Book Image

Asynchronous Android

By : Steve Liles
Book Image

Asynchronous Android

By: Steve Liles

Overview of this book

With more than a million apps available from Google Play, it is more important than ever to build apps that stand out from the crowd. To be successful, apps must react quickly to user input, deliver results in a flash, and sync data in the background. The key to this is understanding the right way to implement asynchronous operations that work with the platform, instead of against it. Asynchronous Android is a practical book that guides you through the concurrency constructs provided by the Android platform, illustrating the applications, benefits, and pitfalls of each.Learn to use AsyncTask correctly to perform operations in the background, keeping user-interfaces running smoothly while avoiding treacherous memory leaks. Discover Handler, HandlerThread and Looper, the related and fundamental building blocks of asynchronous programming in Android. Escape from the constraints of the Activity lifecycle to load and cache data efficiently across your entire application with the Loader framework. Keep your data fresh with scheduled tasks, and understand how Services let your application continue to run in the background, even when the user is busy with something else.Asynchronous Android will help you to build well-behaved apps with smooth, responsive user-interfaces that delight users with speedy results and data that's always fresh, and keep the system happy and the battery charged by playing by the rules.
Table of Contents (14 chapters)
Asynchronous Android
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Combining Loaders


In the preceding sections we developed an AsyncTaskLoader that can load a single image thumbnail as a Bitmap, and a CursorLoader that loads a list of all available images on the device. Let's bring them together to create an app that tiles thumbnails of all the images on the device in a scrollable grid, performing all loading in the background.

Thanks to our CursorLoader, we already have access to the IDs of the images we need to load—we're displaying them as text—so we just need to pass those IDs to our ThumbnailLoader for it to asynchronously load the image for us.

Recall that ThumbnailLoader was set up to load one Bitmap and cache it forever (that is, until explicitly removed from LoaderManager). We want to change that so that a single ThumbnailLoader can first be constructed without a mediaId, and later be told to load an image with a particular mediaId.

public ThumbnailLoader(Context context) {
    super(context);
}

We'll enable ThumbnailLoader to load a new image instead...