Android AsyncTask 与 ListView 包含 Button onClickListener

Question

我有一个列表视图，其中填充了 sqlitedatabase 中的数据。列表视图元素包含一个 TextView、一个按钮和一个复选框。单击该按钮将显示一个时间选择器对话框。从 timepickerdialog 接受时间会启动 AsyncTask。当我单击按钮时，总会创建一个新的 AsyncTask。

现在，当我单击第七个列表项时，第一个列表项会更新。线程可能有错误。

活动：

public class SettingsActivity extends Activity 
{
    private static final String TAG = "SettingsActivity";
    private ReminderBusAdapter busAdapter;
    private List<Reminder> reminderGoalsList;
    private static final int TIME_PICKER_DIALOG = 1;
    private static final String TIME_FORMAT = "kk:mm";
    private Calendar mCalendar;

    // view elements
    TextView tvStatus;
    ListView listViewReminder;

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

        // fetch required data reminder
        busAdapter = new ReminderBusAdapter(this);
        loadSettingsData();

        // generate view
        displayView();

        mCalendar = Calendar.getInstance();
    }

    private void loadSettingsData() 
    {
        Log.i(TAG, "loadSettingsData");
        reminderGoalsList = new ArrayList<Reminder>();
        reminderGoalsList = busAdapter.receiveReminders();

        Iterator<Reminder> iter = reminderGoalsList.iterator();
        Log.i(TAG, "iterate through all Reminders fetched from db");

        int cnt = 0;
        while (iter.hasNext()) 
        {
            cnt++;
            Log.i(TAG, cnt + "] " + iter.next().toString());
        }
    }

    private void displayView() 
    {
        Log.i(TAG, "displayView");
        tvStatus = (TextView) findViewById(R.id.settingsTextView);
        listViewReminder = (ListView) findViewById(R.id.settingsListView);
        listViewReminder.setAdapter(new SettingsAdapter(this,
                            R.layout.settings_reminder_listview, reminderGoalsList));
    }

    @Override
    protected Dialog onCreateDialog(int id, Bundle b) 
    {
        switch (id) 
        {
            case TIME_PICKER_DIALOG:
                return showTimePicker(b);
        }
        return super.onCreateDialog(id);
    }

    private Dialog showTimePicker(final Bundle b) 
    {
        TimePickerDialog timePicker = new TimePickerDialog(this, 0,
                        new TimePickerDialog.OnTimeSetListener() 
                        {
                            @Override
                            public void onTimeSet(TimePicker view, int hourOfDay, int minute) 
                            {
                                mCalendar.set(Calendar.HOUR_OF_DAY, hourOfDay);
                                mCalendar.set(Calendar.MINUTE, minute);

                                Reminder rem = (Reminder) b.get("reminder");
                                Log.i(TAG, rem.toString() + " got from adapter");

                                SimpleDateFormat dateFormat = new SimpleDateFormat(TIME_FORMAT);
                                String dateForTimeButton = dateFormat.format(mCalendar.getTime());

                                rem.setTime(dateForTimeButton);

                                new UpdateTimerByBtn().execute(new String[] 
                                                        {
                                                            rem.getTime(),
                                                            new String(Integer.toString(rem.getId())) 
                                                        });
                            }
                        }, mCalendar.get(Calendar.HOUR_OF_DAY),
                        mCalendar.get(Calendar.MINUTE), true);
        return timePicker;
    }

    class UpdateTimerByBtn extends AsyncTask<String, Integer, String> 
    {
        @Override
        protected String doInBackground(String... params) 
        {
            Log.i(TAG, "Starting AsyncTask " + "UpdateTimerByBtn new time="
                                             + params[0] + " from id= " + params[1]);

            busAdapter.updateReminder(params[0], Integer.parseInt(params[1])); 
            return "finish";
        }

        @Override
        protected void onPostExecute(String result) 
        {
            super.onPostExecute(result);
            loadSettingsData();
            displayView();
        }
    }
}

public class SettingsAdapter extends ArrayAdapter<Reminder> 
{
    protected static final String TAG = "SettingsAdapter";
    private static final int TIME_PICKER_DIALOG = 1;
    private List<Reminder> arrayListReminders;
    private int layout;
    private Activity activity;

    public SettingsAdapter(Activity activity, int layout, List<Reminder> objects) 
    {
        super(activity, layout, objects);

        this.arrayListReminders = objects;
        this.layout = layout;
        this.activity = activity;
    }

    static class ViewHolder 
    {
        private TextView listReminderTextView;
        private Button listReminderTimeButton;
        private CheckBox listReminderCheckBox;
    }

    @Override
    public View getView(int position, View convertView, android.view.ViewGroup parent) 
    {
        final Reminder rem = arrayListReminders.get(position);
        View view = convertView;
        ViewHolder viewHolder = null;

        if (view == null) 
        {
            LayoutInflater layoutInflater = (LayoutInflater) getContext()
                                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = layoutInflater.inflate(layout, parent, false);
        }

        if (view != null) 
        {
            viewHolder = new ViewHolder();
            viewHolder.listReminderTextView = (TextView) view.
                                        findViewById(R.id.list_reminder_day_textview);

            viewHolder.listReminderTimeButton = (Button) view
                                .findViewById(R.id.settings_reminder_list_time_button);

            viewHolder.listReminderCheckBox = (CheckBox) view
                                .findViewById(R.id.settings_reminder_list_checkbox);

            switch (rem.getId()) 
            {
                case 1:
                    viewHolder.listReminderTextView.setText(R.string.Mo);
                    break;
                case 2:
                    viewHolder.listReminderTextView.setText(R.string.Di);
                    break;
                case 3:
                    viewHolder.listReminderTextView.setText(R.string.Mi);
                    break;
                case 4:
                    viewHolder.listReminderTextView.setText(R.string.Do);
                    break;
                case 5:
                    viewHolder.listReminderTextView.setText(R.string.Fr);
                    break;
                case 6:
                    viewHolder.listReminderTextView.setText(R.string.Sa);
                    break;
                case 7:
                    viewHolder.listReminderTextView.setText(R.string.So);
                    break;
                default:
                    break;
            }

            viewHolder.listReminderTimeButton.setText(rem.getTime() + " " + "Uhr");

            viewHolder.listReminderTimeButton
                      .setOnClickListener(new OnClickListener() 
                        {
                            @Override
                            public void onClick(View v) 
                            {
                                Log.i(TAG, "clicked " + rem.toString());

                                Bundle bundle = new Bundle();
                                bundle.putSerializable("reminder", rem);

                                ((SettingsActivity) activity).showDialog(TIME_PICKER_DIALOG, bundle);
                            }
                        });

            viewHolder.listReminderCheckBox.setChecked(rem.isEnabled() ? true : false);
        }
        return view;
    };
}

---

感谢您的帮助 - 我更改了 getView 方法并开始调试所有内容。

我认为问题在于 TimePicker 对话框在 Activity 中创建的位置。

private Dialog showTimePicker(final Bundle b) 
{
    TimePickerDialog timePicker = new TimePickerDialog(this, 0,
                        new TimePickerDialog.OnTimeSetListener() 
                        {
                            @Override
                            public void onTimeSet(TimePicker view, int hourOfDay,int minute) 
                            {
                                mCalendar.set(Calendar.HOUR_OF_DAY, hourOfDay);
                                mCalendar.set(Calendar.MINUTE, minute);

                                Reminder rem = (Reminder) b.get("reminder");
                                Log.i(TAG, rem.toString() + " got from adapter");

                                SimpleDateFormat dateFormat = new SimpleDateFormat(TIME_FORMAT);
                                String dateForTimeButton = dateFormat.format(mCalendar.getTime());

                                rem.setTime(dateForTimeButton);
                                Log.i(TAG, rem.toString());
                                new UpdateTimerByBtn().execute(new String[] {
                                            rem.getTime(),
                                            new String(Integer.toString(rem.getId())) 
                                        });
                            }
                        }, mCalendar.get(Calendar.HOUR_OF_DAY)
                        , mCalendar.get(Calendar.MINUTE), true);
    return timePicker;
}

我从 Bundle 中获取所需的对象。当我将新的 Bundle 从适配器传输到活动时，此 Bunlde 是最终的并且永远不会改变。当我单击另一个按钮时，会显示相同的对话框（具有相同的值），并且 OnTimeSetListener 会与最终的捆绑包一起执行。有没有办法处理对话框表单适配器？我应该为 ViewHolder 中的每一行创建一个对话框吗？

Answer 1

听起来 SettingsAdapter 类中的 getView 方法有问题。首先，您错误地使用了 ViewHolder 模式。 ViewHolder 模式的要点是避免每次使用回收视图时调用 findViewById。

当convertView为null时，您需要实例化一个新视图，这就是您正在做的事情。问题是，在这种情况下，您没有赋予其子视图任何值......您只是返回视图。

使用 ViewHolder 模式的典型 getView 看起来像这样：

public View getView(int position, View convertView,
    android.view.ViewGroup parent) {
  View view = convertView;
  ViewHolder viewHolder;

  if(view == null) {
    view = layoutInflater.inflate ... // instantiate new view here

    // note that i'm instantiating my View holder when view == null,
    // where you are instantiating it when view != null...
    viewHolder = new ViewHolder();
    viewHolder.subview1 = (TextView)view.findViewById(R.id.subview1);
    ...
    viewHolder.subviewN = (CheckBox)view.findViewById(R.id.subviewN);
    view.setTag(viewHolder);
  }

  viewHolder = (ViewHolder)view.getTag();

  // view and viewHolder are now appropriately set, so do with them what you must

  viewHolder.subview1.setText("blah blah");
  ...

  return view;
}

正如我之前所说，只有在 ConvertView 不为 null 时，才为视图的 TextView、Button 和 CheckBox 赋值...换句话说，当您创建一个新 View 时，您只需按原样返回即可。也许这将是开始调试的好地方。