ListView在Android中无法正常构建

Question

I am working with simple List view using this code,

public class RadioDemoActivity extends Activity {
ArrayList<String> list = new ArrayList<String>();
MyListAdapter mla;
ListView lv;
int position = -1;

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

    lv = (ListView) findViewById(R.id.listView1);

    list.add("one");
    list.add("two");
    list.add("three");
    list.add("four");
    list.add("five");
    list.add("six");
    list.add("seven");
    list.add("eight");
    list.add("nine");
    list.add("ten");
    list.add("eleven");
    list.add("twelve");
    list.add("thirteen");
    list.add("fourteen");
    list.add("fifteen");
    list.add("sixteen");
    list.add("seventeen");
    list.add("eightteen");
    list.add("nineteen");
    list.add("twenty");

    mla = new MyListAdapter(this);
    lv.setAdapter(mla);

}


public class MyListAdapter extends BaseAdapter {
    private LayoutInflater mInflater;

    public MyListAdapter(Context context) {
        mInflater = LayoutInflater.from(context);

    }

    public int getCount() {
        return list.size();
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.cust_list, null);

            TextView tv = (TextView)convertView.findViewById(R.id.txt_title);
            ImageView iv = (ImageView)convertView.findViewById(R.id.imageView1);
            tv.setText(list.get(position));
            Log.v("log_tag","position In"+list.get(position));

        }
        return convertView;
    }
  }
}

but result is like in Image after eleven its showing me one,one, two. please help me

Answer 1

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
         ListHolder holder = null;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.cust_list, null);
            holder=new ListHolder();
            holder.tv = (TextView)convertView.findViewById(R.id.txt_title);
            holder.iv = (ImageView)convertView.findViewById(R.id.imageView1);
            Log.v("log_tag","position In"+list.get(position));
            convertView.setTag(holder);
        }
         else
        {
        holder=(ListHolder) convertView.getTag();
        }
        holder.tv.setText(list.get(position));
        return convertView;
    }
 static class ListHolder
{
    TextView tv;

    ImageView iv;
}

Always write else condition in holder.

Answer 2

change your getView() to:

public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.cust_list, null);
    }
    TextView tv = (TextView)convertView.findViewById(R.id.txt_title);
    ImageView iv = (ImageView)convertView.findViewById(R.id.imageView1);
    tv.setText(list.get(position));
    Log.v("log_tag","position In"+list.get(position));

    return convertView;
}

Answer 3

Can't add the comment in "right" place, but Niteesh Mehra's suggestion above to put LV in scrollview is wrong. LV is a view that shows items in a vertically scrolling list, so there's no point of doing so again.

As for your problem - your getView() implementation is wrong. You should reuse view given if convertView is not null, but reuse means you got view (layout) already baked, but you still have to fill it with content right for this row. So you should do something like:

if( convertView == null ) {
 convertView = <inflate view from XML>;
}

Then you your data in view's elements unconditionally .

Answer 4

I changed my getView() like this and problem solved.

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

        convertView = mInflater.inflate(R.layout.cust_list, null);

        TextView tv = (TextView) convertView.findViewById(R.id.txt_title);
        ImageView iv = (ImageView) convertView.findViewById(R.id.imageView1);

        tv.setText(list.get(position));
        tv.setTag(list.get(position));

        if (RadioDemoActivity.this.position==position)
            iv.setImageResource(R.drawable.greenround);

        return convertView;

    }

Answer 5

change getView method like this

if (convertView == null) {
        convertView = mInflater.inflate(R.layout.cust_list, null);
        }
        TextView tv = (TextView)convertView.findViewById(R.id.txt_title);
        ImageView iv = (ImageView)convertView.findViewById(R.id.imageView1);
        tv.setText(list.get(position));
        Log.v("log_tag","position In"+list.get(position));