My UIImage is loaded but doesn't appear on screen - ios

Question

i'm writing an app that changes an image through different conditions. When i debug everything is set but i do not see the image on my screen. Can anybody please help me?
-(void)setLuminanceImageSource
{
self.luminanceImageView.image = nil;
UIImage *image;
switch (self.luminanceImageSource) {
case FULL_LIGHT:
image = [UIImage imageNamed:#"belichting-goed"];
[self.luminanceImageView setImage:image];
NSLog(#"full");
break;
case HALF_LIGHT:
image = [UIImage imageNamed:#"belichting-matig"];
[self.luminanceImageView setImage:image];
NSLog(#"half");
break;
case BAD_LIGHT:
image= [UIImage imageNamed:#"belichting-slecht"];
[self.luminanceImageView setImage:image];
NSLog(#"bad");
break;
default:
image = [UIImage imageNamed:#"belichting-goed"];
break;
}
[self.luminanceImageView setImage:image];
[self.luminanceImageView setNeedsDisplay];
[self.view addSubview:self.luminanceImageView];
[self.view bringSubviewToFront:self.luminanceImageView];
}
This is my method that controls the image. I have an UIImageView in the .xib file and when i run the app i see the image i have selected in attribute inspector, but it disappears when this method is called.
EDIT: I have changed the names to the conventional naming style.
This is my debug-console, the image object is not nil but the luminanceImageView stays nil.
I have created a github repository where i cloned my project in so you can see my code.
CameraApp repository
Only difference is the location of the luminaceImageView, now it is located in the middle of the screen so i can be sure that it is in view of the device.

Answer 1

You say that:
the image object is not nil but the luminanceImageView stays nil.
Of course, you need to create the image view first, before you can set its image. The easiest in your case is probably to create it and set its image in one go, and then add it to your view:
self.luminanceImageView = [[UIImageView alloc] initWithImage:image];
[self.view addSubview:self.luminanceImageView];
EDIT (after looking at the GitHub):
You currently set the view like this:
self.luminanceImageView = [[UIImageView alloc] init];
[self.luminanceImageView setImage:image];
That means that if you set it in the xib (I have not checked that), then you override it here.
There are three problems with this:
the luminanceImageView still needs to be added to your view, as I
already stated above
the plain init creates an imageView with
size (0, 0). This is unlike the initWithImage:, which creates a imageView with the size of the image.
the setImage: does not resize the imageView. From the
UIWebView documentation:
Setting the image property does not change the size of a UIImageView. Call sizeToFit to adjust the size of the view to match the image.
If you have correctly set the imageView with its size in the XIB, then leave out everything else and just do:
[self.luminanceImageView setImage:image];
If the size is not correct, then follow this with:
[self.luminanceImageView sizeToFit];
EDIT (after debugging the code):
Your problem is that you set the image from a background thread. Almost all view operation in iOS need to be done from the main thread. Doing like this solves your problem:
dispatch_async(dispatch_get_main_queue(), ^{
[self.luminanceImageView setImage:image];
[self.view bringSubviewToFront:self.luminanceImageView];
});
BTW, you also change self.layer in your code. That is probably not a good idea and may lead to problems later. Use a separate view for the camera, and use [cameraView.layer addSublayer:newLayer] to get around that.

Answer 2

try this edit from your code
-(void)setLuminanceImageSource
{
[self.sess stopRunning];
//[self.layer removeFromSuperlayer];
UIImage *image;
switch (self.luminanceImageSource) {
case FULL_LIGHT:
{
image = [UIImage imageNamed:#"belichting-goed.png"];
NSLog(#"full");
break;
}
case HALF_LIGHT:
{
image = [UIImage imageNamed:#"belichting-matig.png"];
NSLog(#"half");
break;
}
case BAD_LIGHT:
{
image= [UIImage imageNamed:#"belichting-slecht.png"];
NSLog(#"bad");
break;
}
default:
{
image = [UIImage imageNamed:#"belichting-goed.png"];
break;
}
}
[self.luminanceImageView setImage:image];
[self.layer addSublayer: self.luminanceImageView.layer];
//[self.view bringSubviewToFront:self.luminanceImageView];
// NSLog(#"%#", self.luminanceImageView.image);
// NSLog(#"lumi X:%f, Y:%f", self.luminanceImageView.frame.origin.x, self.luminanceImageView.frame.origin.y);
// NSLog(#"view X:%f, Y:%f",self.view.frame.origin.x, self.view.frame.origin.y);
// NSLog(#"window %#", self.view.window);
}