Android的：如何重新查询光标删除数据库行之后刷新的ListView？ [英] Android: How to requery a Cursor to refresh ListView after deleting database row?
问题描述
我需要一些帮助，我的code在这里，它的驾驶我坚果。这可能是一个小白的问题，但我是很新的这一切的SQLite数据库内光标适配器-的ListView，做它，正确-东西
我有什么：
在我的 MainActivity 我有一个的ListView 。我使用 SQLite数据库并填充的ListView 与自定义适配器延长 SimpleCursorAdapter 。通过点击一个项目在我的动作条我激活上下文操作模式。一切工作至今。
我要什么：
通过点击我的 ListView项特定的图标将根据数据库行应该被删除，的ListView 应进行刷新。
我的问题：
我如何更新我的光标和我的的ListView 是否正确？当我不在使用 cursor.requery（）我的 OnClickListener 和使用光标= dbm.getIOIOSensorsCursor（），而不是我得到一个 CursorIndexOutOfBoundsException 低于该行几行
int型的state = cursor.getInt（cursor.getColumnIndex（IOIOSensorSchema.STATE））;
我的应用程序崩溃，但重装后的数据库已被删除，根据 ListView项走了。
我想撞车必须是与 _position 中的get getView 的方法，因为 _position 是最后。但是，当我使用 cursor.requery（）一切正常，因为它应该。
但是... （总有一个但是）这个方法去precated，它的文档中说的不要使用这个...的。我是正确的编码的一个朋友（我还是一个初学者，想学code以正确的方式，而不是快速和肮脏的），想知道如何做到这一点的权利。我不知道这是否是重要的，但我只在我的（非常快）的Nexus 4，测试我的应用程序似乎有没有问题刷新光标速度不够快，但我不知道这是否会在较慢的设备。在情况下，它是非常重要的，你我的数据库将包含10〜20行，12列。我想这是一个非常小的数据库，但正如我在开始时说，这是大家很新的给我。
下面是我的自定义适配器相关code：
公共类IOIOSensorCursorAdapterCam扩展SimpleCursorAdapter
{
静态类ViewHolder
{
ImageView的stateIV，removeIV;
TextView的nameTV，pinNumberTV，feedIDTV，freqTV;
}
私人上下文CTX;
私人光标指针;
私人IodDatabaseManager DBM;
公共IOIOSensorCursorAdapterCam（上下文_context，INT _layout，
光标_cursor，字符串[] _from，INT [] _to，诠释_flags）
{
超（_context，_layout，_cursor，_from，_to，_flags）;
CTX = _context;
光标= _cursor;
DBM =新IodDatabaseManager（_context）;
}
@覆盖
公共查看getView（最终诠释_position，查看_convertView，
的ViewGroup _parent）
{
ViewHolder支架=无效;
LayoutInflater充气=（LayoutInflater）CTX
.getSystemService（Context.LAYOUT_INFLATER_SERVICE）;
//没有认为在这个位置，我们创建了一个新的。在这种情况下
//通过膨胀的XML布局。
如果（_convertView == NULL）
{
//充气布局
_convertView = inflater.inflate（R.layout.listview_item_sensor_cam，
空值）;
持有人=新ViewHolder（）;
holder.stateIV =（ImageView的）_convertView
.findViewById（R.id.stateImageView）;
holder.nameTV =（TextView中）_convertView
.findViewById（R.id.sensorNameTextView）;
holder.pinNumberTV =（TextView中）_convertView
.findViewById（R.id.sensorPinNumberTextView）;
holder.feedIDTV =（TextView中）_convertView
.findViewById（R.id.sensorFeedIDTextView）;
holder.freqTV =（TextView中）_convertView
.findViewById（R.id.sensorFrequencyTextView）;
holder.removeIV =（ImageView的）_convertView
.findViewById（R.id.removeImageView）;
_convertView.setTag（保持器）;
}
//我们回收一个视图已经存在。
其他
{
支架=（ViewHolder）_convertView.getTag（）;
}
//设置一个OnClickListener的删除图标
holder.removeIV.setOnClickListener（新OnClickListener（）
{
@燮pressWarnings（德precation）
@覆盖
公共无效的onClick（查看_view）
{
cursor.moveToPosition（_position）;
//删除传感器从数据库这里
INT sensorID = cursor.getInt（光标
.getColumnIndex（IOIOSensorSchema.SENSOR_ID））;
dbm.deleteIOIOSensor（sensorID）;
//这导致了CursorIndexOutOfBoundsException，不能
//用来刷新的ListView
//光标= dbm.getIOIOSensorsCursor（）;
//刷新的ListView
cursor.requery（）;
notifyDataSetChanged（）;
}
}）;
cursor.moveToPosition（_position）;
如果（cursor.getCount（）大于0）
{
INT状态= cursor.getInt（光标
.getColumnIndex（IOIOSensorSchema.STATE））;
如果（国家== 0）
{
holder.stateIV.setImageResource（R.drawable.av_play_over_video）;
holder.stateIV.setColorFilter（ctx.getResources（）的getColor（
R.color.hint_lighter_gray））;
// _convertView.setAlpha（（浮点）0.5）;
holder.nameTV.setTextColor（ctx.getResources（）的getColor（
R.color.hint_darker_gray））;
}
其他
{
holder.stateIV.setImageResource（R.drawable.av_pause_over_video）;
holder.stateIV.setColorFilter（ctx.getResources（）的getColor（
android.R.color.holo_green_light））;
// _convertView.setAlpha（（浮点）1）;
holder.nameTV.setTextColor（ctx.getResources（）的getColor（
android.R.color.black））;
}
//设置传感器的名称为根据的TextView
字符串sensorName = cursor.getString（光标
.getColumnIndex（IOIOSensorSchema.NAME））;
holder.nameTV.setText（sensorName）;
//设置传感器的引脚数为根据的TextView
INT pinNumber = cursor.getInt（光标
.getColumnIndex（IOIOSensorSchema.PIN_NUMBER））;
holder.pinNumberTV.setText（+ pinNumber）;
//设置传感器的进料ID为根据的TextView
INT feedID = cursor.getInt（光标
.getColumnIndex（IOIOSensorSchema.FEED_ID））;
holder.feedIDTV.setText（+ feedID）;
//设置传感器的频率为依据的TextView
INT频率= cursor.getInt（光标
.getColumnIndex（IOIOSensorSchema.FREQUENCY））;
INT TIMEUNIT = cursor.getInt（光标
.getColumnIndex（IOIOSensorSchema.TIME_UNIT））;
字符串frequencyTextViewText =;
开关（TIMEUNIT）
{
案例IodIOIOSensor.TIME_UNIT_MINUTES：
frequencyTextViewText =频率+分;
打破;
案例IodIOIOSensor.TIME_UNIT_HOURS：
frequencyTextViewText =频率+H;
打破;
默认：
frequencyTextViewText =频率+秒;
打破;
}
holder.freqTV.setText（frequencyTextViewText）;
}
返回_convertView;
}
}
编辑：
下面是从OnCickListener我的相关code inplementing解决方案后：
//设置一个OnClickListener的删除图标
holder.removeIV.setOnClickListener（新OnClickListener（）
{
@覆盖
公共无效的onClick（查看_view）
{
cursor.moveToPosition（_position）;
//删除传感器从数据库这里
INT sensorID = cursor.getInt（光标
.getColumnIndex（IOIOSensorSchema.SENSOR_ID））;
dbm.deleteIOIOSensor（sensorID）;
Toast.makeText（CTX，R.string.toast_sensor_deleted，
Toast.LENGTH_SHORT）.show（）;
//刷新的ListView
光标= dbm.getIOIOSensorsCursor（）;
swapCursor（光标）;
notifyDataSetChanged（）;
}
}）;
我如何更新我的光标和我的ListView正确？
您用C再次运行$ C $，以获得光标刷新[你]光标，使用code您用来创建原始光标（在后台线程，请）。您刷新的ListView 致电 changeCursor（）或 swapCursor（）的的CursorAdapter 。
I need some help with my code here, it's driving me nuts. this might be a noob question but I'm quite new to all this SQLite-Database-Cursor-Adapter-ListView-Do-It-Properly-Stuff.
What I have:
In my MainActivity I have a ListView. I use an SQLite database and populate the ListView with a custom adapter extending SimpleCursorAdapter. By clicking on an item in my ActionBar I activate Contextual Action Mode. Everything is working so far.
What I want:
By clicking on a certain icon in my ListView item the according database row should be deleted and the ListView should be refreshed.
My question:
How do I refresh my Cursor and my ListView properly? When I don't use cursor.requery() in my OnClickListener and use cursor = dbm.getIOIOSensorsCursor() instead I get a CursorIndexOutOfBoundsException a few rows below at the line
int state = cursor.getInt(cursor.getColumnIndex(IOIOSensorSchema.STATE));
My app crashes, but after reloading it the database has been deleted and the according ListView item is gone.
I guess the crash must have something to do with _position in get getView method because _position is final. However, when I use cursor.requery() everything works as it should.
BUT... (there's always a but) this method is deprecated and it's documentation says "Don't use this...". I'm a friend of coding properly (I'm still a beginner and want to learn to code the right way and not quick-and-dirty) and want to know how to do this right. I don't know if it's important but I'm testing my app only on my (really fast) Nexus 4. There seem to be no problems with refreshing the Cursor fast enough, but I wonder if it will work on slower devices. In case it's important for you my database will contain about 10-20 rows with about 12 columns. I guess this is a really small database, but as I said in the beginning, this is all very new to me.
Here is the relevant code of my custom adapter:
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;
}
}
Edit:
Here is my relevant code from the OnCickListener after inplementing the solution:
// 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();
}
});
How do I refresh my Cursor and my ListView properly?
You "refresh [your] Cursor" by running your code again to get the Cursor, using the code you used to create the original Cursor (on a background thread, please). You refresh your ListView by calling changeCursor() or swapCursor() on the CursorAdapter.
这篇关于Android的：如何重新查询光标删除数据库行之后刷新的ListView？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
