获取Android当前显示(最外层)的Activity的全名

public static String getTopActivityComponet(Context context)
{
try {
ActivityManager am = (ActivityManager) context
.getSystemService(Context.ACTIVITY_SERVICE);
ComponentName cn = am.getRunningTasks(1).get(0).topActivity;
return cn.getClassName();
} catch (Exception e) {
e.printStackTrace();
return null;
}
}