如何从SQLite检索整数数据并在textview中显示它？

Question

I'm new in SQLite and I have this code that shows the points in textview which retrieves the data from the database and if I click the button, it should retrieve the data, add some integers and append it to the database. However whenever I run the app, the app crashes.

Here's my mainActivity

 import android.widget.TextView; public class MainActivity extends Activity { DatabaseHelper mydb; private static TextView txt_stars; @ Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mydb = new DatabaseHelper(this); onButtonClickListener(); txt_stars = (TextView) findViewById(R.id.txtStars); //I already clean my code here } public void onButtonClickListener { button_next = (Button) findViewById(R.id.btnNext); button_next.setOnClickListener( new View.OnClickListener() { @Override public void onClick(View v) { AlertDialog.Builder alert = new AlertDialog.Builder(context); alert.setMessage("You have earned 50 stars"); alert.setCancelable(false); alert.setPositiveButton("next", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { //retrieve data, add 50, append data and return to main with a textview of 50 stars. How do I do this? } }); AlertDialog alertDialog = alert.create(); alertDialog.show(); } } ); } } 

Here's my DatabaseHelper.java

 import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DatabaseHelper extends SQLiteOpenHelper { public static final String DATABASE_NAME = "star.db"; public static final String TABLE_NAME = "stars_table"; public static final String COL1 = "stars"; public DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, 1); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL("create table" + TABLE_NAME + "(" + COL1 + ")"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS" + TABLE_NAME); onCreate(db); } public boolean insertData(Integer stars) { SQLiteDatabase db = this.getWritableDatabase(); ContentValues contentValues = new ContentValues(); contentValues.put(COL1, stars); long result = db.insert(TABLE_NAME, null, contentValues); if (result == -1) return false; else return true; } public Cursor getAllData() { SQLiteDatabase db = this.getWritableDatabase(); Cursor res = db.rawQuery("select stars from" + TABLE_NAME, null); return res; } } 

Thanks a lot!

Answer 1

your code getAllData() is wrong ...change it following format

public ArrayList<Model> getAllData() {

    cartList.clear();//your arraylist

    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery("select * from stars_table", null);
    if (cursor.getCount() != 0) {
        if (cursor.moveToFirst()) {
            do {
                Model item = new Model();//your object
                item.status =  cursor.getString(cursor.getColumnIndex("stars"));  //your variable


                cartList.add(item);

            } while (cursor.moveToNext());
        }
    }
    cursor.close();
    db.close();
    return cartList;
}