将子视图添加到选择器中的主uiview

Question

我正在处理拖放应用，当用户放下图像时，我想在跳出的点上从中复制，然后原始的返回到它的初始点。 我决定在执行touchesEnded后将uiimageview添加到我的viewcontroller，

我有拖动视图类，其中包含方法：

 - (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{

CGPoint activePoint = [[touches anyObject] locationInView:self];
UIImageView *myimage;
myimage.image = self.image;
myimage.center = activePoint;


ViewController *cview ;
cview = [[ViewController alloc]init];
[cview getpoint: myimage];

}

现在在视图控制器中，这是getpoint选择器：

-(void) getpoint : (UIImageView *) mine{
UIImageView *newimage;
newimage = mine;
[self.view addSubview:newimage];


NSLog(@" in getpoint");

}

当我放下对象时，会出现此错误：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'

但是当我删除addsubview语句时，NSlog正确

任何解决方案？

Answer 1

您实际上并没有为UIImageViews分配内存。这段代码很可疑：

CGPoint activePoint = [[touches anyObject] locationInView:self];
UIImageView *myimage;
myimage.image = self.image;
myimage.center = activePoint;

您需要分配/初始化图像视图

CGPoint activePoint = [[touches anyObject] locationInView:self];
UIImageView *myimage = [[UIImageView alloc] initWithFrame:rect];
myimage.image = self.image;
myimage.center = activePoint;

其中rect变量包含您要添加到层次结构的图像视图的矩形尺寸。您无法将nil对象添加到NSArray。因此，由于UIImageView为nil，此调用将失败：

[self.view addSubview:newimage];