Android:如何在删除数据库行后重新查询Cursor以刷新ListView？

Question

这可能是一个noob问题,但我对所有这些SQLite-Database-Cursor-Adapter-ListView-Do-It-Properly-Stuff都很新.

是)我有的:

在我,MainActivity我有一个ListView.我使用an SQLite database并使用ListView自定义适配器扩展填充SimpleCursorAdapter.点击ActionBar我激活的项目Contextual Action Mode.到目前为止一切正常.

我想要的是:

通过单击我ListView item的相应数据库中的某个图标,应删除该行,并ListView应刷新.

我的问题:

如何刷新我Cursor和我的ListView正确？当我不使用cursor.requery()我OnClickListener而使用时,cursor = dbm.getIOIOSensorsCursor()我会在CursorIndexOutOfBoundsException该行下方输入几行

int state = cursor.getInt(cursor.getColumnIndex(IOIOSensorSchema.STATE));

我的应用程序崩溃,但重新加载后,数据库已被删除,相应ListView item的消失.

我想崩溃必须与_positionget getView方法有关,因为_position是final.但是,当我使用cursor.requery()一切正常的时候.

但是这种方法已被弃用,它的文档说"不要使用它......".我是正确编码的朋友(我还是一个初学者,想要学习正确的编码而不是快速和肮脏),并想知道如何正确编码.我不知道它是否重要,但我只在我的(非常快)Nexus 4上测试我的应用程序.刷新Cursor速度似乎没有问题,但我想知道它是否适用于速度较慢的设备.如果它对您很重要,我的数据库将包含大约10-20行,大约12列.我想这是一个非常小的数据库.

这是我的自定义适配器的相关代码:

public class IOIOSensorCursorAdapterCam extends SimpleCursorAdapter
{
static class ViewHolder
{
ImageView stateIV, removeIV;
TextView nameTV, pinNumberTV, feedIDTV, freqTV;
}

private Context ctx;
private Cursor cursor;
private IodDatabaseManager dbm;

public IOIOSensorCursorAdapterCam(Context _context, int _layout,
    Cursor _cursor, String[] _from, int[] _to, int _flags)
{
super(_context, _layout, _cursor, _from, _to, _flags);
ctx = _context;
cursor = _cursor;
dbm = new IodDatabaseManager(_context);
}

@Override
public View getView(final int _position, View _convertView,
    ViewGroup _parent)
{
ViewHolder holder = null;

LayoutInflater inflater = (LayoutInflater) ctx
    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

// There is no view at this position, we create a new one. In this case
// by inflating an xml layout.
if (_convertView == null)
{
    // Inflate a layout
    _convertView = inflater.inflate(R.layout.listview_item_sensor_cam,
        null);

    holder = new ViewHolder();
    holder.stateIV = (ImageView) _convertView
        .findViewById(R.id.stateImageView);
    holder.nameTV = (TextView) _convertView
        .findViewById(R.id.sensorNameTextView);
    holder.pinNumberTV = (TextView) _convertView
        .findViewById(R.id.sensorPinNumberTextView);
    holder.feedIDTV = (TextView) _convertView
        .findViewById(R.id.sensorFeedIDTextView);
    holder.freqTV = (TextView) _convertView
        .findViewById(R.id.sensorFrequencyTextView);
    holder.removeIV = (ImageView) _convertView
        .findViewById(R.id.removeImageView);
    _convertView.setTag(holder);
}
// We recycle a View that already exists.
else
{
    holder = (ViewHolder) _convertView.getTag();
}

// Set an OnClickListener to the "Delete Icon"
holder.removeIV.setOnClickListener(new OnClickListener()
{
    @SuppressWarnings("deprecation")
    @Override
    public void onClick(View _view)
    {
    cursor.moveToPosition(_position);

    // Delete sensor from database here
    int sensorID = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.SENSOR_ID));
    dbm.deleteIOIOSensor(sensorID);

    // This leads to a "CursorIndexOutOfBoundsException" and cannot
    // be used to refresh the ListView
//      cursor = dbm.getIOIOSensorsCursor();

    // Refresh ListView
    cursor.requery();
    notifyDataSetChanged();
    }
});

cursor.moveToPosition(_position);

if (cursor.getCount() > 0)
{
    int state = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.STATE));

    if (state == 0)
    {
    holder.stateIV.setImageResource(R.drawable.av_play_over_video);
    holder.stateIV.setColorFilter(ctx.getResources().getColor(
        R.color.hint_lighter_gray));
    // _convertView.setAlpha((float) 0.5);
    holder.nameTV.setTextColor(ctx.getResources().getColor(
        R.color.hint_darker_gray));
    }
    else
    {
    holder.stateIV.setImageResource(R.drawable.av_pause_over_video);
    holder.stateIV.setColorFilter(ctx.getResources().getColor(
        android.R.color.holo_green_light));
    // _convertView.setAlpha((float) 1);
    holder.nameTV.setTextColor(ctx.getResources().getColor(
        android.R.color.black));
    }

    // Set the sensor's name to the according TextView
    String sensorName = cursor.getString(cursor
        .getColumnIndex(IOIOSensorSchema.NAME));
    holder.nameTV.setText(sensorName);

    // Set the sensor's pin number to the according TextView
    int pinNumber = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.PIN_NUMBER));
    holder.pinNumberTV.setText("" + pinNumber);

    // Set the sensor's feed ID to the according TextView
    int feedID = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.FEED_ID));
    holder.feedIDTV.setText("" + feedID);

    // Set the sensor's frequency to the according TextView
    int frequency = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.FREQUENCY));
    int timeUnit = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.TIME_UNIT));
    String frequencyTextViewText = "";
    switch (timeUnit)
    {
    case IodIOIOSensor.TIME_UNIT_MINUTES:
    frequencyTextViewText = frequency + " min";
    break;
    case IodIOIOSensor.TIME_UNIT_HOURS:
    frequencyTextViewText = frequency + " h";
    break;
    default:
    frequencyTextViewText = frequency + " sec";
    break;
    }
    holder.freqTV.setText(frequencyTextViewText);
}
return _convertView;
}
}

编辑:

这是我在实现解决方案后来自OnCickListener的相关代码:

// Set an OnClickListener to the "Delete Icon"
holder.removeIV.setOnClickListener(new OnClickListener()
{
    @Override
    public void onClick(View _view)
    {
    cursor.moveToPosition(_position);

    // Delete sensor from database here
    int sensorID = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.SENSOR_ID));
    dbm.deleteIOIOSensor(sensorID);

    Toast.makeText(ctx, R.string.toast_sensor_deleted,
        Toast.LENGTH_SHORT).show();

    // Refresh ListView
    cursor = dbm.getIOIOSensorsCursor();
    swapCursor(cursor);

    notifyDataSetChanged();
    }
});

Answer 1

如何正确刷新我的Cursor和ListView？

您可以通过再次运行代码来"刷新[your] Cursor" Cursor,使用您用于创建原始代码的代码Cursor(请在后台线程中).你可以ListView通过电话changeCursor()或swapCursor()上电来刷新你的CursorAdapter.