Obj-C，“NSRangeException”，原因：“ -[NSMutableArray objectAtIndex:]: 索引 2 超出范围 [0 .. 1]'

Question

前几天我发布了一个问题，但我没有包含足够的代码，并且遇到了进一步的问题。我不确定我是否应该使用 [[UIApplication sharedApplication] windows]，但自从修复后，我建议有一天数组没有正确数量的值。

有人可以建议/告诉我哪里出了问题以及使用 [[UIApplication sharedApplication] windows] 是否正确？

- (void) addDoneToKeyboard {

    doneButton.hidden =  NO;

    //Add a button to the top, above all windows
    NSArray *allWindows = [[UIApplication sharedApplication] windows];
    NSUInteger topWindowIndex = [allWindows count];// fix - 1;
    UIWindow *topWindow = [allWindows objectAtIndex:topWindowIndex]; //SIGABRT

由于未捕获的异常“NSRangeException”而终止应用程序，原因：“-[NSMutableArray objectAtIndex:]：索引 2 超出范围 [0 .. 1]”

    // check if top window is of keypad or else
    NSString *topViewClassName = [NSString stringWithFormat:@"%@", 
             [topWindow class]];
    while (![topViewClassName isEqualToString:@"UITextEffectsWindow"] ) {
        --topWindowIndex;

        if(topWindowIndex < 1) // fix 0
            break;

        topWindow = [allWindows objectAtIndex:topWindowIndex];
        topViewClassName = [NSString stringWithFormat:@"%@", [topWindow class]];
    }

//

    if(topWindowIndex < 1) { // fix 0
        topWindowIndex = [allWindows count] - 1;
        topWindow = [allWindows objectAtIndex:topWindowIndex];
    }

    if (doneButton.superview)
        [doneButton removeFromSuperview];

    [topWindow addSubview:doneButton];

    if (!doneButtonShownRecently) {
        [UIView beginAnimations:nil context:nil];
        [UIView setAnimationBeginsFromCurrentState:YES];
        [UIView setAnimationDuration:SLIDE_IN_ANIMATION_DURATION];
        [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
        doneButton.frame = CGRectMake(0, 480-53, 
                         doneButton.frame.size.width, 53);
        [UIView commitAnimations];
    } else {
        doneButton.frame = CGRectMake(0, 427, 
                         doneButton.frame.size.width, 53);
    }

    doneButtonShown = YES;
}

Answer 1

这里的代码注释似乎已经告诉您需要做什么：

NSUInteger topWindowIndex = [allWindows count] - 1;  
UIWindow *topWindow = [allWindows objectAtIndex:topWindowIndex];

计数从 1 开始，而数组索引从 0 开始 - 您的两个数组索引值是 0（对于您的第一个窗口）和 1（对于您的第二个窗口），但是您正在尝试访问索引值 2。

编辑：请注意，以下代码现在在上面完全是多余的：  

if(topWindowIndex < 1) { // fix 0
topWindowIndex = [allWindows count] - 1;
topWindow = [allWindows objectAtIndex:topWindowIndex];
}

Answer 2

您这里的代码也是错误的：

// check if top window is of keypad or else
NSString *topViewClassName = [NSString stringWithFormat:@"%@", 
         [topWindow class]];
while (![topViewClassName isEqualToString:@"UITextEffectsWindow"] ) {
    --topWindowIndex;

    if(topWindowIndex < 1) // fix 0
        break;

    topWindow = [allWindows objectAtIndex:topWindowIndex];
    topViewClassName = [NSString stringWithFormat:@"%@", [topWindow class]];
}

您真正想要的是：

// check if top window is of keypad or else
BOOL foundTextEffectsWindow = NO;
while (topWindowIndex >= 0) {
    topWindow = [allWindows objectAtIndex:topWindowIndex];
    if ([topWindow isKindOfClass:[UITextEffectsWindow class]]) {
      foundTextEffectsWindow = YES;
      break;
    }

    topWindowIndex--;
}
if (foundTextEffectsWindow) {
   // do stuff with the window
}