这里运用到的andorid知识模块主要有Notification和Service，和一个android-async-http-master开源框架
android项目中，有时会有这样一种需求：客户每隔一段时间，就像服务器发送一个请求，以获取某些重要的、实时更新的消息。比如天气预报。
如何让应用实现在后台一直处于运行状态，并且每个一段时间就向服务器发一个请求？android里的四大组件之一：服务，就为我们提供了这种功能。
因此，我们可以尝试在服务里边定义一个线程，只要服务不停止，线程就一直在运行，让它每隔一段时间，就向服务器发送一个请求。
我们来看一下核心代码
1.在Activity中，我们可以通过startService()来启动服务
[java] view plaincopy在CODE上查看代码片派生到我的代码片
public void open(View view) {
Intent intent = new Intent(this, PushSmsService.class);
// 启动服务
startService(intent);
}
2.这里我们需要自定义一个服务类，去继承android的Service类
[java]
/**
*
* 短信推送服务类，在后台长期运行，每个一段时间就向服务器发送一次请求
*
* @author jerry
*
*/
public class PushSmsService extends Service {
private MyThread myThread;
private NotificationManager manager;
private Notification notification;
private PendingIntent pi;
private AsyncHttpClient client;
private boolean flag = true;
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
@Override
public void onCreate() {
System.out.println("oncreate()");
this.client = new AsyncHttpClient();
this.myThread = new MyThread();
this.myThread.start();
super.onCreate();
}
@Override
public void onDestroy() {
this.flag = false;
super.onDestroy();
}
private void notification(String content, String number, String date) {
// 获取系统的通知管理器
manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
notification = new Notification(R.drawable.ic_menu_compose, content,
System.currentTimeMillis());
notification.defaults = Notification.DEFAULT_ALL; // 使用默认设置，比如铃声、震动、闪灯
notification.flags = Notification.FLAG_AUTO_CANCEL; // 但用户点击消息后，消息自动在通知栏自动消失
notification.flags |= Notification.FLAG_NO_CLEAR;// 点击通知栏的删除，消息不会依然不会被删除
Intent intent = new Intent(getApplicationContext(),
ContentActivity.class);
intent.putExtra("content", content);
intent.putExtra("number", number);
intent.putExtra("date", date);
pi = PendingIntent.getActivity(getApplicationContext(), 0, intent, 0);
notification.setLatestEventInfo(getApplicationContext(), number
+ "发来短信", content, pi);
// 将消息推送到状态栏
manager.notify(0, notification);
}
private class MyThread extends Thread {
@Override
public void run() {
String url = "http://110.65.99.66:8080/jerry/PushSmsServlet";
while (flag) {
System.out.println("发送请求");
try {
// 每个10秒向服务器发送一次请求
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
// 采用get方式向服务器发送请求
client.get(url, new AsyncHttpResponseHandler() {
@Override
public void onSuccess(int statusCode, Header[] headers,
byte[] responseBody) {
try {
JSONObject result = new JSONObject(new String(
responseBody, "utf-8"));
int state = result.getInt("state");
// 假设偶数为未读消息
if (state % 2 == 0) {
String content = result.getString("content");
String date = result.getString("date");
String number = result.getString("number");
notification(content, number, date);
}
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void onFailure(int statusCode, Header[] headers,
byte[] responseBody, Throwable error) {
Toast.makeText(getApplicationContext(), "数据请求失败", 0)
.show();
}
});
}
}
}
}
注意我们要在清单文件中注册Service
[plain]
<service android:name=".PushSmsService"></service>
由于通知信息使用到了手机的震动功能和网络访问，所以需要配置权限
[plain]
<uses-permission android:name="android.permission.VIBRATE"/>
<uses-permission android:name="android.permission.INTERNET"/>
我们再定义一个Activity，用于用户点击下拉通知栏里的某条消息后，跳转到详细的消息界面
[java]
public class ContentActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_content);
Intent intent = getIntent();
TextView tv_content = (TextView) this.findViewById(R.id.tv_content);
TextView tv_number = (TextView) this.findViewById(R.id.tv_number);
TextView tv_date = (TextView) this.findViewById(R.id.tv_date);
if (intent != null) {
String content = intent.getStringExtra("content");
String number = intent.getStringExtra("number");
String date = intent.getStringExtra("date");
tv_content.setText("内容：" + content);
tv_number.setText("号码：" + number);
tv_date.setText("日期：" + date);
}
}
}
同样，我们需要在清单文件中注册新的Activity
[plain]
<activity android:name=".ContentActivity"></activity>
注意到上边的代码是需要服务器提供支持的，我们去新建一个简单的服务器，里边添加一个Servlet和一个实体类就可以了
[java]
public class PushSmsServlet extends HttpServlet {
private static int index = 1;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println(index);
// List<Sms> smsList = new ArrayList<Sms>();
Sms sms = new Sms(index,
"我爱你我爱你我爱你我爱你我爱你我爱你我爱你我爱你我爱你我爱你我爱你我爱你" + index, "2013-03-03",
"13522224444");
index++;
// smsList.add(sms);
// sms = new Sms(0, "我真的爱你", "2013-04-04", "13522224444");
// smsList.add(sms);
// sms = new Sms(1, "我真的真的爱你", "2013-05-05", "13522224444");
// smsList.add(sms);
response.setContentType("text/html");
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();
Gson gson = new Gson();
// 将Sms类的数据转换为json数据格式
String json = gson.toJson(sms);
out.write(json);
out.flush();
out.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}
再定义封装用于存放消息的类
[java]
public class Sms {
private int state;
private String content;
private String date;
private String number;
public Sms(int state, String content, String date, String number) {
super();
this.state = state;
this.content = content;
this.date = date;
this.number = number;
}
}
这里只贴出核心代码
