为什么我的android不在Downloads文件夹中读取此文件？

Question

我的Downloads文件夹中有一个名为“mysimulation.txt”的文件。

            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();
            }

为什么我的手机在“下载”文件夹中没有读取此文件？ 我找到了一个未找到的文件Exception。

Answer 1

对于任何大于android 6.0（masrshmallow）的android。将以下代码添加到Java代码中以授予读写权限：

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();