IBAction 中跳过的用户界面命令

Question

这是我的代码：

-(IBAction)saveDownloadedImage
{
    NSLog(@"Test");    EXECUTED
    indicatorView.hidden = NO;  NOT EXECUTED
    [indicatorView startAnimating];  NOT EXECUTED
    [statusLabel setText:@"WHY?"];  NOT EXECUTED
    [currentPicture setImage:[imageView image]];   EXECUTED
    ImageFileManager *fileManager = [[ImageFileManager alloc] init]; EXECUTED
    [fileManager saveImageToDisk:currentPicture]; EXECUTED
    indicatorView.hidden = YES;
    [statusLabel setText:@"Image saved successfully."]; EXECUTED
    saveButton.enabled = NO; EXECUTED

}

保存过程大约需要 5 秒。所以在 UI 中看到该指示器是正常的。但什么也没发生！有什么想法吗？

Answer 1

您需要向这样的发送者声明您的方法

-(IBAction)saveDownloadedImage:(id)sender

Answer 2

一切都被执行了。您的问题是 saveImageToDisk 调用是同步的，并且您是从 UI 线程调用它。当您阻塞 UI 线程时，不会重新绘制任何内容。指示器已显示，但无法将其绘制到屏幕上，直到 IBAction 返回（此时它将再次隐藏）。

您必须异步调用保存方法。
阻塞 UI 线程从来都不是一个好主意。

编辑：请参阅以下问题的答案以获得正确的解决方案： asynchronous requests to database in ios

Edit2：可能的解决方案之一（未测试）

-(IBAction)saveDownloadedImage {
    indicatorView.hidden = NO; //Note you can use hidesWhenStopped property for this
    [indicatorView startAnimating];
    [statusLabel setText:@"BECAUSE..."];
    [currentPicture setImage:[imageView image]];

    [NSThread detachNewThreadSelector:@selector(save) toTarget:self withObject:nil]
}

- (void)save {
    @autoreleasepool {
        ImageFileManager *fileManager = [[ImageFileManager alloc] init];
        [fileManager saveImageToDisk:currentPicture];

        [self performSelectorOnMainThread:@selector(updateUI) withObject:nil waitUntilDone:NO];
    }
}

- (void)updateUI {
    indicatorView.hidden = YES;
    [statusLabel setText:@"Image saved successfully."];
    saveButton.enabled = NO;
}

Answer 3

您确定

1）indicatorView 和 statusLabel 不为 null，并且

2）indicatorView 和 statusLabel 作为子视图添加到 self.view 中吗？

Answer 4

在我的看法中，您正在启动活动指示器主线程。

相反，在主线程上显示指示器，

您应该在单独的线程上调用指示器，如下所示。

-(IBAction)saveDownloadedImage
{
NSLog(@"Test");    EXECUTED
commented below code
//indicatorView.hidden = NO;  NOT EXECUTED
// [indicatorView startAnimating];  NOT EXECUTED
//instead of main thread create new Thread as Below
[NSThread detachNewThreadSelector:@selector(showloader) toTarget:self withObject:nil];
[statusLabel setText:@"WHY?"];  NOT EXECUTED
[currentPicture setImage:[imageView image]];   EXECUTED
ImageFileManager *fileManager = [[ImageFileManager alloc] init]; EXECUTED
[fileManager saveImageToDisk:currentPicture]; EXECUTED

[statusLabel setText:@"Image saved successfully."]; EXECUTED
saveButton.enabled = NO;
[indicatorView stopAnimating:YES];
indicatorView.hidden = YES;
}


//Custome method For shoing the Indicator.
-(void)showloader{
//call below method  here indicatorView object created already.
[indicatorView startAnimating]
}

It'll definitely work