What is AsyncQueryHandler?

Class to use when executing queries asynchronously as heavy queries may be blocked on the UI thread
Query execution with AsyncQueryHandler is performed on HandlerThread included in AsyncQueryHandler.

Motivation

There are few pages to refer to
When I thought about using it, I got a little stuck.
There was a case where the data was not inserted properly because the timing to return the value of asynchronous processing was shifted.

Main methods

Method name	Overview
startDelete(int token, Object cookie, Uri uri, String selection, String[] selectionArgs)	Delete asynchronously.
startInsert(int token, Object cookie, Uri uri, ContentValues initialValues)	Insert asynchronously.
startQuery(int token, Object cookie, Uri uri, String[] projection, String selection, String[] selectionArgs, String orderBy)	Query asynchronously.
startUpdate(int token, Object cookie, Uri uri, ContentValues values, String selection, String[] selectionArgs)	Update asynchronously.
onDeleteComplete(int token, Object cookie, int result)	Called when the startDelete method completes
onInsertComplete(int token, Object cookie, Uri uri)	Called when the startInsert method completes
onQueryComplete(int token, Object cookie, Cursor cursor)	Called when the startQuery method completes
onUpdateComplete(int token, Object cookie, int result)	Called when the startUpdate method completes

The token of the first argument is the value used to identify the process. The second argument cookie is the object to pass when completed The third argument of the method called at completion is the return value of each corresponding method

Premise

Create DB with ContentProvider etc.

program

Class that inherits AsyncQueryHandler

class CustomAsyncQueryHandler extends AsyncQueryHandler {

    private static final String[] PROJECTION = new String[]{UserColumns.ID, UserColumns.NAME, UserColumns.EMAIL};

    private final AsyncQueryHandlerActivity activity;

    CustomAsyncQueryHandler(ContentResolver cr, AsyncQueryHandlerActivity activity) {
        super(cr);
        this.activity = activity;
    }

    @Override
    protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
        super.onQueryComplete(token, cookie, cursor);
        SimpleCursorAdapter adapter = new SimpleCursorAdapter(
                activity,
                android.R.layout.simple_list_item_2,
                cursor,
                PROJECTION,
                new int[]{android.R.id.text1, android.R.id.text2});

        activity.setListAdapter(adapter);
    }

    void insert(String name, String address) {
        ContentValues value = new ContentValues();
        value.put(UserColumns.NAME, name);
        value.put(UserColumns.EMAIL, address);
        startInsert(0, null, UserColumns.CONTENT_URI, value);
    }

    void delete() {
        startDelete(0, null, UserColumns.CONTENT_URI, null, null);
    }

    void findAll() {
        startQuery(0, null, UserColumns.CONTENT_URI, PROJECTION, null, null, null);
    }

    void findById(String where, String[] value) {
        startQuery(0, null, UserColumns.CONTENT_URI, PROJECTION, where, value, null);
    }
}

Activity

public class HogeHogeActivity extends ListActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        CustomAsyncQueryHandler asyncQueryHandler = new CustomAsyncQueryHandler(getContentResolver(), this);

        // Delete
        asyncQueryHandler.delete();

        // Insert
        for (int i = 1; i <= 50; i++) {
            asyncQueryHandler.insert(UserColumns.NAME + i, UserColumns.EMAIL + i);
        }

        // Select
        asyncQueryHandler.findAll();

    }

}

Perhaps there is a better way, but this was the solution at the time.

reference

https://developer.android.com/reference/android/content/AsyncQueryHandler.html http://shop.oreilly.com/product/0636920029397.do

To make heavy queries asynchronously