java - 使用 SQLiteDatabase 为 AutoCompleteTextView 迁移到 CursorLoader 和 LoaderManager

Question

我有一个 AutoCompleteTextView , 它显示了从 SQLiteDatabase 中获取的建议下拉列表询问。目前它使用 SimpleCursorAdapter ，但是它有几个问题(我在这里有一个关于这个问题的单独问题:SimpleCursorAdapter issue - "java.lang.IllegalStateException: trying to requery an already closed cursor")。

尽管如此，我还是被建议往CursorLoader的方向看。和 LoaderManager ，并且我已经尝试过，但无法正常工作。如果有人指导/推荐/展示将我的代码迁移到 CursorLoader/LoaderManager 概念的正确方法，我将不胜感激。非常感谢任何形式的帮助!

mAdapter = new SimpleCursorAdapter(this,
                R.layout.dropdown_text,
                null,
                new String[]{CITY_COUNTRY_NAME},
                new int[]{R.id.text}, 0);
        mAutoCompleteTextView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            public void onItemClick(AdapterView<?> listView, View view, int position, long id) {
                Cursor cursor = (Cursor) listView.getItemAtPosition(position);
                cityCountryName = cursor.getString(cursor.getColumnIndexOrThrow(CITY_COUNTRY_NAME));
                mAutoCompleteTextView.setText(cityCountryName);
                JSONWeatherTask task = new JSONWeatherTask();
                task.execute(new String[]{cityCountryName});
            }
        });
        mAdapter.setFilterQueryProvider(new FilterQueryProvider() {
            public Cursor runQuery(CharSequence sequence) {
                String constraint = sequence.toString();
                String queryString = "SELECT " + ID + ", " + CITY_ID + ", " + CITY_COUNTRY_NAME + " FROM " + TABLE_1;
                constraint = constraint.trim() + "%";
                queryString += " WHERE " + CITY_COUNTRY_NAME + " LIKE ?";
                String params[] = {constraint};
                try {
                    Cursor cursor = database.rawQuery(queryString, params);
                    if (cursor != null) {
                        startManagingCursor(cursor);
                        cursor.moveToFirst();
                        return cursor;
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                }
                return null;
            }
        });
        mAutoCompleteTextView.setAdapter(mAdapter);

这是供引用的整个项目(如果需要，您可以在那里提出拉取请求):Open Weather App

Answer 1

不幸的是，在 SO 上没有人提出解决方案，但一位同事(他没有 SO 帐户)提出了一个包含迁移修复的拉取请求。它工作得很好，我决定也在这里发布正确的答案。

如果您对这些改进在实际代码中的表现感兴趣，欢迎您访问 GitHub 上的原始开源项目页面:Open Weather App

这是新的适配器:

mAdapter = new SimpleCursorAdapter(this,
                R.layout.dropdown_text,
                null,
                new String[]{CITY_COUNTRY_NAME},
                new int[]{R.id.text},0);
        mAdapter.setFilterQueryProvider(new FilterQueryProvider() {
            @Override
            public Cursor runQuery(CharSequence constraint) {
                if (constraint != null) {
                    if (constraint.length() >= 3 && !TextUtils.isEmpty(constraint)) {
                        Bundle bundle = new Bundle();
                        String query = charArrayUpperCaser(constraint);
                        bundle.putString(CITY_ARGS, query);
                        getLoaderManager().restartLoader(0, bundle, MainActivity.this).forceLoad();
                    }
                }
                return null;
            }
        });

这是 onCreateLoader() 回调:

@Override
public android.content.Loader<Cursor> onCreateLoader(int id, Bundle args) {
    String s = args.getString(CITY_ARGS);
    WeatherCursorLoader loader = null;
    if (s != null && !TextUtils.isEmpty(s)) {
        loader = new WeatherCursorLoader(this, database, s);
    }
    return loader;
}

自定义 CursorLoader 本身:

private static class WeatherCursorLoader extends CursorLoader {

    private SQLiteDatabase mSQLiteDatabase;
    private String mQuery;

    WeatherCursorLoader(Context context, SQLiteDatabase cDatabase, String s) {
        super(context);
        mSQLiteDatabase = cDatabase;
        mQuery = s + "%";
        Log.d(TAG, "WeatherCursorLoader: " + mQuery);
    }


    @Override
    public Cursor loadInBackground() {
        return mSQLiteDatabase.query(TABLE_1, mProjection,
                CITY_COUNTRY_NAME + " like ?", new String[] {mQuery},
                null, null, null, "50");
    }
}