问题
I'm using a fragment to create a ListView filled with CheckBoxes. I tried my best to find the solution based on other questions but I can't seem to fix it. When I run the script without using the:
convertView.getTag();
My app runs fine but the positions of the Item s in the list don't save so. The view items jump around. However when I do use that method I get an error. The log cat states:
01-02 23:54:20.662: E/InputEventReceiver(1209): Exception dispatching input event.
01-02 23:54:20.672: D/AndroidRuntime(1209): Shutting down VM
01-02 23:54:20.672: W/dalvikvm(1209): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
01-02 23:54:20.782: E/AndroidRuntime(1209): FATAL EXCEPTION: main
01-02 23:54:20.782: E/AndroidRuntime(1209): java.lang.ClassCastException: com.MrBabilin.youdeserveadrink.Items cannot be cast to com.MrBabilin.youdeserveadrink.AlcoholList$MyCustomAdapter$ViewHolder
01-02 23:54:20.782: E/AndroidRuntime(1209): at com.MrBabilin.youdeserveadrink.AlcoholList$MyCustomAdapter.getView(AlcoholList.java:169)
01-02 23:54:20.782: E/AndroidRuntime(1209): at android.widget.AbsListView.obtainView(AbsListView.java:2255)
01-02 23:54:20.782: E/AndroidRuntime(1209): at android.widget.ListView.makeAndAddView(ListView.java:1769)
01-02 23:54:20.782: E/AndroidRuntime(1209): at android.widget.ListView.fillDown(ListView.java:672)
01-02 23:54:20.782: E/AndroidRuntime(1209): at android.widget.ListView.fillGap(ListView.java:636)
01-02 23:54:20.782: E/AndroidRuntime(1209): at android.widget.AbsListView.trackMotionScroll(AbsListView.java:5040)
01-02 23:54:20.782: E/AndroidRuntime(1209): at
This Activity consist of 3 classes. The main one: IngredientsActivity
public class IngredientsActivity extends FragmentActivity implements ActionBar.TabListener {
private static final String STATE_SELECTED_NAVIGATION_ITEM = "selected_navigation_item";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.check_list);
getActionBar().setTitle("Search");
getActionBar().setIcon(R.drawable.search_1);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// For each of the sections in the app, add a tab to the action bar.
actionBar.addTab(actionBar.newTab().setText("Alcahol").setTabListener(this));
actionBar.addTab(actionBar.newTab().setText("Juice").setTabListener(this));
actionBar.addTab(actionBar.newTab().setText("Other").setTabListener(this));
}
@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
if (savedInstanceState.containsKey(STATE_SELECTED_NAVIGATION_ITEM)) {
getActionBar().setSelectedNavigationItem(savedInstanceState.getInt(STATE_SELECTED_NAVIGATION_ITEM));
}
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(STATE_SELECTED_NAVIGATION_ITEM, getActionBar().getSelectedNavigationIndex());
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
return true;
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
if (tab.getPosition() == 0) {
AlcoholList simpleListFragment = new AlcoholList();
getSupportFragmentManager().beginTransaction().replace(R.id.containert, simpleListFragment).commit();
}
else if (tab.getPosition() == 1) {
JuiceList androidlidt = new JuiceList();
getSupportFragmentManager().beginTransaction().replace(R.id.containert, androidlidt).commit();
}
else {
OtherList androidversionlist = new OtherList();
getSupportFragmentManager().beginTransaction().replace(R.id.containert, androidversionlist).commit();
}
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
public static class DummySectionFragment extends Fragment {
public DummySectionFragment() {
}
public static final String ARG_SECTION_NUMBER = "section_number";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
TextView textView = new TextView(getActivity());
textView.setGravity(Gravity.CENTER);
Bundle args = getArguments();
textView.setText(Integer.toString(args.getInt(ARG_SECTION_NUMBER)));
return textView;
}
}
}
then the fragment : AlcoholList
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.ListView;
public class AlcoholList extends ListFragment{
MyCustomAdapter dataAdapter = null;
private Set<String> recipesList = new HashSet<String>();
private ArrayList<Items> stateList = new ArrayList<Items>();
public AlcoholList() {
Items _states1 = new Items ("Gin",false);
stateList.add(_states1);
Items _states2 = new Items ("Ginger Liqueur",false);
stateList.add(_states2);
Items _states3 = new Items ("Citrus Vodka",false);
stateList.add(_states3);
Items _states4 = new Items ("Champagne",false);
stateList.add(_states4);
Items _states5 = new Items ("Coconut Rum",false);
stateList.add(_states5);
Items _states6 = new Items ("Pear Vodka",false);
stateList.add(_states6);
Items _states7 = new Items ("Rum",false);
stateList.add(_states7);
Items _states8 = new Items ("Tequila",false);
stateList.add(_states8);
Items _states9 = new Items ("Triple Sec",false);
stateList.add(_states9);
Items _states10 = new Items ("Kahlua",false);
stateList.add(_states10);
Items _states11 = new Items ("Vanilla Vodka",false);
stateList.add(_states11);
Items _states12 = new Items ("Sake",false);
stateList.add(_states12);
Items _states13 = new Items ("Bourbon",false);
stateList.add(_states13);
Items _states14 = new Items ("Vodka",false);
stateList.add(_states14);
Items _states15 = new Items ("Beer",false);
stateList.add(_states15);
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
dataAdapter = new MyCustomAdapter(this.getActivity(),R.layout.da_item, stateList);
setListAdapter(dataAdapter);
SharedPreferences sharedPreferences = PreferenceManager
.getDefaultSharedPreferences(getActivity());
recipesList = sharedPreferences.getStringSet("string", recipesList);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.list_fragment, container, false);
}
@Override
public void onListItemClick(ListView list, View v, int position, long id) {
}
private class MyCustomAdapter extends ArrayAdapter<Items>
{
private ArrayList<Items> stateList;
public MyCustomAdapter(Context context, int textViewResourceId,
ArrayList<Items> stateList)
{
super(context, textViewResourceId, stateList);
this.stateList = new ArrayList<Items>();
this.stateList.addAll(stateList);
}
private class ViewHolder
{
CheckBox name;
}
@Override
public View getView (int position, View convertView, ViewGroup parent)
{
ViewHolder holder = null;
Log.v("ConvertView", String.valueOf(position));
if (convertView == null)
{
LayoutInflater vi = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = vi.inflate(R.layout.da_item, null);
holder = new ViewHolder();
convertView.setTag(holder);
holder.name = (CheckBox) convertView.findViewById(R.id.ingredientbox);
holder.name.setOnClickListener( new View.OnClickListener()
{
public void onClick(View v)
{
CheckBox cb = (CheckBox) v;
Items _state = (Items) cb.getTag();
_state.setSelected(cb.isChecked());
}
});
}
else
{
holder = (ViewHolder) convertView.getTag(); // THIS IS THE PROBLEM
}
Items state = stateList.get(position);
holder.name.setText(state.getName());
holder.name.setChecked(state.isSelected());
holder.name.setTag(state);
return convertView;
}
}
}
then the Array class : Items
public class Items {
String name ;
boolean selected;
public Items(String name, boolean selected){
super();
this.name=name;
this.selected=selected;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public boolean isSelected() {
return selected;
}
public void setSelected(boolean selected) {
this.selected = selected;
}
}
I don't know if this is helpful but, this problem did not occur before I tried to implement fragment views. The code that worked was:
public class IngredientsActivity extends Activity {
MyCustomAdapter dataAdapter = null;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.check_list);
//Generate list View from ArrayList
displayListView();
}
private void displayListView()
{
//Array list of countries
ArrayList<Items> stateList = new ArrayList<Items>();
Items _states2 = new Items ("420" ,false);
stateList.add(_states2);
Items _states3 = new Items ("Amanda Bynes" ,false);
stateList.add(_states3);
Items _states4 = new Items ("Angelina Jolie" ,false);
stateList.add(_states4);
Items _states5 = new Items ("Anne Hathaway" ,false);
stateList.add(_states5);
Items _states6 = new Items ("Bachelorette Contestants" ,false);
stateList.add(_states6);
Items _states7 = new Items ("Beauty and the Beast" ,false);
stateList.add(_states7);
Items _states8 = new Items ("Beyonce" ,false);
stateList.add(_states8);
Items _states9 = new Items ("Big Boi" ,false);
stateList.add(_states9);
Items _states10 = new Items ("Charlie Sheen" ,false);
stateList.add(_states10);
}
//create an ArrayAdaptar from the String Array
dataAdapter = new MyCustomAdapter(this,R.layout.da_item, stateList);
ListView listViews = (ListView) findViewById(R.id.ingList2);
// Assign adapter to ListView
listViews.setAdapter(dataAdapter);
}
private class MyCustomAdapter extends ArrayAdapter<Items>
{
private ArrayList<Items> stateList;
public MyCustomAdapter(Context context, int textViewResourceId,
ArrayList<Items> stateList)
{
super(context, textViewResourceId, stateList);
this.stateList = new ArrayList<Items>();
this.stateList.addAll(stateList);
}
private class ViewHolder
{
CheckBox name;
}
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
ViewHolder holder = null;
Log.v("ConvertView", String.valueOf(position));
if (convertView == null)
{
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = vi.inflate(R.layout.da_item, null);
holder = new ViewHolder();
holder.name = (CheckBox) convertView.findViewById(R.id.ingredientbox);
convertView.setTag(holder);
holder.name.setOnClickListener( new View.OnClickListener()
{
public void onClick(View v)
{
CheckBox cb = (CheckBox) v;
Items _state = (Items) cb.getTag();
_state.setSelected(cb.isChecked());
}
});
}
else
{
holder = (ViewHolder) convertView.getTag();
}
Items state = stateList.get(position);
holder.name.setText(state.getName());
holder.name.setChecked(state.isSelected());
holder.name.setTag(state);
return convertView;
}
}
}
The Question is : How can I prevent my application from crashing, when calling convertView.getTag()
回答1:
R.layout.da_item file only contains R.id.ingredientbox so your covertView and holder.name are referring to the same object.
Now when you call
convertView.setTag(holder);
holder set to tag of convertView object and then you call
holder.name.setTag(state);
which overrides the tag as both objects are same.
Try to remove 2nd call and check.
EDIT Change your holder class to:
private class ViewHolder
{
Items state;
CheckBox name;
}
don't write holder.name.setTag(state);. Instead do following:
holder.state=state;
Now when you want items just say:
Items _state = ((ViewHolder) cb.getTag()).state;
来源：https://stackoverflow.com/questions/20896930/convertview-gettag-creates-cast-error