android 9.x 实现应用内更新安装

折腾了3天，总算解决了问题。

依赖如下

implementation 'androidx.core:core:1.0.2'
//  implementation 'com.android.support:support-compat:28.0.0'
support包，试了几个版本总是提示一堆

Duplicate class android.support.v4. ……
切换到依赖 androidx，则不能忘记在 androidManifest.xml中替换 name值

    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.INTENT" />
    <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />
    <application
        android:theme="@style/AppTheme"
        android:networkSecurityConfig="@xml/network_security_config"
        >
        <activity android:name=".UpdateActivity" />
        <provider  android:authorities= "${applicationId}.fileprovider"
            android:name="androidx.core.content.FileProvider"
            android:exported="false"
            android:grantUriPermissions="true" >
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/filepath" />
        </provider>
    </application>

工具类如下

    public static void installApk(Activity activity, File apkFile){
        Intent intent =new Intent();
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        //Uri uri = Uri.fromFile(apkFile);
        Uri uri = null;
        //todo N FileProvider
        //todo O install permission
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.N){
            uri = androidx.core.content.FileProvider.getUriForFile(activity,activity.getPackageName()+".fileprovider", apkFile);
            intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
            intent.addFlags(Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
        }else{
            uri = Uri.fromFile(apkFile);
        }
        intent.setDataAndType(uri, "application/vnd.android.package-archive");
        activity.startActivity(intent);
    }

另外为了单纯一点，避免错误提示

Duplicate class android.support.v4.app.INotificationSideChannel found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.app.INotificationSideChannel$Stub found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.app.INotificationSideChannel$Stub$Proxy found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.os.IResultReceiver found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.os.IResultReceiver$Stub found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.os.IResultReceiver$Stub$Proxy found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.os.ResultReceiver found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.os.ResultReceiver$1 found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.os.ResultReceiver$MyResultReceiver found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)
Duplicate class android.support.v4.os.ResultReceiver$MyRunnable found in modules classes.jar (androidx.core:core:1.0.2) and classes.jar (com.android.support:support-compat:25.3.1)

Go to the documentation to learn how to Fix dependency resolution errors.

解决办法为，在gradle.properties中添加如下代码

android.useAndroidX=true
android.enableJetifier=true

最后贴一下 androidManifest.xml中提到的2个xml文件，在res/xml文件夹下

network_security_config.xml

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <base-config cleartextTrafficPermitted="true" />
</network-security-config>

filepath.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <root-path name="root" path="." />
    <files-path name="files" path="." />
    <external-path name="external" path="." />
    <external-cache-path name="external_cache" path="." />
    <external-files-path name="external_file" path="." />
</paths>