Loader droid pro для андроид

Part 4: Tutorial: AppListLoader. Here is a very brief summary of what this blog has covered so far. Life Before Loaders part 1 described the flaws of the pre-Honeycomb 3. These UI-unfriendly APIs resulted in unresponsive applications and were the primary motivation for introducing the Loader and the LoaderManager in Android 3.

Loaders in a reset state should not execute new loads, should not deliver new results, and should not monitor for changes.

These characteristics make Loaders a powerful addition to the Android SDK for several reasons:. They encapsulate the actual loading of data. They abstract out the idea of threads from the client. This reduces code complexity and eliminates potential thread-related bugs. They are entirely event-driven. Loaders monitor the underlying data source and automatically perform new loads for up-to-date results when changes are detected. This makes working with Loaders easy, as the client can simply trust that the Loader will auto-update its data on its own.

The SampleLoader queries a list of SampleItem objects and delivers a to the client:. The superclass method does this for us. I hope these posts were useful and gave you a better understanding of how Loaders and the LoaderManager work together to perform asynchronous, auto-updating queries. Remember that Loaders are your friends… if you use loader droid pro для андроид, your app will benefit in both responsiveness and the amount of code you need to write to get everything working properly!

What Makes Up a Loader?. A task to perform the asynchronous load. To ensure that loads are done on a separate thread, subclasses should extend as opposed to the class. When subclassed, implementing the asynchronous task is as simple as implementing the abstract loadInBackground method, which is called on a worker thread to perform the data load.

This is the only state in which onLoadFinished will ever be called. Loaders in a stopped state continue to monitor for changes but should not deliver results to the client. From a stopped state, the Loader may either be started or reset.

When a loader enters a reset state, it loader droid pro для андроид invalidate and free any data associated with it for garbage collection likewise, loader droid pro для андроид client should make sure they remove any references to this data, since it will no longer be available.

Understanding the LoaderManager part 2 introduced the LoaderManager class and its role in delivering asynchronously loaded data to the client. Loaders are responsible for performing queries on a separate thread, monitoring the data source for changes, and delivering new results to a registered listener usually the LoaderManager when changes are detected.

Loaders should deliver results to these registered listeners with a call to Loader deliverResult D result. One of three 2 distinct states. Any given Loader will either be in a started, stopped, or reset state:. Loaders in a started state execute loads and may deliver their results to the listener at any time. Started Loaders should monitor for changes and perform loader droid pro для андроид loads when changes are detected. Once started, the Loader will remain in a started state until it is either stopped or reset.

Hopefully I could help lessen the learning curve a bit by detailing them out!. That said, in my experience implementing onAbandon is usually not necessary. Last updated January 16,

An observer to receive notifications when the data source has changed. Loaders should implement an observer of some sort i.

For example, when an Activity is first started, the Activity instructs the LoaderManager to start each of its Loaders in Activity onStart. The code below serves as a template of what a Loader implementation typically looks like.

Everything in between is done by the Loader. Loaders are a somewhat advanced topic and may take some time getting used to. We begin by analyzing its four defining characteristics in the next section.

When a change is detected, the observer should call Loader onContentChangedwhich will either a force a new load if the Loader is in a started state or, b raise loader droid pro для андроид flag indicating that a change has been made so that if the Loader is ever started again, it will know that it should reload its data. By now you should have a basic understanding of how Loaders work.

More often than not, reset Loaders will never be called again; however, in some cases they may be started, so they should be able to start running properly again if necessary.

If not, I suggest you let it sink in for a bit and come back later to read through once more reading the documentation never hurts either! As I stated earlier, there is a lot that you must keep in mind when implementing your own custom Loaders. Subclasses must implement loadInBackground and should override onStartLoadingonStopLoadingonResetonCanceledloader droid pro для андроид deliverResult D results to achieve a fully functioning Loader.