Question

我知道有很多重复的问题，但我还没找到答案。

这是我的代码：我有DatabaseHandler类，我有两个方法createTestTable(db); 和initializeTestTable(db);

        public class DatabaseHandler extends SQLiteOpenHelper {

        // Database Version
        private static final int DATABASE_VERSION = 1;

        // Database Name
        private static final String DATABASE_NAME = "AttendanceManagement";

        private static DatabaseHandler sInstance;

        public static synchronized DatabaseHandler getInstance(Context context) {

            if (sInstance == null) {
                sInstance = new DatabaseHandler(context.getApplicationContext());
            }
            return sInstance;
        }

        private DatabaseHandler(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        // Creating Tables
        @Override
        public void onCreate(SQLiteDatabase db) {
            createTestTable(db);
            initializeTestTable(db);
        }

        private void createTestTable(SQLiteDatabase db) {
            String CREATE_TEST_TABLE = "CREATE TABLE IF NOT EXISTS test" + "("
                    + "name TEXT" + ")";

            db.execSQL(CREATE_TEST_TABLE);
        }

        private void initializeTestTable(SQLiteDatabase db) {

//      SQLiteDatabase db = this.getWritableDatabase();
//      when I execute above code line I get following error.
//      java.lang.IllegalStateException: getDatabase called recursively
            ContentValues values = new ContentValues();

            values.put("name", "test1");

            // Inserting Row
            db.insert("test", null, values);
            db.close();

        }

    }

在我的活动中，我在onCreate()

中有以下代码

db = DatabaseHandler.getInstance(this);
db.getWritableDatabase();

我的应用程序在第二行db.getWritableDatabase();

之后崩溃

我正在关注崩溃日志

05-03 10:46:33.130: E/AndroidRuntime(5727): FATAL EXCEPTION: main
05-03 10:46:33.130: E/AndroidRuntime(5727): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cms.attendance/com.cms.attendance.fingerprintreader.newui.DashboardActivity}: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.cms.attendance/databases/AttendanceManagement
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.os.Looper.loop(Looper.java:137)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.app.ActivityThread.main(ActivityThread.java:5041)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at java.lang.reflect.Method.invokeNative(Native Method)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at java.lang.reflect.Method.invoke(Method.java:511)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:817)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at dalvik.system.NativeStart.main(Native Method)
05-03 10:46:33.130: E/AndroidRuntime(5727): Caused by: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.cms.attendance/databases/AttendanceManagement
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.database.sqlite.SQLiteDatabase.endTransaction(SQLiteDatabase.java:520)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:263)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at com.cms.attendance.fingerprintreader.newui.DashboardActivity.onCreate(DashboardActivity.java:96)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.app.Activity.performCreate(Activity.java:5104)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-03 10:46:33.130: E/AndroidRuntime(5727):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-03 10:46:33.130: E/AndroidRuntime(5727):     ... 11 more

请告诉我如何解决此问题。

Answer 1

您可以尝试

 public void onCreate(SQLiteDatabase db) {
            createTestTable(db);
            initializeTestTable(getInstance(context));
        }

当你需要重新初始化数据库然后你可以关闭它。

Answer 2

查看本教程http://www.androidhive.info/2011/11/android-sqlite-database-tutorial/
确保在进行任何修改后，您可以增加数据库的版本，以便重新创建数据库。
但是在onCreate方法中，您不应该关闭数据库，因为实现帮助程序的最佳实践中没有这样做。

Answer 3

您可以在应用程序类中打开数据库

public class MyApplication extends Application {

    private DatabaseHandler dbAdapter;


    @Override
    public void onCreate() {
        dbAdapter = new DatabaseHandler (getApplicationContext());
        dbAdapter.open();
    }

在课堂上你可以通过以下代码获得

MyApplication myApplication = (MyApplication) this.getApplication();
DatabaseAdapter dbAdapter= myApplication.getDatabaseAdapter();

在初始化数据库，android时尝试重新打开已关闭的对象sqlitedatabase

3 个答案: