[英]Android ListView Filtering using AsyncTask
我有两个相互竞争的问题。
情况
在尝试更改时,我尝试通过EditText
筛选出大量的Listview 10k +项目。
错误1
我在UI线程上进行了过滤操作(在当时看来是合理的),并且我认为这是导致某些手机出现错误的原因...
尝试修复错误1
创建了一个AsyncTask
专门用于调用我的过滤器功能...
/// <summary>
/// Implementation of Android AsyncTask to perform the StudentFiltering in background
/// </summary>
internal class FilterStudentsTask : AsyncTask
{
private Student[] _students;
private StudentList _outer;
private StudentListAdapter _adapter;
private string _filterText;
public FilterStudentsTask(StudentList outer, StudentListAdapter adapter, string filterText)
{
this._outer = outer;
this._adapter = adapter;
this._filterText = filterText;
}
protected override Java.Lang.Object DoInBackground(params Java.Lang.Object[] @params)
{
// filter the list
this._adapter.filterStudents(this._filterText);
return true;
}
protected override void OnPostExecute(Java.Lang.Object result)
{
// Notify adapter of Data Change (to trigger re-draw)
this._adapter.NotifyDataSetChanged();
base.OnPostExecute(result);
}
}
错误2
所以现在,因为我还有另一个线程负责过滤,所以这并不是说我不应该对这种类型的操作使用后台线程,而应该只在UI线程上发生。
E/AndroidRuntime( 9738): FATAL EXCEPTION: main
E/AndroidRuntime( 9738): java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sur
e the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(2131361885, class mapdroid.ColorFade
ListView) with Adapter(class mapdroid.StudentList_StudentListAdapter)]
E/AndroidRuntime( 9738): at android.widget.ListView.layoutChildren(ListView.java:1510)
E/AndroidRuntime( 9738): at android.widget.AbsListView.onLayout(AbsListView.java:1260)
E/AndroidRuntime( 9738): at android.view.View.layout(View.java:7175)
E/AndroidRuntime( 9738): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
E/AndroidRuntime( 9738): at android.view.View.layout(View.java:7175)
E/AndroidRuntime( 9738): at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
E/AndroidRuntime( 9738): at android.view.View.layout(View.java:7175)
E/AndroidRuntime( 9738): at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
E/AndroidRuntime( 9738): at android.view.View.layout(View.java:7175)
E/AndroidRuntime( 9738): at android.view.ViewRoot.performTraversals(ViewRoot.java:1140)
E/AndroidRuntime( 9738): at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
E/AndroidRuntime( 9738): at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime( 9738): at android.os.Looper.loop(Looper.java:130)
E/AndroidRuntime( 9738): at android.app.ActivityThread.main(ActivityThread.java:3683)
E/AndroidRuntime( 9738): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 9738): at java.lang.reflect.Method.invoke(Method.java:507)
E/AndroidRuntime( 9738): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
E/AndroidRuntime( 9738): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
E/AndroidRuntime( 9738): at dalvik.system.NativeStart.main(Native Method)
W/ActivityManager( 111): Force finishing activity MapDroid.MapDroid/mapdroid.StudentList
W/ActivityManager( 111): Activity pause timeout for HistoryRecord{40670aa0 MapDroid.MapDroid/mapdroid.StudentList}
我是否缺少某些内容,但是这些错误似乎存在冲突吗? 您如何调和他们?
我认为这个问题在这里
protected override Java.Lang.Object DoInBackground(params Java.Lang.Object[] @params)
{
// filter the list
this._adapter.filterStudents(this._filterText);
return true;
}
您无法通过非UI线程访问Apapter类。 尝试做这样的事情
protected override Java.Lang.Object DoInBackground(params Java.Lang.Object[] @params)
{
// filter the list
result = students.filterStudents(this._filterText);
return true;
}
protected override void OnPostExecute(Java.Lang.Object result)
{
// Notify adapter of Data Change (to trigger re-draw)
this._adapter.SetItems(result);
this._adapter.NotifyDataSetChanged();
base.OnPostExecute(result);
}
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