can not display file content in text view

Question

i am trying to select a file from the alert dialog and when i press OK i should display the content of the selected file in a text View by using the method display Content() that take the selected file read it and display the content line by line, but it does not display anything and i think the problem is with the call because i already use the method in another app and it work.

this is the code i have and how i call displayContent()

            AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
            dialogBuilder.setTitle("Single Choice List")
                    .setSingleChoiceItems(files, 0, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            selectionID = which;
                        }
                    })
                    .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            //display the content of the selected file
                            displayContent();
                            Toast.makeText(View_Records.this, "You selected " + files[selectionID], Toast.LENGTH_SHORT).show();

                        }
                    })

this is the code for displayContent():

private void displayContent(){

    try {
        myFilesDirectory = new File(getFilesDir(), "MyFiles");
        String fileName = files[selectionID] + ".txt";
        File file = new File(myFilesDirectory, fileName);
        String text;
        FileInputStream fis = new FileInputStream(file);
        InputStreamReader isr = new InputStreamReader(fis);
        BufferedReader br = new BufferedReader(isr);
        StringBuilder sb = new StringBuilder();
        while ((text = br.readLine()) != null) {
            sb.append(text).append("\n");
        }
        txtViewRecords.setText(sb.toString());
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

Answer 1

Replace

AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
            dialogBuilder.setTitle("Single Choice List")
                    .setSingleChoiceItems(files, 0, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            selectionID = which;
                        }
                    })
                    .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            //display the content of the selected file
                            displayContent();
                            Toast.makeText(View_Records.this, "You selected " + files[selectionID], Toast.LENGTH_SHORT).show();

                        }
                    })

with calling for another Activity (startActivityForResult()) with dialog style where you will pick a File and return it's path with Intent and then inside onActivityResult() you just use it to open File and then display it's content inside TextView.

Otherwise you can try to use create() first and add onDismissListener(). Like this:

AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
// do you things with builder
AlertDialog ad = builder.create();
ad.setOnDismissListener(new DialogInterface.OnDismissListener() {
            @Override
            public void onDismiss(DialogInterface dialogInterface) {
                // here you open file, read content and put it inside TextView`
            }
        });
ad.show()

I'm not sure, but this should do the job with AlertDialog without creating Activity for this.

This is for getting all files from directory:

public static ArrayList<File> listFiles(File folder) {
        if (folder.isDirectory()) {
            ArrayList<File> tempList = new ArrayList<>();
            File[] files = folder.listFiles();
            for (File inFile : files) {
                if (!inFile.isDirectory()) {
                    tempList.add(inFile);
                }
            }
            /*Collections.sort(tempList, new Comparator<File>() { //you can sort by name
                @Override
                public int compare(File file1, File file2) {
                    return file1.getName().compareTo(file2.getName());
                }
            });*/
            return tempList;
        }
        return null;
    }

And you just send myFilesDirectory as a parameter. Also you can skip checking if(!inFile.isDirectory()) if you are 100% sure that all files are files, not directories and return Array. And then you just get your file using list.get(selectionID) or array[selectionID] depending what you are going to return from method.

Also method doesn't need to be static. I've got it static for my project needs.