15_Canvas画图形

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.view.Menu;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;

public class MainActivity extends Activity {
  
    
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         requestWindowFeature(Window.FEATURE_NO_TITLE);
         getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                              WindowManager.LayoutParams.FLAG_FULLSCREEN);
         setContentView(new RenderView(this));
     }
 }

class RenderView extends View {       
    Paint paint;
   
    public RenderView(Context context) {
        super(context);
        paint = new Paint();           
    }
   
    protected void onDraw(Canvas canvas) {
     //背景
        canvas.drawRGB(255, 255, 255);      
        //划线
        paint.setColor(Color.RED);
        canvas.drawLine(0, 0, canvas.getWidth()-1, canvas.getHeight()-1, paint);
       
        //画园
        paint.setStyle(Style.STROKE);
        paint.setColor(0xff00ff00);           
        canvas.drawCircle(canvas.getWidth() / 2, canvas.getHeight() / 2, 40, paint);
                   
        //画矩形
        paint.setStyle(Style.FILL);
        paint.setColor(0x770000ff);
        canvas.drawRect(100, 100, 200, 200, paint);
        invalidate();
    }
}