android之view的TouchDelegate

标签：android开发   frameworks   源码   类   delegate   

    public void setTouchDelegate(TouchDelegate delegate) {
        mTouchDelegate = delegate;
    }

第一步:首先来看看TouchDelegate类的一段原文说明,在文件TouchDelegate.java有如下说明:

第二步:要深刻理解,我觉得需要查看源码,看看他是如何实现的.

 /**
     * View that should receive forwarded touch events
     */
    private View mDelegateView;//需要扩大触摸区域的view
    
    /**
     * Bounds in local coordinates of the containing view that should be mapped to the delegate
     * view. This rect is used for initial hit testing.
     */
    private Rect mBounds;//定义了这个扩大的触目区域
               
    /**
     * mBounds inflated to include some slop. This rect is to track whether the motion events
     * should be considered to be be within the delegate view.
     */
    private Rect mSlopBounds;//这是一个相对于mBounds溢出的触摸区域:实际上就是比mBounds大一点的区域(宽高分别大8),其目的时消除触摸误差.
    
    public TouchDelegate(Rect bounds, View delegateView) {//构造函数:bounds 表示触摸的区域；delegateView 需要扩大触摸区域的view
        mBounds = bounds;

        mSlop = ViewConfiguration.get(delegateView.getContext()).getScaledTouchSlop();//这里获取的是触摸滑动距离的判断:就是触摸滑动距离为mSlop时候裁判为是在触摸滑动move.其默认值为8
        mSlopBounds = new Rect(bounds);
        mSlopBounds.inset(-mSlop, -mSlop);//这里扩大触摸滑动区域(宽高扩大8),其目的时消除触摸时候的误差.达到一个触摸安全处理.
        mDelegateView = delegateView; //需要扩大触摸区域的view(需要改变触摸区域的view)
    }
    
    public boolean onTouchEvent(MotionEvent event) {//这是核心代码:判断当前触摸是否在这个区域:mBounds.如果在是则会让这次的触摸事件真的在mDelegateView真实的区域内.
        int x = (int)event.getX();
        int y = (int)event.getY();//记录这次触摸点位置
        boolean sendToDelegate = false;//标记这次触摸是否有效(应该传递给mDelegateView)
        boolean hit = true; //标记这次触摸是否在这个区域内(mBounds)
        boolean handled = false;

        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            Rect bounds = mBounds;

            if (bounds.contains(x, y)) {//ACTION_DOWN是否在这个区域内
                mDelegateTargeted = true;//标记这一次触摸事件在这个区域(在mDelegateView内)
                sendToDelegate = true;
            }
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_MOVE:
            sendToDelegate = mDelegateTargeted;
            if (sendToDelegate) {
                Rect slopBounds = mSlopBounds;
                if (!slopBounds.contains(x, y)) {
                    hit = false;
                }
            }
            break;
        case MotionEvent.ACTION_CANCEL:
            sendToDelegate = mDelegateTargeted;
            mDelegateTargeted = false;
            break;
        }
        if (sendToDelegate) {//这次触摸有效:则把触摸事件传递给 mDelegateView
            final View delegateView = mDelegateView;
            //模拟这次触摸真的在mDelegateView区域内:从新计算event的触摸点,以保证这次的event事件的触摸点在mDelegateView真实的区域内
            if (hit) {
                // Offset event coordinates to be inside the target view
                event.setLocation(delegateView.getWidth() / 2, delegateView.getHeight() / 2);
            } else {
                // Offset event coordinates to be outside the target view (in case it does
                // something like tracking pressed state)
                int slop = mSlop;
                event.setLocation(-(slop * 2), -(slop * 2));
            }
            handled = delegateView.dispatchTouchEvent(event);//把计算后的触摸事件传递给mDelegateView的dispatchTouchEvent使其相应触摸事件.
        }
        return handled;
    }

   public boolean onTouchEvent(MotionEvent event) {
        final int viewFlags = mViewFlags;

        if (DBG_MOTION) {
            Xlog.d(VIEW_LOG_TAG, "(View)onTouchEvent 1: event = " + event + ",mTouchDelegate = "
                    + mTouchDelegate + ",enable = " + isEnabled() + ",clickable = " + isClickable()
                    + ",isLongClickable = " + isLongClickable() + ",this = " + this);
        }

        if ((viewFlags & ENABLED_MASK) == DISABLED) {
            /// M: we need to reset the pressed state or remove prepressed callback either up or cancel event happens.
            final int action = event.getAction();
            if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL) {
                if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
                    setPressed(false);
                } else if ((mPrivateFlags & PFLAG_PREPRESSED) != 0) {
                    Xlog.d(VIEW_LOG_TAG, "View onTouch event, if view is DISABLED & PFLAG_PREPRESSED, remove callback mPrivateFlags = "
                                + mPrivateFlags + ", this = " + this);
                    removeTapCallback();
                }
            }
            // A disabled view that is clickable still consumes the touch
            // events, it just doesn't respond to them.
            return (((viewFlags & CLICKABLE) == CLICKABLE ||
                    (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE));
        }

        if (mTouchDelegate != null) {//判断是否有TouchDelegate对象
            if (mTouchDelegate.onTouchEvent(event)) {执行onTouchEvent
                return true;//如果这个触摸事件在TouchDelegate设置的区域内,这返回.不会执行其他
            }
        }
        .....
       

最后,来看看一个实例.下面是一个父view夸大自己view触摸区域的方法:

    public static void enlargeBtnTouchScope(View parent, Button btn, Rect rect, float width, float height){
		rect.top = btn.getTop();
		rect.bottom = btn.getBottom();
		rect.left = btn.getLeft();
		rect.right = btn.getRight();
		
		rect.top -= height;
		rect.bottom += height;
		rect.left -= width;
		rect.right += width;
		
		parent.setTouchDelegate(new TouchDelegate(rect, btn));
    }

android之view的TouchDelegate

标签：android开发   frameworks   源码   类   delegate   

原文地址：http://blog.csdn.net/green_shing/article/details/46551121