我使用后台线程从 url 加载注释。在移动或缩放地图视图之前，图钉不会显示。我如何更新我的视图？
我的观点确实出现了
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
//Create the thread
[NSThread detachNewThreadSelector:@selector(loadPList) toTarget:self withObject:nil];
}
加载PList
- (void) loadPList { //Load the plist NSString *urlStr = [[NSString alloc] initWithFormat:@"http://www.domain.com/data.xml"];
NSURL *url = [NSURL URLWithString:urlStr]; NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfURL:url];
NSMutableArray *annotations = [[NSMutableArray alloc]init];
NSArray *annotationsOnMap = mapView.annotations; if ([annotationsOnMap count] > [annotations count]) { [mapView removeAnnotations:annotationsOnMap];
} else { //Do nothing }
if ([[NSUserDefaults standardUserDefaults] boolForKey:@"blackKey"]) {
NSArray *ann = [dict objectForKey:@"Category1"];
for(int i = 0; i < [ann count]; i++) {
NSString *coordinates = [[ann objectAtIndex:i] objectForKey:@"Coordinates"];
double realLatitude = [[[coordinates componentsSeparatedByString:@","] objectAtIndex:1] doubleValue];
double realLongitude = [[[coordinates componentsSeparatedByString:@","] objectAtIndex:0] doubleValue];
MyAnnotation *myAnnotation = [[MyAnnotation alloc] init];
CLLocationCoordinate2D theCoordinate;
theCoordinate.latitude = realLatitude;
theCoordinate.longitude = realLongitude;
myAnnotation.coordinate=CLLocationCoordinate2DMake(realLatitude,realLongitude);
myAnnotation.title = [[ann objectAtIndex:i] objectForKey:@"Name"];
myAnnotation.subtitle = [[ann objectAtIndex:i] objectForKey:@"Address"];
myAnnotation.icon = [[ann objectAtIndex:0] objectForKey:@"Icon"];
[mapView addAnnotation:myAnnotation];
[annotations addObject:myAnnotation];
}
}
else { //Do nothing }
//And same with other categories....
//Update the ui dispatch_async(dispatch_get_main_queue(), ^{
}); }
您正在从非 UI 更新 UI - 线程这将不起作用
您必须调用 UIThread 块内更新 ui 的代码段，如下所示：
例如
[mapView removeAnnotations:annotationsOnMap];
必须在UI线程中调用
dispatch_async(dispatch_get_main_queue(), ^{
//Update UI if you have to
[mapView removeAnnotations:annotationsOnMap];
});
请注意，您必须在 main_queue 线程内调用所有 UI 更新
dispatch_async(dispatch_get_main_queue(), ^{
//All UI updating code must come here
});
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