iOS7 - 触摸屏幕前不会显示地图视图引脚 [英] iOS7 - Map view pin do not appear until screen is touched

问题描述

在我的应用程序中，我使用json从Web服务下载一组点。
将应用程序实现到iOS7，我正在尝试解决这个问题：下载了位置，但是在用户触摸并移动地图之前，地图上的图钉不会被绘制。然后它们出现并且都像在iOS6中那样工作。

In my app, I download a set of point from a web service using json. Actualizing the app to iOS7, I am experimenting that problem: the locations are downloaded but pins on the map are not painted until user touchs and "moves" the map. Then they appear and all work as in iOS6.

如何纠正这种行为？

编辑：
在接收数据的方法结束时调用AddAnnotation，解析json并将它们传递给mylocaction对象：

AddAnnotation is called at the end of a method that receive data, parse the json and pass them to mylocaction object:

- (void)plotBarPosition:(NSString *)data_string {
    // Parse the string into JSON
    NSDictionary *json = [(NSDictionary*)[datos_string1 JSONValue]objectForKey:@"features"];

    for (int i = 0; i < [json count]; i++){

      /*
      PARSING EACH POINT
      */

    MyLocation *location =[[MyLocation alloc] initWithName:nameLoc coordinate:coordinate estado:status antenaId:antenaId];

    [_mapView addAnnotation:location];
     }

}   

我也试过：

[_mapView performSelectorOnMainThread: @selector(addAnnotations:) withObject: location waitUntilDone: NO];

但在这种情况下，注释根本不会出现。

but in this case, annotations do not appear at all.

推荐答案

作为此答案和评论通过@RAJA建议，在主线程上调用 addAnnotation：或 addAnnotations：。您可以使用GCD或 performSelectorOnMainThread 执行此操作。

As this answer and the comment by @RAJA suggest, call addAnnotation: or addAnnotations: on the main thread. You could do this using GCD or performSelectorOnMainThread.

对现有代码进行最少更改的选项是调用 addAnnotation：（单数）：

The option with the least changes to your existing code is to call addAnnotation: (singular):

- (void)plotBarPosition:(NSString *)data_string {
    // Parse the string into JSON
    NSDictionary *json = [(NSDictionary*)[datos_string1 JSONValue]objectForKey:@"features"];

    for (int i = 0; i < [json count]; i++){

        /*
         PARSING EACH POINT
         */

        MyLocation *location =[[MyLocation alloc] initWithName:nameLoc coordinate:coordinate estado:status antenaId:antenaId];

        //[_mapView addAnnotation:location];
        [_mapView performSelectorOnMainThread:@selector(addAnnotation:) 
                                   withObject:location 
                                waitUntilDone:YES];
    }
}

或者，使用 addAnnotations：（复数），首先将注释添加到本地数组，然后在单个调用中将它们一起提供给地图视图。以下更改标有>>> ：

Alternatively, to use addAnnotations: (plural), you first add your annotations to a local array and give them to the map view all together in a single call. Changes below are marked with >>>:

- (void)plotBarPosition:(NSString *)data_string {
    // Parse the string into JSON
    NSDictionary *json = [(NSDictionary*)[datos_string1 JSONValue]objectForKey:@"features"];

    //>>> initialize array to hold annotations...
    NSMutableArray *annotationsToAdd = [NSMutableArray array];

    for (int i = 0; i < [json count]; i++){

        /*
         PARSING EACH POINT
         */

        MyLocation *location =[[MyLocation alloc] initWithName:nameLoc coordinate:coordinate estado:status antenaId:antenaId];

        //>>> comment out direct addAnnotation...
        //[_mapView addAnnotation:location];

        //>>> add annotation to local array...
        [annotationsToAdd addObject:location];
    }

    //>>> call addAnnotations: (plural) on main thread...
    [_mapView performSelectorOnMainThread:@selector(addAnnotations:) 
                               withObject:annotationsToAdd 
                            waitUntilDone:YES];
}

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