write_external_storage也read_external_storage

Question

我的代码未创建新文件夹，也无法保存，请提供帮助。

我已经添加了一个Android清单write_external_storage以及read_external_storage

public class MainActivity extends AppCompatActivity {
EditText editText,editText2;
Button button,button2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = findViewById(R.id.button);
        button2 = findViewById(R.id.button2);
        editText = findViewById(R.id.editText);
        editText2 = findViewById(R.id.editText2);

    }

    public void save(View view) {
        String state;
        state=Environment.getExternalStorageState();
        if(Environment.MEDIA_MOUNTED.equals(state)){
            File Root = Environment.getExternalStorageDirectory();
            File Dir = new File(Root.getAbsolutePath()+"/AppFile");
            if(!Dir.exists()){
                Dir.mkdir();
            }
            File file = new File(Dir,"kupalkana.txt");
            String Message = editText.getText().toString();
            try {
                FileOutputStream fileOutputStream = new FileOutputStream(file);
                fileOutputStream.write(Message.getBytes());
                fileOutputStream.close();
                editText.setText("");
                Toast.makeText(this, "Message Saved", Toast.LENGTH_LONG).show();

            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }else{
            Toast.makeText(this, "External Storage not Found", Toast.LENGTH_LONG).show();
        }

    }
    public void load(View view) {
        File Root = Environment.getExternalStorageDirectory();
        File Dir = new File(Root.getAbsolutePath()+"/AppFile");
        File file = new File(Dir,"kupalkana.txt");
        String Message;
        try {
            FileInputStream fileInputStream=new FileInputStream(file);
            InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            StringBuffer stringBuffer = new StringBuffer();
            while((Message=bufferedReader.readLine())!=null){
            stringBuffer.append(Message+"\n");
            }
            editText2.setText(stringBuffer.toString());
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }