Android - get DocumentFile with write access for any file path on sd card (having allready gained sd card permission)

问题

In my app I gain sd card write permission using the following intent. If the user selects the sd card folder from the system file explorer then I have sd card write access.

Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
intent.putExtra("android.content.extra.SHOW_ADVANCED", true);
startActivityForResult(intent, 42);

After that I am able to modify files in th sd card using the DocumentFile class. But I'm having problem getting a DocumentFile for a random file path.

Document.fromFile(new File(path));
Document.fromSingleUri(Uri.fromFile(new File(path)));

both return a DocumentFile object that returns false on .canWrite(). Even though I allready have sd card permission.

So I wrote the method posted in the end of my question to get a DocumentFile that returns true on .canWrite(). But this is slow...And also feels very wrong! There has to be a better way to do this. I also wrote a method that returns the same string as

String docFileUriString = docFile.getUri().toString();

for any file, where docFile is the DocumentFile that is returned by the method below. But

DocumentFile.fromTreeUri(Uri.parse(docFileUriString ));

returns a DocumentFile that points to the root of the sd card instead of the DocumentFile path. Which is just weird. Can someone suggest a more elegant solution?

public static DocumentFile getDocumentFileIfAllowedToWrite(File file, Context con){ 

    List<UriPermission> permissionUris = con.getContentResolver().getPersistedUriPermissions();

    for(UriPermission permissionUri:permissionUris){

        Uri treeUri = permissionUri.getUri();
        DocumentFile rootDocFile = DocumentFile.fromTreeUri(con, treeUri);
        String rootDocFilePath = FileUtil.getFullPathFromTreeUri(treeUri, con);

        if(file.getAbsolutePath().startsWith(rootDocFilePath)){

            ArrayList<String> pathInRootDocParts = new ArrayList<String>();
            while(!rootDocFilePath.equals(file.getAbsolutePath())){
                pathInRootDocParts.add(file.getName());
                file = file.getParentFile();
            } 

            DocumentFile docFile = null;  

            if(pathInRootDocParts.size()==0){ 
                docFile = DocumentFile.fromTreeUri(con, rootDocFile.getUri()); 
            }
            else{
                for(int i=pathInRootDocParts.size()-1;i>=0;i--){
                    if(docFile==null){docFile = rootDocFile.findFile(pathInRootDocParts.get(i));}
                    else{docFile = docFile.findFile(pathInRootDocParts.get(i)); }  
                }
            }
            if(docFile!=null && docFile.canWrite()){ 
                return docFile; 
            }else{
                return null;
            }

        }
    }
    return null; 
}

回答1:

to respond to @AndiMar (21 Mar), I just check if it exists on internal storage, if it does no need to worry.

       try {
        if (sourcefile.toString().contains(Environment.getExternalStorageDirectory().toString())) {
            if (sourcefile.exists()) {
                sourcefile.delete();
            }
        } else {
            FileUtilities fio = new FileUtilities();
            DocumentFile filetodelete = fio.getDocumentFileIfAllowedToWrite(sourcefile, context);
            if (filetodelete.exists()) {
                filetodelete.delete();
            }
        }

    } catch (Exception e) {
        e.printStackTrace();

    }

来源：https://stackoverflow.com/questions/36242311/android-get-documentfile-with-write-access-for-any-file-path-on-sd-card-havin

标签

android

android-sdcard

documentfile