Objective C：在 UIScrollView 中触摸时绘制（写入）

Question

我在 TouchMoved 上有这段代码，但像其他代码一样，它在 UIScrollView 上不起作用

这是在我的 TouchMoved 上：

touchSwiped = YES;

    currentTouch = [touch locationInView:self.view];
    currentTouch.y -= 5;

    UIGraphicsBeginImageContext(self.view.frame.size);
    [writeView.image drawInRect:CGRectMake(0, 0, 768, 1024)];

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetLineCap(context, kCGLineCapRound);
    CGContextSetLineWidth(context, 15);
    CGContextSetRGBStrokeColor(context, 0, 0, 0, 1);
    CGContextSetBlendMode(context, kCGBlendModeNormal);
    CGContextMoveToPoint(context, endPoint.x, endPoint.y);
    CGContextAddLineToPoint(context, currentTouch.x, currentTouch.y);
    CGContextStrokePath(context);
    writeView.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    endPoint = currentTouch;

    touchMoved++;

    if (touchMoved == 10) {
        touchMoved = 0;
    }

所以，我使用手势识别器传输它，但它仍然不起作用。

我在这里使用了 PanGestureRecognizer

：

- (void) writePan:(UIPanGestureRecognizer *)writingRecognizerP {
    switch (writingRecognizerP.state)
    {
        case UIGestureRecognizerStateChanged:

            [scrollView setScrollEnabled:NO];
            [scrollView setUserInteractionEnabled:NO];

            touchSwiped = YES;

            currentTouch = [writingRecognizerP locationInView:scrollView];
            currentTouch.y -= 5;

            UIGraphicsBeginImageContext(self.view.frame.size);
            [writeView.image drawInRect:CGRectMake(0, 0, 768, 1024)];

            CGContextRef context = UIGraphicsGetCurrentContext();

            CGContextSetLineCap(context, kCGLineCapRound);
            CGContextSetLineWidth(context, 15);
            CGContextSetRGBStrokeColor(context, 0, 0, 0, 1);
            CGContextSetBlendMode(context, kCGBlendModeNormal);
            CGContextMoveToPoint(context, endPoint.x, endPoint.y);
            CGContextAddLineToPoint(context, currentTouch.x, currentTouch.y);
            CGContextStrokePath(context);
            writeView.image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();

            endPoint = currentTouch;

            touchMoved++;

            if (touchMoved == 10) {
                touchMoved = 0;
            }


            break;

        case UIGestureRecognizerStateEnded:
            [scrollView setScrollEnabled:YES];
            [scrollView setUserInteractionEnabled:YES];
            break;

    }

}

任何人都知道我如何能够在触摸上书写？

我们将不胜感激！ :)

Answer 1

您应该在 -drawRect: 中完成所有绘图，并且当发生更改时发送您的视图 -setNeedsDisplay 或 setNeedsDisplayInRect: 消息。