sqlite + listview + new活动：从未在数据库上显式调用close（）吗？

Question

I have made an app that has 3 activities. In the fisrt activity(Import) i just import some values to a sqlite database.

This is my DatabaseHelper class:

   public class DatabaseHelper_bp extends SQLiteOpenHelper {

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

    // Database creation sql statement
    private static final String DATABASE_CREATE = "create table bp_import ( _id integer primary key, datetime text not null, systolic text not null, diastolic text not null, pulses text not null, notes text not null);";

    public DatabaseHelper_bp(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // Method is called during creation of the database
    @Override
    public void onCreate(SQLiteDatabase database) {
        database.execSQL(DATABASE_CREATE);
    }

    // Method is called during an upgrade of the database,
    @Override
    public void onUpgrade(SQLiteDatabase database, int oldVersion,
            int newVersion) {
        Log.w(DatabaseHelper_bp.class.getName(),
                "Upgrading database from version " + oldVersion + " to "
                        + newVersion + ", which will destroy all old data");
        database.execSQL("DROP TABLE IF EXISTS bp_import");
        onCreate(database);
    }
}

And my DAO class for my measures/values:

    public class BpDAO {

    private DatabaseHelper_bp dbHelper;

    private SQLiteDatabase database;
    /**
     * bp table related constants.
     */
    public final static String bp_TABLE = "bp_import";
    public final static String bp_ID = "_id";
    public final static String bp_DT = "datetime";
    public final static String bp_SYS = "systolic";
    public final static String bp_DIA = "diastolic";
    public final static String bp_PUL = "pulses";
    public final static String bp_NOT = "notes";

    /**
     * 
     * @param context
     */
    public BpDAO(Context context) {
        dbHelper = new DatabaseHelper_bp(context);
        database = dbHelper.getWritableDatabase();
    }

    /**
     * \ Creates a new blood pressure measure
     * 
     * @param datetime
     * @param systolic
     * @param diastolic
     * @param pulses
     * @param notes
     * @return
     */
    public long importBP(String datetime, String systolic, String diastolic,
            String pulses, String notes) {
        ContentValues values = new ContentValues();
        values.put(bp_DT, datetime);
        values.put(bp_SYS, systolic);
        values.put(bp_DIA, diastolic);
        values.put(bp_PUL, pulses);
        values.put(bp_NOT, notes);
        return database.insert(bp_TABLE, null, values);
    }

    public void close() {
           database.close();
    }

    /**
     * Fetch all bp
     * 
     * @return
     */
    public Cursor fetchAll_bp() {
        Cursor mCursor = database.query(true, bp_TABLE, new String[] { bp_SYS,
                bp_DIA, bp_DT, bp_ID }, null, null, null, null, null, null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;
    }
}

In the second activity(History) i have a List that is populated by the database,all ok

Here is the code of 2 Activity(history):

public class HistoryActivity extends ListActivity {

private BpDAO dao;

private SimpleCursorAdapter dbAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    dao = new BpDAO(this);
    Cursor bpList = dao.fetchAll_bp();
    String[] from = new String[] { BpDAO.bp_SYS, BpDAO.bp_DIA, BpDAO.bp_DT };
    int[] target = new int[] { R.id.bpSysHolder, R.id.bpDiaHolder,
            R.id.bpDtHolder };
    dbAdapter = new SimpleCursorAdapter(this, R.layout.history_bp, bpList,
            from, target);
    setListAdapter(dbAdapter);
}

@Override
public void onListItemClick(ListView l, View view, int position, long id) {
    // TODO Auto-generated method stub
    super.onListItemClick(l, view, position, id);
    Log.d("BPT", "Selected bp id =" + id);
            // log says that i have selected an item with id : 11 

    Cursor selectedBpDetails = (Cursor) l.getItemAtPosition(position);

    String bp_DT = selectedBpDetails.getString(selectedBpDetails
            .getColumnIndex(BpDAO.bp_DT));
    String bp_SYS = selectedBpDetails.getString(selectedBpDetails
            .getColumnIndex(BpDAO.bp_SYS));
    String bp_DIA = selectedBpDetails.getString(selectedBpDetails
            .getColumnIndex(BpDAO.bp_DIA));
    String bp_PUL = selectedBpDetails.getString(selectedBpDetails
            .getColumnIndex(BpDAO.bp_PUL));
    String bp_NOT = selectedBpDetails.getString(selectedBpDetails
            .getColumnIndex(BpDAO.bp_NOT));

    Log.d("BPT", "Selected bp details = { date=" + bp_DT + ", systolic="
            + bp_SYS + ", diastolic=" + bp_DIA + ", pulses=" + bp_PUL
            + ", notes=" + bp_NOT + " }");

    Intent intent = new Intent(HistoryActivity.this, FromHistory.class);
    intent.putExtra("bp_SYS", bp_SYS);
    intent.putExtra("bp_DIA", bp_DIA);
    intent.putExtra("bp_DT", bp_DT);
    intent.putExtra("bp_PUL", bp_PUL);
    intent.putExtra("bp_NOT", bp_NOT);
    startActivity(intent);
}

}

When i click on a list item i start a new activity that i show all the infos of the measure from the database.

But i have in logcat:

1.close() was never explicitly called on database
2.android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the cursor or database object that was opened here
3.E/System(561): java.lang.IllegalStateException: Don't have database lock!

I have seen some other questions but didn't manage to find how to close it for my situation.

Answer 1

When you are done with cursor you need to close()

Example:

selectedBpDetails.close();

Answer 2

Either you close the cursor directly after the fetching of your data by calling close() on it, or you can override the onDestroy method for your activity and then in the implementation of this method you close the cursor(s) that you have opened.

public class HistoryActivity extends ListActivity {
    // ...
    Cursor bpList;
    // ...

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // ...
        bpList = dao.fetchAll_bp();
        // ...
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        bpList.close();
    }

    @Override
    public void onListItemClick(ListView l, View view, int position, long id) {
        // ...
        Cursor selectedBpDetails = (Cursor) l.getItemAtPosition(position);
        // ...
        selectedBpDetails.close();
    }

    // ...
}

Answer 3

(You should close your Cursors when you are done with them as the others have pointed out, but...)
The error is telling you that you need to close your SQLiteDatabase. Add this method to your BpDAO class:

public void close() {
    database.close();
}

And whenever you create a new BpDAO object in any Activity you need to call close() , you can do this as soon as you are done or in onDestroy() :

@Override
protected void onDestroy() {
    super.onDestroy();
    dao.close();
}