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标题: ios - 使用后台线程从 url 加载注释。在移动或缩放 mapView 之前，引脚不显示 [打印本页]

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作者: 菜鸟教程小白    时间: 2022-12-12 21:14
标题: ios - 使用后台线程从 url 加载注释。在移动或缩放 mapView 之前，引脚不显示

我使用后台线程从 url 加载注释。在我移动或缩放 mapView 之前，图钉不显示。如何更新我的 View ？

我的 viewDidAppear

- (void)viewDidAppearBOOL)animated
{

[super viewDidAppear:animated];

//Create the thread 
[NSThread detachNewThreadSelectorselector(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(), ^{

}); }

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Best Answer-推荐答案

您正在从非 UI 更新 UI - 线程这将不起作用

您将不得不在 UIThread block 中调用更新您的 ui 的代码段，如下所示:

例如

[mapView removeAnnotations:annotationsOnMap];

必须在 UI-Thread 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 线程中调用所有 UI 更新

   dispatch_async(dispatch_get_main_queue(), ^{
        //All UI updating code must come here
    });

关于ios - 使用后台线程从 url 加载注释。在移动或缩放 mapView 之前，引脚不显示，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/10862914/

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