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这个问题是不久前另一个 SO 问题的后续问题：zooming using pinch but not using transform methods。我让缩放几乎完美地工作，但是它仍然会使绘制的图像“跳跃”，正如我一直所说的那样。代码中最重要的部分如下：

当观察到捏事件时，调用此方法：

[代码片段 1]

- (IBAction)handlePinchGesture:(UIGestureRecognizer *)sender {
    float previousZoomLevel = zoomLevel;
    UIPinchGestureRecognizer *pinch = (UIPinchGestureRecognizer *)sender;

    float zoomIncreaseFactor = [self getZoomFactor:[pinch scale]]; //= 13 or 7 or 10
    float estimatedDelta = (previousZoomLevel * zoomIncreaseFactor) / 150;

    if ([pinch scale] > previousScale) {
        zoomLevel += estimatedDelta;
    }

    if ([pinch scale] < previousScale) {
        zoomLevel -= estimatedDelta;
    }

    previousScale = [pinch scale];

    if (zoomLevel < MIN_ZOOM_LEVEL) {
        zoomLevel = MIN_ZOOM_LEVEL;
    }

    if (zoomLevel > MAX_ZOOM_LEVEL) {
        zoomLevel = MAX_ZOOM_LEVEL;
    }

    CGPoint loc = [pinch locationInView:self];

    NSLog(@"loc: {%.1f,%.1f}, lastPinchLoc: {%.1f,%.1f}", loc.x,loc.y,lastPinchLocation.x,lastPinchLocation.y);

    //uncomment the below part to always zoom from the first zoom location.
    //if (lastPinchLocation.x != 0 && lastPinchLocation.y != 0) {
        //loc.x += lastPinchLocation.x - loc.x;
        //loc.y += lastPinchLocation.y - loc.y;
    //}

    //NSLog(@"newLastPinchLocation: {%.1f,%.1f}", loc.x,loc.y);

    lastPinchLocation = loc;

    hasBeenMoved = YES;

    if (zoomLevel != previousZoomLevel) {
        [self setNeedsDisplay];
    }
}

当我在整个屏幕上捏合时，上面的 NSLog 会给出以下打印：

2012-10-16 10:15:19.357 App[2609:907] loc: {147.0,232.0}, lastPinchLoc: {0.0,0.0}
2012-10-16 10:15:19.391 App[2609:907] loc: {147.0,231.0}, lastPinchLoc: {147.0,232.0}
2012-10-16 10:15:19.436 App[2609:907] loc: {148.0,232.0}, lastPinchLoc: {147.0,231.0}
2012-10-16 10:15:19.457 App[2609:907] loc: {148.0,232.0}, lastPinchLoc: {148.0,232.0}
2012-10-16 10:15:19.474 App[2609:907] loc: {148.0,233.0}, lastPinchLoc: {148.0,232.0}
2012-10-16 10:15:19.507 App[2609:907] loc: {147.0,233.0}, lastPinchLoc: {148.0,233.0}
2012-10-16 10:15:19.573 App[2609:907] loc: {103.0,355.0}, lastPinchLoc: {147.0,233.0}
2012-10-16 10:15:20.324 App[2609:907] loc: {585.0,710.0}, lastPinchLoc: {103.0,355.0}
2012-10-16 10:15:20.340 App[2609:907] loc: {584.0,709.0}, lastPinchLoc: {585.0,710.0}
2012-10-16 10:15:20.356 App[2609:907] loc: {584.0,710.0}, lastPinchLoc: {584.0,709.0}
2012-10-16 10:15:20.374 App[2609:907] loc: {584.0,710.0}, lastPinchLoc: {584.0,710.0}
2012-10-16 10:15:20.407 App[2609:907] loc: {583.0,710.0}, lastPinchLoc: {584.0,710.0}
2012-10-16 10:15:20.456 App[2609:907] loc: {512.0,811.0}, lastPinchLoc: {583.0,710.0}
2012-10-16 10:15:21.056 App[2609:907] loc: {645.0,163.0}, lastPinchLoc: {512.0,811.0}
2012-10-16 10:15:21.090 App[2609:907] loc: {647.0,164.0}, lastPinchLoc: {645.0,163.0}
2012-10-16 10:15:21.107 App[2609:907] loc: {647.0,165.0}, lastPinchLoc: {647.0,164.0}
2012-10-16 10:15:21.156 App[2609:907] loc: {602.0,249.0}, lastPinchLoc: {647.0,165.0}
2012-10-16 10:15:21.839 App[2609:907] loc: {153.0,702.0}, lastPinchLoc: {602.0,249.0}
2012-10-16 10:15:21.856 App[2609:907] loc: {157.0,703.0}, lastPinchLoc: {153.0,702.0}
2012-10-16 10:15:21.874 App[2609:907] loc: {159.0,704.0}, lastPinchLoc: {157.0,703.0}
2012-10-16 10:15:21.890 App[2609:907] loc: {160.0,704.0}, lastPinchLoc: {159.0,704.0}
2012-10-16 10:15:21.906 App[2609:907] loc: {123.0,796.0}, lastPinchLoc: {160.0,704.0}
2012-10-16 10:15:21.923 App[2609:907] loc: {125.0,794.0}, lastPinchLoc: {123.0,796.0}
2012-10-16 10:15:22.706 App[2609:907] loc: {368.0,303.0}, lastPinchLoc: {125.0,794.0}
2012-10-16 10:15:22.723 App[2609:907] loc: {369.0,307.0}, lastPinchLoc: {368.0,303.0}
2012-10-16 10:15:22.725 App[2609:907] loc: {369.0,307.0}, lastPinchLoc: {369.0,307.0}
2012-10-16 10:15:22.739 App[2609:907] loc: {371.0,312.0}, lastPinchLoc: {369.0,307.0}
2012-10-16 10:15:22.756 App[2609:907] loc: {374.0,312.0}, lastPinchLoc: {371.0,312.0}
2012-10-16 10:15:22.773 App[2609:907] loc: {338.0,392.0}, lastPinchLoc: {374.0,312.0}

就在 CGContext 上绘制项目之前，将 x 和 y 放入此方法中，然后我在返回的位置上绘制项目。类变量“zoomTouchLocation”与上述代码段中的“lastPinchLocation”具有相同的值。

[代码片段2]

- (CGPoint)handleCoordinatesX:(float)x y:(float)y {
    x -= zoomTouchLocation.x;
    y -= zoomTouchLocation.y;

    x = x * zoomLevel;
    y = y * zoomLevel;

    x += zoomTouchLocation.x;
    y += zoomTouchLocation.y;

    return CGPointMake(x, y);
}

如果我每次都捏在大致相同的位置，它会按预期工作，但是当我在整个屏幕上捏时，图像会像疯了一样跳来跳去。

现在基本上我的问题是，是否有人可以帮助我解决这个“跳跃”问题，并让图像从我放大的位置缩放而不跳跃。如果您需要更多信息，请在下面的评论中提问。

（而且我知道我的代码发生跳跃是很正常的，我只是找不到阻止它这样做的方法）

4

2 回答 2

1

没有整个代码很难提供帮助，但您应该尝试将 view.layer.anchorPoint 设置为您的 pinchLocation（如果尚未完成）。像这样，当变换完成后，这个点就不动了。对于旋转或缩放非常有用。

于 2012-10-19T08:36:09.443 回答
1

应在离散事件期间跟踪和/或重置您的缩放增量和坐标。也就是说，您需要了解并使用UIPinchGestureRecognizer.state来确定要重置跟踪逻辑和增量的位置，以及何时更新您为缩放位置跟踪的坐标。

这方面的一个基本说明来自 Touches 示例：

- (void)scalePiece:(UIPinchGestureRecognizer *)gestureRecognizer
{
    [self adjustAnchorPointForGestureRecognizer:gestureRecognizer];

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged) {
        [gestureRecognizer view].transform = CGAffineTransformScale([[gestureRecognizer view] transform], [gestureRecognizer scale], [gestureRecognizer scale]);
        [gestureRecognizer setScale:1];
    }
}
于 2012-10-26T04:24:31.173 回答