ios - 旋转后翻译 UIView

Question

我正在尝试翻译已使用用户触摸旋转和/或缩放的 UIView。我也尝试用用户输入来翻译它:

- (void)handleObjectMove:(UIPanGestureRecognizer *)recognizer
{
    static CGPoint lastPoint;
    UIView *moveView = [recognizer view];
    CGPoint newCoord = [recognizer locationInView:playArea];

    // Check if this is the first touch
    if( [recognizer state]==UIGestureRecognizerStateBegan )
    {
        // Store the initial touch so when we change positions we do not snap
        lastPoint = newCoord;
    }

    // Create the frame offsets to use our finger position in the view.
    float dX = newCoord.x;
    float dY = newCoord.y;

    dX-=lastPoint.x;
    dY-=lastPoint.y;

    // Figure out the translation based on how we are scaled
    CGAffineTransform transform = [moveView transform];
    CGFloat xScale = transform.a;
    CGFloat yScale = transform.d;

    dX/=xScale;
    dY/=yScale;

    lastPoint = newCoord;

    [moveView setTransform:CGAffineTransformTranslate( transform, dX, dY )];

    [recognizer setTranslation:CGPointZero inView:playArea];
}

但是当我触摸并移动 View 时，它会以各种奇怪的方式进行转换。我可以应用某种使用旋转值的公式来正确翻译吗？

Answer 1

我发现必须使用最少的数学运算的最佳解决方案是分别存储原始平移、旋转和缩放值，并在它们发生更改时重做变换。我的解决方案是使用以下属性对 UIView 进行子类化:

@property (nonatomic) CGPoint translation;
@property (nonatomic) CGFloat rotation;
@property (nonatomic) CGPoint scaling;

以及以下函数:

- (void)rotationDelta:(CGFloat)delta
{
    [self setRotation:[self rotation]+delta];
}

- (void)scalingDelta:(CGPoint)delta
{
    [self setScaling:
     (CGPoint){ [self scaling].x*delta.x, [self scaling].y*delta.y }];
}

- (void)translationDelta:(CGPoint)delta
{
    [self setTranslation:
     (CGPoint){ [self translation].x+delta.x, [self translation].y+delta.y }];
}

- (void)transformMe
{
    // Start with the translation
    CGAffineTransform transform = CGAffineTransformMakeTranslation( [self translation].x, [self translation].y );
    // Apply scaling
    transform = CGAffineTransformScale( transform, [self scaling].x, [self scaling].y );
    // Apply rotation
    transform = CGAffineTransformRotate( transform, [self rotation] );

    [self setTransform:transform];
}

- (void)setScaling:(CGPoint)newScaling
{
    scaling = newScaling;
    [self transformMe];
}

- (void)setRotation:(CGFloat)newRotation
{
    rotation = newRotation;
    [self transformMe];
}

- (void)setTranslation:(CGPoint)newTranslation
{
    translation = newTranslation;
    [self transformMe];
}

并在处理程序中使用以下内容:

- (void)handleObjectPinch:(UIPinchGestureRecognizer *)recognizer
{
    if( [recognizer state] == UIGestureRecognizerStateEnded
        || [recognizer state] == UIGestureRecognizerStateChanged )
    {
        // Get my stuff
        if( !selectedView )
            return;

        SelectableImageView *view = selectedView;

        CGFloat scaleDelta = [recognizer scale];
        [view scalingDelta:(CGPoint){ scaleDelta, scaleDelta }];

        [recognizer setScale:1.0];
    }
}

- (void)handleObjectMove:(UIPanGestureRecognizer *)recognizer
{
    static CGPoint lastPoint;
    SelectableImageView *moveView = (SelectableImageView *)[recognizer view];
    CGPoint newCoord = [recognizer locationInView:playArea];

    // Check if this is the first touch
    if( [recognizer state]==UIGestureRecognizerStateBegan )
    {
        // Store the initial touch so when we change positions we do not snap
        lastPoint = newCoord;
    }

    // Create the frame offsets to use our finger position in the view.
    float dX = newCoord.x;
    float dY = newCoord.y;

    dX-=lastPoint.x;
    dY-=lastPoint.y;
    lastPoint = newCoord;

    [moveView translationDelta:(CGPoint){ dX, dY }];

    [recognizer setTranslation:CGPointZero inView:playArea];
}

- (void)handleRotation:(UIRotationGestureRecognizer *)recognizer
{
    if( [recognizer state] == UIGestureRecognizerStateEnded
       || [recognizer state] == UIGestureRecognizerStateChanged )
    {
        if( !selectedView )
            return;

        SelectableImageView *view = selectedView;

        CGFloat rotation = [recognizer rotation];
        [view rotationDelta:rotation];

        [recognizer setRotation:0.0];
    }
}