Android Graphics

Education is not limited to just classrooms. It can be gained anytime, anywhere... - Ravi Ranjan (M.Tech-NIT)

Android Simple Graphics Example

The android.graphics.Canvas can be used to draw graphics in android. It provides methods to draw oval, rectangle, picture, text, line etc.

The android.graphics.Paint class is used with canvas to draw objects. It holds the information of color and style.

In this example, we are going to display 2D graphics in android.

activity_main.xml

File: activity_main.xml
  1. <RelativeLayout xmlns:androclass="http://schemas.android.com/apk/res/android"  
  2.     xmlns:tools="http://schemas.android.com/tools"  
  3.     android:layout_width="match_parent"  
  4.     android:layout_height="match_parent"  
  5.     android:paddingBottom="@dimen/activity_vertical_margin"  
  6.     android:paddingLeft="@dimen/activity_horizontal_margin"  
  7.     android:paddingRight="@dimen/activity_horizontal_margin"  
  8.     android:paddingTop="@dimen/activity_vertical_margin"  
  9.     tools:context=".MainActivity" >  
  10.   
  11.     <TextView  
  12.         android:layout_width="wrap_content"  
  13.         android:layout_height="wrap_content"  
  14.         android:text="@string/hello_world" />  
  15.   
  16. </RelativeLayout>  

Activity class

File: MainActivity.java

  1. package com.example.simplegraphics;  

  2.   

  3. import android.os.Bundle;  

  4. import android.app.Activity;  

  5. import android.view.Menu;  

  6. import android.content.Context;  

  7. import android.graphics.Canvas;  

  8. import android.graphics.Color;  

  9. import android.graphics.Paint;  

  10. import android.view.View;  

  11.   

  12. public class MainActivity extends Activity {  

  13.   

  14.     DemoView demoview;  

  15.     /** Called when the activity is first created. */  

  16.     @Override  

  17.     public void onCreate(Bundle savedInstanceState) {  

  18.         super.onCreate(savedInstanceState);  

  19.         demoview = new DemoView(this);  

  20.         setContentView(demoview);  

  21.     }  

  22.   

  23.     private class DemoView extends View{  

  24.         public DemoView(Context context){  

  25.             super(context);  

  26.         }  

  27.   

  28.         @Override protected void onDraw(Canvas canvas) {  

  29.             super.onDraw(canvas);  

  30.   

  31.             // custom drawing code here  

  32.             Paint paint = new Paint();  

  33.             paint.setStyle(Paint.Style.FILL);  

  34.   

  35.             // make the entire canvas white  

  36.             paint.setColor(Color.WHITE);  

  37.             canvas.drawPaint(paint);  

  38.               

  39.             // draw blue circle with anti aliasing turned off  

  40.             paint.setAntiAlias(false);  

  41.             paint.setColor(Color.BLUE);  

  42.             canvas.drawCircle(20, 20, 15, paint);  

  43.   

  44.             // draw green circle with anti aliasing turned on  

  45.             paint.setAntiAlias(true);  

  46.             paint.setColor(Color.GREEN);  

  47.             canvas.drawCircle(60, 20, 15, paint);  

  48.   

  49.             // draw red rectangle with anti aliasing turned off  

  50.             paint.setAntiAlias(false);  

  51.             paint.setColor(Color.RED);  

  52.             canvas.drawRect(100, 5, 200, 30, paint);  

  53.                            

  54.             // draw the rotated text  

  55.             canvas.rotate(-45);  

  56.                       

  57.             paint.setStyle(Paint.Style.FILL);  

  58.             canvas.drawText("Graphics Rotation", 40, 180, paint);  

  59.               

  60.             //undo the rotate  

  61.             canvas.restore();  

  62.         }  

  63.     }  

  64.     @Override  

  65.     public boolean onCreateOptionsMenu(Menu menu) {  

  66.         // Inflate the menu; this adds items to the action bar if it is present.  

  67.         getMenuInflater().inflate(R.menu.main, menu);  

  68.         return true;  

  69.     }  

  70. }  

Output:

android simple graphics example output 1