[英]Need help with Database Access in Android
我在我的应用程序中使用sqlite数据库。 我在这样的服务类中有这个dbhelper类。
public class MushroomService {
private int downloadprogress;
private int databasesize;
private DataBaseHelper myDbHelper;
}
public MushroomService(Context context)
{
myDbHelper = new DataBaseHelper(context);
downloadprogress = 0;
}
服务类是我的应用程序类的成员,如下所示:
public class fungifieldguideapplication extends Application {
public MushroomService service = new MushroomService(this);
}
在我的活动类中,我访问此应用程序并将其保留为本地变量,如下所示:
public class Cat_Genus extends Activity {
fungifieldguideapplication appState;
ListView list_Genus;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.cat_genus);
appState = ((fungifieldguideapplication)this.getApplication());
Cursor cursor_genuslist = appState.service.GetGenusList(this);
startManagingCursor(cursor_genuslist);
}
}
我的服务电话如下所示:
public Cursor GetGenusList(Context context)
{
myDbHelper = new DataBaseHelper(context);
Cursor cursor;
try
{
myDbHelper.openDataBase();
SQLiteDatabase db = myDbHelper.myDataBase;
cursor = db.query(true, "Mushrooms", GenusListColumns, null, null, "Genus", null, "Genus ASC", null);
}
catch(SQLException sqle)
{
throw sqle;
}
return cursor;
}
我添加了这些替代,以消除我的内存泄漏。
@Override
public void onDestroy() {
list_Genus.setAdapter(null);
appState.service.CloseDB();
super.onDestroy();
}
@Override
public void onPause() {
appState.service.CloseDB();
super.onPause();
}
@Override
public void onResume() {
appState.service.OpenDB();
super.onResume();
}
但是我无法阻止我的内存泄漏。 有人可以帮我弄清楚如何摆脱这些内存泄漏吗? 这些泄漏属于以下类型:
07-27 17:38:44.613: ERROR/Database(26175): Leak found
07-27 17:38:44.613: ERROR/Database(26175): java.lang.IllegalStateException: /data/data/net.daleroy.fungifieldguide/databases/Mushrooms.db SQLiteDatabase created and never closed
07-27 17:38:44.613: ERROR/Database(26175): at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1695)
07-27 17:38:44.613: ERROR/Database(26175): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:739)
07-27 17:38:44.613: ERROR/Database(26175): at net.daleroy.fungifieldguide.data.DataBaseHelper.openDataBase(DataBaseHelper.java:79)
07-27 17:38:44.613: ERROR/Database(26175): at net.daleroy.fungifieldguide.services.MushroomService.GetSpeciesListByGenus(MushroomService.java:113)
07-27 17:38:44.613: ERROR/Database(26175): at net.daleroy.fungifieldguide.activities.Cat_Species.onCreate(Cat_Species.java:46)
07-27 17:38:44.613: ERROR/Database(26175): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-27 17:38:44.613: ERROR/Database(26175): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)
07-27 17:38:44.613: ERROR/Database(26175): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
07-27 17:38:44.613: ERROR/Database(26175): at android.app.ActivityThread.access$2200(ActivityThread.java:119)
07-27 17:38:44.613: ERROR/Database(26175): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
07-27 17:38:44.613: ERROR/Database(26175): at android.os.Handler.dispatchMessage(Handler.java:99)
07-27 17:38:44.613: ERROR/Database(26175): at android.os.Looper.loop(Looper.java:123)
07-27 17:38:44.613: ERROR/Database(26175): at android.app.ActivityThread.main(ActivityThread.java:4363)
07-27 17:38:44.613: ERROR/Database(26175): at java.lang.reflect.Method.invokeNative(Native Method)
07-27 17:38:44.613: ERROR/Database(26175): at java.lang.reflect.Method.invoke(Method.java:521)
07-27 17:38:44.613: ERROR/Database(26175): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
07-27 17:38:44.613: ERROR/Database(26175): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
07-27 17:38:44.613: ERROR/Database(26175): at dalvik.system.NativeStart.main(Native Method)
也许我是错的,但也许是因为您在与数据库进行交互之后没有关闭数据库。 每当我在android上进行数据库工作时,我都会在Try {} finally {}子句中包围交互,该子句会在finally上关闭连接。
例如
try{
//database stuff
} finally{
db.close
}
您的程序正在终止,因为您两次打开数据库
myDbHelper = new DataBaseHelper(context); // first here
Cursor cursor;
try
{
myDbHelper.openDataBase(); //then here
您可能可以删除“ myDbHelper.openDataBase();”
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.