A quick Android example with code snippet to demonstrate ListView parallax effect with sticky header. In our previous tutorial, we saw Creating ListView Header Parallax Animation, now in this example we will go little further and make the list header parallax animation with an view stick to top when list is scrolled.
You need to follow the following steps as described below to create the list view parallax effect.
The output of this example in the following attached video.
1. Declare Activity Layout
To begin with let us start declaring your activity layout. It is a bit tricky. Let us take an frame layout that hosts the hero image, sticky view and a ListView.
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/heroImageView"
android:layout_width="match_parent"
android:layout_height="250dp"
android:background="@drawable/wallpaper"
android:scaleType="fitCenter" />
<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:divider="#9E9E9E"
android:dividerHeight="1dp"
android:scrollbars="none"></ListView>
<TextView
android:id="@+id/stickyView"
android:layout_width="match_parent"
android:layout_height="50dp"
android:background="#222"
android:gravity="center_vertical"
android:paddingLeft="10dp"
android:text="Heading1"
android:textColor="#fff"
android:textSize="20sp"
android:textStyle="bold" />
</FrameLayout>
The following screenshot depicts how out activity layout is defined.
2. Declare List Header Layout
Now declare the layout for list header. In this example, I have declared an ImageView inside FrameLayout. The header view is declared as follows.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<Space
android:layout_width="match_parent"
android:layout_height="250dp" />
<Space
android:id="@+id/stickyViewPlaceholder"
android:layout_width="match_parent"
android:layout_height="50dp" />
</LinearLayout>Notice that in the above header layout,
- We have declared
Spaceobjects. Android Space widget is subclass of View, used to occupy invisible, transparent space on the screen. You cannot apply any style, such as color, background etc. - The height of both Space objects are same as the height of hero image and sticky widget as declared in your activity layout.
- These two invisible views will be useful to calculate the view position and will help to create the parallel effect.
3. Declare List Row Layout
Declare another layout for your list view row. In this example, for sake of simplicity I have declared a simple TextView. You may design fancy list of your choice by declaring your own custom adapter.
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#FAFAFA"
android:gravity="center_vertical"
android:text="List Item"
android:padding="8dp"
android:minHeight="40dp"
android:textColor="#222"/>
4. Handle ListView Scroll Events
Following step will guide you with the necessary things required in your activity to create list view, add list header and implement parallax effect.
- Implement
setOnScrollListenerfor your list view to handle the user scroll event. - Calculate the position of the sticky header view according to the position of the first item in the ListView.
- When the first item is already reached to top, you don’t need to re-position the sticky header view.
- Set the hero image to scroll half of the amount that of ListView
import android.content.Context;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.AbsListView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
/**
* <p/>
* Calculate the position of the sticky header view according to the
* position of the first item in the ListView. When the first item is already
* reached to top, you don't need to position the sticky header view.
*
* @author Nilanchala
*/
public class MainActivity extends ActionBarActivity {
private TextView stickyView;
private ListView listView;
private View heroImageView;
private View stickyViewSpacer;
private int MAX_ROWS = 20;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/* Initialise list view, hero image, and sticky view */
listView = (ListView) findViewById(R.id.listView);
heroImageView = findViewById(R.id.heroImageView);
stickyView = (TextView) findViewById(R.id.stickyView);
/* Inflate list header layout */
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View listHeader = inflater.inflate(R.layout.list_header, null);
stickyViewSpacer = listHeader.findViewById(R.id.stickyViewPlaceholder);
/* Add list view header */
listView.addHeaderView(listHeader);
/* Handle list View scroll events */
listView.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
/* Check if the first item is already reached to top.*/
if (listView.getFirstVisiblePosition() == 0) {
View firstChild = listView.getChildAt(0);
int topY = 0;
if (firstChild != null) {
topY = firstChild.getTop();
}
int heroTopY = stickyViewSpacer.getTop();
stickyView.setY(Math.max(0, heroTopY + topY));
/* Set the image to scroll half of the amount that of ListView */
heroImageView.setY(topY * 0.5f);
}
}
});
/* Populate the ListView with sample data */
List<String> modelList = new ArrayList<>();
for (int i = 0; i < MAX_ROWS; i++) {
modelList.add("List item " + i);
}
ArrayAdapter adapter = new ArrayAdapter(this, R.layout.list_row, modelList);
listView.setAdapter(adapter);
}
}