andorid- 利用非ui线程绘图步骤

andorid- 利用非ui线程绘图方法
Android UI操作并不是线程安全的并且这些操作必须在UI线程中执行，常用的方法是利用Handler来实现UI线程的更新的，其本质就是利用ui主线程发送消息由另外一个非ui线程进行具体的绘制工作。

使用方法非常简单，下面的例子就是利用一个Handler的handleMessage复写方法收取Message对象发送的消息进行绘制一个运行于蓝色直线上的滚动的圆形。

package com.test.surfaceview;import java.lang.reflect.Field;import java.util.ArrayList;import android.app.Activity;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.Rect;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.util.Log;import android.view.SurfaceHolder;import android.view.SurfaceView;import android.view.View;public class TestsurfaceviewActivity extends Activity {private final static String TAG = "TestsurfaceviewActivity";/** Called when the activity is first created. */@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);onHanlderTest();}private final static int MSG_UPDATE_START = 1;private final static int MSG_UPDATE_STOP = 2;private final static int MSG_UPDATE_REGION = 3;private DrawViewer dv = null;private void onHanlderTest(){dv = new DrawViewer(this);new Thread(new myTestThread()).start(); this.setContentView(dv); //请务必注意这句，否则其内容将不是画在此DrawViewer上面}private class DrawViewer extends View {private int center = 0;public DrawViewer(Context ctx) {super(ctx);this.center = 30;}@Overrideprotected void onDraw(Canvas canvas){Log.i(TAG,"onDraw curr position = "+ center);center+= 10;if(center >= 1280) center = 0;Paint mPaint = new Paint(); mPaint.setAntiAlias(true); mPaint.setColor(Color.RED); mPaint.setAlpha(0x80); canvas.drawCircle(center, 320, 40, mPaint); mPaint.setColor(Color.BLUE); canvas.drawLine(0, 360, 1280, 360, mPaint);}}Handler myHandler = new Handler() {public void handleMessage(Message msg) { switch(msg.what){case MSG_UPDATE_START:Log.i(TAG,"revice MSG_UPDATE_START msg");break;case MSG_UPDATE_STOP:Log.i(TAG,"revice MSG_UPDATE_STOP msg");break;case MSG_UPDATE_REGION:Log.i(TAG,"revice MSG_UPDATE_REGION msg");/** * Invalidate the whole view. If the view is visible, * onDraw(Canvas) will be called at some point in the future. * This must be called from a UI thread. To call from a non-UI * thread, call postInvalidate(). */dv.invalidate(); //实际调用的函数是DrawViewer中的onDraw()函数break;}super.handleMessage(msg);}};class myTestThread implements Runnable {private void sendMsg(int what) {Message message = new Message();message.what = what;myHandler.sendMessage(message);}public void run() {this.sendMsg(MSG_UPDATE_START);while (!Thread.currentThread().isInterrupted()) {try {this.sendMsg(MSG_UPDATE_REGION);Thread.sleep(500);} catch (InterruptedException e) {Thread.currentThread().interrupt();}}this.sendMsg(MSG_UPDATE_STOP);}}}

用handler可以更好地使用我们在windows平台写代码的通过消息驱动的程序设计，比较容易理解，android还有其它的方法，后续!