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我有一个实现了滚动的自定义视图，但它似乎在图像上滚动。
即使我找到图像的边缘，它也会一直滚动到空白背景。

我不能使用 WebView，因为我也有一些 Canvas sutff。
有谁知道如何为这个问题设置限制？
如何适合滚动的图像边缘？


编辑：我在@JosephEarl 的帮助下找到了最好的解决方案。
我只设置了左侧和顶部边界，因为我的图像比屏幕大。
此外，我在使用缩放功能时关闭了边界，否则我无法再移动它。

1) 在onTouch事件的 ACTION_MOVE 情况下，插入以下代码：

if(!isZoomed) {
    if(mPosX < 0)
        mPosX = 0;
    else if(mPosX > mWidth)
        mPosX = mWidth;
    if(mPosY < 0)
        mPosY = 0;
    else if(mPosY > mHeight)
        mPosY = mHeight;
}


2)使用缩放时打开或关闭边界。
将以下代码添加到您的 ACTION_POINTER_UP 案例中：

case MotionEvent.ACTION_POINTER_UP: {

    final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
    final int pointerId = ev.getPointerId(pointerIndex);

    if (pointerId == mActivePointerId) {
        final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
        mLastTouchX = ev.getX(newPointerIndex);
        mLastTouchY = ev.getY(newPointerIndex);
        mActivePointerId = ev.getPointerId(newPointerIndex);
        isZoomed = true;

    } else
        isZoomed = false;

    break;

}


就这样。
以下是所有相关方法和完整的onTouch事件：

private float scaleFactor = 1.f;
private ScaleGestureDetector detector;

private static final int INVALID_POINTER_ID = -1;
private int mActivePointerId = INVALID_POINTER_ID;

private float mPosX;
private float mPosY;
private float mLastTouchX;
private float mLastTouchY;

private float mWidth;
private float mHeight;
private boolean isZoomed = false;

// OTHER CODE GOES HERE

@Override
public boolean onTouchEvent(MotionEvent ev) {
    detector.onTouchEvent(ev);

    final int action = ev.getAction();
    switch (action & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN: {
            final float x = ev.getX();
            final float y = ev.getY();

            mLastTouchX = x;
            mLastTouchY = y;
            mActivePointerId = ev.getPointerId(0);
            break;
        }

        case MotionEvent.ACTION_MOVE: {
            final int pointerIndex = ev.findPointerIndex(mActivePointerId);
            final float x = ev.getX(pointerIndex);
            final float y = ev.getY(pointerIndex);

            if (!detector.isInProgress()) {
                final float dx = x - mLastTouchX;
                final float dy = y - mLastTouchY;
                mPosX += dx;
                mPosY += dy;

                if(!isZoomed) {
                    if(mPosX < 0)
                        mPosX = 0;
                    else if(mPosX > mWidth)
                        mPosX = mWidth;
                    if(mPosY < 0)
                        mPosY = 0;
                    else if(mPosY > mHeight)
                        mPosY = mHeight;
                }

                invalidate();
            }

            mLastTouchX = x;
            mLastTouchY = y;

            break;
        }

        case MotionEvent.ACTION_UP: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }

        case MotionEvent.ACTION_CANCEL: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }

        case MotionEvent.ACTION_POINTER_UP: {

            final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
            final int pointerId = ev.getPointerId(pointerIndex);

            if (pointerId == mActivePointerId) {
                final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                mLastTouchX = ev.getX(newPointerIndex);
                mLastTouchY = ev.getY(newPointerIndex);
                mActivePointerId = ev.getPointerId(newPointerIndex);
                isZoomed = true;

            } else
                isZoomed = false;

            break;

        }
    }

    return true;
}

private class ScaleListener extends
        ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        scaleFactor *= detector.getScaleFactor();
        scaleFactor = Math.max(MIN_ZOOM, Math.min(scaleFactor, MAX_ZOOM));
        invalidate();
        return true;
    }
}

@Override
protected void onSizeChanged(int xNew, int yNew, int xOld, int yOld){
     super.onSizeChanged(xNew, yNew, xOld, yOld);
     mWidth = xNew;
     mHeight = yNew;
}

// OTHER CODE GOES HERE
4

1 回答 1

2

从您的代码看来，您在任何时候都不会尝试检测可滚动区域的大小并将位置限制在这些范围内，即您应该检查以确保mPosX不mPosY超过它们的范围。

系统不会自动限制你自定义View的位置，需要你自己做。

上界和左界将是 0, 0 - 您应该确保mPosX并且mPosY不大于此值。

右边界将是（容器视图的宽度 - 滚动视图的宽度）——这应该是负数（如果它大于则将右边界设置为 0）并且您应该确保mPosX不小于这个值。下限将是（容器的高度 - 滚动视图的高度）——这又应该是负数，你应该确保mPosY不小于这个值。

总而言之，当触摸事件开始计算边界时：

// Calculate our bounds.
int leftBound = 0;
int topBound = 0;
int rightBound = imageWidth - getWidth();
if (rightBound > 0) {
    rightBound = 0;
}
int bottomBound = imageHeight - getHeight();
if (bottomBound > 0) {
    bottomBound = 0;
}

您正在滚动的任何内容的宽度和高度在哪里imageWidth以及是哪里。imageHeight

然后在滚动时确保遵守边界：

if (mPosX > leftBound) {
    mPosX = leftBound;
} else if (mPosX < rightBound) {
    mPosX = rightBound;
}

if (mPosY > topBound) {
    mPosY = topBound;
} else if (mPosY < bottomBound) {
    mPosY = bottomBound;
}
于 2012-11-20T22:47:45.560 回答