Need help with Java for app development

I'm trying to make an app for a class project and the prof is no real help and we've only just started learning Java in another class so any help from anyone that knows Java would be awesome =D

Just a heads up I know very little when it comes to Java, like simple starter stuff. Writing some classes and methods and see if they work, hardly 20-30 lines of code, so that's your warning for running away xDDD

What I want to build is an app that will list the books I have stored in an emulator's storage (I'm coding in Android Studio and the emulator is a Nexus 9 tablet). I've put some files in the emulator's storage which is located in Settings->Storage->Explore->Downloads.

So the main screen of the app has a floating button that when you click on it, the app on the background (not visible to the user) will access the aforementioned folder in the storage, filter the file types and display the books it found there (cover, title and author).

I can post the MainActivity as it is now or the part of the code on the MainActivity that I've put in (after much google searching) that supposedly does what I mentioned I want but I haven't managed to make it work 'cos like I said complete novice here walking blind.

So yeah... anyone experienced/knowledgeable or something that can help?

Tough one. If it was python... I suggest you go to stackoverflow

https://stackoverflow.com/

@libertypo

I had made a thread but no one seemed to answer so I deleted it

Stackoverflow is a great place for Java questions too, not just python.
As for the problem, it's hard to tell what the exact problem is without more detail.

Is it not working because the button isn't working? Or is it something else? Are you using Reader? Scanner? or Stream?

Did you import all the relevant Classes?

Is it just not displaying?

What part isn't working?

EDIT re:Stackoverflow thread:
Were you specific about your problem there? Generally, you need to be extremely specific about the issue for someone to answer. Also, don't be afraid to put a bit of your code out there. It'll make it easier for someone to spot the problem.

@peilicanhelican
Everything that needs to be imported is imported, frankly Android Studio is great like that and I have mastered the Alt+Enter when it comes to importing xDD

I don't know how to code the whole accessing the external storage's downloads folder so for now what the button does is taking you here: Imgur: The most awesome images on the Internet

which isn't what I want and I'm pretty sure except of this part of the code that does what is shown on the pic:

Code:

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btn = (FloatingActionButton) findViewById(R.id.addButton);        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(Intent.ACTION_GET_CONTENT);                Uri uri = Uri.parse(Environment.getExternalStorageDirectory().getPath() + "/external_sd/Downloads/");                intent.setDataAndType(uri, "*/*");                startActivity(Intent.createChooser(intent, "Open folder"));

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the rest of it doesn't work:

Code:

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root = new File(Environment.getExternalStorageDirectory().getAbsolutePath());        //getfile(root);          for (int i = 0; i < fileList.size(); i++) {            TextView textView = new TextView(this);            textView.setText(fileList.get(i).getName());            textView.setPadding(5, 5, 5, 5);              System.out.println(fileList.get(i).getName());              if (fileList.get(i).isDirectory()) {                textView.setTextColor(Color.parseColor("#FF0000"));            }            view.addView(textView);        }          btn = (FloatingActionButton) findViewById(R.id.addButton);        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(Intent.ACTION_GET_CONTENT);                Uri uri = Uri.parse(Environment.getExternalStorageDirectory().getPath() + "/external_sd/Downloads");                intent.setDataAndType(uri, "*/*");                startActivity(Intent.createChooser(intent, "Open folder"));                  //Intent intent = new Intent(Intent.ACTION_GET_CONTENT);                //Uri uri = Uri.parse(Environment.getExternalStorageDirectory().getPath() + "/external_sd/Downloads");                //intent.setDataAndType(uri, "*/*");                //startActivity(Intent.createChooser(intent, "Open folder"));            }        });    }      public ArrayList<File> getfile(File dir) {        File listFile[] = dir.listFiles();        if (listFile != null && listFile.length > 0) {            for (int i = 0; i < listFile.length; i++) {                  if (listFile[i].isDirectory()) {                    fileList.add(listFile[i]);                    getfile(listFile[i]);                  }                else {                    if (listFile[i].getName().endsWith(".mobi")                            || listFile[i].getName().endsWith(".epub")) {                        fileList.add(listFile[i]);                    }                }              }        }        return fileList;    }      @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        super.onActivityResult(requestCode, resultCode, data);        if(resultCode==PICKFILE_RESULT_CODE){            Log.d("TAG", "File Uri " +data.getData());        }    }

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This is only the part of the code that is relevant to what I want to do, but I'll post the whole MainActivity if that might help. Also actually I just realized that since mobi and epub aren't recognizable files to the emulator maybe I should change the filtering to pdfs or something

@tina21
I haven't done a lot of Java but I'll try to help figure out the issue. For this line:

Uri uri = Uri.parse(Environment.getExternalStorageDirectory( ).getPath() + "/external_sd/Downloads/");

Check to see if the path is directed to the correct location. Environment.getExternalStorageDirectory() is probably already going to /external_sd/Downloads/ so it's redundant to add that. Give /Downloads/ a try instead. This StackOverflow answer might explain more: link

Or if you can somehow print out the path to Android Studio's console so you can see the entire path, that would be useful.

Tip: could you also paste your code in something that will preserve the whitespace? (eg. Pastebin, Github) It'll be easier to read and debug too, something to keep in mind for the future.

Please post the entire class as well as your pom.xml, any resource folder contents, MANAFEST.MF, on pastebin and link here or publish your entire project to github. Please also include the stack trace, or at least root cause exception. It may also help to know how you're running and publishing your code (eg: andriod sdk version and emulator or some other ide ....)

Thank you.