View-based Animation

The main activity file (AnimationViewAnimation.java) :

 package com.ava;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
public class AnimationViewAnimation extends Activity {
  ListView lv;
  @Override
  public void onCreate(Bundle savedInstanceState)
  {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.list_layout);
   setupListView();
   this.setupButton();
  }
  private void setupListView()
  {
   String[] listItems = new String[]
   {
     "Item 1", "Item 2", "Item 3",
     "Item 4", "Item 5", "Item 6",
   };
   ArrayAdapter listItemAdapter =
      new ArrayAdapter(this
      ,android.R.layout.simple_list_item_1
      ,listItems);
   lv = (ListView)this.findViewById(R.id.list_view_id);
   lv.setAdapter(listItemAdapter);
  }
  private void setupButton()
  {
   Button b = (Button)this.findViewById(R.id.btn_animate);
   b.setOnClickListener(
     new Button.OnClickListener(){
      public void onClick(View v)
      {
        animateListView();
      }
     });
  }
  private void animateListView()
  {
   ListView lv = (ListView)this.findViewById(R.id.list_view_id);
   lv.startAnimation(new ViewAnimation(lv));
  }
}

The animation class (ViewAnimation.java):

 package com.ava;
import android.app.Activity;
import android.opengl.Matrix;
import android.text.Layout;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.LinearInterpolator;
import android.view.animation.Transformation;
import android.widget.ListView;
public class ViewAnimation extends Animation
{ ListView v;
public ViewAnimation(ListView _v){v = _v;}
@Override
public void initialize(int width, int height, int parentWidth,
             int parentHeight)
{
super.initialize(width, height, parentWidth, parentHeight);
setDuration(2500);
setFillAfter(true);
setInterpolator(new LinearInterpolator());
}
@Override
protected void applyTransformation(float interpolatedTime, Transformation t)
{ float centerX = (float)v.getWidth()/2, centerY = (float)v.getHeight()/2;
final android.graphics.Matrix matrix = t.getMatrix();
matrix.setScale(interpolatedTime, interpolatedTime);
matrix.preTranslate(-centerX, -centerY);
matrix.postTranslate(centerX, centerY);
}
}

The layout file (list_layout.xml):

 <?xml version="1.0" encoding="utf-8"?>
<!-- This file is at /res/layout/list_layout.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button
android:id="@+id/btn_animate"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Start Animation"
/>
<ListView
android:id="@+id/list_view_id"
android:persistentDrawingCache="animation|scrolling"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
</LinearLayout>

The java files put in src folder.
The layout xml file put in res/layout folder.