无法从数据库中的cursor方法检索数据到应用程序主页中的simplecursor适配器。我尝试了我的水平最好，我做了堆栈溢出和其他网站的所有研究，但没有能够得到预期的解决方案
//这是我为存储城市数据而创建的表格
public static final String City="Citi";
public static final String rowid="_id";
private static final int DATABASE_VERSION=8;
SQLiteDatabase db;
private Context context;
//Creating Cities Database table
public static final String CreateCities="CREATE TABLE IF NOT EXISTS "+Citietable+" ("+City+" VARCHAR(255),"+rowid+" INTEGER PRIMARY KEY)";
//这是我用于从数据库中检索数据到SimpleCursor适配器
的游标方法 public Cursor CitiesData(){
SQLiteDatabase db=foodCourt_loginData.getReadableDatabase(); //calling database to get writable data
Cursor citi=db.query(FoodCourt_LoginData.Citietable,new String[]{FoodCourt_LoginData.City,FoodCourt_LoginData.rowid},null,null,null,null,null);
if(citi.moveToNext()){
return citi;
}else {
Message.message(context, "there is nothing to show");
}
return citi;
}
//这是我的主页代码，包含我的simplecursor适配器
//Initializing database
foodCourt_userLoginDatabase=new FoodCourt_UserLoginDatabase(rootView.getContext());
//这是将城市数据库从SQLite数据库转换为Simplecursor适配器
的代码Cursor cursor=foodCourt_userLoginDatabase.CitiesData();
String[] cities = new String[]{FoodCourt_UserLoginDatabase.FoodCourt_LoginData.City};
int[] to=new int[]{R.id.citispinner};
mycursoradapter=new SimpleCursorAdapter(rootView.getContext().getApplicationContext(),android.R.layout.simple_spinner_item,cursor,cities,to,0);
mycursoradapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
Citieslist.setAdapter(mycursoradapter);
//这是我得到的错误日志，我不知道为什么它声明'_id'不可用，但我创建了_id列，其名称为rowid ..
01-13 15:44:02.083 23855-23855/com.example.dell.foodcourt E/SQLiteLog: (1) no such column: _id
01-13 15:44:02.098 1380-1422/? W/audio_hw_generic: Hardware backing HAL too slow, could only write 0 of 720 frames
01-13 15:44:02.107 23855-23855/com.example.dell.foodcourt D/AndroidRuntime: Shutting down VM
01-13 15:44:02.109 1380-1422/? W/audio_hw_generic: Hardware backing HAL too slow, could only write 0 of 720 frames
01-13 15:44:02.113 23855-23855/com.example.dell.foodcourt E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.dell.foodcourt, PID: 23855
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.dell.foodcourt/com.example.dell.foodcourt.Userhome}: android.database.sqlite.SQLiteException: no such column: _id (code 1): , while compiling: SELECT Citi, _id FROM CityTable
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: android.database.sqlite.SQLiteException: no such column: _id (code 1): , while compiling: SELECT Citi, _id FROM CityTable
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1318)
at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1165)
at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1036)
at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1204)
at com.example.dell.foodcourt.FoodCourt_UserLoginDatabase.CitiesData(FoodCourt_UserLoginDatabase.java:55)
at com.example.dell.foodcourt.HomeFragment.onCreateView(HomeFragment.java:47)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2239)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1332)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1574)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1641)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:794)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2415)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2200)
at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2153)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2063)
at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:388)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:554)
at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:177)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1248)
at android.app.Activity.performStart(Activity.java:6696)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2628)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)