我正在尝试向iOS应用添加撤消/重做功能。我希望能够绘制几行,然后撤消每一行......我可以删除整个事情,但这还不够好......我真的很感激帮助,因为这是我第一次尝试使用CG ..
我的.h声明包括:
CGPoint lastPoint;
NSMutableArray *pathArray;
UIBezierPath *myPath;
在.m,我有:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
NSLog(@"%s", __FUNCTION__);
UITouch *touch = [touches anyObject];
myPath=[[UIBezierPath alloc]init];
lastPoint = [touch locationInView:self.view];
[myPath moveToPoint:lastPoint];
lastPoint.y -= 20;
[pathArray addObject:myPath];
NSLog(@"pathArray count is %i", [pathArray count]);
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
NSLog(@"%s", __FUNCTION__);
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
currentPoint.y -= 20;
UIGraphicsBeginImageContext(self.view.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
savedImage.image = drawImage.image;
UIGraphicsEndImageContext();
lastPoint = currentPoint;
}
在touchesBegin结束时,pathArray计数始终为零.. :(
要实现撤消,我正在使用此代码:
- (void)undoButtonTapped {
NSLog(@"%s", __FUNCTION__);
NSLog(@"pathArray count is %i", [pathArray count]);
if([pathArray count]>0){
UIBezierPath *_path=[pathArray lastObject];
[bufferArray addObject:_path];
[pathArray removeLastObject];
[self.view setNeedsDisplay];
}
}
这里的数量也是零......
所有这些都是在UIViewController中处理的。我欢迎任何建议/改进/建议。
由于
答案 0 :(得分:1)
我要说[pathArray count]
中touchesBegan
为零的原因是我的代码中没有任何地方可以看到
pathArray = [[NSMutableArray alloc] init];
所以你要向空指针发送消息(允许但不做任何事情)。
你也在分配pathArray?或者它是否为空?