Question

我需要使用默认委托方法处理绘图应用程序触摸开始和触摸移动。

但是当我在屏幕的任意一点画一条线时，它们的x和y位置会自动改变。

我的应用程序中的实际问题是：我在一个位置画一条线，但该线显示在另一个位置。我该怎么做才能解决这个问题？

我的代码是：

drawImage = [[UIImageView alloc] initWithImage:nil];
///drawImage.frame=CGRectMake(0,0, 320, 380);
drawImage.frame = self.view.frame;
[self.view addSubview:drawImage];

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event 
{
    NSLog(@"touches moved method");
    mouseSwiped = YES;

    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)];
    ///[drawImage.image drawInRect:CGRectMake(0, 0, 320, 380)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);

    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), components[0],components[1],components[2],alpha);

    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    lastPoint = currentPoint;
    ///mouseMoved++;

    mouseMoved++;

    if (mouseMoved == 10) 
    {
        NSLog(@"if mouse moved is equal to 10");
        mouseMoved = 0;
    }
    NSLog(@"touches moved method ended");
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{
    NSLog(@"touches Ended method starting");
    UITouch *touch = [touches anyObject];

    if ([touch tapCount] == 2)
    {
        NSLog(@"touches tap count==2");
        ///drawImage.image = nil;
        return;
    }    

    if(!mouseSwiped) 
    {
        NSLog(@"not equla mouse swiped");
        UIGraphicsBeginImageContext(self.view.frame.size);
        [drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
        ///[drawImage.image drawInRect:CGRectMake(0, 0, 320, 380)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        if (tagindex==1)
        {
            NSLog(@"1111");
            CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
        }
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        CGContextFlush(UIGraphicsGetCurrentContext());
        drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
}

先谢谢

Answer 1

尝试替换

UIGraphicsBeginImageContext(self.view.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];

与

UIGraphicsBeginImageContext(drawImage.frame.size);
[self.firma.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)];

如果您没有状态栏，请删除：currentPoint.y - = 20; 希望这是问题。

如何绘制具有精确x和y位置的线？

1 个答案: