UIImagePicker收到称为viewDidLoad的内存警告，并清除UITextField

Question

I am displaying a UIImagePicker from my UIViewController , in my UIViewController I have a few UITextField .

Now a user has filled out some values in this UITextField and then he selects an image from the UIImagePicker , after that it receives a memory warning, and calls viewDidLoad again, but then all the data that the user had entered in the UITextField is missing . How do I deal with this?

Code:

- (void) showImageSelector: (UITapGestureRecognizer *) tapGestureRecognizer
{
    UIActionSheet *actionSheet;
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
        actionSheet = [[UIActionSheet alloc] initWithTitle:[PNRConstants kChoosePhoto] delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:[PNRConstants kPhotoLibrary], [PNRConstants kTakeAPicture], nil];
    }
    else{
        actionSheet = [[UIActionSheet alloc] initWithTitle:[PNRConstants kChoosePhoto] delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:[PNRConstants kPhotoLibrary], nil];
    }
    [actionSheet showInView:self.view.window];
}

#pragma -
#pragma UIActionSheetDelegate
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
    if (buttonIndex != actionSheet.cancelButtonIndex) {
        UIImagePickerController *controller = [[UIImagePickerController alloc] init];
        controller.delegate = self;
        controller.allowsEditing = YES;
        if (buttonIndex == 0) {
            // Photo Library
            controller.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        }
        else {
            // Camera
            controller.sourceType = UIImagePickerControllerSourceTypeCamera;
        }
        [self presentViewController:controller animated:YES completion:nil];
    }
}

Answer 1

When there is low memory and view controller's views are not needed, the views are unloaded from the memory. (This however isn't the case from iOS 6.0, as views are no longer purged from the memory).

So when you receive memory warning, the views are unloaded from the memory. When you get back to it, the view controller's view is requested again and hence it is created/loaded again. Thus, you get viewDidLoad called again.

At this time, this is all new fresh view that got loaded. It has lost all it's previous properties.

In order to avoid this, what you can do is - when user had set text field's properties (it's text most probably), you must have hold these values somewhere in variables, etc.

So, In your viewDidLoad , check if that variable exists and/or holds any values. If it doesn't, it means it's the very first time view has loaded. Here, you do nothing.

However, once user set's some text in to the text field, the controller's view gets unloaded, it gets loaded again later, it's viewDidLoad gets called. Here, at this time the variable holds the text value that was entered earlier. So set the set of the textField.

In short, the code would look something like this:

-(void) viewDidLoad {
    [super viewDidLoad];

    if (yourVariableHoldingTextInput) {
        // Variable holding the text field's input exists. This means user had set some input to the text field. View was purged from memory and is now loaded again.
        yourTextField.text = yourVariableHoldingTextInput; // Essentially, set the text field's text with the variable's value.
    }else {
        // Here we do nothing. This clearly means the controller's view loaded very first time.
    }
}

Answer 2

UIImagePicker consumes more memory from processor.. So you need to solve first this Memory Warning.

I got same kind of issue when i was using camera and photo library for Video.

After i tricks used and it solved. Here are the tricks

Globally define UIImagePickerController and access

And here i have use code to call library

-(UIImagePickerController *)getImagePickerController{
    if (!imagePickerController) {
        imagePickerController = [[UIImagePickerController alloc]init];
    }
    return imagePickerController;
}

After call this UIImagePicker instance to videoPicker

videoPicker = [self getImagePickerController]; 
    videoPicker = [[UIImagePickerController alloc] init];
    videoPicker.sourceType =  UIImagePickerControllerSourceTypePhotoLibrary;
    videoPicker.delegate = self;
    videoPicker.allowsEditing = YES;
    videoPicker.mediaTypes =  [NSArray arrayWithObject:(NSString *)kUTTypeMovie];    
    videoPicker.videoQuality = UIImagePickerControllerQualityTypeHigh;
    videoPicker.videoMaximumDuration = 30.0;
    NSArray *sourceTypes = [UIImagePickerController availableMediaTypesForSourceType:videoPicker.sourceType];
    if (![sourceTypes containsObject:(NSString *)kUTTypeMovie ])
    {
        NSLog(@"no video");
    }
    else
    {
        [self presentModalViewController:videoPicker animated:YES];
    }

After cancel or select any media dismiss Picker only and release. Dont release and dismiss do with videoPicker .

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
{   
    [picker dismissModalViewControllerAnimated:YES];
}

And if already picker instance is there than dont alloc once again.