UIWebview captures screenshot only for .doc files - ios

Question

Trying to create thumb pictures of documents that has been opened in my app with openurl.
My app can open and save .doc .xls and .pdf file, but when I try to save the screenshot it can correctly save the .doc content, for pdf and xls it only saves a blank white picture.
here are some sample documents I am testing:
.doc,
.pdf,
excel
Here is my code:
-(void)webViewDidFinishLoad:(UIWebView *)webViewCapture
{
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
NSLog(#"webViewDidFinishLoad");
NSLog(#"webview %#",webView);
NSLog(#"webViewCapture %#",webViewCapture);
UIGraphicsBeginImageContext(webView.bounds.size);
[webView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Convert UIImage to JPEG
NSData *imgData = UIImageJPEGRepresentation(viewImage, 1);
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *filePathLocal = [documentsDirectory stringByAppendingPathComponent:#"Inbox"];
NSArray *partialDates =[self.imageFilename componentsSeparatedByString:#"."];//split string where - chars are found
NSString* fileDescription= [partialDates objectAtIndex: 0];
//creatre unique name for image _AKIAIVLFQKM11111
NSString *uniqueFileName=[NSString stringWithFormat:#"%#_AKIAIVLFQKM11111_%#.jpeg",fileDescription,[partialDates objectAtIndex: 1]];
NSString *finalFileName= [filePathLocal stringByAppendingPathComponent:uniqueFileName];
NSError *error = nil;
if ([imgData writeToFile:finalFileName options:NSDataWritingAtomic error:&error]) {
// file saved
} else {
// error writing file
NSLog(#"Unable to write PDF to %#. Error: %#", finalFileName, error);
}
}
NSLOG:
webViewDidFinishLoad
webview <UIWebView: 0xaa79070; frame = (0 44; 768 960); autoresize = W+H; layer = <CALayer: 0xaa51000>>
webViewCapture <UIWebView: 0xaa79070; frame = (0 44; 768 960); autoresize = W+H; layer = <CALayer: 0xaa51000>>
Why I cant save real content for other types of documents with above code?

Answer 1

Perhaps it's a problem with the methode you are using to take the screenShot, use the one indicated by apple :
- (UIImage*)screenshot
{
// Create a graphics context with the target size
// On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
// On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
CGSize imageSize = [[UIScreen mainScreen] bounds].size;
if (NULL != UIGraphicsBeginImageContextWithOptions)
UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);
else
UIGraphicsBeginImageContext(imageSize);
CGContextRef context = UIGraphicsGetCurrentContext();
// Iterate over every window from back to front
for (UIWindow *window in [[UIApplication sharedApplication] windows])
{
if (![window respondsToSelector:#selector(screen)] || [window screen] == [UIScreen mainScreen])
{
// -renderInContext: renders in the coordinate space of the layer,
// so we must first apply the layer's geometry to the graphics context
CGContextSaveGState(context);
// Center the context around the window's anchor point
CGContextTranslateCTM(context, [window center].x, [window center].y);
// Apply the window's transform about the anchor point
CGContextConcatCTM(context, [window transform]);
// Offset by the portion of the bounds left of and above the anchor point
CGContextTranslateCTM(context,
-[window bounds].size.width * [[window layer] anchorPoint].x,
-[window bounds].size.height * [[window layer] anchorPoint].y);
// Render the layer hierarchy to the current context
[[window layer] renderInContext:context];
// Restore the context
CGContextRestoreGState(context);
}
}
// Retrieve the screenshot image
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
For more detail : Screen Capture in UIKit Applications

Answer 2

So two ways I can think of working this out are as follows:
1.) Subclass UIWebview and implement drawRect. in drawRect save a screenshot as you have direct access to the graphicsContext. After you have a screenshot assign it to a custom property on the webview. Then whenever you need it, it should be readily available.
2.) take screenshot asynchronously and guarantee that the webview will exist or do proper error handling on the asynch task to handle the event that the webview no longer exists.
I personally would prefer #2 as it pulls some heavy lifting off the main thread and should still work properly.