTouchStartY = ev.getY();
            mScrollLock = SCROLL_LOCK_NONE;

            /**
             * Deliver the down event to the Gallery to avoid jerky scrolling
             * if we decide to redirect the ScrollView events to ourself
             */
            super.onTouchEvent(ev);
            break;

        case MotionEvent.ACTION_MOVE:
            if (mScrollLock == SCROLL_LOCK_VERTICAL) {
                // keep returning false to pass the events
                // onto the ScrollView
                return false;
            }

            final float touchDistanceX = (ev.getX() - mTouchStartX);
            final float touchDistanceY = (ev.getY() - mTouchStartY);

            if (Math.abs(touchDistanceY) > mDragBoundsInPx) {
                mScrollLock = SCROLL_LOCK_VERTICAL;
                return false;
            }
            if (Math.abs(touchDistanceX) > mDragBoundsInPx) {
                mScrollLock = SCROLL_LOCK_HORIZONTAL; // gallery action
                return true; // redirect MotionEvents to ourself
            }
            break;

        case MotionEvent.ACTION_CANCEL:
        case MotionEvent.ACTION_UP:
            // if we're still intercepting at this stage, make sure the gallery
            // also recieves the up/cancel event as we gave it the down event earlier
            super.onTouchEvent(ev);
            break;
        }

        return false;
    }
}