如何在等待服务器响应时显示活动指示条？答案

【问题标题】：How to show an activity indicator bar while waiting for response from a server?如何在等待服务器响应时显示活动指示条？
【发布时间】：2014-06-05 04:56:37
【问题描述】：

全部！首先，我已经看到了所有此类问题，但仍然感到困惑，这就是我问的原因。我有一个“翻译”按钮。当我按下按钮时，它会向服务器发送请求并得到响应。因此，在等待答案时，我需要显示活动指示条。我尝试了一些代码，但没有任何效果。有人可以帮我吗？这是我的代码。我的活动指标是 activityInd。

-(IBAction)translate
{
NSDictionary *dict=[NSDictionary dictionaryWithObjectsAndKeys:[[self textView1] text], @"SourceText",@"8a^{F4v", @"CheckCode",@"0",@"TranslateDirection",@"1",@"SubjectBase", nil];
NSError *error=nil;
    NSData *result=[NSJSONSerialization dataWithJSONObject:dict options:0 error:&error];
    NSURL *url=[NSURL URLWithString:@"http://fake.com/notRealUrl"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60];


    [request setHTTPMethod:@"POST"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    [request setHTTPBody:result];

    NSURLResponse *response=nil;

    NSData *POSTReply = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];

    NSString *theReply = [[NSString alloc] initWithBytes:[POSTReply bytes] length:[POSTReply length] encoding: NSUTF8StringEncoding ];

    NSString *str=theReply;
    str= [str substringWithRange:NSMakeRange(51, str.length - 51 - 2)];

    NSString *result2=[str stringByReplacingOccurrencesOfString:@"\\r\\n" withString:@""];
    _textView.text=result2;
}

谢谢大家！我找到了一种使用异步请求的方法。现在一切正常。

【问题讨论】：

标签： ios ios7 activity-indicator

【解决方案1】：

您正在发出同步请求。所以它将在主线程上执行。这将使您的主线程忙碌，并且您的 UI 在此期间不会更改。使通信请求异步，您的 UI 将使用活动视图进行更新。

【讨论】：

【解决方案2】：

试试这个：

   //set ivar in your view controller
   UIActivityIndicatorView * spinner;

   //alloc init it  in the viewdidload
    spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    [self addSubview:spinner];
    [spinner setFrame:CGRectMake(0, 0, 100, 100)];
    [spinner setCenter:CGPointMake(self.center.x, 150)];
    spinner.transform = CGAffineTransformMakeScale(2, 2);
    [spinner setColor:[UIColor darkGrayColor]];

在请求之前添加以下代码：

[self bringSubviewToFront:spinner];
[spinner startAnimating];

完成后：

[spinner stopAnimating];

【讨论】：

【解决方案3】：

您只能在主线程上更改 UI。

-(void)translate
{
//maybe your app is running on main thread so Start Spinner in main thread.
UIActivityIndicatorView * spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];

[spinner setCenter:self.view.center];
[self.view addSubview:spinner];
[self.view bringSubviewToFront:spinner];
[spinner startAnimating];

// Create this temporary block.
[self callService:^(NSData *data, BOOL success)
{
    /*--- When you get response execute code in main thread and stop spinner. ---*/
    dispatch_async(dispatch_get_main_queue(), 
    ^{
        // now app is in main thread so stop animate.
        [spinner stopAnimating];
        if (success)
        {
            NSString *theReply = [[NSString alloc] initWithBytes:[data bytes] length:[data length] encoding: NSUTF8StringEncoding ];
            //do what you want.

        }
    });
}];
}

-(void)callService:(void(^)(NSData *data,BOOL success))block
{
//we are calling Synchronous service in background thread.
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{

    NSDictionary *dict=[NSDictionary dictionaryWithObjectsAndKeys:@"", @"SourceText",@"8a^{F4v", @"CheckCode",@"0",@"TranslateDirection",@"1",@"SubjectBase", nil];
    NSError *error=nil;
    NSData *result=[NSJSONSerialization dataWithJSONObject:dict options:0 error:&error];
    NSURL *url=[NSURL URLWithString:@"http://fake.com/notRealUrl"];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60];

    [request setHTTPMethod:@"POST"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    [request setHTTPBody:result];

    NSURLResponse *response=nil;

    NSData *POSTReply = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];

    // When we got response we check that we got data or not . if we get data then calling this block again.
    if (POSTReply)
        block(POSTReply,YES);
    else
        block(nil,NO);
});
}

也许这会对你有所帮助。

【讨论】：