如何从 asyncTask 使用 ManagedQuery
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26-10-2019 - |
题
我正在尝试制作一个Android音乐播放器。为了让事情变得更容易,我决定将手机上的艺术家复制到本地数据库,然后对本地数据进行一些自定义查询。我知道如何将托管查询复制到数据库,但无法在 AsyncTask 上执行此操作,因为托管查询只能由 Activity 类访问。我试图在应用程序启动时在我的应用程序类中进行此调用。有谁知道在 AsyncTask 内部调用 ManagedQuery 的方法吗?我真的不想在我的第一个被调用的活动中执行此操作,因为它会显着降低我的加载速度。
这就是我想做的,尽管我知道这不会编译......
public class AplayApplication extends Application implements
OnSharedPreferenceChangeListener {
private static final String TAG = AplayApplication.class.getSimpleName();
private SharedPreferences prefs;
protected MusicData musicData;
protected PlayerHandler mMediaPlayer;
protected boolean isPlaying;
private boolean prefUseDefaultShuffle;
private boolean prefUseSmartShuffle;
private int prefArtistSkipDuration;
private int prefUnheardArtistPct;
protected TabHost tabHost;
protected Song currentSong;
protected int currentSongPosition;
private static final String PREFERENCE_KEY = "seekBarPreference";
protected boolean hasLoadedSongs;
private static AplayApplication aplayapp;
@Override
public void onCreate() {
super.onCreate();
prefs = PreferenceManager.getDefaultSharedPreferences(this);
prefs.registerOnSharedPreferenceChangeListener(this);
setPrefs();
Log.i(TAG, "Application started");
mMediaPlayer = new PlayerHandler();
// code in question below this line
musicData = new MusicData(this); // this creates instance of database helper to access db
// will call execute on async task here.
// new getArtist().execute();
}
private class getArtists extends AsyncTask<Void, Void, Boolean>{
Cursor artCursor;
@Override
protected Boolean doInBackground(Void... params) {
String[] proj = {
MediaStore.Audio.Artists._ID,MediaStore.Audio.Artists.ARTIST,
};
artCursor = managedQuery(
MediaStore.Audio.Artists.EXTERNAL_CONTENT_URI, proj, null,
null, MediaStore.Audio.Artists.ARTIST + " ASC");
ContentValues values = new ContentValues();
artCursor.moveToPosition(-1);
while (artCursor.moveToNext()) {
values.put(
MusicData.S_DISPLAY,
newMusicCursor.getString(newMusicCursor
.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME)));
values.put(MusicData.S_ARTIST, newMusicCursor
.getString(newMusicCursor
.getColumnIndex(MediaStore.Audio.Media.ARTIST)));
values.put(MusicData.S_FILE, newMusicCursor
.getString(newMusicCursor
.getColumnIndex(MediaStore.Audio.Media.DATA)));
this.musicData.insertMastSong(values);
}
return true;
}
//// code continues.....
解决方案
正如 Sparky 所说,您可以使用 CursorLoader 而不是 ManagedQuery。
如果您正在开发 sdk 8,则需要添加 支持包 到你的项目。
为了避免延迟您的应用程序启动,也许您可以使用 服务.
这是一个使用服务的小例子,从 url 获取数据,然后将其插入数据库
public class GetArticlesService extends IntentService {
private static final String TAG = "GetArticlesService";
public GetArticlesService() {
super("GetdArticlesService");
}
/* (non-Javadoc)
* @see android.app.IntentService#onHandleIntent(android.content.Intent)
*/
@Override
protected void onHandleIntent(Intent intent) {
String url = "http://example.com/artists.json";
String response = null;
try {
response = Utils.httpPost(getApplicationContext(), url + "/api/GetArticles", null);
} catch (HttpHostConnectException e) {
e.printStackTrace();
}
if(!TextUtils.isEmpty(response)){
try {
JSONArray list = new JSONArray(response);
if(list.length() > 0){
ContentValues toInsert = new ContentValues[];
JSONObject art = null;
int cant = list.length();
for(int i = 0;i< cant; i++){
toInsert.clear();
art = list.getJSONObject(i);
toInsert = new ContentValues();
toInsert.put(Articles._ID, art.getInt("id"));
toInsert.put(Articles.DESCRIPTION, art.getString("description"));
toInsert.put(Articles.BARCODE, art.getString("barcode"));
toInsert.put(Articles.RUBRO, art.getString("rubro"));
toInsert.put(Articles.CLAVE, art.getString("clave"));
getContentResolver().inert(Articles.CONTENT_URI, toInsert);
}
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
其他提示
托纳德克里 被弃用。改用Cursorloader。
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