问题描述

使用 OnItemClickListener 从 List items 中检索 null 值

我想获取一个 OnItemClickListener 从 list items 中检索值。现在是点击后，也不能获得值。
下面是相关的代码：

public class DiarySchedule extends ListActivity implements OnClickListener
{
    private DiaryDataSource datasource;
    private static final String TAG = "MAD Diary Schedule";
    private String delTitle;
    private String delDate;
    private String delTime;
    private String editTitle;
    private String editDate;
    private String editTime;
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.diary_schedule);
    datasource = new DiaryDataSource(this);
    datasource.open();
    List<DiaryEntry> values = datasource.getAllDiaryEntries();
    DiaryScheduleAdapter adapter = new DiaryScheduleAdapter(this,values);
    setListAdapter(adapter);
    registerForContextMenu(getListView());
}
public class DiaryScheduleAdapter extends ArrayAdapter<DiaryEntry>
{
    private LayoutInflater li;
    public DiaryScheduleAdapter(Context context, List<DiaryEntry> values)
    {
        super(context, 0, values);
        li = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        DiaryEntry diaryEntry = getItem(position);
        View v = convertView;
        if ( v == null )
        {
            v = li.inflate(R.layout.diary_schedule, null);
        }
        TextView date = (TextView)v.findViewById(R.id.scheduleListDate);
        String initialDate = diaryEntry.getDate();
        String formattedDate = ConvertToDate(initialDate);
        date.setText(formattedDate);
        TextView link = (TextView)v.findViewById(R.id.scheduleListLink);
        link.setText(" at ");
        TextView time = (TextView)v.findViewById(R.id.scheduleListTime);
        time.setText(diaryEntry.getTime());
        TextView title = (TextView)v.findViewById(R.id.scheduleListTitle);
        title.setText(diaryEntry.getTitle());
        v.setOnClickListener(new OnItemClickListener(position));
        return v;
    }
}
@Override
public boolean onCreateOptionsMenu (Menu menu)
{
    new MenuInflater(getApplication()).inflate(R.menu.diary_menu, menu);
    return (super.onCreateOptionsMenu(menu));
}
@Override
public boolean onOptionsItemSelected (MenuItem item)
{
    switch (item.getItemId())
    {
        case R.id.add:
            Intent intent = new Intent(DiarySchedule.this, DiaryAddEntry.class);
            startActivity(intent);
            break;
    }
    return super.onOptionsItemSelected(item);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo)
{
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.diary_context_menu, menu);
}
@Override
public boolean onContextItemSelected(MenuItem item)
{
    AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
    switch (item.getItemId())
    {
        case R.id.edit:
            Intent editIntent = new Intent(DiarySchedule.this, DiaryEditEntry.class);
            editTitle = (String) ((TextView) info.targetView.findViewById(R.id.scheduleListTitle)).getText();
            editDate = (String) ((TextView) info.targetView.findViewById(R.id.scheduleListDate)).getText();
            editDate = GetInfoConvertToDate(editDate);
            editTime = (String) ((TextView) info.targetView.findViewById(R.id.scheduleListTime)).getText();
            editIntent.putExtra("title", editTitle);
            editIntent.putExtra("date", editDate);
            editIntent.putExtra("time", editTime);
            startActivity(editIntent);
            break;
        case R.id.delete:
            delTitle = (String) ((TextView) info.targetView.findViewById(R.id.scheduleListTitle)).getText();
            delDate = (String) ((TextView) info.targetView.findViewById(R.id.scheduleListDate)).getText();
            delDate = GetInfoConvertToDate(delDate);
            delTime = (String) ((TextView) info.targetView.findViewById(R.id.scheduleListTime)).getText();
            Log.v(TAG, "Hopefully title is: " + delTitle + " with date of " + delDate + " and time of " + delTime);
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setMessage("Are you sure?").setPositiveButton("Yes", dialogClickListener)
                .setNegativeButton("No", dialogClickListener).show();
            break;
    }
    return super.onContextItemSelected(item);
}
DialogInterface.OnClickListener dialogClickListener = new DialogInterface.OnClickListener()
{
    @Override
    public void onClick(DialogInterface dialog, int which)
    {
        switch (which)
        {
            case DialogInterface.BUTTON_POSITIVE:
            datasource.deleteDiaryEntry(delTitle, delDate, delTime);

            // IN CASE NEED TO DELETE ALL DB ENTRIES UNCOMMENT THIS
            // (AND COMMENT THE ABOVE METHOD)
            //datasource.deleteAll();
            Intent intent = new Intent(DiarySchedule.this, DiarySchedule.class);
            startActivity(intent);
            break;
            case DialogInterface.BUTTON_NEGATIVE:
            // No action taken
            break;
        }
    }
};
@Override
public void onClick(View v)
{
    // TODO Auto-generated method stub

}
 private class OnItemClickListener implements OnClickListener
{
    private int mPosition;

    OnItemClickListener(int position)
    {
            mPosition = position;
    }

    @Override
    public void onClick(View v)
    {
        Log.v(TAG, "onItemClick at position" + mPosition);
        final String title = (String) ((TextView) findViewById(R.id.scheduleListTitle)).getText();
        System.out.println("Title is: " + title);
        String date = (String) ((TextView) findViewById(R.id.scheduleListDate)).getText();
        date = GetInfoConvertToDate(date);
        System.out.println("Date is: " + date);
        final String time = (String) ((TextView) findViewById(R.id.scheduleListTime)).getText();
        System.out.println("Time is: " + time);
        Intent descIntent = new Intent(DiarySchedule.this, DiaryDetailed.class);
        descIntent.putExtra("title", title);
        descIntent.putExtra("date", date);
        descIntent.putExtra("time", time);
        startActivity(descIntent);
    }
}
}

当调试到 OnItemClickListener 点击方法时，能顺利运行但是不能获取值，出现的是空值。什么原因啊？

解决方案

  final String title = (String) ((TextView) findViewById(R.id.scheduleListTitle)).getText();

每个 都改成v.findViewById看看：

 final String title = (String) ((TextView)v.findViewById(R.id.scheduleListTitle)).getText();