以模拟器屏幕的宽和高作为画板

• 代码文件

public class DrawDemoActivity extends Activity {
    private ImageView iv;
    Display current = null;
    Canvas cv = null;
    Paint paint = null;
    Bitmap bitmap = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        iv=(ImageView) findViewById(R.id.iv);
        current = getWindowManager().getDefaultDisplay();
        //以模拟器屏幕的宽高作为画板
        bitmap = Bitmap.createBitmap(current.getWidth(), current.getHeight(),
                Bitmap.Config.ARGB_8888);//可变视图创建完成
        //绘制画布
        cv=new Canvas(bitmap);
        //绘制画笔
        paint=new Paint();
        //设置颜色
        int color=Color.argb(128, 50, 98, 60);
        paint.setColor(color);
        //设置样式
        paint.setStrokeWidth(12.5f);//笔的宽度
        paint.setStyle(Paint.Style.STROKE);//填充或者不填充
        //绘制图形
        cv.drawPoint(50, 50, paint);//点
        cv.drawLine(50, 50, 160, 200, paint);//直线
        cv.drawRect(80, 80, 220, 220, paint);//矩形
        
        //绘制圆
        RectF rf=new RectF(60, 60, 100, 120);
        cv.drawOval(rf, paint);
        
        //路径 moveto  lineto
        Path p=new Path();
        //绘制封闭图形
        p.moveTo(60, 60);
        p.lineTo(80,90);
        p.lineTo(100, 120);
        p.lineTo(150, 180);
        p.lineTo(200, 220);
        //绘制路径
        cv.drawPath(p, paint);
        
        //绘制文本
        paint.setColor(Color.BLUE);
        paint.setStrokeWidth(2.0f);//画笔宽度
        paint.setTextSize(100);
        cv.drawText("你好，",20, 80, paint);
        //将绘制好的图形在显示器上显示出来
        iv.setImageBitmap(bitmap);
    }
}

• 布局文件

<ImageView 
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />