已解决，我开启了adb logcat，发现manifest文件中又少了一个元数据标签:

Solved, I enabled adb logcat and found that there is another metadata tag missing in the manifest file:

<meta-data android:name="com.google.android.gms.appstate.APP_ID"
    android:value="@string/app_id" />

刚刚添加了这个标签，它工作正常.

Just added this tag and it is working properly.