Why don’t my data insert into SQLite database on android?

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I’m creating a simple todo list. So, I have activity (NewTaskActivity) Xml code:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ScrollView
            android:scrollbars="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <EditText
                  android:id="@+id/et_new_task_input"
                  android:hint="@string/new_task_input_hint"
                  android:textSize="15sp"
                  android:layout_margin="20dp"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content" />

          </ScrollView>

         <android.support.design.widget.FloatingActionButton
           android:id="@+id/fb_float_button_apply"
           android:src="@drawable/ic_check"
           app:fabSize="normal"
           android:layout_margin="10dp"
           android:layout_alignParentBottom="true"
           android:layout_alignParentRight="true"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:layout_alignParentEnd="true" />

    </RelativeLayout>

 </LinearLayout>

And I have a class NewTaskActivity.java:

   public class NewTaskActivity extends AppCompatActivity {
   private DBHelper dbHelper;
   private SQLiteDatabase database;

   @Override
   protected void onCreate (Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.new_task_activity);

       dbHelper = new DBHelper(NewTaskActivity.this);
       database = dbHelper.getWritableDatabase();

    FloatingActionButton floatingActionButton = 
    findViewById(R.id.fb_float_button_apply);
    floatingActionButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick (View v) {
            addNewTask();
        }
    });
}

@Override
protected void onDestroy () {
    super.onDestroy();

    dbHelper.close();
}

@SuppressLint("SimpleDateFormat")
private void addNewTask () {
    EditText task_input = findViewById(R.id.et_new_task_input);

    if (!task_input.getText().toString().equals("")) {
        ContentValues contentValues = new ContentValues();

        contentValues.put("task", task_input.getText().toString());
        contentValues.put("date", 
       new SimpleDateFormat("dd/MM/yymm:hh").
        format(Calendar.getInstance().getTime()));

        database.insert("tasks", null, contentValues);

        finish();
      }
   }
 }

In this class(NewTaskActivity.java) I want to add data in database. Database class (DBHelper.java):

    public class DBHelper extends SQLiteOpenHelper {
    private static final int DB_VERSION = 2;
    private static final String DB_NAME = "simpletodo";

    public DBHelper (@Nullable Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate (SQLiteDatabase db) {
        db.execSQL("CREATE TABLE IF NOT EXISTS tasks (_id INT NOT NULL PRIMARY 
       KEY, task TEXT NOT NULL, date TEXT NOT NULL)");
    }

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

        onCreate(db);
    }
}

And my data don’t insert into database. Why? I checked for data in NewTaskActivity.java using Log.d() after ‘insert’ and before ‘finish’ but they got me nothing. I’ve done todo list later but I have no such problems.

Answer

Your CREATE statement defines the column _id as INT NOT NULL PRIMARY KEY but not AUTOINCREMENT so you have to supply it yourself but you don’t.
Of course it’s better to make it AUTOINCREMENT:

_id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE

Edit: uninstall the app from the emulator/device and then run the modified code, otherwise the changes won’t affect your db because the onCreate() method of SQLOpenHelper() won’t be triggered.



Source: stackoverflow