创建一个广播接受者

private BroadcastReceiver mHomeKeyEventReceiver = new BroadcastReceiver() {  
        String SYSTEM_REASON = "reason";  
        String SYSTEM_HOME_KEY = "homekey";  
        String SYSTEM_HOME_KEY_LONG = "recentapps";  
           
        @Override  
        public void onReceive(Context context, Intent intent) {  
            String action = intent.getAction();  
            if (action.equals(Intent.ACTION_CLOSE_SYSTEM_DIALOGS)) {  
                String reason = intent.getStringExtra(SYSTEM_REASON);  
                if (TextUtils.equals(reason, SYSTEM_HOME_KEY)) {  
                     //表示按了home键,程序到了后台 
                }else if(TextUtils.equals(reason, SYSTEM_HOME_KEY_LONG)){  
                    //表示长按home键,显示最近使用的程序列表  
                }  
            }   
        }  
    }; 

在Activity或者Service中注册监听

registerReceiver(mHomeKeyEventReceiver, new IntentFilter(  Intent.ACTION_CLOSE_SYSTEM_DIALOGS));