Question

当用户点击按钮时，我试图清除数据库中的所有数据。我不确定如何在不删除整个数据库的情况下这样做。

（我希望列和表保持创建状态，以便他们以后仍然可以在应用中添加项目）

public class MyProgress extends BaseActivity{
    Button btnClear;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_progress);
        mToolBar = activateToolbar();
        setUpNavigationDrawer();
        getSupportActionBar().setTitle("My Progress");
        btnClear.findViewById(R.id.btnClear);

        RecordsDatabase helper = new RecordsDatabase(this);
        Cursor c = helper.getRecords();
        ListView listViewRec = (ListView) findViewById(R.id.listViewRecord);
        final TodoCursorAdapter adapter = new TodoCursorAdapter(this, c);
        listViewRec.setAdapter(adapter);


        btnClear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //NEED TO CLEAR DB HERE
                adapter.notifyDataSetChanged();
            }
        });
    }
}

我的记录数据库：

public class RecordsDatabase extends SQLiteOpenHelper {

    public static final int DATABASE_VERSION = 1;

    public RecordsDatabase(Context context) {
        super(context, RecordContract.RecordInfo.DATABASE_NAME, null, DATABASE_VERSION);
        Log.d("Database operations", "Database created");
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + RecordContract.RecordInfo.TABLE_NAME + " ("
                + BaseColumns._ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
                        + RecordContract.RecordInfo.RECORDS_DATE + " TEXT NOT NULL,"
                + RecordContract.RecordInfo.RECORDS_SQUAT + " TEXT NOT NULL,"
                + RecordContract.RecordInfo.RECORDS_BENCH + " TEXT NOT NULL,"
                + RecordContract.RecordInfo.RECORDS_DEAD + " TEXT NOT NULL,"
                + RecordContract.RecordInfo.RECORDS_TOTAL + " TEXT NOT NULL)"

        );
        Log.d("Database operations", "Table created");

    }

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

    }

    public void putInformation(String date, String squat, String bench, String dead, String total) {
        SQLiteDatabase SQ = getWritableDatabase();
        ContentValues contentValues = new ContentValues();

        contentValues.put(RecordContract.RecordInfo.RECORDS_DATE, date);
        contentValues.put(RecordContract.RecordInfo.RECORDS_SQUAT, squat);
        contentValues.put(RecordContract.RecordInfo.RECORDS_BENCH, bench);
        contentValues.put(RecordContract.RecordInfo.RECORDS_DEAD, dead);
        contentValues.put(RecordContract.RecordInfo.RECORDS_TOTAL, total);
        long k = SQ.insert(RecordContract.RecordInfo.TABLE_NAME, null, contentValues);
        Log.d("Database operations", "Record added(1 row)");

    }

    public Cursor getRecords() {
        SQLiteDatabase SQ = getReadableDatabase();
        String[] columns = {RecordContract.RecordInfo._ID, RecordContract.RecordInfo.RECORDS_DATE, RecordContract.RecordInfo.RECORDS_SQUAT, RecordContract.RecordInfo.RECORDS_BENCH
        , RecordContract.RecordInfo.RECORDS_DEAD, RecordContract.RecordInfo.RECORDS_TOTAL};
        Cursor CR = SQ.query(RecordContract.RecordInfo.TABLE_NAME, columns,null, null, null, null, null);
        return CR;

    }
}

我正在考虑在RecordsDatabase.java中添加clearInfo()，但不知道我该怎么做。

Answer 1

删除表格然后创建表格然后尝试从表格中删除数据会更快。

如果要进行整个删除，也可以删除整个数据库并重新创建。

Answer 2

这样的事情可以起作用：

btnClear.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {

    sqLiteDatabase = dbHelper.getWritableDatabase();
    sqLiteDatabase.delete(RecordContract.RecordInfo.TABLE_NAME, null, null);
    sqLiteDatabase.execSQL("delete from " + RecordContract.RecordInfo.TABLE_NAME);
    sqLiteDatabase.close();

    adapter.notifyDataSetChanged();
    }
});

当然，您应该根据自己的需要调整代码。

清除sqlite db中的数据

2 个答案: