无法在Android中获取文件

这里是我之前写的代码

在resultActivity中:

File sdcard = Environment.getExternalStorageDirectory();
                    File file = new File(sdcard, data.getData().getPath());
                    ParseFileAggiornamentoAsyncTask asyncTaskLetturaFile = new ParseFileAggiornamentoAsyncTask(MainActivity.this,file);
                    asyncTaskLetturaFile.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);

file.exist() 它的返回总是错误的,所以我无法阅读它和其他东西。

根据评论更新

下面是触发startActivityForResult的代码

if (checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                        MainConstant.MY_PERMISSIONS_REQUEST_READ_EXTERNAL_STORAGE);
            }else {
                Intent fileintent = new Intent(Intent.ACTION_GET_CONTENT);
                fileintent.setType("*/*");
                fileintent.addCategory(Intent.CATEGORY_OPENABLE);
                try {
                    startActivityForResult(Intent.createChooser(fileintent, "Select a File to Upload"), PICKFILE_RESULT_CODE);
                } catch (ActivityNotFoundException e) {
                    Toast.makeText(MainActivity.this, MainActivity.this.getString(R.string.generic_error), Toast.LENGTH_LONG).show();
                    Log.e("tag", "No activity can handle picking a file. Showing alternatives.");
                }
                return true;
            }