学步园

ActivityManager是android框架的一个重要部分，它负责一新ActivityThread进程创建，Activity生命周期的维护，是与系统所有正在运行着的Acitivity进行交互，对系统所有运行中的Activity相关信息（Task，Memory，Service，App）进行管理和维护；提供了相应的接口用于获取这些信息。

1.//判断应用是否在运行
ActivityManager am = (ActivityManager)context.getSystemService(Context.ACTIVITY_SERVICE);
List<RunningTaskInfo> list = am.getRunningTasks(100);
String MY_PKG_NAME = "com.cyberblue.iitag";
for (RunningTaskInfo info : list) {
if (info.topActivity.getPackageName().equals(MY_PKG_NAME) ||  
                      info.baseActivity.getPackageName().equals(MY_PKG_NAME)) {
Log.i("程序是否运行？", "是");
break;
}
}

2.
/**
* 检测某ActivityUpdate是否在当前Task的栈顶
*/
public boolean isTopActivy(String cmdName){
        ActivityManager manager = (ActivityManager) context.getSystemService(ACTIVITY_SERVICE);
        List<RunningTaskInfo> runningTaskInfos = manager.getRunningTasks(1);
        String cmpNameTemp = null;
        if(null != runningTaskInfos){
                cmpNameTemp=(runningTaskInfos.get(0).topActivity).toString);
                Log.e("cmpname","cmpname:"+cmpName);
        }
       if(null == cmpNameTemp)return false;
       return cmpNameTemp.equals(cmdName);
}

3.android 取当前显示的activity是什么
ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
ComponentName cn = am.getRunningTasks(1).get(0).topActivity;
Log.d("", "pkg:"+cn.getPackageName());
Log.d("", "cls:"+cn.getClassName());

4.android 如何判断程序是否在前台运行
private boolean isTopActivity(){  
        List<RunningTaskInfo>  tasksInfo = activityManager.getRunningTasks(1);  
        if(tasksInfo.size() > 0){  
            //应用程序位于堆栈的顶层  
            if(packageName.equals(tasksInfo.get(0).topActivity.getPackageName())){  
                return true;  
            }  
        }  
        return false;  
    }  
以上4种需要配置权限

<uses-permission android:name="android.permission.GET_TASKS"/>

5.获得系统可用内存信息  

      //获得ActivityManager服务的对象  
        mActivityManager = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);  
//获得系统可用内存信息  
    private String getSystemAvaialbeMemorySize(){  
        //获得MemoryInfo对象  
        MemoryInfo memoryInfo = new MemoryInfo() ;  
        //获得系统可用内存，保存在MemoryInfo对象上  
        mActivityManager.getMemoryInfo(memoryInfo) ;  
        long memSize = memoryInfo.availMem ;    
        //字符类型转换  
        String availMemStr = formateFileSize(memSize); 
        return availMemStr ;  
    }

相关链接：

ActivityManager的表层讲解

http://blog.163.com/sammie_zhang/blog/static/21124868820121029115833919/

 
进一步讲解

http://blog.csdn.net/caowenbin/article/details/6036726

代理模式 与 Am

http://www.cnblogs.com/bastard/archive/2012/05/25/2517522.html

ActivityManager类的详解

http://blog.csdn.net/qinjuning/article/details/6978560