Question

I’m trying move an item between two list views (one contains the checked items and the other the nonchecked items). So when an item is clicked its checked state has changed so it is moved to the other listview. But it is not working.

Java code:

public class T_C_Activity extends Activity {
    /**
     * Called when the activity is first created.
     */

    //private EditText edittext;
    private Button button;
    private  ArrayAdapter<String> adapter;
    private  ArrayAdapter<String> adapter1;

    private boolean[] check = new boolean[10];

    String[] countries = new String[]{
            "India",
            "Pakistan",
            "Sri Lanka",
            "China",
            "Bangladesh",
            "Nepal",
            "Afghanistan",
            "North Korea",
            "South Korea",
            "Japan"
    };


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        ListView lvc = (ListView) findViewById(R.id.lvc);

        ListView lvnc = (ListView) findViewById(R.id.lvnc);

        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice, countries);
        //lvnc.setChoiceMode(AbsListView.CHOICE_MODE_MULTIPLE);
        lvnc.setAdapter(adapter); lvnc.setAdapter(adapter);

        adapter1 = new ArrayAdapter<String>( this, android.R.layout.simple_list_item_multiple_choice, new String[0]);

                lvc.setAdapter(adapter1);

        lvnc.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                //To change body of implemented methods use File | Settings | File Templates.
                String s = adapter.getItem(i);
                adapter1.add(s);
                adapter.remove(s);
                adapter1.notifyDataSetChanged();
                adapter.notifyDataSetChanged();
            }
        });

        lvc.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                //To change body of implemented methods use File | Settings | File Templates.
                String s = adapter.getItem(i);
                adapter.add(s);
                adapter1.remove(s);
                adapter.notifyDataSetChanged();
                adapter1.notifyDataSetChanged();
            }
        });

    }
}

xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
        >

<ListView
        android:id="@+id/lvc"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:choiceMode="multipleChoice"
        />

    <ListView
            android:id="@+id/lvnc"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:choiceMode="multipleChoice"
            />

    </LinearLayout>

Here is the crash output:

11-01 04:39:15.478: ERROR/AndroidRuntime(613): FATAL EXCEPTION: main
        java.lang.UnsupportedOperationException
        at java.util.AbstractList.add(AbstractList.java:404)
        at java.util.AbstractList.add(AbstractList.java:425)
        at android.widget.ArrayAdapter.add(ArrayAdapter.java:179)
        at com.app.T_C_Activity$1.onItemClick(T_C_Activity.java:56)
        at android.widget.AdapterView.performItemClick(AdapterView.java:298)
        at android.widget.AbsListView.performItemClick(AbsListView.java:1086)
        at android.widget.AbsListView$PerformClick.run(AbsListView.java:2859)
        at android.widget.AbsListView$1.run(AbsListView.java:3533)
        at android.os.Handler.handleCallback(Handler.java:615)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4745)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
        at dalvik.system.NativeStart.main(Native Method)

When an Item in the lvnc (ListView) is clicked the app stops. What is wrong? Also, I do not see a separation between the two listviews. Thanks.

Answer 1

The problem is that you’re initializing the two ArrayAdapters with simple string arrays, which do not support dynamic adding/removing of elements.

Instead, you can give each ArrayAdapter an ArrayList:

ArrayList<String> countryArrayList = new ArrayList<String>(countries);
adapter = new ArrayAdapter<String>(this, ..., countryArrayList);
lvnc.setAdapter(adapter); // Note: your code does this line twice

ArrayList<String> secondArrayList = new ArrayList<String>();
adapter1 = new ArrayAdapter<String>( this, ..., secondArrayList);

To manipulate the lists, call .add() and .remove() on countryArrayList and secondArrayList as appropriate, and then call notifyDataSetChanged() on the adapters.