Beginning iOS 5 Application Development

SUMMARY

In this chapter, you have seen the usefulness of the NSTimer class and how it can help you perform some simple animations. You have also learned about the various affine transformations supported by the iOS SDK. Next, you learned how the Image View enables you to animate a series of images at a regular time interval. Last, but not least, you learned how to play back a video in your iPhone application.

EXERCISES

1. Name the three affine transformations supported by the iPhone SDK.
2. How do you pause an NSTimer object and then resume it?
3. What is the purpose of enclosing your block of code using the animateWithDuration:delay:options:animations:completion: method of the UIView class, as shown in the following code snippet?

   [UIView animateWithDuration:slider.value
                         delay:0.0f
                       options:UIViewAnimationOptionAllowUserInteraction ||
                                UIViewAnimationOptionCurveLinear
                   animations:^{
                       //---code to effect visual change---
                   }
                   completion:nil];

4. Name the class that you can use for video playback.

   Answers to the exercises can be found in Appendix D.

WHAT YOU LEARNED IN THIS CHAPTER

TOPIC	KEY CONCEPTS
Using the NSTimer object to create timers	Create a timer object that will call the onTimer method every half-second: timer = [NSTimer scheduledTimerWithTimelnterval: 0.5 target:self selector:@selector(onTimer) userInfo:nil repeats:YES];
Stopping the NSTimer object	[timer invalidate]; ...