notificationManager = (NotificationManager)this.getSystemService(NOTIFICATION_SERVICE);
notification = new Notification(R.drawable.touxiang,"信息",System.currentTimeMillis());

sendButton.setOnClickListener(new OnClickListener()
{
  @Override
  public void onClick(View v)
  {
    Intent intent = new Intent(NotificationActivity.this,NotificationActivity.class);
    PendingIntent pendingIntent = PendingIntent.getActivity(NotificationActivity.this, 0, intent, 0);
    notification.setLatestEventInfo(NotificationActivity.this, "你的一条信息", "来自张三的信息", pendingIntent);
    notificationManager.notify(ID,notification);
    notificationManager.notify(ID+1, notification);
  }
})

package com.study.android;
import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity {
  private Button startBtn;
  private Button cancelBtn;
  private static final int HELLO_ID = 1;
  NotificationManager mNotificationManager;
  Notification mNotification;
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    startBtn = (Button)findViewById(R.id.startBtn);
    cancelBtn = (Button)findViewById(R.id.cancelBtn);
    // ① 获取NotificationManager的引用
    String ns = Context.NOTIFICATION_SERVICE;
    mNotificationManager = (NotificationManager)this.getSystemService(ns);
    // ② 初始化Notification
    int icon = R.drawable.ic_launcher;
    CharSequence tickerText = "Hello";
    long when = System.currentTimeMillis();
    mNotification = new Notification(icon,tickerText,when);
    mNotification.defaults = Notification.DEFAULT_ALL;
    mNotification.flags |= Notification.FLAG_NO_CLEAR;
    mNotification.flags |= Notification.FLAG_SHOW_LIGHTS;
    // ③ 定义notification的消息 和 PendingIntent
    Context context = this;
    CharSequence contentTitle ="My notification";
    CharSequence contentText = "Hello World";
    Intent notificationIntent = new Intent(this,MainActivity.class);
    PendingIntent contentIntent = PendingIntent.getActivity(context, 0, notificationIntent,0 );
    mNotification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);
    // ④ 把封装好的notification传入NotificationManager
    // 开启通知
    startBtn.setOnClickListener(new OnClickListener() {
      @Override
      public void onClick(View v) {
        mNotificationManager.notify(HELLO_ID,mNotification);
      }
    });
    // 取消通知
    cancelBtn.setOnClickListener(new OnClickListener() {
      @Override
      public void onClick(View v) {
        mNotificationManager.cancel(HELLO_ID);
      }
    });
  }
}