列表视图数据不断重复

Question

我正在尝试按照 this 教程学习如何在 SQLite 数据库中保留复选框状态。一切正常，但每次重新启动项目时 Listview 中的数据都会重复。如何防止这种情况发生？

Screenshot

适配器：

class CustomCursorAdapter extends CursorAdapter{

private SQLiteDatabase dh=DatabaseHelper.getInstance().getDb();
private LayoutInflater mInflater;
private Context mContext;
private Cursor cursor;
CustomCursorAdapter(Context context, Cursor c) {
    super(context, c);
    // TODO Auto-generated constructor stub
    mInflater = LayoutInflater.from(context);
    mContext = context;
    cursor=c;
}

@Override
public void bindView(View view, Context context, final Cursor cursor) {
    // TODO Auto-generated method stub
    ViewHolder holder=(ViewHolder)view.getTag();

    holder.setTextView((TextView)view.findViewById(R.id.textview));
    holder.setCheckBox((CheckBox)view.findViewById(R.id.checkbox));
    CheckBox cb=holder.getCheckBox();

    holder.getTextView().setText( cursor.getString(cursor.getColumnIndex("username")));

    cb.setTag(cursor.getPosition());

    CompoundButton.OnCheckedChangeListener checkedChange= new CompoundButton.OnCheckedChangeListener() {

        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            // TODO Auto-generated method stub

            ContentValues contentValues=new ContentValues();
            Integer currentPosition = (Integer)buttonView.getTag();
            String currentPositionString=Double.toString(currentPosition);
            if(cursor.moveToPosition(currentPosition))
            {
                String rowID=cursor.getString(cursor.getColumnIndex("_id"));
                if(isChecked){
                    contentValues.put("selected", "1");
                    dh.update(DatabaseHelper.USER_PASSWORD, contentValues, "_id=?", new String[]{rowID});
                }else {
                    contentValues.put("selected", "0");
                    dh.update(DatabaseHelper.USER_PASSWORD, contentValues, "_id=?", new String[]{rowID});
                }

            }

        }
    };

    cb.setOnCheckedChangeListener(checkedChange);
    if(cursor.getString(cursor.getColumnIndex("selected")).compareTo("1")==0)
    {
        cb.setChecked(true);
    }
    else
    {
        cb.setChecked(false);
    }
}

@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
    // TODO Auto-generated method stub
    ViewHolder holder;
    View convertView = mInflater.inflate(R.layout.custom, parent,false);
    holder = new ViewHolder(convertView);
    convertView.setTag(holder);
    return convertView;
}

MainActivity.java:

public class MainActivity extends ListActivity{

Cursor cursor;
SQLiteDatabase dh;
CustomCursorAdapter myCursorAdapter;
ContentValues values;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    AndroidContext.setContext(this);

    dh=DatabaseHelper.getInstance().getDb();
    values = new ContentValues();
    // Inserting some data in SQLite to populate list view
    insertData("Avinash" , "123456");
    insertData("Rakesh" , "qwerty");
    insertData("Prateek", "onMobile");
    insertData("Rajesh", "Symphony");
    insertData("Rahul", "password123");
    insertData("Kanishk", "_smi1234");
    insertData("Ahmad", "asdfgh");
    insertData("Akkie", "zxcvbn");
    insertData("Ankur", "asdadd");
    insertData("Rohit", "bigb");
    insertData("Abhi", "rajjwe");
    insertData("Sone", "qwerty");
    createListView();
}

private void createListView() {
    setContentView(R.layout.main);

    cursor=dh.query(DatabaseHelper.USER_PASSWORD, new String[]{"_id","username","selected"}, null, null, null, null, "username ASC");

    startManagingCursor(cursor);
    myCursorAdapter= new CustomCursorAdapter(this,cursor);
    this.getListView().setAdapter(myCursorAdapter);
}

private void insertData(String firstName ,String password){
    if(values!= null){
        values.clear();
    }
    if (values != null) {
        values.put("username", firstName);
    }
    if (values != null) {
        values.put("password", password);
    }
    dh.insert(DatabaseHelper.USER_PASSWORD, null, values);
}

public void clickHandler(View view){

    if(view.getId() == R.id.checkbox){
        cursor.requery(); /* to get the updated values from sqlite on changing the check of checkbox*/
    }
}

Answer 1

您正在 activity 的 onCreate() 中插入新数据。

这应该只发生一次，在数据库创建之后。正确的位置是数据库打开助手的 onCreate().

列表视图数据不断重复

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