iOS UIButton 在将背景图像设置为 nil 后消失

Question

我有一个没有标题或初始背景图像的 UIButton。按下时，按钮背景图像会发生变化，再次按下时，背景图像将设置为零。现在，在 iOS 6.x 中，该按钮完全消失了。这是我的代码:

- (IBAction)resetAll: (id) sender {
[self reset];

for (UIView *view in self.view.subviews) {

    if ([[[view class] description] isEqualToString:@"UIRoundedRectButton"]) {
        UIButton *theButton = (UIButton *)view;         

        int nTag = theButton.tag;

        switch (nTag) {
            case 11: {
                theButton.tag = 10;
                [theButton setBackgroundImage:nil forState:UIControlStateNormal];
                break;
            }
            case 21: {
                theButton.tag = 20;
                [theButton setBackgroundImage:nil forState:UIControlStateNormal];
                [theButton setEnabled:YES];
                break;
            }
            case 31: {
                theButton.tag = 30;
                [theButton setBackgroundImage:nil forState:UIControlStateNormal];
                [theButton setEnabled:YES];
                break;
            }
            case 41: {
                theButton.tag = 40;
                [theButton setBackgroundImage:nil forState:UIControlStateNormal];
                [theButton setEnabled:YES];
                break;
            }
            case 51: {
                theButton.tag = 50;
                [theButton setBackgroundImage:nil forState:UIControlStateNormal];
                [theButton setEnabled:YES];
                break;
            }
        }
    }
}
return;

这段代码工作正常:

- (IBAction)ButtonClicked: (id) sender {
UIButton *btn = (UIButton *)sender;

// Get the current tag value
int currentTag = [sender tag];

// Toggle the check buttons
if (currentTag == 10 || currentTag == 20 || currentTag == 30 || currentTag == 40 || currentTag == 50) {
        [btn setBackgroundImage:[UIImage imageNamed:@"check.png"] forState:UIControlStateNormal];
        btn.tag = ++currentTag;
}

else
    if (currentTag == 11 || currentTag == 21 || currentTag == 31 || currentTag == 41 || currentTag == 51) {
        [btn setBackgroundImage:nil forState:UIControlStateNormal];
        btn.tag = --currentTag;
}

[self calculate];

如有任何建议或帮助，我们将不胜感激!

Answer 1

与其在 UIControlStateNormal 中更改按钮的背景图像，为什么不直接更改按钮的状态呢？如果您以编程方式创建按钮，则只需添加以下行

[btn setBackgroundImage:[UIImage imageNamed:@"check.png"] forState:UIControlStateSelected];

然后，当按下并且您希望它成为箭头图像时:

[btn setSelected:YES];

并将其设置回默认外观:

[btn setSelected:NO];

如果您在 XIB 中制作了按钮，则可以通过将状态配置更改为“选定”并在那里设置图像来设置状态图像。