Making a middle element to get stuck in the header (ScrollView/ListView)

android, android-listview, android-scrollview

Solution

I have used(or rather, tried to use) the `StickyListHeaders` library in the past. After having some issues with it, I came up with the following. It is not much different from what other posters have suggested.

The main layout file `activity_layout.xml` consists of a `ListView` and a `LinearLayout` which is invisible by default. Using the OnScrollListener's onScroll() method, the `LinearLayout's` visibility is toggled. You don't need to inflate another layout or add views dynamically to your layout's parent. This is what the `onScroll` method looks like:

public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    if (firstVisibleItem > 3) {        // 5th row will stick
        llHeader.setVisibility(View.VISIBLE);
    } else {
        llHeader.setVisibility(View.GONE);
    }
}

Simply, toggle the visibility to get the desired effect. You can take a look at the following code. Its a working example of what you can expect. The activity contains a `ListView` with a strictly barebone extension of `BaseAdapter`. The `ListView` is populated with numbered Buttons(one on each row, starting at 0, and going up to 19).

public class StickyHeader extends Activity {    

    LinearLayout llHeader;  
    ListView lv;
    SHAdapter shAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_layout);

        lv = (ListView) findViewById(R.id.listView1);        
        llHeader = (LinearLayout) findViewById(R.id.llHeader);        
        shAdapter = new SHAdapter();        
        lv.setAdapter(shAdapter);

        lv.setOnScrollListener(new OnScrollListener() {

            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {}

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                if (firstVisibleItem > 3) {
                    llHeader.setVisibility(View.VISIBLE);
                } else {
                    llHeader.setVisibility(View.GONE);
                }
            }
        });
    }   

    public class SHAdapter extends BaseAdapter {

        Button btCurrent;
        int[] arr = new int[] {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19};

        @Override
        public int getCount() {
            return 20;
        }

        @Override
        public Object getItem(int arg0) {
            return arr[arg0];
        }

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

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            convertView = getLayoutInflater().inflate(R.layout.list_item_layout, null);         
            btCurrent = (Button) convertView.findViewById(R.id.button1);            

            if ((Integer)getItem(position) == 4) {
                btCurrent.setText("Number " + getItem(position) + " is sticky");
            } else {
                btCurrent.setText("" + getItem(position));
            }

            return convertView;
        }
    }
}

activity_layout.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <ListView
        android:id="@+id/listView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

    <!-- This LinearLayout's visibility is toggled -->

    <!-- Improvement suggested by user 'ar34z' 
         (see comment section below) --> 
    <include layout="@layout/list_item_layout" />

</RelativeLayout>

list_item_layout

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/llHeader"
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:background="@color/white"
    android:orientation="vertical" >

    <Button
        android:id="@+id/button1"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

Problem

Original source