Question

我有一个无法应对的问题。我从数据库本身下载有关玩家，两列，id和玩家姓名的数据（在DatabaseHelper类中）：

public ArrayList<HashMap<String, String>> getAllPlayers() {
    try {
        ArrayList<HashMap<String, String>> arraylist = new ArrayList<HashMap<String, String>>();
        HashMap<String, String> map;
        SQLiteDatabase db = this.getReadableDatabase();
        String sqlSelect = "SELECT " + _id + ", " +
                columnPlayerName  + " FROM " + TABLE_NAME;
        Cursor select = db.rawQuery(sqlSelect, null);
        if(select != null) {
            if(select.moveToFirst()) {
                do {
                    map = new HashMap<String, String>();
                    map.put("_id", select.getString(0));
                    map.put("PLAYER_NAME", select.getString(1));
                    arraylist.add(map);
                }
                while(select.moveToNext());
            }
        }
        select.close();
        db.close();
        return arraylist;
    }
    catch (Exception e) {
        return null;
    }
}

好的，然后将列表中显示的数据下载到两列（MainActivity类）：

public class MainActivity extends AppCompatActivity {

ListView playersList;
DatabaseHelperPlayer playerDb = new DatabaseHelperPlayer(this);


@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu, v, menuInfo);
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu_players_list_view, menu);
}

@Override
public boolean onContextItemSelected(MenuItem item) {
    AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
    switch (item.getItemId()) {
        case R.id.delete_id:
            TextView tv = (TextView) findViewById(R.id.playerNameListView);
            String n = tv.getText().toString();
            playerDb.deletePlayer(info.id);



    }
    return super.onContextItemSelected(item);
}

private void playersListView() {
    ArrayList<HashMap<String, String>> playerList = playerDb.getAllPlayers();
    playersList = (ListView) findViewById(R.id.listPlayer);
    SimpleAdapter adt = new SimpleAdapter(this, playerList, R.layout.row_players, new String[]{"_id", "PLAYER_NAME"}, new int[]{R.id.id, R.id.playerNameListView});
    playersList.setAdapter(adt);
}


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

    playersListView();
    registerForContextMenu(playersList);

}

}

当您按住列表上的项目时，在我选择删除时显示菜单，运行我应该从数据库中删除列表中所选行的方法。不幸的是，这种情况并没有发生。我不能处理它。请帮忙。

方法删除：

public Cursor deletePlayer(long id) {
    SQLiteDatabase db = this.getWritableDatabase();
    String sql = "DELETE FROM " + TABLE_NAME + " WHERE " + columnPlayerName + " = " + id;
    Cursor delete = db.rawQuery(sql, null);
    if(delete != null) {
        delete.moveToFirst();
    }
    return delete;
}

Answer 1

不要使用rawQuery来执行删除。试试这个：

db.execSQL(sql);

而不是

Cursor delete = db.rawQuery(sql, null);

或直接使用db.delete方法。请参阅此处了解API：http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html

Answer 2

没关系？

public void deletePlayer(long id) {
    SQLiteDatabase db = this.getWritableDatabase();
    String sql = "DELETE FROM " + TABLE_NAME + " WHERE " + columnPlayerName + " = " + id;
    db.execSQL(sql);       
}

但遗憾的是我不知道如何获取要删除的列表中的ID项。你能帮忙吗？

使用上下文菜单删除行表单数据库

2 个答案: