Dibujando con Canvas

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);

        MyCanvasView myCanvasView = new MyCanvasView(this);
        setContentView(myCanvasView);
    }

    private class MyCanvasView extends View {

        /**
         * Constructor de clase
         * */
        public MyCanvasView(Context context) {
            super(context);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);

            Paint paint = new Paint();
            paint.setColor(Color.WHITE);//color blanco
            canvas.drawPaint(paint);//pinta fondo

            //Texto
            paint.setColor(Color.RED);
            paint.setTextSize(42);//tamaño de texto
                            //texto , X, Y, Paint
            canvas.drawText("Hola Mundo Cruel!!!", 10, 56, paint);//pinta texto

            //linea
            paint.setAntiAlias(true);//para evitar efecto sierra
            paint.setStyle(Paint.Style.STROKE);//estilo
            paint.setStrokeWidth(10);//grosor de linea
            paint.setColor(Color.BLUE);
                            //x1 , y1, x2, y2
            canvas.drawLine(0, 100, canvas.getWidth(), 100, paint);

            // rectangulo
            paint.setAntiAlias(true);
            paint.setColor(Color.RED);
            paint.setStyle(Paint.Style.FILL);//relleno
                            // x, y, ancho , alto
            canvas.drawRect(40, 140, canvas.getWidth() - 40, 280, paint);

            // Circulo
            paint.setAntiAlias(true);
            paint.setColor(Color.GREEN);
            paint.setStyle(Paint.Style.STROKE);//borde
            paint.setStrokeWidth(3.6f);
                             // centro X, centro Y, radio
            canvas.drawCircle(canvas.getWidth() / 2 , 400, 100, paint);

            //poligono
            Path path = new Path();
            paint.setColor(Color.MAGENTA);
            paint.setStyle(Paint.Style.FILL);
            path.moveTo(canvas.getWidth() / 2, 550);
            path.lineTo(canvas.getWidth() / 2 + 100, 700);
            path.lineTo(canvas.getWidth() / 2 - 100, 700);
            path.close();
            canvas.drawPath(path, paint);

            //imagen
            Bitmap bmp = BitmapFactory.decodeResource(getResources(),
                    R.mipmap.ic_launcher );//Icono de android
                              //imagen, X, Y
            canvas.drawBitmap(bmp,canvas.getWidth() / 2,760,paint);

        }
    }

}//end  Main