这可能是一个菜鸟问题,但我对所有这些 SQLite-Database-Cursor-Adapter-ListView-Do-It-Properly-Stuff 都很陌生。
我有什么:
在我的 MainActivity
中,我有一个 ListView
。我使用 SQLite 数据库
并使用扩展 SimpleCursorAdapter
的自定义适配器填充 ListView
。通过单击我的 ActionBar
中的一个项目,我激活了 Contextual Action Mode
。到目前为止一切正常。
我想要的:
通过单击我的 ListView 项目
中的某个图标,应删除相应的数据库行并刷新 ListView
。
我的问题:
如何正确刷新我的 Cursor
和 ListView
?当我在 OnClickListener
中不使用 cursor.requery()
并使用 cursor = dbm.getIOIOSensorsCursor()
时,我得到一个 CursorIndexOutOfBoundsException
行下方几行
int state = cursor.getInt(cursor.getColumnIndex(IOIOSensorSchema.STATE));
我的应用程序崩溃了,但在重新加载后,数据库已被删除,相应的 ListView item
也不见了。
我猜崩溃一定与 get getView
方法中的 _position
有关,因为 _position
是 final
.但是,当我使用 cursor.requery()
时,一切正常。
但此方法已被弃用,它的文档说“不要使用此...”。我是正确编码的 friend (我仍然是初学者,想学习以正确的方式而不是快速和肮脏的方式编码)并且想知道如何正确地做到这一点。我不知道这是否重要,但我只在我的(非常快的)Nexus 4 上测试我的应用程序。足够快地刷新 Cursor
似乎没有问题,但我想知道它是否将在较慢的设备上工作。如果它对你很重要,我的数据库将包含大约 10-20 行和大约 12 列。我想这是一个非常小的数据库。
这里是我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();
}
});
最佳答案
How do I refresh my Cursor and my ListView properly?
您通过再次运行您的代码来“刷新 [您的] Cursor”以获取 Cursor
,使用您用于创建原始 Cursor
的代码(在后台线程上, 请)。您可以通过调用 CursorAdapter
上的 changeCursor()
或 swapCursor()
来刷新您的 ListView
。
关于Android:删除数据库行后如何重新查询游标以刷新ListView?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16937839/