Question

我试图创建列表视图我在方向更改时遇到一些问题。问题是：当我更改屏幕列表视图的方向时，在列表中添加重复列表项。如何限制此数据更改

代码是：

   public class DayPlannerActivity extends Activity {

    private TextView txtHeader;
    private Context mContext;
    private ListView lvDayplanner;
    private DayPlannerAdapter adapter;
    private Activity activity;
    private static Vector<DayPlanner> list = new Vector<DayPlanner>();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dayplanner);
        mContext = this;    
        activity = this;
        txtHeader = (TextView) findViewById(R.id.txtHeader);
        txtHeader.setText(R.string.haivlate);
        String[] Checks = {"select","Check1","Check2"};
        DayPlanner dp = new  DayPlanner("11:00 PM", Checks);
        list.add(dp);
        dp = new  DayPlanner("12:00 PM", Checks);
        list.add(dp);
        lvDayplanner = (ListView) findViewById(R.id.lvDayplanner);
        adapter= new DayPlannerAdapter(activity,list);
        lvDayplanner.setAdapter(adapter);
   }

}

列表适配器：

   public class DayPlannerAdapter extends BaseAdapter {

    private Activity mActivity;
    private static Vector<DayPlanner> list;
    private static LayoutInflater inflater;
    public DayPlannerAdapter ( Activity _activity,Vector<DayPlanner> _list) {
        mActivity = _activity;
        list = _list;
        inflater = (LayoutInflater)mActivity.getSystemService(mActivity.LAYOUT_INFLATER_SERVICE);
    }

    public static class ViewHolder{
        public TextView txtScheduledTime;
        public Spinner spnrChecks;
        public Button btnGo;
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub

         View vi=convertView;
            ViewHolder holder;
            if(convertView==null){
                vi = inflater.inflate(R.layout.dayplanner_listitem, null);
                holder=new ViewHolder();
                holder.txtScheduledTime=(TextView)vi.findViewById(R.id.txtScheduledTime);
                holder.spnrChecks = (Spinner) vi.findViewById(R.id.spnrChecks);
                holder.btnGo = (Button) vi.findViewById(R.id.btnGo);
                vi.setTag(holder);
            }
            else
              holder=(ViewHolder)vi.getTag();

            holder.txtScheduledTime.setText(list.get(position).getScheduledTime());
            ArrayAdapter<String> spnrAdapter=new ArrayAdapter<String>(mActivity,
                    android.R.layout.simple_spinner_item, list.get(position).getChecks());
            spnrAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);   
            holder.spnrChecks.setAdapter(spnrAdapter);

            holder.btnGo.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                     Intent i = new Intent();
                     i.setClass(mActivity,DayPlannerFormActivity.class);
                     mActivity.startActivity(i);
                }
            });

        return vi;
    }

}

Answer 1

由于Android会在方向发生变化时自动保存View个状态，因此您需要一种方法来了解它是否不是第一次调用onCreate。幸运的是，它很容易：覆盖onSaveInstanceState，并存储甚至1个值，以使您在onCreate中获得的包不为空。

@Override
public void onSaveInstanceState(Bundle outInstanceState) {
    outInstanceState.putInt("value", 1);
}

然后，当重新创建活动时，savedInstanceState中的参数onCreate将不为空。所以只做测试：

if(savedInstanceState != null)

在向视图添加数据之前。

Answer 2

因为你的dayplanner对象列表是静态的，所以当你改变视图的方向时它会重新创建活动，但是因为在java中没有重新创建静态对象，而是为该类型保存，它会使列表中有两个同样的。

Answer 3

这里的派对太迟了，仍然会回答，因为它可能对其他人有用。我也遇到了PROPERLY implementing the view holder design pattern解决的问题。

ListView在屏幕方向更改时添加了列表中的重复项

3 个答案: