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How to properly close a cursor in android

由 梦想与她 提交于 2019-12-04 11:45:18

问题


I have this database using sqlite, and I'm having problem with closing the cursor its saying that Application did not close the cursor or database object that was opened here here's the logcat

10-18 08:40:56.354: E/Cursor(331): android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the cursor or database object that was opened here
10-18 08:40:56.354: E/Cursor(331):  at android.database.sqlite.SQLiteCursor.<init>(SQLiteCursor.java:210)
10-18 08:40:56.354: E/Cursor(331):  at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:53)
10-18 08:40:56.354: E/Cursor(331):  at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1345)
10-18 08:40:56.354: E/Cursor(331):  at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1229)
10-18 08:40:56.354: E/Cursor(331):  at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1184)
10-18 08:40:56.354: E/Cursor(331):  at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1264)
10-18 08:40:56.354: E/Cursor(331):  at standard.internet.marketing.mymovingfriend.SQLHandler.checkMove(SQLHandler.java:1094)
10-18 08:40:56.354: E/Cursor(331):  at standard.internet.marketing.mymovingfriend.ListMovingNames$3.onKey(ListMovingNames.java:98)
10-18 08:40:56.354: E/Cursor(331):  at android.view.View.dispatchKeyEvent(View.java:3735)
10-18 08:40:56.354: E/Cursor(331):  at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:788)
10-18 08:40:56.354: E/Cursor(331):  at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:788)
10-18 08:40:56.354: E/Cursor(331):  at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:788)
10-18 08:40:56.354: E/Cursor(331):  at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:788)
10-18 08:40:56.354: E/Cursor(331):  at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:1667)
10-18 08:40:56.354: E/Cursor(331):  at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1102)
10-18 08:40:56.354: E/Cursor(331):  at android.app.Activity.dispatchKeyEvent(Activity.java:2063)
10-18 08:40:56.354: E/Cursor(331):  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1643)
10-18 08:40:56.354: E/Cursor(331):  at android.view.ViewRoot.deliverKeyEventToViewHierarchy(ViewRoot.java:2471)
10-18 08:40:56.354: E/Cursor(331):  at android.view.ViewRoot.handleFinishedEvent(ViewRoot.java:2441)
10-18 08:40:56.354: E/Cursor(331):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1735)
10-18 08:40:56.354: E/Cursor(331):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-18 08:40:56.354: E/Cursor(331):  at android.os.Looper.loop(Looper.java:123)
10-18 08:40:56.354: E/Cursor(331):  at android.app.ActivityThread.main(ActivityThread.java:4627)
10-18 08:40:56.354: E/Cursor(331):  at java.lang.reflect.Method.invokeNative(Native Method)
10-18 08:40:56.354: E/Cursor(331):  at java.lang.reflect.Method.invoke(Method.java:521)
10-18 08:40:56.354: E/Cursor(331):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-18 08:40:56.354: E/Cursor(331):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-18 08:40:56.354: E/Cursor(331):  at dalvik.system.NativeStart.main(Native Method)

this issue's been bugging me for 3 days.

here some relevant code:

public class SQLHandler {

    public static final String KEY_MOVENAME = "movename";
    public static final String KEY_ID1 = "_id";
    public static final String KEY_ID5 = "_id";
    public static final String KEY_MOVEDATE = "movedate";
    public static final String KEY_TOTALMOVEWEIGHT = "totalmoveweight";
    public static final String KEY_TOTALITEM = "totalitem";

    private static final String DATABASE_NAME = "mymovingfriend";
    private static final int DATABASE_VERSION = 1;

    public static final String KEY_LISTITEMNAME = "listitemname";
    public static final String KEY_LISTITEMWEIGHT = "listitemweight";
    public static final String KEY_LISTITEMROOM = "listitemroom";

    private static final String DATABASE_TABLE1 = "movingname";
    private static final String DATABASE_TABLE5 = "listitem";

    public static final String CREATE_TABLE_1 = "CREATE TABLE " + DATABASE_TABLE1 + " (" + 
            KEY_ID1 + " INTEGER PRIMARY KEY AUTOINCREMENT," + 
            KEY_MOVEDATE + " TEXT NOT NULL, " + 
            KEY_TOTALMOVEWEIGHT + " TEXT NOT NULL, " + 
            KEY_TOTALITEM + " INTEGER NOT NULL, " +
            KEY_MOVENAME + " TEXT NOT NULL);";

    public static final String CREATE_TABLE_2 = "CREATE TABLE " + DATABASE_TABLE2 + " (" + 
            KEY_ID2 + " INTEGER PRIMARY KEY AUTOINCREMENT," + 
            KEY_ROOMMOVEHOLDER + " TEXT NOT NULL, " + 
            KEY_ROOMWEIGHT + " TEXT NOT NULL, " + 
            KEY_ROOM + " TEXT NOT NULL);";

    public static final String CREATE_TABLE_5 = "CREATE TABLE " + DATABASE_TABLE5 + " (" + 
            KEY_ID5 + " INTEGER PRIMARY KEY AUTOINCREMENT," + 
            KEY_LISTITEMNAME + " TEXT NOT NULL, " + 
            KEY_LISTITEMWEIGHT + " TEXT NOT NULL, " +
            KEY_LISTITEMROOM + " TEXT NOT NULL);";

    private DbHelper ourHelper;
    private final Context ourContext;
    private SQLiteDatabase ourDatabase;

    private static class DbHelper extends SQLiteOpenHelper{

        public DbHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
            // TODO Auto-generated constructor stub
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            // TODO Auto-generated method stub
            db.execSQL(CREATE_TABLE_1);
            db.execSQL(CREATE_TABLE_2);
            db.execSQL(CREATE_TABLE_3);
            db.execSQL(CREATE_TABLE_4);
            db.execSQL(CREATE_TABLE_5);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldversion, int newversion) {
            // TODO Auto-generated method stub
            db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE1);
            db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE2);
            db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE3);
            db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE4);
            db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE5);
            onCreate(db);
        }
    }

    public SQLHandler(Context c){
        ourContext = c;
    }

    public SQLHandler open() throws SQLException{
        ourHelper = new DbHelper(ourContext);
        ourDatabase = ourHelper.getWritableDatabase();
        return this;
    }

    public void close(){
        ourDatabase.close();
        ourHelper.close();
    }

    public long createMove(String smovename){
        ContentValues cv = new ContentValues();
        cv.put(KEY_MOVENAME, smovename);
        cv.put(KEY_MOVEDATE, "Not yet set");
        cv.put(KEY_TOTALMOVEWEIGHT, "0");
        cv.put(KEY_TOTALITEM, 0);
        return ourDatabase.insert(DATABASE_TABLE1, null, cv);
    }

    public void createList(){

        String[] sroom = new String[]{"Kitchen", "Bedroom", "Dinning Room"};
        String[] sitem = new String[]{"Dishwasher", "Bed", "Table"};
        String[] sweight = new String[]{"40", "25", "15"};

        for (int i = 0; i < sroom.length; i++) {
            cv.put(KEY_LISTITEMROOM, sroom[i]);
            cv.put(KEY_LISTITEMNAME, sitem[i]);
            cv.put(KEY_LISTITEMWEIGHT, sweight[i]);
            ourDatabase.insert(DATABASE_TABLE5, null, cv);
        }
    }

    public void setMoveDate(String smovedate, String smovename){
        ContentValues cv = new ContentValues();
        cv.put(KEY_MOVEDATE, smovedate);
        ourDatabase.update(DATABASE_TABLE1, cv, KEY_MOVENAME + "='" + smovename + "'", null);
    }

    public void setMoveWeight(String smoveweight, String smovename){
        ContentValues cv = new ContentValues();
        cv.put(KEY_TOTALMOVEWEIGHT, smoveweight);
        ourDatabase.update(DATABASE_TABLE1, cv, KEY_MOVENAME + "='" + smovename + "'", null);
    }

    public void setTotalItem(String smovename, int imoveitem){
        ContentValues cv = new ContentValues();
        cv.put(KEY_TOTALITEM, imoveitem);
        ourDatabase.update(DATABASE_TABLE1, cv, KEY_MOVENAME + "='" + smovename + "'", null);
    }

    public void renameRoom(String movename, String roomname, String currentroom){
        ContentValues cv = new ContentValues();
        cv.put(KEY_ROOM, roomname);
        ourDatabase.update(DATABASE_TABLE2, cv, KEY_ROOMMOVEHOLDER + "='" + movename + "'" + " AND " + KEY_ROOM + "='" + currentroom + "'", null);
    }

    public void setRoomWeight(String sroomweight, String smovename, String sroomname){
        ContentValues cv = new ContentValues();
        cv.put(KEY_ROOMWEIGHT, sroomweight);
        ourDatabase.update(DATABASE_TABLE2, cv, KEY_ROOMMOVEHOLDER + "='" + smovename + "'" + " AND " + KEY_ROOM + "='" + sroomname + "'", null);
    }

    public long addRooms(String sroommoveholder, String sroom){
        ContentValues cv = new ContentValues();
        cv.put(KEY_ROOMMOVEHOLDER, sroommoveholder);
        cv.put(KEY_ROOM, sroom);
        cv.put(KEY_ROOMWEIGHT, "0");
        return ourDatabase.insert(DATABASE_TABLE2, null, cv);
    }

    public long addNewItems(String sitemmoveholder, String sroomholder, String sitemname, String sitemvalue, String sitemweight){
        ContentValues cv = new ContentValues();
        cv.put(KEY_ITEMMOVEHOLDER, sitemmoveholder);
        cv.put(KEY_ROOMHOLDER, sroomholder);
        cv.put(KEY_ITEMNAME, sitemname);
        cv.put(KEY_ITEMVALUE, sitemvalue);
        cv.put(KEY_ITEMWEIGHT, sitemweight);
        return ourDatabase.insert(DATABASE_TABLE3, null, cv);
    }

    public void updateItems(String sitemmoveholder, String sroomholder, String sitemname, String sitemvalue, String sitemweight){
        ContentValues cv = new ContentValues();
        cv.put(KEY_ITEMVALUE, sitemvalue);
        cv.put(KEY_ITEMWEIGHT, sitemweight);
        ourDatabase.update(DATABASE_TABLE3, cv, KEY_ITEMMOVEHOLDER + "='" + sitemmoveholder + "'" + " AND " + 
                KEY_ROOMHOLDER + "='" + sroomholder + "'" + " AND " + KEY_ITEMNAME + "='" + sitemname + "'", null);
    }

    public Cursor getMove(){
        String[] columns = new String[]{KEY_ID1, KEY_MOVENAME};

        Cursor c = null;
        try {
            c = ourDatabase.query(DATABASE_TABLE1, columns, null, null, null, null, null);
        } catch (Exception e) {
            c.close();
        }
        return c;
    }

    public String getTotalWeight(String m) throws SQLException{
        String[] columns = new String[]{KEY_ID1, KEY_MOVENAME, KEY_MOVEDATE, KEY_TOTALMOVEWEIGHT};

        Cursor c = null;
        try {
            c = ourDatabase.query(DATABASE_TABLE1, columns, KEY_MOVENAME + "= '" + m + "'", null, null, null, null);
            if (c != null) {
                c.moveToFirst();
                String totalWeight = c.getString(3);
                return totalWeight;
            }
        } catch (Exception e) {
            c.close();
        }
        return null;

    }

    public String getTotalWeightLBS(String m) throws SQLException{
        String[] columns = new String[]{KEY_ID1, KEY_MOVENAME, KEY_MOVEDATE, KEY_TOTALMOVEWEIGHT};

        Cursor c = null;
        try {
            c = ourDatabase.query(DATABASE_TABLE1, columns, KEY_MOVENAME + "= '" + m + "'", null, null, null, null);
            if (c != null) {
                c.moveToFirst();
                int x = Integer.parseInt(c.getString(3)) * 7;
                String totalWeight = "" + x + " lbs";
                return totalWeight;
            }
        } catch (Exception e) {
            c.close();
        }
        return null;

    }

    public String getDateMove(String md){
        String[] columns = new String[]{KEY_ID1, KEY_MOVENAME, KEY_MOVEDATE};

        Cursor c = null;try {
            c = ourDatabase.query(DATABASE_TABLE1, columns, KEY_MOVENAME + "= '" + md + "'", null, null, null, null);

            if (c != null) {
                c.moveToFirst();
                String moveDate = c.getString(2);
                return moveDate;
            }
        } catch (Exception e) {
            c.close();
        }
        return null;
    }

    public ArrayList<String> loadRooms(String mn) throws SQLException{
        String[] columns = new String[]{KEY_ID2, KEY_ROOMMOVEHOLDER, KEY_ROOM};

        ArrayList<String> array = new ArrayList<String>();

        Cursor c = null;
        try {
            c = ourDatabase.query(DATABASE_TABLE2, columns,KEY_ROOMMOVEHOLDER + "='" + mn + "'", 
                    null, null, null, null);
            int iroom = c.getColumnIndex(KEY_ROOM);

            for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
                array.add(c.getString(iroom));
            }
        } catch (Exception e) {
            c.close();
        }
        return array;
    }

    public void deleteMove(String m) throws SQLException{
        ourDatabase.delete(DATABASE_TABLE1, KEY_MOVENAME + "='" + m + "'", null);
        ourDatabase.delete(DATABASE_TABLE2, KEY_ROOMMOVEHOLDER + "='" + m + "'", null);
        ourDatabase.delete(DATABASE_TABLE3, KEY_ITEMMOVEHOLDER + "='" + m + "'", null);
        ourDatabase.delete(DATABASE_TABLE4, KEY_TODOMOVE + "='" + m + "'", null);
    }

    public ArrayList<String> getitems(){
        String[] columns = new String[]{KEY_ID5, KEY_ITEMNAME};
        ArrayList<String> items;
        items = new ArrayList<String>();

        Cursor c = null;
        try {
            c = ourDatabase.query(DATABASE_TABLE5, columns, null, null, null, null, null);

            for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
                items.add(c.getString(1));
            }
        } catch (Exception e) {
            c.close();
        }

        return items;
    }

    public ArrayList<String> getitemweight(){
        String[] columns = new String[]{KEY_ID5, KEY_ITEMWEIGHT};
        ArrayList<String> items = new ArrayList<String>();

        Cursor c = null;
        try {
            c = ourDatabase.query(DATABASE_TABLE5, columns, null, null, null, null, null);
            for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
                items.add(c.getString(1));
            }
        } catch (Exception e) {
            c.close();
        }

        return items;
    }

    public ArrayList<String> getitemclass(){
        String[] columns = new String[]{KEY_ID5, KEY_LISTITEMROOM};
        ArrayList<String> items = new ArrayList<String>();

        Cursor c = null;
        try {
            c = ourDatabase.query(DATABASE_TABLE5, columns, null, null, null, null, null);

            for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
                items.add(c.getString(1));
            }
        } catch (Exception e) {
            c.close();
        }

        return items;
    }

}

回答1:


You're not closing cursor in getDateMove, getTotalWeightLBS, loadRooms,...

Everywhere where cursor is not needed anymore close it. In those methods use try-finally, it will guarantee to execute code in finally block even when thrown exception occur.

Change code in your methods from this:

try{
  // get data from cursor
} catch (Exception e) {
    c.close();
}

to this:

try {
   // get data from cursor
} catch (Exception e) {
   // exception handling
} finally {
   if(c != null){
       c.close();
   }
}



回答2:


Closing cursor in finally will guarantee it will be closed;

public void myfunc() {

    Cursor c = null;

    try {

      c = ... // Open cursor here
      return .... // maybe return something

    } finally {
       if(c != null) { c.close(); }
    } 
}



回答3:


If an element is implementing AutoCloseable (like the Cursor.class does), I would recommend to do a try-with-resources, like described here. If you use Retrolambda it has the try-with-resources backported.

So your code:

Cursor cursor = db.query("tableName", columns, null, null, null, null, null);
try {
    if (cursor.moveToFirst()) return cursor.getString(3);
    else return null;
} finally {
   cursor.close();
}

would simply turn into:

try (Cursor cursor = db.query("tableName", columns, null, null, null, null, null)) {
    if (cursor.moveToFirst()) return cursor.getString(3);
    else return null;
}



回答4:


close your database in onStop() or onDestroy() method of your activity!




回答5:


You are trying to close cursor inside catch block using 

catch (Exception e) {
            c.close();
        }

But if you did not get any exception then how it will close

so put it inside the finally block

finally {
            c.close();
        }



回答6:


Try this,

In onStop() or onDestroy()

Check whether the cursor is null

@Override
public void onStop(){
 Cursor cursor;

 if(cursor!=null){
  cursor.close();}
 }

If not then close the cursor.

EDIT

To Close the database object

DatabaseObject db;
if(db!=null)
{ db.close();}

Hope it helps.




回答7:


If you use Kotlin (also available in Java in a bit different way), and Android 4.1 and above, you can use this:

    cursor?.use { 
       //..do stuff
    }

As an example, you can check here.

If you want to use Java, do something like:

        try (Cursor cursor = ...) {
            // do something
        }


来源：https://stackoverflow.com/questions/12950725/how-to-properly-close-a-cursor-in-android

标签
android
android-sqlite
android-cursor
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