Use following code:
MainActivity.java
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_my);
    ArrayList<HashMap<String, String>> itemsList = new ArrayList<HashMap<String, String>>();
    ListView listView = (ListView) findViewById(R.id.listView);
    for (int i = 0; i < 5; i++) {
        // creating new HashMap
        HashMap<String, String> map = new HashMap<String, String>();
        // adding each child node to HashMap key => value
        map.put("key1", "value1");
        map.put("key2", "value2");
        // adding HashList to ArrayList
        itemsList.add(map);
    }
    ListAdapter listAdapter = new ListAdapter(this, itemsList);
    listView.setAdapter(listAdapter);
}
list_row.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/imageView"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:src="@drawable/ic_launcher" />
<ProgressBar
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/progressBar"
    android:layout_toEndOf="@+id/imageView"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />
</RelativeLayout>
ListAdapter.java
@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View vi = convertView;
    if (convertView == null)
        vi = inflater.inflate(R.layout.list_row, null);
    ImageView imageView = (ImageView) vi.findViewById(R.id.imageView);
    final ProgressBar progressBar = (ProgressBar) vi.findViewById(R.id.progressBar);
    //This line shows progressBar again for recycled view
    progressBar.setVisibility(View.VISIBLE);
    Picasso.with(activity.getApplicationContext()).load(imagePath).resize(100, 100)
            .into(imageView, new Callback() {
                @Override
                public void onSuccess() {
                    progressBar.setVisibility(View.GONE);
                }
                @Override
                public void onError() {
                    //error
                }
            });
    return vi;
}
Don't forget to add import for Picasso Callback
import com.squareup.picasso.Callback;