判斷android當前執行在前臺還是後臺，有兩種解決方案：

第一種：當app1開啟顯示在最上面頁面時返回true， 但是當app1開啟執行在後臺，app開啟執行在最上面頁面時也返回true。

    private boolean isTopActivity() {
        ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
        ComponentName cn = am.getRunningTasks(1).get(0).topActivity;
        BreezeLog.d(TAG,
 
"pkg:"+cn.getPackageName());
        BreezeLog.d(TAG, "cls:"+cn.getClassName());
        List<ActivityManager.RunningTaskInfo> taskInfo = am.getRunningTasks(1);
        if (taskInfo.size() > 0) {
            if (PACKAGE_NAME.equals(taskInfo.get(0).topActivity.getPackageName())) {
                
 
return true;
            }
        }
       return false;
    }

第二種：當app1開啟顯示在最上面頁面時返回true， 但是當app1開啟執行在後臺，app開啟執行在最上面頁面時返回false。

    private boolean isTopActivity() {
        ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
        List<ActivityManager.RunningAppProcessInfo> appProcesses = am.getRunningAppProcesses();
        
 
if (appProcesses == null) {
            return false;
        }
        for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) {
            if (appProcess.processName.equals(PACKAGE_NAME) && appProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
                return true;
            }
        }
        return false;
    }