Question

我查看了有关此错误的stackoverflow上的很多帖子，看起来修复程序正在重写onDestroy（）方法并关闭数据库。但这似乎不适用于我的情况。当Eclipse最初在我的手机上运行应用程序时，我实际上没有收到任何错误，但当我关闭应用程序并在我的手机上重新启动时 - 就在close() was never explicitly called on database显示在LogCat中时。我正在调用我的资产文件夹中的外部数据库，不确定它是否与它有任何关系。

将对DBAdapter：

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

public class DBAdapter extends SQLiteOpenHelper {

public static final String KEY_ROWID = "_id";
public static final String KEY_HDATE = "date";
public static final String KEY_MONTHDAY = "monthday";
public static final String KEY_YEAR = "year";
public static final String KEY_HD = "happened";

// The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.vdm.whtt/databases/";
private static String DB_NAME = "wht.db";
private static final String DB_TABLE = "historydaytable";

private SQLiteDatabase db;

private final Context ourContext;

public DBAdapter(Context context) {
    super(context, DB_NAME, null, 1);
    this.ourContext = context;
}

public void createDataBase() throws IOException {

    boolean dbExist = checkDataBase();

    if (dbExist) {
        // do nothing - database already exist
    } else {

        // By calling this method and empty database will be created into
        // the default system path
        // of your application so we are gonna be able to overwrite that
        // database with our database.
        this.getReadableDatabase();

        try {

            copyDataBase();

        } catch (IOException e) {

            throw new Error("Error copying database");

        }
    }

}

private boolean checkDataBase() {
    SQLiteDatabase checkDB = null;

    try {
        String myPath = DB_PATH + DB_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READONLY);
    } catch (SQLiteException e) {
        // database does't exist yet.
    }

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

    return checkDB != null ? true : false;
}

private void copyDataBase() throws IOException {
    InputStream myInput = ourContext.getAssets().open(DB_NAME);
    String outFileName = DB_PATH + DB_NAME;
    OutputStream myOutput = new FileOutputStream(outFileName);

    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer)) > 0) {
        myOutput.write(buffer, 0, length);
    }

    myOutput.flush();
    myOutput.close();
    myInput.close();
}

public void open() throws SQLException {
    String myPath = DB_PATH + DB_NAME;
    db = SQLiteDatabase.openDatabase(myPath, null,
            SQLiteDatabase.OPEN_READONLY);
}

@Override
public synchronized void close() {
    if (db != null)
        db.close();
    super.close();
}

@Override
public void onCreate(SQLiteDatabase db) {
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + DB_TABLE);
    onCreate(db);
}

public String[] getTH(long aLong) { 
    String[] columns = new String[] { KEY_YEAR, KEY_MONTHDAY, KEY_HD };
    Cursor cursor = db.query(DB_TABLE, columns, KEY_HDATE + "=" + aLong,
            null, null, null, null);

    if (cursor != null) {
        cursor.moveToFirst();
        String hpToday[] = new String[3];
        hapToday[0] = cursor.getString(0);
        hapToday[1] = cursor.getString(1);
        hapToday[2] = cursor.getString(2);
        cursor.close();
        this.db.close();
        return hpToday;
    }
    return null;
}

public String[] getFirstRandomAnswer(int randomNum1) {
    String[] columns = new String[] { KEY_YEAR, KEY_MONTHDAY, KEY_HD };
    Cursor cursor = db.query(DB_TABLE, columns, null,
            null, null, null, null);
    if (cursor != null) {
        cursor.moveToPosition(randomNum1);
        String r1Str[] = new String[3];
        r1Str[0] = cursor.getString(0);
        r1Str[1] = cursor.getString(1);
        r1Str[2] = cursor.getString(2);
        cursor.close();
        this.db.close();
        return r1Str;
    }
    return null;
}

public String[] getSecondRandomAnswer(int randomNum2) {
    String[] columns = new String[] { KEY_YEAR, KEY_MONTHDAY, KEY_HD };
    Cursor cursor = db.query(DB_TABLE, columns, null,
            null, null, null, null);
    if (cursor != null) {
        cursor.moveToPosition(randomNum2);
        String r2Str[] = new String[3];
        r2Str[0] = cursor.getString(0);
        r2Str[1] = cursor.getString(1);
        r2Str[2] = cursor.getString(2);
        cursor.close();
        this.db.close();
        return r2Str;
    }
    return null;
}
}

MainActivity：

    import java.io.IOException;
import java.util.Locale;
import java.util.Date;
import java.text.ParseException;
import java.text.SimpleDateFormat;

import android.os.Bundle;
import android.text.Html;
import android.widget.TextView;
import android.app.Activity;
import android.database.SQLException;

public class MainActivity extends Activity {
private DBAdapter dba;
TextView hiddenDBdatetv, todayIstv, optionAtv;
String MMdStr;
String[] todayArray;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    hiddenDBdatetv = (TextView) findViewById(R.id.hiddenDBdate_TV);
    todayIstv = (TextView) findViewById(R.id.todayIs_TV);
    optionAtv = (TextView) findViewById(R.id.optionA_TV);

    dba = new DBAdapter(this);

    try {
        dba.createDataBase();
    } catch (IOException ioe) {
        throw new Error("Unable to create database");
    }
    try {
        dba.open();
    } catch (SQLException sqle) {
        throw sqle;
    }

    getMMdDate();
    getTH();
}

private void getMMdDate() {
    Date anotherCurDate = new Date();
    SimpleDateFormat formatter = new SimpleDateFormat("MMd", Locale.US);
    MMdStr = formatter.format(anotherCurDate);
    SimpleDateFormat dateFormat = new SimpleDateFormat("MMd");
    Date myDate = null;
    try {
        myDate = dateFormat.parse(MMdStr);
    } catch (ParseException e) {
        e.printStackTrace();
    }
    SimpleDateFormat timeFormat = new SimpleDateFormat("MMMMMMMMMM d");
    String finalDate = timeFormat.format(myDate);
}

private void getTH() {
    long aLong = Long.parseLong(MMdStr);
    dba.open();
    todayArray = dba.getTH(aLong);
    dba.close();
    optionAtv.setText(todayArray[2]);
}

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

}

Answer 1

您将在createDatabase()（dbExist == false时）离开一个开放式数据库，并在onCreate()中再次打开数据库，然后再次在getTH()中打开数据库。

避免此错误的诀窍是跟踪数据库何时已打开并确保在使用完毕后关闭它。如果您发现自己多次打开数据库，请在尝试打开数据库之前检查isOpen()。

Answer 2

在getFirstRandomAnswer（int randomNum1）和getSecondRandomAnswer（int randomNum2）方法中，尝试关闭if语句之外的游标和db。而不是检查游标对null只是使用moveToFirst（）方法：

if (cursor.mnoveToFirst) {  // Means that cursor is not equal to null
    cursor.moveToPosition(randomNum2);
    String r2Str[] = new String[3];
    r2Str[0] = cursor.getString(0);
    r2Str[1] = cursor.getString(1);
    r2Str[2] = cursor.getString(2);
}

    cursor.close();
    this.db.close();

    return r2Str;

在Android和SQlite中从不显式调用close（）

2 个答案: