Calling a method after view is Popped or Dismissed

[vatsa.devil]

I have a view with a button to launch the camera. and after taking the picture, i need to send it over to a server AND display the image in a UIImageView. everything works fine, except that, the function that is sending the pic to the server gets called before the camera view is dismissed. i.e. after taking the pic, i hit 'use' and the app just freezes for about 20 seconds (highly unacceptable) and then comes back to the original view. Where as what i want is the camera view should just pop and come back to the original view and ten send the data over. Can't figure out what i'm doing wrong.

Following are some relevant code.

//For launching the camera

-(void)takeAPicPressed:(id)sender{
        picker.sourceType = UIImagePickerControllerSourceTypeCamera;
	[self presentModalViewController:picker animated:YES];
}

save the captured image in lastCapturedBg;

 - (void)imagePickerController:(UIImagePickerController *) Picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
	picUpdated=TRUE;
        lastCapturedBg = [info objectForKey:UIImagePickerControllerOriginalImage];
	[[Picker parentViewController] DismissModalViewControllerAnimated:NO];

}

viewWillAppear

-(void)viewWillAppear:(BOOL)animated{
	NSLog(@"viw will appr");
	bgImage.image=lastCapturedBg;
	
        //just to make sure the method doesn't get called on the first run..
	if (picUpdated) {
		picUpdated=FALSE;
		[self uploadPicToServer:lastCapturedBg];
	}
	
	
}

sending file over to the server

 -(void)uploadPicToServer:(UIImage*)myPic{
	
	NSString *urlString = @"http://xxx.xxx.xx.xx/xxxxxxxxxxx/uploadFile";
	NSString *filename = g_userEmailId;
	NSURLRequest* request= [[[NSMutableURLRequest alloc] init] autorelease];
	[request setURL:[NSURL URLWithString:urlString]];
	[request setHTTPMethod:@"POST"];
	NSString *boundary = @"-----------------------------4664151417711";
	NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
	[request addValue:contentType forHTTPHeaderField: @"Content-Type"];
	NSMutableData *postbody = [NSMutableData data];
	[postbody appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
	[postbody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userfile\"; filename=\"%@.jpg\"\r\n", filename] dataUsingEncoding:NSUTF8StringEncoding]];
	[postbody appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
		 
	 NSData *myData= UIImagePNGRepresentation(myPic);
	[postbody appendData:[NSData dataWithData:myData]];
	[postbody appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",@"-----------------------------4664151417711",@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
	[request setHTTPBody:postbody];
	
	NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
	NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
	NSLog(returnString);	
	 
}

putting breakpoints shows that the modelView has been dismissed before the method gets called, but the 'picker' view is still shown on the screen. Any help is appreciated. Thank you.

[nobre84]

Try to send it on the viewDidAppear method, and set a UIActivityView or something like that on the viewWillAppear method, because the UI will still be blocked while you send it.

[Duncan C]

Originally Posted by vatsa.devil

I have a view with a button to launch the camera. and after taking the picture, i need to send it over to a server AND display the image in a UIImageView. everything works fine, except that, the function that is sending the pic to the server gets called before the camera view is dismissed. i.e. after taking the pic, i hit 'use' and the app just freezes for about 20 seconds (highly unacceptable) and then comes back to the original view. Where as what i want is the camera view should just pop and come back to the original view and ten send the data over. Can't figure out what i'm doing wrong.

Following are some relevant code.

//For launching the camera

-(void)takeAPicPressed:(id)sender{
        picker.sourceType = UIImagePickerControllerSourceTypeCamera;
	[self presentModalViewController:picker animated:YES];
}

save the captured image in lastCapturedBg;

 - (void)imagePickerController:(UIImagePickerController *) Picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
	picUpdated=TRUE;
        lastCapturedBg = [info objectForKey:UIImagePickerControllerOriginalImage];
	[[Picker parentViewController] DismissModalViewControllerAnimated:NO];

}

viewWillAppear

-(void)viewWillAppear:(BOOL)animated{
	NSLog(@"viw will appr");
	bgImage.image=lastCapturedBg;
	
        //just to make sure the method doesn't get called on the first run..
	if (picUpdated) {
		picUpdated=FALSE;
		[self uploadPicToServer:lastCapturedBg];
	}
	
	
}

sending file over to the server

 -(void)uploadPicToServer:(UIImage*)myPic{
	
	NSString *urlString = @"http://xxx.xxx.xx.xx/xxxxxxxxxxx/uploadFile";
	NSString *filename = g_userEmailId;
	NSURLRequest* request= [[[NSMutableURLRequest alloc] init] autorelease];
	[request setURL:[NSURL URLWithString:urlString]];
	[request setHTTPMethod:@"POST"];
	NSString *boundary = @"-----------------------------4664151417711";
	NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
	[request addValue:contentType forHTTPHeaderField: @"Content-Type"];
	NSMutableData *postbody = [NSMutableData data];
	[postbody appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
	[postbody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userfile\"; filename=\"%@.jpg\"\r\n", filename] dataUsingEncoding:NSUTF8StringEncoding]];
	[postbody appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
		 
	 NSData *myData= UIImagePNGRepresentation(myPic);
	[postbody appendData:[NSData dataWithData:myData]];
	[postbody appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",@"-----------------------------4664151417711",@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
	[request setHTTPBody:postbody];
	
	NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
	NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
	NSLog(returnString);	
	 
}

putting breakpoints shows that the modelView has been dismissed before the method gets called, but the 'picker' view is still shown on the screen. Any help is appreciated. Thank you.

You have a couple of issues.

First, and most importantly, you're using synchronous calls to upload your image to the server. That will cause your UI to freeze until the upload is complete. Your NSURLConnection sendSynchronousRequest: call is the culprit. You should rewrite that code to submit an async request. That way, the upload will take place in the background. I'd suggest doing a search on the web for asynchronous NSURLConnection. It will involve setting yourself up as a delegate and handling a few delegate methods that notify you about the progress of the upload.

If you want to take the easy route, and just pop your view before you begin a synchronous request, just rewrite your code that calls uploadPicToServer to let the pop take place first:

  [self uploadPicToServer:lastCapturedBg];

becomes

  [self performSelector: @selector(uploadPicToServer:) 
    withObject: lastCapturedBg
    afterDelay: 0];

What that does is to queue the call to uploadPicToServer: for later. Next time through the app's event loop, it will switch view controllers, and THEN do your call to uploadPicToServer: