为什么我的Android不读取“下载”文件夹中的该文件？

Question

I have a file named "mysimulation.txt" in my Downloads folder.

            Scanner input = new Scanner(System.in);
            String filename = "/mysimulation.txt";

            try {
                input = new Scanner(new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + filename));
                Toast.makeText(this, "found", Toast.LENGTH_SHORT).show();
            } catch (FileNotFoundException e) {
                Toast.makeText(this, "not found " + Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), Toast.LENGTH_LONG).show();
            }

Why isn't my phone reading this file in the Downloads folder? I get a file not found Exception.

Answer 1

For any android greater than android 6.0 (masrshmallow). Add the following code to your java code to grant read and write permissions:

File file = new File(path);
 ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE},
                            123);
 //Check if the file is writable or readable (.canRead()) 
 Toast.makeText(this, file.canWrite() ? "y" : "no ", Toast.LENGTH_SHORT).show();