SurfaceView is a class in Android that provides you a drawing surface. You can embed the SurfaceView in the view hierarchy. The SurfaceView punches a hole in its window to display its surface. You use the getHolder() method of the SurfaceView to access the underlying surface. You must ensure that the surface is valid before you can draw something on it. The surface is valid after it is created and before it is destroyed. You can use the surfaceCreated() and surfaceDestroyed() methods to discover when the surface is created and destroyed.
In the previous post, you learnt how to use the SurfaceView to render 3gp view. In this Android tip, I am going to show you how to circles on the SurfaceView and make them animated.

To have a workable example application that draws and animates circles, you create a new Android project. Then modify the activity_main.xml file to add a SurfaceView as shown below.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity"
     
     >
   <SurfaceView
 	android:id="@+id/surfaceView1"
 	android:layout_width="wrap_content"
 	android:layout_height="wrap_content"
 	/>
 </LinearLayout>

 package com.example.andtip;
 import android.app.Activity;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.SurfaceHolder;
 import android.view.SurfaceView;
 import android.view.View;
 
 import android.widget.ImageView;
 
 
 
 public class MainActivity extends Activity implements SurfaceHolder.Callback{
 	
    private SurfaceView surfaceView;
    SurfaceHolder surfaceHolder;
    Paint p;
  	protected void onCreate(Bundle savedInstanceState) {
    	//TODO Auto-generated method stub
    	super.onCreate(savedInstanceState);
    	setContentView(R.layout.activity_main);
    	//make a reference to the SurfaceVeiw
    	surfaceView = (SurfaceView) findViewById(R.id.surfaceView1);
    	//get surface holder
    	surfaceHolder = surfaceView.getHolder();
    	//set Callback interface to the surface holder
    	surfaceHolder.addCallback(this);
    	
    }
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.main, menu);
         //create a LayoutTransition object
         
   	 	  return true;
     }
     @Override
     public void surfaceChanged(SurfaceHolder holder, int format, int width,
     int height) {
     // TODO Auto-generated method stub
 
     }
 
     @Override
     public void surfaceCreated(SurfaceHolder holder) {
    	 p=new Paint(); //create Paint object
    	 p.setColor(Color.BLUE); //set Paint color
    	 p.setStyle(Paint.Style.STROKE); //set Paint style
    	 p.setStrokeWidth(10); //set Paint stroke with
    	 Thread th=new Thread(){
    		 public void run(){
    			 //draw and animate circles
    			 for(float i=5.0f;i<50.0f;i+=5.0f){
    				 Canvas canvas =surfaceHolder.lockCanvas();
    				 canvas.drawCircle(i, i, 2*i,p);
    				 //delay drawing
    				 try {
    						Thread.sleep(1000);
    					} catch (InterruptedException e) {
    						// TODO Auto-generated catch block
    						e.printStackTrace();
    					}
    				 surfaceHolder.unlockCanvasAndPost(canvas);
    				 
    			 }   			 
    	      
    	      
    		 }
    	 };
    	 th.start();
    	
     }
 
     @Override
     public void surfaceDestroyed(SurfaceHolder holder) {
     // TODO Auto-generated method stub
 
     }
 
 }

Posted by: Dara | post date: 07-14-2014 | Subject: Android Apps Development