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To perform a query, create the , set up its query, and pass it to the loader framework. From then on, the framework manages everything. It runs the query on a background thread, returns the results to the foreground, and watches for changes to the data associated with the query. http://blog.csdn.net/sergeycao

Pass a to the loader framework in your implementation of. The loader framework calls this method when youcreate a loader by calling . You can create a anywhere, but the preferred way is to create it in, because this defers creation until the object is actually needed.

Notice that will only if the doesn't already exist; otherwise, it re-uses the existing. The loader framework tracks instance using theid value passed to .

Define and Launch the Query

To create a and define its query at the same time, call the constructor. Thecontext and uri arguments are required, but the others are optional. To use the default value for an optional argument, pass innull. The runs the query against the identified by uri, just as if you had called with the same arguments.

For example:

public Loader
   
     onCreateLoader(int loaderID, Bundle bundle){    /*     * Takes action based on the ID of the Loader that's being created     */    switch (loaderID) {        case URL_LOADER:            /*             * Return a new CursorLoader             */            return new CursorLoader(                this,                           // Context                DataProviderContract.IMAGE_URI, // Provider's content URI                PROJECTION,                     // Columns to return                null,                           // Return all rows                null,                           // No search arguments                null);                          // Default search order        default:            // An invalid id was passed in            return null;    }}