Iphone drawRect和setNeedsDisplay永远不会被调用

我添加了一个uiview（带有uimageview的holderview）作为子视图，并使用

imageview=[[UIImageView alloc]initWithFrame:[holderView frame]]； [imageview setImage:cppobject->OutputImage]； imageview.contentMode=UIViewContentModeScaleAspectFit

[holderView addSubview:imageview];
holderView.contentMode = UIViewContentModeScaleAspectFit ;

UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scale:)];
[pinchRecognizer setDelegate:self];
[holderView addGestureRecognizer:pinchRecognizer];
[pinchRecognizer release];

UIRotationGestureRecognizer *rotationRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotate:)];
[rotationRecognizer setDelegate:self];
[holderView addGestureRecognizer:rotationRecognizer];
[rotationRecognizer release];

panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(move:)];
[panRecognizer setMinimumNumberOfTouches:1];
[panRecognizer setMaximumNumberOfTouches:1];
[panRecognizer setDelegate:self];
[holderView addGestureRecognizer:panRecognizer];
holderView.tag=101;
[self.view addSubview:holderView];
[holderView sizeToFit];
[self AddInformation];
[holderView retain];
[self retain];

然后在装甲识别器功能（移动）中，我想使用

         UIPanGestureRecognizer *gR = (UIPanGestureRecognizer *) sender ; 


        NSValue *value = [NSValue valueWithCGPoint: [gR locationInView:gR.view]]; 





        [Points addObject:value];


        [holderView setNeedsDisplay];

        NSLog(@"End of measuring") ; 

我将使用点中的点在中的所有子视图上方绘制线

-（void）drawRect:（CGRect）rect { NSLog（@“已输入绘制矩形”）

if（测量）{
[[UIColor redColor]设置行程]；
UIBezierPath*pathToDraw=[UIBezierPath bezierPath]；
对于（int n=1；n<[点数]-1；n++）{
NSValue*value=[点对象索引：（NSInteger）n]；
CGPoint point=[value CGPointValue]；
[路径绘制移动点：点]；
值=[点对象索引：（NSInteger）n+1]；
点=[value CGPointValue]；
[pathToDraw addLineToPoint:point]；
}
[路径绘制笔划]；
}

}

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问题是[holderView setNeedsDisplay]；决不要调用或激发drawRect任何建议或帮助，因为您需要将UIView子类化，并在子类中实现drawRect

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然后在创建holderview时，确保实例化的是子类UIView，而不是默认UIView。

您需要子类UIView并在子类中实现drawRect

然后在创建holderview时，确保实例化的是子类UIView，而不是默认UIView

if (Measuring) {

    [[UIColor redColor] setStroke];

    UIBezierPath *pathToDraw = [UIBezierPath bezierPath]; 

    for (int n = 1; n < [Points count] - 1 ; n++) { 

    NSValue * value = [Points objectAtIndex:(NSInteger)n];

        CGPoint  point = [value CGPointValue]; 

        [pathToDraw moveToPoint:point];


        value = [Points objectAtIndex:(NSInteger)n+1];

        point = [value CGPointValue];

        [pathToDraw addLineToPoint:point];



    }



    [pathToDraw stroke];







}