判断当前Activity是否存在

Intent intent = new Intent();
        intent.setClassName(MyApp.getAPPContext().getPackageName(), className);
        ResolveInfo resolveInfo = MyApp.getAPPContext().getPackageManager().resolveActivity(intent, PackageManager.MATCH_DEFAULT_ONLY);
        if(ResolveInfo!=null){
            //存在
        }else{
            //不存在
        }