Question

我是SQLite的新手，我有这个代码，它显示了textview中从数据库中检索数据的点，如果我点击按钮，它应该检索数据，添加一些整数并将其附加到数据库。但是，每当我运行应用程序时，应用程序都会崩溃。

这是我的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();
        }
      }
    );

  }


}

这是我的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;
  }

}

非常感谢！

Answer 1

你的代码getAllData（）是错误的......按照格式

更改它

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;
}

如何从SQLite中检索整数数据并在textview中显示？

1 个答案: