Question

This is my code. It loads more data when being out of data. I want to add a footer ProgressBar to GridView when it loads more data. How to do? I’ve seen many questions on StackOverflow but there is no answer for it.

public class MainActivity extends Activity {
    private static final String TAG = "MainActivity";
    private final List<Integer> commonImageList = new ArrayList<Integer>();
    private int index = 0;
    private boolean isLoading = false;
    private static final int NUM = 18;
    private ImageAdapter adapter;

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

        final Task task = new Task(mThumbIds, index);
        task.setOnPostExecuteListener(new OnPostExecuteListener<List<Integer>>() {
            @Override
            public void onPostExecute(final List<Integer> result) {
                System.out.println("RESULT: " + result);
                if(result.isEmpty()) {
                    return;
                }

                // Store it.
                commonImageList.addAll(result);

                // Prepare gridView.
                final GridView gridview = (GridView) findViewById(R.id.gridview);
                adapter = new ImageAdapter(MainActivity.this, commonImageList);
                gridview.setAdapter(adapter);

                gridview.setOnScrollListener(new OnScrollListener() {
                    @Override
                    public void onScrollStateChanged(final AbsListView view, final int scrollState) {

                    }

                    @Override
                    public void onScroll(final AbsListView view, final int firstVisibleItem,
                            final int visibleItemCount, final int totalItemCount) {
                        System.out.println("firstVisibleItem: " + firstVisibleItem);
                        System.out.println("visibleItemCount: " + visibleItemCount);
                        System.out.println("totalItemCount: " + totalItemCount);

                        final boolean loadMore = (firstVisibleItem + visibleItemCount >= totalItemCount);
                        System.out.println("loadMore: " + loadMore);
                        System.out.println("isLoading: " + isLoading);

                        if(loadMore && !isLoading) {
                            // TODO Show footer here.


                            ShowLog.showLogInfo(TAG, "============= LOAD MORE =============");
                            // Get more images.
                            index = index + NUM;
                            final Task task = new Task(mThumbIds, index);
                            task.setOnPreExecuteListener(new OnPreExecuteListener() {
                                @Override
                                public void onPreExecute() {
                                    isLoading = true;
                                }
                            });
                            task.setOnPostExecuteListener(new OnPostExecuteListener<List<Integer>>() {
                                @Override
                                public void onPostExecute(final List<Integer> result) {
                                    System.out.println("RESULT222: " + result);

                                    if(result.isEmpty()) {
                                        return;
                                    }
                                    System.out.println("HIEU THONG MINH");

                                    // Update common list.
                                    commonImageList.addAll(result);

                                    // Update adapter.
                                    adapter.notifyDataSetChanged();

                                    isLoading = false;
                                }
                            });
                            task.execute();
                        }
                    }
                });
            }
        });
        task.execute();

    }

    private class Task extends AbstractWorkerTask<Void, Void, List<Integer>> {
        private final Integer []thumbs;
        private final int index;

        public Task(final Integer []thumbs, final int index) {
            this.thumbs = thumbs;
            this.index = index;
        }

        @Override
        protected List<Integer> doInBackground(final Void... params) {
            final List<Integer> list = new ArrayList<Integer>();
            for(int i = index; i < index + NUM && i < thumbs.length; ++i) {
                list.add(thumbs[i]);
            }
            return list;
        }
    }

    public static class ImageAdapter extends BaseAdapter {
        private final Context context;              
        private final List<Integer> imageList;

        public ImageAdapter(final Context c, final List<Integer> imageList) {
            context = c;
            this.imageList = imageList;
        }

        @Override
        public int getCount() {
            return imageList.size();
        }

        @Override
        public Object getItem(final int position) {
            return null;
        }

        @Override
        public long getItemId(final int position) {
            return 0;
        }

        // create a new ImageView for each item referenced by the Adapter
        @Override
        public View getView(final int position, final View convertView, final ViewGroup parent) {
            ImageView imageView;
            if (convertView == null) {  // if it's not recycled, initialize some attributes
                imageView = new ImageView(context);
                imageView.setLayoutParams(new GridView.LayoutParams(150, 150));
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setPadding(8, 8, 8, 8);

            } else {
                imageView = (ImageView) convertView;
            }

            imageView.setImageResource(imageList.get(position));
            return imageView;
        }
    }

    // references to our images
    private static final Integer[] mThumbIds = {
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
    };
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/gridview"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    android:columnWidth="150dp"
    android:numColumns="3"
    android:verticalSpacing="10dp"
    android:horizontalSpacing="10dp"
    android:stretchMode="columnWidth"
    android:gravity="center"
/>

Answer 1

Here the logic i did to add load more item in GridView
1. Create a fake item at the last of Adapter’s input data

public class MediaGridAdapter extends BaseAdapter {

    private ArrayList<Media> list;
    private final Media special = new Media("-1", "", "", "", ""); 

    public MediaGridAdapter(Context context, int imageID, ArrayList<Media> array, int type) {

        list = array;

        if(list != null) {
            list.add(special);
        }
            }

public void appendDataList(ArrayList<Media> appendedList, boolean isEnd) { //called in postExecute to append new data

    //remove special element in original list
    list.remove(list.size() - 1);
    //append collection of media to list
    list.addAll(appendedList);
    //check to add special element
    if(!isEnd) {

        list.add(special);
    }
}   
}

2. In getView method : Check if it’s the last position (is our fake item) return special layout( progress bar…) for this.

    if(position == (list.size() - 1)) {

        Context context = parent.getContext();
        item = (RelativeLayout) LayoutInflater.from(context).inflate(R.layout.item_special_more, null);
        item.setTag(MORE_BUTTON);
        return item;
    }

The last in onItemClick check tag to start getMoreAsyncTask

if (v.getTag().equals(MediaGridAdapter.MORE_BUTTON)) {    

                        GetMoreItems task = new GetMoreItems();
                        task.execute(url);
                        return;
                    }