迁移到CursorLoader&带有SQLiteDatabase的AutoCompleteTextView的LoaderManager [英] Migrating to CursorLoader & LoaderManager for AutoCompleteTextView with SQLiteDatabase

问题描述

我有一个 AutoCompleteTextView ，它显示了从 SQLiteDatabase 查询中获取的建议的下拉列表。目前它使用 SimpleCursorAdapter ，但是它有几个问题（我对此有单独的疑问： SimpleCursorAdapter问题- java.lang.IllegalStateException：尝试重新查询已经关闭的游标。）。

I have an AutoCompleteTextView, which shows dropdown list of suggestions taken from a SQLiteDatabase query. At the moment it uses SimpleCursorAdapter, however there are several problems with it (I have a separate question about the issue here: SimpleCursorAdapter issue - "java.lang.IllegalStateException: trying to requery an already closed cursor").

不过，我还是建议我朝 CursorLoader 和 LoaderManager code>，并且我已经尝试过了，但是无法正常运行。如果有人能指导/推荐/展示将我的代码正确移植到CursorLoader / LoaderManager概念的正确方法，我将不胜感激。任何帮助都非常感谢！

Nevertheless, I was advised to look in the direction of CursorLoader and LoaderManager, and I've tried it, yet couldn't make it work. I'd be grateful if someone would guide/recommend/show the right way of migrating my code below to CursorLoader/LoaderManager concept. Any kind of help very appreciated!

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);

这里是供参考的整个项目（您可以在此处提出拉取请求） ：开放天气应用

Here is the whole project for the reference (you can make a pull request there, if you wish): Open Weather App

推荐答案

很遗憾，此处没有人提出解决方案，但是一位同事（他没有SO帐户）提出了带有迁移修复程序的请求请求。

Unfortunately, here on SO nobody came up with a solution, yet a colleague (he doesn't have an SO account) made a pull request with the migration fixes. It works perfectly, and I decided to post the correct answer here as well.

如果您对这些改进在实际代码中的外观感兴趣，欢迎您。访问GitHub上原始的开源项目页面： Open Weather App

If you're interested in how these improvements look inside the actual code, you're welcome to visit the original open source project page on GitHub: 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");
    }
} 

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