在程序中如果需要在后台长时间做一件事情,比如联网获取数据等操作,就要用到线程。
但为了提高用户体验,有以下几点需要注意:
1、程序可见时线程开始运行;
2、程序不可见时线程暂停;
3、程序退出时停止线程;
以下根据我自己的程序提出一个公用的代码,大家可以把自己的业务逻辑套进去:
public class NetUtil2 extends Thread { //NewsBrief为新闻实体类; private List<NewsBrief> loopList = new ArrayList<NewsBrief>(); private boolean isClose = false; //IObtainData为一个接口,因为很多程序在用,因此拿Map存储; private Map<Integer, IObtainData> obtainMap = new HashMap<Integer, IObtainData>(); private int currentPage = 0; private boolean isPause = false; private NetUtil2() { } private static NetUtil2 single = null; public synchronized static NetUtil2 getInstance() { if (single == null) { single = new NetUtil2(); } return single; } public synchronized void addNewsBrief(NewsBrief newsBrief) { loopList.add(newsBrief); //有数据要处理时唤醒线程 this.notify(); } public void setObtainDataListener(int channelId, IObtainData iod) { //添加回调 if (!obtainMap.containsKey(channelId)) { obtainMap.put(channelId, iod); } } public void setCurrentPage(int page) { currentPage = page; } /** * 暂停线程 */ public synchronized void onThreadPause() { isPause = true; } /** * 线程等待,不提供给外部调用 */ private void onThreadWait() { try { synchronized (this) { this.wait(); } } catch (Exception e) { e.printStackTrace(); } } /** * 线程继续运行 */ public synchronized void onThreadResume() { isPause = false; this.notify(); } /** * 关闭线程 */ public synchronized void closeThread() { try { notify(); setClose(true); interrupt(); } catch (Exception e) { e.printStackTrace(); } } public boolean isClose() { return isClose; } public void setClose(boolean isClose) { this.isClose = isClose; } @Override public void run() { while (!isClose && !isInterrupted()) { if (loopList.size() > 0 && !isPause) { int index = 0; NewsBrief newsBrief = null; // 当前页面优先加载 for (int i = 0; i < loopList.size(); i++) { if (loopList.get(i).getChannelId() == currentPage) { newsBrief = loopList.get(i); index = i; break; } } if (null == newsBrief) { newsBrief = loopList.get(0); } String reslut = getNewsContent(newsBrief); if (!"-1".equals(reslut)) { // 获取成功,更新 if (obtainMap.containsKey(newsBrief.getChannelId())) { obtainMap.get(newsBrief.getChannelId()) .updateNewsBrief(newsBrief); } synchronized (loopList) { loopList.remove(index); } } else { //获取失败,移至队尾 synchronized (loopList) { NewsBrief nb = loopList.remove(index); loopList.add(nb); } } try { Thread.sleep(300); } catch (InterruptedException e) { e.printStackTrace(); } } else { onThreadWait(); } } } }
注意:
线程的暂停用isPause控制,说白了其实就是不让线程进入wait状态;