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

public class MainActivity extends Activity {
    public void onCreate(Bundle bundle) {
        super.onCreate(bundle);
        setContentView(new MyView(this));
    }
}

 class MyView extends View {
     public MyView(Context context) {
        super(context);
        setBackgroundColor(Color.GREEN);    }
     protected void onDraw(Canvas canvas) {
        Paint paint = new Paint();
        paint.setTextSize(100);
        canvas.drawText("Hello Android Studio!", 0, 100, paint);
    }
}