ScrollView和Gallery干扰

Question

我有一个由许多ScrollView组成的Gallery,每个ScrollView占据整个屏幕.问题是ScrollViews的onTouchEvent返回true,因此阻止DOM中的任何其他视图处理相同的事件(在ScrollView级别处理后被吞下).因此,Gallery不再滚动.另一方面,如果我像这样重写onTouchEvent:

   @Override
   public boolean onTouchEvent(MotionEvent ev) {
      super.onTouchEvent(ev);
      return false; // <<<<<<<<<<<<<<<<<
   }   

然后Gallery接收其on事件进行处理,但SrollView不再滚动.无论哪种方式,你输了!或者你呢？

问题听起来很令人费解,但我相信如果你在过去偶然发现它会立即认出它,因为它是一个非常可怕的人!

谢谢

Answer 1

这是我在与纵向合作的画廊的尝试ScrollViews.

它使用自己的实例GestureDetector并MotionEvents从中提供onInterceptTouchEvent.

当手势检测器识别出滚动时,我们确定它是水平还是垂直并锁定方向,直到手势结束.这避免了对角线滚动.

如果它是一个水平滚动,onInterceptTouchEvent将返回true,以便将来继续运动事件进行Gallery.onTouchEvent实际滚动.

Gallery自己的手势探测器(mGestureDetectorin Gallery.java)没有得到所有的动作事件,因此有时会报告巨大的突然滚动,导致画廊跳转.我放了一个令人讨厌的黑客,丢弃了那些.

代码:

import android.content.Context;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.Gallery;

public class BetterGallery extends Gallery {
    /* This gets set when we detect horizontal scrolling */
    private boolean scrollingHorizontally = false;

    /* This gets set during vertical scrolling. We use this to avoid detecting
     * horizontal scrolling when vertical scrolling is already in progress
     * and vice versa. */
    private boolean scrollingVertically = false;

    /* Our own gesture detector, Gallery's mGestureDetector is private.
     * We'll feed it with motion events from `onInterceptTouchEvent` method. */
    private GestureDetector mBetterGestureDetector;

    public BetterGallery(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mBetterGestureDetector = new GestureDetector(new BetterGestureListener());
    }

    public BetterGallery(Context context, AttributeSet attrs) {
        super(context, attrs);
        mBetterGestureDetector = new GestureDetector(new BetterGestureListener());
    }

    public BetterGallery(Context context) {
        super(context);
        mBetterGestureDetector = new GestureDetector(new BetterGestureListener());
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        // Limit velocity so we don't fly over views
        return super.onFling(e1, e2, 0, velocityY);
    } 

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        // Documentation on this method's contract:
        // http://developer.android.com/reference/android/view/ViewGroup.html#onInterceptTouchEvent(android.view.MotionEvent)

        // Reset our scrolling flags if ACTION_UP or ACTION_CANCEL
        switch (ev.getAction()) {
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            scrollingHorizontally = false;
            scrollingVertically = false;
        }       

        // Feed our gesture detector
        mBetterGestureDetector.onTouchEvent(ev);

        // Intercept motion events if horizontal scrolling is detected
        return scrollingHorizontally;
    }


    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        // Hack: eat jerky scrolls caused by stale state in mGestureDetector
        // which we cannot directly access
        if (Math.abs(distanceX) > 100) return false;

        return super.onScroll(e1, e2, distanceX, distanceY);
    }


    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // Reset our scrolling flags if ACTION_UP or ACTION_CANCEL
        switch(event.getAction()) {
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            scrollingHorizontally = false;
            scrollingVertically = false;
        }

        super.onTouchEvent(event);
        return scrollingHorizontally;
    }

    private class BetterGestureListener implements GestureDetector.OnGestureListener {

        @Override
        public boolean onDown(MotionEvent arg0) {
            return false;
        }

        @Override
        public boolean onFling(MotionEvent arg0, MotionEvent arg1, float arg2, float arg3) {
            return false;
        }

        @Override
        public void onLongPress(MotionEvent arg0) {
        }

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            if (scrollingHorizontally || scrollingVertically) {
                // We already know we're scrolling, ignore this callback.
                // This avoids changing scrollingHorizontally / scrollingVertically
                // flags mid-scroll.
                return false;
            }

            scrollingHorizontally |= Math.abs(distanceX) > Math.abs(distanceY);
            // It's a scroll, and if it's not horizontal, then it has to be vertical
            scrollingVertically = !scrollingHorizontally;

            return false;
        }

        @Override
        public void onShowPress(MotionEvent arg0) {

        }

        @Override
        public boolean onSingleTapUp(MotionEvent arg0) {
            return false;
        }
    }
}

警告:类名中的"更好"一词可能会产生误导!

更新:

忘了提一下,我还设置了将其转发onTouchEvent到图库的活动:

@Override
public boolean onTouchEvent(MotionEvent event) {
    return mGallery.onTouchEvent(event);
}

更新2:

我对这段代码进行了一些改进,并把它放在了bitbucket上.还有一个示例应用程序.它演示了这个小部件与ListView作为子问题: - /

更新3:

从切换Gallery到HorizontalScrollView作为我的自定义插件的基类.更多关于这里.随着孩子的工作,Flings工作,ListViews和ExpandableListViews,在Android 1.6,2.2,2.3.4上测试.它的行为现在非常接近谷歌应用程序,IMO.

更新4:

谷歌发布了ViewPager!

Answer 2

我编写了这个自定义类来解决这个问题，到目前为止，它似乎是一个不错的解决方案。它并不完美，我还没有在其中插入叉子来称其完成，但希望这对某人有用:-)

import android.content.Context;
import android.view.MotionEvent;
import android.widget.Gallery;
import android.widget.ScrollView;

public class GalleryFriendlyScrollView extends ScrollView{

    private static int NONE = -1;
    private static int DOSCROLLVIEW = 0;
    private static int DOGALLERY = 1;

    private float lastx = 0;
    private float lasty = 0;
    private float firstx = 0;
    private float firsty = 0;
    private float lastRawx = 0;
    private float lastRawy = 0;
    private int gestureRecipient = NONE;
    private boolean donewithclick = true;
    private Gallery parent = null;
    private boolean firstclick = true;

    public GalleryFriendlyScrollView(Context context) {
        super(context);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        boolean retthis = true;
        //Indicating a fresh click
        if(donewithclick){
            firstx = ev.getX();
            firsty = ev.getY();
            lastx = firstx;
            lasty = firsty;
            lastRawx = ev.getRawX();
            lastRawy = ev.getRawY();
            donewithclick = false;
            firstclick = true;
        }
        //We don't know where these gesture events are supposed to go to. 
        //We have movement on the x and/or why axes, so we can determine where they should go now.
        if((gestureRecipient == NONE) && (lastx != ev.getX() || lasty != ev.getY())){
            //Determine whether there's more movement vertically or horizontally
            float xdiff = ev.getX() - lastx;
            float ydiff = ev.getY() - lasty;
            if(xdiff < 0)xdiff = xdiff * -1;
            if(ydiff < 0)ydiff = ydiff * -1;
            if((xdiff) > (ydiff)){
                gestureRecipient = DOGALLERY;
            } else {
                gestureRecipient = DOSCROLLVIEW;
            }
        }
        if(gestureRecipient == DOGALLERY){
            if(!firstclick){
                //After you drag the screen left or right a bit, the baseline for where it calculates
                //x and y from changes, so we need to adjust the offset to our original baseline
                float offsetx = (((ev.getX() - lastx) - (ev.getRawX() - lastRawx)) * -1);
                float offsety = (((ev.getY() - lasty) - (ev.getRawY() - lastRawy)) * -1);
                ev.offsetLocation(offsetx, offsety);
            }
            retthis = getGallery().onTouchEvent(ev);
            firstclick = false;
        } else if(gestureRecipient == DOSCROLLVIEW){
            retthis = super.onTouchEvent(ev);
        }
        if(ev.getAction() == MotionEvent.ACTION_UP){
            //User's finger has been lifted
            if(((firstx == ev.getX()) && (firsty == ev.getY()))){
                //Since there isn't any movement in either direction, it's a click
                getGallery().onSingleTapUp(ev);
                super.onTouchEvent(ev);
            }
            donewithclick = true;
            gestureRecipient = NONE;
        }
        //And record our coordinate data
        lastx = ev.getX();
        lasty = ev.getY();
        lastRawx = ev.getRawX();
        lastRawy = ev.getRawY();
        return retthis;
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        getGallery().onTouchEvent(ev);
        return super.onInterceptTouchEvent(ev);
    }

    private Gallery getGallery(){
        //Gets the gallery, in this case assuming the ScrollView is the direct child in the gallery.
        //Adjust as needed
        if(parent == null){
            parent = (Gallery) this.getParent();
        }
        return parent;
    }
}

我很想听听人们的经验以及您的任何建议。