nullnullDefining and Launching the Query 定义和启动查询

PS:今天上午，非常郁闷，有很多简单基础的问题搞得我有些迷茫，哎，代码几天不写就忘。目前又不当COO，还是得用心记代码哦！

    To perform a query, create the CursorLoader, 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 CursorLoader to the loader framework in your implementation ofonCreateLoader(). The loader framework calls this method when youcreate a loader by calling initLoader(). You can create aCursorLoader anywhere, but the preferred way is to create it inonCreateLoader(), because this defers creation until the object is actually needed.

    Notice that initLoader() will only onCreateLoader() if theCursorLoader doesn't already exist; otherwise, it re-uses the existingCursorLoader. The loader framework tracks CursorLoader instance using theid value passed to initLoader().

    

Define and Launch the Query

    每日一道理
微笑，是春天里的一丝新绿，是秋日里的一缕阳光，是骄阳下的一片浓荫，是冬雪中的一株梅红……微笑着去面对吧，你会感到人生是那样的温馨与甜蜜！

    To create a CursorLoader and define its query at the same time, call the constructorCursorLoader(context, uri, projection, selection, selectionArgs, sortOrder). Thecontext and uri arguments are required, but the others are optional. To use the default value for an optional argument, pass innull. The CursorLoader runs the query against theContentProvider identified by uri, just as if you had calledContentResolver.query() with the same arguments.

    For example:

public Loader<Cursor> 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;
    }
}

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