handler的简单使用

实现简单的动画：

public class MainActivity extends Activity {// 定义周期性显示的图片的IDint[] imageIds = new int[] { R.drawable.java, R.drawable.ee,R.drawable.ajax, R.drawable.xml, R.drawable.classic };int currentImageId = 0;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);final ImageView show = (ImageView) findViewById(R.id.show);final Handler myHandler = new Handler() {@Overridepublic void handleMessage(Message msg) {// 如果该消息是本程序所发送的if (msg.what == 0x1233) {// 动态地修改所显示的图片show.setImageResource(imageIds[currentImageId++]);if (currentImageId >= 4) {currentImageId = 0;}}}};// 定义一个计时器，让该计时器周期性地执行指定任务new Timer().schedule(new TimerTask() {@Overridepublic void run() {// 新启动的线程无法访问该Activity里的组件// 所以需要通过Handler发送信息Message msg = new Message();msg.what = 0x1233;// 发送消息myHandler.sendMessage(msg);}}, 0, 800);}}