How to interact with listview items

Question

I'm trying to interact with CheckBox instances in ListView. I made an array of CheckBox, copied CheckBox item in ListView to it, and then made a public method - checkIfNull - to get this array, but it says all the elements in the array are null. Would you please help me to figure this out? Below is my code of ListAtapter that extends BaseAdapte, the main activity and the layout of my listview.

Thank you in advance

<TableLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="wrap_content">
    <TableRow android:id="@+id/tableRow1" 
        android:layout_width="wrap_content" android:layout_height="wrap_content">

    <CheckBox android:layout_height="wrap_content" android:layout_width="wrap_content" 
        android:id="@+id/checkBox1" />
    <TwoLineListItem android:id="@+id/twoLineListItem1" 
        android:layout_weight="1"
        android:paddingTop="10px"
        android:layout_width="wrap_content" android:layout_height="wrap_content">
        <TextView android:id="@+id/textView1" 
                android:text="TextView"
                android:layout_width="wrap_content" android:layout_height="wrap_content" 
                android:textAppearance="?android:attr/textAppearanceMedium" />
        <TextView android:id="@+id/textView2" 
                android:text="TextView"
                android:layout_width="wrap_content" android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceSmall" 
                android:paddingTop="30px"/>
    </TwoLineListItem>
    <TextView android:text="TextView" 
        android:id="@+id/textView3" 
        android:layout_weight="1"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:paddingTop="10px"/>
    <RadioButton android:id="@+id/radioButton1" 
            android:gravity="center|center_vertical"
            android:layout_width="wrap_content" android:layout_height="wrap_content" />
    </TableRow>
</TableLayout>

public class ListViewSampleMain extends ListActivity {
    private String[] list1 = {"Lionel Messi", "Kai Hansen", "Jim Carrey","Christoper Nolan",
            "ABC", "Persona", "Shawdow and Collosuss"};
    private String[] list2 = {"Argentina", "Germany", "Canada", "U.S.A.", 
            "Unknown", "Japan", "Ico"};
    private String[] list3 = {"March 2nd", "January 22th", "December 15th", "Februray 1st",
            "May 4th", "August 23th", "July 17th"};

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    createListViewWithListActivity();        
}

private void createListViewWithListActivity(){
    ListAdapter listAdapter = new ListAdapter(this, list1, list2, list3);
    this.setListAdapter(listAdapter);
    listAdapter.checkIfNull();
}




public class ListAdapter extends BaseAdapter {
    private Context mContext;
    private String[] list1;
    private String[] list2;
    private String[] list3;
    private static LayoutInflater layoutInflater = null;
    private CheckBox[] cb_list;

public ListAdapter(Context context, 
        String[] list1, String[] list2, String[] list3){
    this.mContext = context;
    this.list1 = list1;
    this.list2 = list2;
    this.list3 = list3;
    ListAdapter.layoutInflater =
        (LayoutInflater)this.mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    cb_list = new CheckBox[list1.length];
}

public int getCount() {
    // TODO Auto-generated method stub
    return list1.length;
}

public Object getItem(int arg0) {
    // TODO Auto-generated method stub
    return arg0;
}

public long getItemId(int position) {
    // TODO Auto-generated method stub
    return position;
}

public View getView(int position, View convertView, ViewGroup parent) {
    View view = convertView;
    ViewHolder viewHolder;

    // To interact with OnClickListener()
    final int pos = position;

    if(convertView == null){ // check if convertView exists
        view = layoutInflater.inflate(R.layout.listview_layout, null);

        viewHolder = new ViewHolder();
        viewHolder.tv1 = (TextView)view.findViewById(R.id.textView1);
        viewHolder.tv2 = (TextView)view.findViewById(R.id.textView2);
        viewHolder.tv3 = (TextView)view.findViewById(R.id.textView3);
        viewHolder.cb = (CheckBox)view.findViewById(R.id.checkBox1);

        viewHolder.cb.setOnClickListener(new OnClickListener(){
            public void onClick(View v) {
                Toast.makeText(mContext, "You clicked: "+pos, Toast.LENGTH_SHORT).show();
            }
        });

        cb_list[position] = (CheckBox) view.findViewById(R.id.checkBox1);

        view.setTag(viewHolder);
    }
    else{
        viewHolder = (ViewHolder)view.getTag();
    }
    viewHolder.tv1.setText(this.list1[position]);
    viewHolder.tv2.setText(this.list2[position]);
    viewHolder.tv3.setText(this.list3[position]);

    return view;
}

public void checkIfNull(){
    for(int i=0; i<cb_list.length; i++){
        if (cb_list[i] == null)
            Log.d("checkIfNull method", "cb_list["+i+"] is null");
        else if (cb_list[i] != null)
            Log.d("checkIfNull method", "cb_list["+i+"] is not null");
    }
}

public static class ViewHolder{
    public TextView tv1;
    public TextView tv2;
    public TextView tv3;
    public CheckBox cb;
}

}

Answer 1

Why are you checking the checkboxes for null? You would check if the checkbox is "true" checked or "false" unchecked.