Question

我创建了一个包含表格的数据库。当我尝试提取表中的数据时，Android Studio会显示一条错误消息，指出该表不存在。

我在这些链接中提到了帮助

SQL table not found exception
http://mobisys.in/blog/2012/01/tutorial-using-database-in-android-applications/

第一个链接没有回答我的问题，第二个链接太复杂了。

以下是我的代码摘录。

DbHelper.java：

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

    public void onCreate(SQLiteDatabase database) {

        String CREATE_TABLE_NOTES_QUERY = "CREATE TABLE " + 
            NoteEntry.TABLE_NAME_NOTES + " (" +
            NoteEntry._ID_NOTES + " INTEGER NOT NULL AUTOINCREMENT, " +
            NoteEntry.COLUMN_COUNTRY + " TEXT NOT NULL, " +
            NoteEntry.COLUMN_DENOMINATION + " REAL NOT NULL DEFAULT 0, " +
            NoteEntry.COLUMN_YEAR + " INTEGER, " +
            NoteEntry.COLUMN_OBVERSE_DESCRIPTION + " TEXT DEFAULT \"Not Available\", " +
            NoteEntry.COLUMN_REVERSE_DESCRIPTION + " TEXT DEFAULT \"Not Available\", " +
            NoteEntry.COLUMN_LENGTH + " REAL DEFAULT 0.0, " +
            NoteEntry.COLUMN_BREADTH + " REAL DEFAULT 0.0, " +
            NoteEntry.COLUMN_THICKNESS + " REAL DEFAULT 0.0);";

        database.execSQL(CREATE_TABLE_NOTES_QUERY);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}
}

NoteActivity.java：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_note);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(NoteActivity.this, NoteEditorActivity.class);
            startActivity(intent);
        }
    });

    displayDatabaseInfo();
}

private void displayDatabaseInfo() {

    CollectoDbHelper mDbHelper = new CollectoDbHelper(this);
    SQLiteDatabase db = mDbHelper.getReadableDatabase();
    Cursor cursor = db.rawQuery("SELECT * FROM " + CollectoContract.NoteEntry.TABLE_NAME_NOTES, null);
    try {
        TextView displayView = (TextView) findViewById(R.id.textview_note);
        displayView.setText("Number of rows in notes table: " + cursor.getCount());
    } finally {
        cursor.close();
    }
}

logcat的：

07-25 14:55:57.357 9162-9162/com.example.android.collecto E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android.collecto, PID: 9162
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.collecto/com.example.android.collecto.NoteActivity}: android.database.sqlite.SQLiteException: no such table: notes (code 1): , while compiling: SELECT * FROM notes
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2762)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2848)
    at android.app.ActivityThread.-wrap12(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1552)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6334)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
 Caused by: android.database.sqlite.SQLiteException: no such table: notes (code 1): , while compiling: SELECT * FROM notes
    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:1345)
    at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1284)
    at com.example.android.collecto.NoteActivity.displayDatabaseInfo(NoteActivity.java:49)
    at com.example.android.collecto.NoteActivity.onCreate(NoteActivity.java:35)
    at android.app.Activity.performCreate(Activity.java:6743)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2715)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2848) 
    at android.app.ActivityThread.-wrap12(ActivityThread.java) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1552) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:154) 
    at android.app.ActivityThread.main(ActivityThread.java:6334) 
    at java.lang.reflect.Method.invoke(Native Method)

有人可以指导我解决我的错误吗？

Answer 1

尝试拨打onUpgrade()并在内部拨打onCreate();

另请卸载应用并重新安装

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed
    db.execSQL("DROP TABLE IF EXISTS " + CREATE_TABLE_NOTES_QUERY);
    // Create tables again
    onCreate(db);
}

表不存在Android错误

1 个答案: