Android 图形用户界面 之 绘图（一）

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Matrix;

import android.graphics.Paint;

import android.graphics.Rect;

import android.util.Log;

import android.view.SurfaceHolder;

import android.view.SurfaceView;

/**

* http://wallage.blog.163.com/blog/static/173896242010101232220959/
* @author emmet1988.iteye.com

*

*/

public class SurfaceViewDraw extends SurfaceView implements Runnable,SurfaceHolder.Callback {

private Bitmap backgroundBitmap;

private Bitmap rotateBitmap;

SurfaceHolder surfaceHolder;

public SurfaceViewDraw(Context context) {

super(context);

backgroundBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.background_surfaceview);

rotateBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.rotate_surfaceview);

surfaceHolder = this.getHolder();

surfaceHolder.addCallback(this);

}

public void surfaceCreated(SurfaceHolder holder) {

new Thread(this).start();

Log.d("surfaceview", "surfaceCreated");

}

public void surfaceChanged(SurfaceHolder holder, int format, int width,

int height) {

Log.d("surfaceview", "surfaceChanged");

}

public void surfaceDestroyed(SurfaceHolder holder) {

Log.d("surfaceview", "surfaceDestroyed");

}

@Override

public void run() {

Log.d("surfaceview", "run");

Canvas canvas = null;

int rotateValue = 0;//旋转角度

int frameCount = 0;//帧计数器

while (!Thread.currentThread().isInterrupted()) {

try {

// canvas = surfaceHolder.lockCanvas();//获取画布对象(获取整个屏幕的画布)

canvas = surfaceHolder.lockCanvas(new Rect(10, 10, 240, 250));//获取某个区域的画布

Paint paint = new Paint();

Log.d("surfaceview", "rotateValue " +rotateValue+"|frameCount "+frameCount);

if (frameCount++ < 2) {//仅在第一次绘制时绘制背景

/*

* 这里为什么设置成＜2，而不是1，是由于SurfaceView本身的双缓冲技术。

覆盖刷新其实就是将每次的新的图形绘制到上一帧去，

所以如果图像是半透明的，就要考虑重复叠加导致的问题了，

而如果是完全不透明的图形则不会有任何问题。

背景会在背景图和黑色背景之间来回闪。

这个问题其实是源于SurfaceView的双缓冲机制，我理解就是它会缓冲

前两帧的图像交替传递给后面的帧用作覆盖，这样由于我们仅在第一帧

绘制了背景，第二帧就是无背景状态了，且通过双缓冲机制一直保持下

来，解决办法就是改为在前两帧都进行背景绘制。

*/

canvas.drawBitmap(backgroundBitmap, 0, 0, paint);//绘制背景

}

//创建矩阵以控制图片的旋转和平移

Matrix matrix = new Matrix();

rotateValue += 40;

matrix.setRotate(rotateValue, rotateBitmap.getWidth()/2, rotateBitmap.getHeight()/2);

// matrix.postRotate(rotateValue, rotateBitmap.getWidth()/2, rotateBitmap.getHeight()/2);

// matrix.setTranslate(100, rotateValue);

if (rotateValue == 360) {

rotateValue = 0;

}

matrix.setTranslate(80,50);//设置左边距和上边距

//绘制问号

Log.d("surfaceview", "canvas "+canvas);

Log.d("surfaceview", "rotateBitmap "+rotateBitmap);

Log.d("surfaceview", "matrix "+matrix);

Log.d("surfaceview", "paint "+paint);

if (canvas != null) {

canvas.drawBitmap(rotateBitmap, matrix, paint);

//解锁画布，提交画好的图像

surfaceHolder.unlockCanvasAndPost(canvas);

}

Thread.sleep(30);

} catch (InterruptedException e) {

Thread.currentThread().interrupt();

Log.d("surfaceview", "InterruptedException");

} finally {

Log.d("surfaceview", "finally");

}

}

}

}