Detect Retina Display

#define IS_RETINA ([[UIScreen mainScreen] respondsToSelector:@selector(displayLinkWithTarget:selector:)] && ([UIScreen mainScreen].scale == 2.0))

if(IS_RETINA)
{
   // Retina display
} else {
  // non-Retina display

}

Full Screen Dialog

final Dialog instructionDialog = new Dialog(getParent(), android.R.style.Theme);
instructionDialog.getWindow().requestFeature(Window.FEATURE_NO_TITLE);
instructionDialog.setContentView(getLayoutInflater().inflate(R.layout.dialog_instruction
       , null));
instructionDialog.getWindow().setLayout(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
Button btn = (Button) instructionDialog.findViewById(R.id.btn_instruction);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
instructionDialog.dismiss();
}
});
instructionDialog.show();

Convert CGPoint, CGRect or CGSize to String

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    
    CGPoint previousPoint1 = [touch previousLocationInView:self];
    NSLog(@"touch begin %@", NSStringFromCGPoint(previousPoint1));
}

NSStringFromCGRect(CGRect rect)

NSStringFromCGSize(CGSize size)

Resize UIImage

+ (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
    //UIGraphicsBeginImageContext(newSize);
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newImage;
}

Get screen/application/status bar frame dimensions

CGRect rect;
// Get screen dimensions
rect = [[UIScreen mainScreen] bounds];
NSLog(@"Bounds: %1.0f, %1.0f, %1.0f, %1.0f", rect.origin.x, rect.origin.y, rect.size.width, rect.size.height);
// Get application frame dimensions (basically screen - status bar)
rect = [[UIScreen mainScreen] applicationFrame];
NSLog(@"App Frame: %1.0f, %1.0f, %1.0f, %1.0f", rect.origin.x, rect.origin.y, rect.size.width, rect.size.height);
// Get status bar frame dimensions
rect = [[UIApplication sharedApplication] statusBarFrame];
NSLog(@"Statusbar frame: %1.0f, %1.0f, %1.0f, %1.0f", rect.origin.x, rect.origin.y, rect.size.width, rect.size.height);