我正在尝试上传一个PDF文件到Firebase存储。我已经参考了官方文档（* click here *）并修改了代码以满足我的需要。
"我想达到的目的"
1.名为“mypdf.pdf”的文件位于“/storage/emulated/0/downloads”（基本上是公共下载目录）
1.把那个文件上传到存储器。
"我试过了“
我尝试使用Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath() + "/mypdf.pdf"访问该文件，然后将其转换为URI并将其提供给firebase putFile()函数。但是，它给了我一个PERMISSION DENIED的异常，尽管我已经在manifest中提到了权限并在运行时请求权限。应用程序也由用户授予权限。

在onCreate()内部调用

if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {

            File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath() + "/mypdf.pdf");
            if (file.exists()) {
                uploadFileFromFirebaseTut();
                Log.d("FileLog", "onCreate: found the file");
            } else Log.d("MainActivity.this", "onCreate: could not find file");

        } else
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, 81);

上传文件的函数

private void uploadFileFromFirebaseTut() {

        StorageReference storageRef = storage.getReference();
        UploadTask uploadTask;

        Uri file = Uri.fromFile(new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).toString() + "/mypdf.pdf"));
        StorageReference riversRef = storageRef.child("uploads/mypdf.pdf");
        uploadTask = riversRef.putFile(file);

        // Register observers to listen for when the download is done or if it fails
        uploadTask.addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception exception) {
                Log.d("File Upload failed", "onFailure: "+exception);
                Toast.makeText(MainActivity.this, "File Upload Failed...", Toast.LENGTH_SHORT).show();
            }
        }).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
            @Override
            public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
                // taskSnapshot.getMetadata() contains file metadata such as size, content-type, etc.
                // ...
                Toast.makeText(MainActivity.this, "File Uploaded..", Toast.LENGTH_SHORT).show();
            }
        });

    }

日志

An unknown error occurred, please check the HTTP result code and inner exception for server response.
                             Code: -13000 HttpResult: 0
StorageException         E  /storage/emulated/0/Download/mypdf.pdf: open failed: EACCES (Permission denied)
                            java.io.FileNotFoundException: /storage/emulated/0/Download/mypdf.pdf: open failed: EACCES (Permission denied)
                                at libcore.io.IoBridge.open(IoBridge.java:492)
                                at java.io.FileInputStream.<init>(FileInputStream.java:160)
                                at java.io.FileInputStream.<init>(FileInputStream.java:115)
                                at android.content.ContentResolver.openInputStream(ContentResolver.java:1484)
                                at com.google.firebase.storage.UploadTask.<init>(UploadTask.java:152)
                                at com.google.firebase.storage.StorageReference.putFile(StorageReference.java:241)
                                at com.example.firebaseupload.MainActivity.uploadFileFromFirebaseTut(MainActivity.java:84)
                                at com.example.firebaseupload.MainActivity.onCreate(MainActivity.java:55)
                                at android.app.Activity.performCreate(Activity.java:8153)
                                at android.app.Activity.performCreate(Activity.java:8137)
                                at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1310)
                                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3698)
                                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3896)
                                at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
                                at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:140)
                                at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:100)
                                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2326)
                                at android.os.Handler.dispatchMessage(Handler.java:106)
                                at android.os.Looper.loop(Looper.java:263)
                                at android.app.ActivityThread.main(ActivityThread.java:8296)
                                at java.lang.reflect.Method.invoke(Native Method)
                                at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:612)
                                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1006)
                            Caused by: android.system.ErrnoException: open failed: EACCES (Permission denied)
                                at libcore.io.Linux.open(Native Method)
                                at libcore.io.ForwardingOs.open(ForwardingOs.java:166)
                                at libcore.io.BlockGuardOs.open(BlockGuardOs.java:254)
                                at libcore.io.ForwardingOs.open(ForwardingOs.java:166)
                                at android.app.ActivityThread$AndroidOs.open(ActivityThread.java:8178)
                                at libcore.io.IoBridge.open(IoBridge.java:478)
                                at java.io.FileInputStream.<init>(FileInputStream.java:160) 
                                at java.io.FileInputStream.<init>(FileInputStream.java:115) 
                                at android.content.ContentResolver.openInputStream(ContentResolver.java:1484) 
                                at com.google.firebase.storage.UploadTask.<init>(UploadTask.java:152) 
                                at com.google.firebase.storage.StorageReference.putFile(StorageReference.java:241) 
                                at com.example.firebaseupload.MainActivity.uploadFileFromFirebaseTut(MainActivity.java:84) 
                                at com.example.firebaseupload.MainActivity.onCreate(MainActivity.java:55) 
                                at android.app.Activity.performCreate(Activity.java:8153) 
                                at android.app.Activity.performCreate(Activity.java:8137) 
                                at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1310) 
                                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3698) 
                                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3896) 
                                at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
                                at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:140) 
                                at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:100) 
                                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2326) 
                                at android.os.Handler.dispatchMessage(Handler.java:106) 
                                at android.os.Looper.loop(Looper.java:263) 
                                at android.app.ActivityThread.main(ActivityThread.java:8296) 
                                at java.lang.reflect.Method.invoke(Native Method) 
                                at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:612) 
                                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1006) 
StorageException         E  StorageException has occurred.

清单包含这些内容

<uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>