App view appear all white

If your app appear all white full your scrren, maybe your project has more than 1 android.intent.action.MAIN in your all AndroidManifest.xml include modules/app.

<intent-filter>
    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.HOME"/>
    <category android:name="android.intent.category.LAUNCHER" />
</intent-filter>

Because ensure you have only one android.intent.action.MAIN in all of AndroidManifest.xml