xcode iphone MPMoviePlayerViewController CGContext 错误
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iphone MPMoviePlayerViewController CGContext Errors
提问by Joseph
I am writing an app for the iPhone that will play some movies utilizing MPMoviePlayerViewController. So far I have gotten it to play movies, however it is throwing some errors in the debugger that all start with CGContext. I have wracked my brain in trying to fix it. Here are the details of my code:
我正在为 iPhone 编写一个应用程序，该应用程序将使用MPMoviePlayerViewController. 到目前为止，我已经让它播放电影，但是它在调试器中抛出了一些错误，这些错误都以CGContext. 我在试图修复它时绞尽脑汁。以下是我的代码的详细信息：
.h file:
.h 文件：
#import <UIKit/UIKit.h>
#import <MediaPlayer/MediaPlayer.h>
@interface MovieViewController : UIViewController {
MPMoviePlayerViewController *playerController;
}
-(IBAction) playMovie:(id)sender;
.m file:
.m 文件：
@interface MovieViewController ()
@end
@implementation
-(IBAction)playMovie:(id)sender {
NSURL *url = [NSURL fileURLWithPath:[[NSBundle mainBundle]
pathForResource:@"moviename" ofType:@"mp4"]];
playerController = [[MPMoviePlayerViewController alloc]
initWithContentURL:url];
[self presentMoviePlayerViewControllerAnimated:playerController];
playerController.moviePlayer.movieSourceType = MPMovieSourceTypeFile;
[playerController.moviePlayer play];
playerController = nil;
}
When I run the program the movie will play, however when the code executes the line: playerController = [[MPMoviePlayerViewController alloc] initWithContentURL:url];the following errors occur:
当我运行程序时，电影将播放，但是当代码执行该行时：playerController = [[MPMoviePlayerViewController alloc] initWithContentURL:url];出现以下错误：
<Error>: CGContextSaveGState: invalid context 0x0
<Error>: CGContextClipToRect: invalid context 0x0
<Error>: CGContextTranslateCTM: invalid context 0x0
<Error>: CGContextDrawShading: invalid context 0x0
<Error>: CGContextRestoreGState: invalid context 0x0
I do know that invalid context 0x0means that those specific variables do not have a value, but I have no idea how to remedy this. Any help would be greatly appreciated.
我知道这invalid context 0x0意味着那些特定变量没有值，但我不知道如何解决这个问题。任何帮助将不胜感激。
回答by matt
I was having the same issue. Merely saying this:
我遇到了同样的问题。简单说一下：
MPMoviePlayerViewController* mpvc =
[[MPMoviePlayerViewController alloc] initWithContentURL: m];
was causing these invalid contexterror messages. The view controller's view (the fullscreen player) did appear when presented, and played the movie no problem; the only issue was these error messages, which I didn't want showing up in the console.
导致这些invalid context错误消息。视图控制器的视图（全屏播放器）在呈现时确实出现，并且播放电影没有问题；唯一的问题是这些错误消息，我不想显示在控制台中。
Taking a hint from Norman's solution, I simply wrapped the call in an artificial drawing context, like this:
从 Norman 的解决方案中得到提示，我只是将调用包装在一个人工绘图上下文中，如下所示：
UIGraphicsBeginImageContext(CGSizeMake(1,1));
MPMoviePlayerViewController* mpvc =
[[MPMoviePlayerViewController alloc] initWithContentURL: m];
UIGraphicsEndImageContext();
It's silly, but it works.
这很愚蠢，但它有效。
回答by Norman
I think the error messages are a bug in MPMoviePlayerViewController
我认为错误消息是 MPMoviePlayerViewController 中的一个错误
They don't seem to be fatal, although I've made them go away by adding a call to UIGraphicsBeginImageContext(self.view.frame.size); in both readyPlayer() and viewDidLoad().
它们似乎并不致命，尽管我通过添加对 UIGraphicsBeginImageContext(self.view.frame.size); 的调用使它们消失了。在 readyPlayer() 和 viewDidLoad() 中。
I also added a UIGraphicsEndImageContext() to dealloc() to clean up the generated contexts.
我还在 dealloc() 中添加了一个 UIGraphicsEndImageContext() 来清理生成的上下文。
