Question

我正在尝试将整个UIWebView（甚至屏幕外内容）捕获到PNG。以下代码在大多数设备上运行良好，但在某些iPad 1st版本上，它在这一行上崩溃了：

[self.webview.layer renderInContext:resizedContext]; /// crash

如何通过停止renderInContext进程来阻止崩溃？

有关问题的背景，请参阅下面的代码示例：

//Create original tmp bounds
CGRect tmpFrame = self.webview.frame;
CGRect tmpBounds = self.webview.bounds;
CGRect aFrame = self.webview.bounds;
aFrame.size.width = self.webview.frame.size.width;
aFrame.size.height = self.webview.frame.size.height;
self.webview.frame = aFrame;
aFrame.size.height = [self.webview sizeThatFits:[[UIScreen mainScreen] bounds].size].height;

NSLog(@"webpage size %f",self.webview.frame.size.height);

self.webview.frame = aFrame;
UIGraphicsBeginImageContext([self.webview sizeThatFits:[[UIScreen mainScreen] bounds].size]);
CGContextRef resizedContext = UIGraphicsGetCurrentContext();

// crash
[self.webview.layer renderInContext:resizedContext]; // crash
// crash

UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();
self.webview.frame = tmpFrame;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *pngPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",@"TestImage"]];
NSError *error;
[UIImagePNGRepresentation(image) writeToFile:pngPath options:NSDataWritingAtomic error:&error];

NSURL *url = [NSURL fileURLWithPath:pngPath];

//reset webview
self.webview.bounds = tmpBounds;
self.webview.frame = tmpFrame;

模拟器不会崩溃，以下是在设备上运行时控制台的日志记录错误：

May 16 12:33:41 unknown SpringBoard[29] <Warning>: Application 'AppName' exited abnormally     with signal 11: Segmentation fault: 11
May 16 12:33:41 unknown DTMobileIS[652] <Warning>: _memoryNotification : {
    OSMemoryNotificationLevel = 0;
    timestamp = "2012-05-16 19:33:41 +0000";
}
May 16 12:33:41 unknown DTMobileIS[652] <Warning>: _memoryNotification : <NSThread: 0x1d5286d0>{name = (null), num = 1}
May 16 12:33:41 unknown DTMobileIS[652] <Warning>: _memoryNotification : {
    OSMemoryNotificationLevel = 0;
    timestamp = "2012-05-16 19:33:41 +0000";
}

Answer 1

我遇到了同样的问题，并通过首先计算图像的高度是否超过约8,000像素来解决它。

如果是这样，我失败并警告用户，只要是iPad 1硬件版本，该页面对于此过程来说太大了。

我从来没有找到任何真正的解决方案。

iOS - 将UIWebView捕获到图像

1 个答案: