【问题标题】:Is there any method to reset the queue used in dequeueReusableAnnotationViewWithIdentifier?有什么方法可以重置 dequeueReusableAnnotationViewWithIdentifier 中使用的队列吗?
【发布时间】:2014-08-31 10:23:31
【问题描述】:

我在地图视图中添加自定义注释。根据应用程序的内部模型,注释可以改变颜色和标题(尽管位置可能不会改变)。我在方法中使用dequeueReusableAnnotationViewWithIdentifier

- (MKAnnotationView *)mapView:(MKMapView *) viewForAnnotation:(id <MKAnnotation>)

奇怪的是,当模型更改时,注释被“刷新”以使用正确的标题和颜色(我只是使用removeAnnotations: 并添加新的),但后来在使用地图时,一些旧的注释与错误的颜色出队。每次模型更改时,我都会使用不同的标识符。

代码如下:

- (MKAnnotationView *)mapView:(MKMapView *)theMapView viewForAnnotation:(id <MKAnnotation>)annotation{
    // in case it's the user location, we already have an annotation, so just return nil
    if ([annotation isKindOfClass:[MKUserLocation class]]){
        return nil;
    }
    if ([annotation isKindOfClass:[APGSAnnotation class]]){
        APGSAnnotation *gsn = (APGSAnnotation*) annotation;
        NSString *GSAnnotationIdentifier = [NSString stringWithFormat:@"gid_%lu_%@", (unsigned long)gsn.gs.gID, self.car.energyType];

        MKAnnotationView *markerView = [theMapView dequeueReusableAnnotationViewWithIdentifier:GSAnnotationIdentifier]; 
        if (markerView == nil) {
            MKAnnotationView *annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation                                                                            reuseIdentifier:GSAnnotationIdentifier];
            annotationView.canShowCallout = YES;
            annotationView.image = [self customizeAnnotationImage:gsn.gs];
            annotationView.opaque = NO;

            UIImageView *sfIconView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:gsn.logo]];
            annotationView.leftCalloutAccessoryView = sfIconView;

            // http://stackoverflow.com/questions/8165262/mkannotation-image-offset-with-custom-pin-image
            annotationView.centerOffset = CGPointMake(0,-annotationView.image.size.height/2);


            UIButton *rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
            [rightButton addTarget:nil action:nil forControlEvents:UIControlEventTouchUpInside];
            annotationView.rightCalloutAccessoryView = rightButton;

            return annotationView;
        }else{
            markerView.annotation = annotation;
            return markerView;
        }
    }
    return nil;
}

以及自定义方法

- (UIImage*)customizeAnnotationImage:(APGS*)gs{
    UIImage *markerImage;

    if (gs.gID == self.best.gID) {
        markerImage = [UIImage imageNamed:@"marker_red.png"];
    }else if (gs.type == k1){
        markerImage = [UIImage imageNamed:@"marker_blue.png"];
    }else if (gs.type == k2){
        markerImage = [UIImage imageNamed:@"marker_green.png"];
    }else if (gs.type == k3){
        markerImage = [UIImage imageNamed:@"marker_purple.png"];
    }else if (gs.type == k4){
        markerImage = [UIImage imageNamed:@"marker_brown.png"];
    }
    UIImage *logoImage = [UIImage imageNamed:gs.logo];
    // size the flag down to the appropriate size
    CGRect resizeRect;
    resizeRect.size = markerImage.size;
    CGSize maxSize = CGRectInset(self.view.bounds, kAnnotationPadding, kAnnotationPadding).size;

    maxSize.height -= self.navigationController.navigationBar.frame.size.height + kCallOutHeight;

    if (resizeRect.size.width > maxSize.width)
        resizeRect.size = CGSizeMake(maxSize.width, resizeRect.size.height / resizeRect.size.width * maxSize.width);

    if (resizeRect.size.height > maxSize.height)
        resizeRect.size = CGSizeMake(resizeRect.size.width / resizeRect.size.height * maxSize.height, maxSize.height);

    resizeRect.origin = CGPointMake(0.0, 0.0);
    float initialWidth = resizeRect.size.width;

    UIGraphicsBeginImageContextWithOptions(resizeRect.size, NO, 0.0f);
    [markerImage drawInRect:resizeRect];
    resizeRect.size.width = resizeRect.size.width/2;
    resizeRect.size.height = resizeRect.size.height/2;

    resizeRect.origin.x = resizeRect.origin.x + (initialWidth - resizeRect.size.width)/2;
    resizeRect.origin.y = resizeRect.origin.y + kLogoHeightPadding;

    [logoImage drawInRect:resizeRect];


    // Create string drawing context
    UIFont *font = [UIFont fontWithName:@"DBLCDTempBlack" size:11.2];
    NSString * num = [NSString stringWithFormat:@"%4.3f",[gs getL]];
    NSDictionary *textAttributes = @{NSFontAttributeName: font,
                                     NSForegroundColorAttributeName: [UIColor whiteColor]};

    CGSize textSize = [num sizeWithAttributes:textAttributes];

    NSStringDrawingContext *drawingContext = [[NSStringDrawingContext alloc] init];

    //adjust center
    if (resizeRect.size.width - textSize.width > 0) {
        resizeRect.origin.x += (resizeRect.size.width - textSize.width)/2;
    }else{
        resizeRect.origin.x -= (resizeRect.size.width - textSize.width)/2;
    }

    resizeRect.origin.y -= kTextPadding;
    [num drawWithRect:resizeRect
              options:NSStringDrawingUsesLineFragmentOrigin
           attributes:textAttributes
              context:drawingContext];

    UIImage *resizedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return resizedImage;
}

注释应根据汽车类型改变颜色。

【问题讨论】:

  • 从视图中取出后,您应该在返回视图之前重置所有相关属性
  • 我已针对“原样”代码编辑了我的问题。
  • 另外,您的代码不会在所有路径中返回值 - 这会导致问题
  • 请注意,注释视图的属性应根据annotation 参数更新,无论视图是创建还是出列。因此,如果 ... 正在这样做,它应该在整个 if/else 语句之后,return 应该在之后移动。
  • 问题似乎是当视图出队时(当 markerView != nil 时),代码不会更新视图的图像和其他属性(它只是更新注释属性)。因此,可能发生的情况是注释重新使用先前注释中的视图,该注释具有不同的图像等。

标签: ios objective-c mapkit


【解决方案1】:

根据标题,答案是否定的 :)

通常您会将视图出列并重置视图的所有相关属性

解决方法:

您可以考虑的是:如果视图变化太大,您可以切换到不同的重用标识符,从而切换队列并“绕过”缓存的视图

【讨论】:

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