问题概要
我是一个iPad应用,在UIScrollView中有一个UIImageView。我希望用户能够通过使用触控笔和/或手指在UIImageView的顶部进行绘制。
我让它在模拟器上运行良好,但它在iPad上完全滞后(有时崩溃)。当您在UIScrollView上尝试干燥而已经放大时,问题变得更加明显;它变得非常滞后(基本上是冻结),然后崩溃。
(在UIScrollView上滚动并不与绘图冲突,因为它被设置为在绘图活动时需要2个手指)
这里是相关的方法。这些方法都在处理绘图的视图中:
/**
When the user first starts writing
*/
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
isMouseMoved = NO;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:imageView];
if(isEraserOn){
[self changeEraserLocationTo:currentPoint];
}
[self resetEraser:FALSE];
lastPoint = [touch locationInView:imageView];
}
/**
When the user first starts moving the pen
*/
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
isMouseMoved = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:imageView];
// Setting up the context
UIGraphicsBeginImageContext(imageView.frame.size);
[imageView.image drawInRect:CGRectMake(0, 0, imageView.frame.size.width, imageView.frame.size.height)];
if (isEraserOn) {
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), eraserRadius);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);
CGRect eraserFrame = eraser.frame;
eraserFrame.origin.x = currentPoint.x - (eraserRadius/2);
eraserFrame.origin.y = currentPoint.y - (eraserRadius/2);
eraser.frame = eraserFrame;
} else {
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), penRadius);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), r, g, b, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeNormal);
}
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;
mouseMoved++;
if (mouseMoved == 1) {
mouseMoved = 0;
}
}
/**
When the user stops writing
*/
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
[self resetEraser:TRUE];
if (!isMouseMoved) {
UIGraphicsBeginImageContext(imageView.frame.size);
CGContextRef contextRef = UIGraphicsGetCurrentContext();
[imageView.image drawInRect:CGRectMake(0, 0, imageView.frame.size.width, imageView.frame.size.height)];
CGContextSetLineWidth(contextRef, penRadius);
CGContextSetRGBStrokeColor(contextRef, r, g, b, 1.0);
CGContextMoveToPoint(contextRef, lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(contextRef, lastPoint.x, lastPoint.y);
CGContextStrokePath(contextRef);
imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
}
对这个问题的任何帮助都将非常感谢。对于这个问题,我真的束手无策了。
谢谢,亚历克斯
我最近开发了一个允许在图像上绘图的应用程序。我实现它的方式是创建另一个UIView层,然后在那个视图上做我的graphics/gl绘图。然后你可以把所有的触摸事件移动到gl视图。我目前的实现没有任何性能问题,当放大时不应该改变它。还要检查你的内存,你可能会泄漏。
看一下下面的apple代码:
GLPaint
正如你所说,你使用的是手写笔或手指,所以当使用手写笔/手指时,你是如何处理触摸事件的,我的意思是说,当用户拿着手写笔时,他的手会放在ipad屏幕上,然后试着写字,(就像我们在纸上写字一样)所以你的手写笔是否在这种情况下工作。