java.io.FileNotFoundException： /storage/emulated/0/New file.txt： open failed： EACCES （Permission denyed）

我一直在尝试加密文件并将这些文件写回同一个地方。但是我收到错误消息说"java.io.FileNotFoundException: /storage/emulated/0/New file.txt: open failed: EACCES (Permission denied)".

我的文件是这个Manifest

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.tdk.mytestapplication2">

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>


<application
    android:allowBackup="true"

我想我在那里提供了正确的许可。我用来加密文件的代码是这个。

public static void encrypt(SecretKey secretKey, String filePath){
    try {
        // Here you read the cleartext.
        FileInputStream fis = new FileInputStream(filePath);
        // This stream write the encrypted text. This stream will be wrapped by another stream.
        FileOutputStream fos = new FileOutputStream(filePath);

        // Create cipher
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
        // Wrap the output stream
        CipherOutputStream cos = new CipherOutputStream(fos, cipher);

        // Write bytes
        int b;
        byte[] d = new byte[8];
        while ((b = fis.read(d)) != -1) {
            cos.write(d, 0, b);
        }

        // Flush and close streams.
        cos.flush();
        cos.close();
        fis.close();

    }catch(IOException e){
        e.printStackTrace();
    }catch (NoSuchAlgorithmException e){
        e.printStackTrace();
    }catch(NoSuchPaddingException e){
        e.printStackTrace();
    }catch(InvalidKeyException e){
        e.printStackTrace();
    }
}

我在按钮内使用了这种方法

Button btnEncrypt = (Button) findViewById(R.id.btnEnc);
    btnEncrypt.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            aesKey = EncAndDec.generateKey();
            String filePath = editText.getText().toString();
            //Generating the file hash
            String md5Hash = MD5Hash.getMD5(filePath);

            System.out.println(aesKey.toString());
            System.out.println(filePath);
            System.out.println(md5Hash);

            //Encrypting the file
            for(int i=1; i<100; i++) {
                EncAndDec.encrypt(aesKey, filePath);
            }
        }
    });

我仍然无法配置此错误。请有人帮忙！