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在 3.1 中，我一直在使用“屏幕外”MKMapView 来创建可以旋转、裁剪等的地图图像，然后再将它们呈现给用户。在 3.2 和 4.0 中，这种技术不再适用。这是一些说明问题的代码，然后是我的理论。

     // create map view

     _mapView = [[MKMapView alloc] initWithFrame:CGRectMake(0, 0, MAP_FRAME_SIZE, MAP_FRAME_SIZE)];
     _mapView.zoomEnabled = NO;   
     _mapView.scrollEnabled = NO;
     _mapView.delegate = self;    
     _mapView.mapType = MKMapTypeSatellite;

     // zoom in to something enough to fill the screen
     MKCoordinateRegion region;    
     CLLocationCoordinate2D center = {30.267222, -97.763889};

     region.center = center;    
     MKCoordinateSpan span = {0.1, 0.1 };    
     region.span = span;    
     _mapView.region = region;

     // set scrollview content size to full the imageView  
     _scrollView.contentSize = _imageView.frame.size;

     // force it to load

#ifndef __IPHONE_3_2

     // in 3.1 we can render to an offscreen context to force a load    
     UIGraphicsBeginImageContext(_mapView.frame.size);    
     [_mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
     UIGraphicsEndImageContext();

#else

     // in 3.2 and above, the renderInContext trick doesn't work...    
     // this at least causes the map to render, but it's clipped to what appears to be    
     // the viewPort size, plus some padding    
     [self.view addSubview:_mapView];          

#endif

地图加载完成后，我会拍下它的照片并将其填充到我的滚动视图中

- (void)mapViewDidFinishLoadingMap:(MKMapView *)mapView {    
     NSLog(@"[MapBuilder] mapViewDidFinishLoadingMap");

     // render the map to a UIImage
     UIGraphicsBeginImageContext(mapView.bounds.size);

     // the first sub layer is just the map, the second is the google layer, this sublayer structure might change of course

     [[[mapView.layer sublayers] objectAtIndex:0] renderInContext:UIGraphicsGetCurrentContext()];

     // we are done with the mapView at this point, we need its ram!    
     _mapView.delegate = nil;     

     [_mapView release];
     [_mapView removeFromSuperview];    
     _mapView = nil;

     UIImage* mapImage = [UIGraphicsGetImageFromCurrentImageContext() retain];
     UIGraphicsEndImageContext();     

     _imageView.image = mapImage;
     [mapImage release], mapImage = nil;  
}

第一个问题是在 3.1 中渲染到上下文会触发地图开始加载。这不再适用于 3.2、4.0。我发现唯一会触发加载的是将地图临时添加到视图中（即使其可见）。问题是地图只渲染到屏幕的可见区域，加上一点填充。框架/边界很好，但它似乎“有帮助”优化了加载以将图块限制为屏幕上可见或靠近它的图块。

任何想法如何强制地图以全尺寸加载？其他人有这个问题吗？

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