问基本画布用法android

EN

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;


public class Graph extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_graph);

    View curView = ((ViewGroup)findViewById(android.R.id.content)).getChildAt(0); //should return a view without top bar...? http://stackoverflow.com/questions/4486034/get-root-view-from-current-activity

    Bitmap bitmap = Bitmap.createBitmap(400, 400, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);
    canvas.drawColor(0xffffffff);
    canvas.save();
    Paint paint = new Paint();
    paint.setDither(true);
    paint.setColor(0xFF0000FF); //blue hopefully
    paint.setStyle(Paint.Style.STROKE);
    paint.setStrokeJoin(Paint.Join.ROUND);
    paint.setStrokeCap(Paint.Cap.ROUND);
    paint.setStrokeWidth(3);

    canvas.drawCircle(100, 100, 5, paint);
    curView.draw(canvas);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.graph, menu);
    return true;
    }

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".Graph" >