为什么我不能使用FileProvider在Android 9中删除文件？

Question

我正在尝试使用以下代码以编程方式删除Android 9中的文件。该代码在Android 7和Android 8上运行良好，但在Android 9中却无法使用。

删除代码

public void deleteFile(String filePath) {
    Log.v("File Path", filePath);
    File file = new File(filePath);
    if (file.exists()) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M || filePath.startsWith("content://")) {
            ContentResolver contentResolver = getActivity().getContentResolver();
            Uri fileUri = FileProvider.getUriForFile(getContext(), BuildConfig.APPLICATION_ID + ".provider", file);
            Log.v("File Uri", ""+fileUri);
            if(contentResolver.delete(fileUri, null, null) == 0){
                Log.v(">=Marshmallow - File", "File could not be deleted!");
            }else{
                Log.v(">=Marshmallow - File", "File deleted!");
            }
        } else {
                if (file.delete()) {
                    dbHelper.deleteFromPDFAll(filePath);
                    Log.v("File", "File deleted!");
                } else {
                    Log.v("File", "File could not be deleted!");
                }
        }
    } else {
        Log.e("File", "File does not exist!");
    }
}

清单-提供程序

<provider
    android:name="android.support.v4.content.FileProvider"
    android:authorities="${applicationId}.provider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/provider_paths"/>
</provider>

提供者路径（provider_paths.xml）

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

Logcat

2019-07-03 11:37:11.622 15809-15809/com.spicysoftware.pdfviewer V/File Path: /storage/emulated/0/Documents/stammdaten/gem_000004/GemObjekt_00010506.pdf
2019-07-03 11:37:11.623 15809-15809/com.spicysoftware.pdfviewer V/File Uri: content://com.spicysoftware.pdfviewer.provider/external_files/Documents/stammdaten/gem_000004/GemObjekt_00010506.pdf
2019-07-03 11:37:11.626 15809-15809/com.spicysoftware.pdfviewer V/>=Marshmallow - File: File could not be deleted!