超出NSArray的空白的边界异常 [英] Out of Bounds Exception on NSArray thats Empty

问题描述

我有这个代码来创建一个图像数组，以便在视图上显示。我的视图中的大多数页面将有20个图像（5列，4列），但我实际上有43个图像，当我的图像数组包含最后3个时，我得到一个例外，当内部的第4次迭代循环，数组为空。

I have this code for creating an array of images to display on a view. Most of the pages in my view will have 20 images (in columns of 5, rows of 4), but i actually have 43 images and when my images array contains the final 3, i get an exception when on the 4th iteration of the inner loop, the array is empty.

- (void)displayImages:(NSMutableArray *)images {

NSMutableArray *keysArray = [[NSMutableArray alloc] initWithCapacity:5];

for (int column = 0; column < 5; column++){
    [keysArray  addObject:[NSMutableArray arrayWithCapacity:5]];
    for (int row = 0; row < 4; row++) {
        [[keysArray objectAtIndex:column] addObject:[images objectAtIndex:0]];
        [images removeObjectAtIndex:0];
    }
}

....

我可以绕过这个吗？

谢谢。

编辑：

从这个代码开始，是从数组中实际提取图像的代码。但是同样的情况发生在第四次迭代中，它崩溃了。

Following on from this code, is the code which actually pulls the image from the array. But the same scenario occurs... on the fourth iteration it crashes.

for (int column = 0; column < 5; column++) {
    for (int row = 0; row < 4; row++){          
        UIButton *keyButton = [UIButton buttonWithType:UIButtonTypeCustom];
        keyButton.frame = CGRectMake(column*kKeyGap, row*kKeyGap, kKeySize, kKeySize);

        [keyButton setImage:[[keysArray objectAtIndex:column] objectAtIndex:row] forState:UIControlStateNormal];
        [keyButton addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];

        [self.view addSubview:keyButton];
    }
}
[keysArray release];

我无法在此测试图像点数据已经被清空。

I can't test images at this point as the array is emptied already.

推荐答案

尝试使用实际的数组大小而不是 for 循环文本表达式。所以而不是这样：

Try using the actual array sizes instead of constant values in your for loop text expressions. So rather than this:

for (int column = 0; column < 5; column++)

执行此操作：

for (int column = 0; column < [keysArray count]; column++)

如下所示：

for (int column = 0; column < [keysArray count]; column++) {

    NSArray *rowArray = [keysArray objectAtIndex:column];

    for (int row = 0; row < [rowArray count]; row++) {          
        UIButton *keyButton = [UIButton buttonWithType:UIButtonTypeCustom];
        keyButton.frame = CGRectMake(column*kKeyGap, row*kKeyGap, kKeySize, kKeySize);

        [keyButton setImage:[rowArray objectAtIndex:row] forState:UIControlStateNormal];
        [keyButton addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];

        [self.view addSubview:keyButton];
    }
}

顺便说一下，嵌套的邮件表达式可以很酷，但嵌套调用 objectAtIndex：可能永远不是一个好主意。

By the way, nested message expressions can be cool sometimes, but nesting calls to objectAtIndex: is probably never a good idea.

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