包含CheckBoxes的自定义适配器的Listview

Question

I have a ListView which uses a custom adapter as shown:

private class CBAdapter extends BaseAdapter implements OnCheckedChangeListener{

    Context context;
    public String[] englishNames;
    LayoutInflater inflater;
    CheckBox[] checkBoxArray;
    LinearLayout[] viewArray;
    private boolean[] checked;

    public CBAdapter(Context con, String[] engNames){
        context=con;
        englishNames=engNames;
        inflater=(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        checked= new boolean[englishNames.length];
        for(int i=0; i<checked.length; i++){
            checked[i]=false;
            //Toast.makeText(con, checked.toString(),Toast.LENGTH_SHORT).show();
        }
        checkBoxArray = new CheckBox[checked.length];
        viewArray = new LinearLayout[checked.length];
    }

    public int getCount() {
        return englishNames.length;
    }

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

    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;
    }

    public View getView(int position, View convertView, ViewGroup parent) {

        if(viewArray[position] == null){

            viewArray[position]=(LinearLayout)inflater.inflate(R.layout.record_view_start,null);

            TextView tv=(TextView)viewArray[position].findViewById(R.id.engName);
            tv.setText(englishNames[position]);

            checkBoxArray[position]=(CheckBox)viewArray[position].findViewById(R.id.checkBox1);
        }

        checkBoxArray[position].setChecked(checked[position]);
        checkBoxArray[position].setOnCheckedChangeListener(this);
        return viewArray[position];
    }


    public void checkAll(boolean areChecked){
        for(int i=0; i<checked.length; i++){
            checked[i]=areChecked;
            if(checkBoxArray[i] != null)
                checkBoxArray[i].setChecked(areChecked);
        }
        notifyDataSetChanged();
    }

    public void onCheckedChanged(CompoundButton cb, boolean isChecked) {
        for(int i=0; i<checked.length; i++){
            if(cb == checkBoxArray[i])
                checked[i]=isChecked;
        }




    }
    public boolean itemIsChecked(int i){
        return checked[i];
    }

}

The layouts are fairly simple so I won't post them unless anyone thinks they are relevant.

The problem is that some of the CheckBoxes are not responding. It seems to be the ones that are visible when the layout is first displayed. Any that you have to scroll down to work as expected.

Any pointers appreciated.

Answer 1

Your code from the answer works but is inefficient(you can actually see this, just scroll the ListView and check the Logcat to see the garbage collector doing it's work). An improved getView method which will recycle views is the one below:

@Override
public View getView(int position, View convertView, ViewGroup parent) {
     LinearLayout view = (LinearLayout) convertView;
     if (view == null) {
          view = (LinearLayout) inflater.inflate(R.layout.record_view_start, parent, false);
     }
     TextView tv = (TextView) view.findViewById(R.id.engName);
     tv.setText(getItem(position));
     CheckBox cBox = (CheckBox) view.findViewById(R.id.checkBox1);
     cBox.setTag(Integer.valueOf(position)); // set the tag so we can identify the correct row in the listener
     cBox.setChecked(mChecked[position]); // set the status as we stored it        
     cBox.setOnCheckedChangeListener(mListener); // set the listener    
     return view;
}

OnCheckedChangeListener mListener = new OnCheckedChangeListener() {

     public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {   
         mChecked[(Integer)buttonView.getTag()] = isChecked; // get the tag so we know the row and store the status 
     }
};

Regarding your code from your question, at first I thought it was wrong because of the way you setup the rows but I don't see why the adapter will have that behavior as you detached the row view from the list. Also, I even tested the code and it works quite well regarding CheckBoxes (but with very poor memory handling). Maybe you're doing something else that makes the adapter to not work?

Answer 2

Let me first say that you have thrown away one of the main benefits of using an adapter: Reusable views. Holding a hard reference to each created View holds a high risk of hitting the memory ceiling. You should be reusing convertView when it is non-null, and creating your view when convertView is null. There are many tutorials around which show you how to do this.

Views used in an adapter typically have an OnClickListener attached to them by the parent View so that you can set a OnItemClickListener on the ListView . This will supersede any touch listeners on the individual views. Try setting android:clickable="true" on the CheckBox in XML.

Answer 3

This may not be the most elegant or efficient solution but it works for my situation. For some reason attempting to reuse the views either from an array of views or using convertView makes every thing go wobbley and the CheckBoxes fail to respond.

The only thing that worked was creating a new View everytime getView() is called.

    public View getView(final int position, View convertView, ViewGroup parent) {
        LinearLayout view;
        view=(LinearLayout)inflater.inflate(R.layout.record_view_start,null);


        TextView tv=(TextView)view.findViewById(R.id.engName);
        tv.setText(englishNames[position]);

        CheckBox cBox=(CheckBox)view.findViewById(R.id.checkBox1);
        cBox.setChecked(checked[position]);
        cBox.setOnCheckedChangeListener(new OnCheckedChangeListener(){

            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                checked[position]=isChecked;
            }
        });
        return view;
    }

Finding this solution was also hampered by the fact that I was calling a separately defined onCheckedChangedListener, that then identified which CheckBox by id, rather than having a new listener for each CheckBox.

As yet I haven't marked this as the correct answer as I'm hoping that others may have some input regarding the rather wasteful rebuilding the view every time.