在Android P系统的设备上，如果应用使用的是非加密的明文流量的http网络请求，则会导致该应用无法进行网络请求，https则不会受影响，同样地，如果应用嵌套了webview，webview也只能使用https请求。

针对这个问题，有以下三种解决方法：

（1）APP改用https请求

（2）targetSdkVersion 降到27以下

（3）更改网络安全配置

前面两个方法容易理解和实现，具体说说第三种方法，更改网络安全配置。

在AndroidManifest.xml配置文件的<application>标签中直接插入

android:usesCleartextTraffic="true"

<application
    android:name="io.flutter.app.FlutterApplication"
    android:label="alpha"
    android:usesCleartextTraffic="true"
    android:icon="@mipmap/ic_launcher">
    <activity
        android:name=".MainActivity"
        android:launchMode="singleTop"
        android:theme="@style/LaunchTheme"
        android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
        android:hardwareAccelerated="true"
        android:windowSoftInputMode="adjustResize">
        <!-- Specifies an Android theme to apply to this Activity as soon as
             the Android process has started. This theme is visible to the user
             while the Flutter UI initializes. After that, this theme continues
             to determine the Window background behind the Flutter UI. -->
        <meta-data
          android:name="io.flutter.embedding.android.NormalTheme"
          android:resource="@style/NormalTheme"
          />
        <!-- Displays an Android View that continues showing the launch screen
             Drawable until Flutter paints its first frame, then this splash
             screen fades out. A splash screen is useful to avoid any visual
             gap between the end of Android's launch screen and the painting of
             Flutter's first frame. -->
        <meta-data
          android:name="io.flutter.embedding.android.SplashScreenDrawable"
          android:resource="@drawable/launch_background"
          />
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>
            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter>
    </activity>
    <!-- Don't delete the meta-data below.
         This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
    <meta-data
        android:name="flutterEmbedding"
        android:value="2" />
</application>