清单文件里面需要配置

       <provider
            android:name="androidx.core.content.Fileprovider"
            android:authorities="${applicationId}.fileProvider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths" />
        </provider>

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <external-path
        name="files_cache"
        path="Android/data/com.liuan.freereader/cache" />
    <external-path
        name="external_storage_root"
        path="." />
</paths>