Android 6:无法访问错误文件

安卓6的问题让我发疯了。从服务器下载pdf文件（在localhost中运行。服务器响应为HTTP 200（因此未发现问题），但当我尝试打开文件时，出现错误：“错误文件无法访问”

这是下载文件的Asynctack：

private class DownloadContent extends AsyncTask<String,Integer,String> {
    private Context context;
    private PowerManager.WakeLock mWakeLock;
    private String ris;

    public DownloadContent(Context context) {
        this.context = context;
    }

    @Override
    protected String doInBackground(String... params) {
        String nomefile=params[0];
        String email=params[1];
        String id=params[2];
        InputStream input = null;
        String[] saveFiles;
        OutputStream output = null;
        HttpURLConnection connection = null;
        try {
            URL url = new URL("http://192.168.1.8:8080/com.appcampus/rest/content/"+nomefile+"/"+email+"/"+id);

            connection = (HttpURLConnection) url.openConnection();
            connection.connect();

            if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
                return "Server returned HTTP " + connection.getResponseCode()
                        + " " + connection.getResponseMessage();
            }

            int fileLength = connection.getContentLength();

            // download the file
            java.io.File xmlFile = new java.io.File(Environment
                    .getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)
                    + "/"+nomefile);
            input = connection.getInputStream();
            int permissionCheck = ContextCompat.checkSelfPermission(getApplicationContext(),
                    Manifest.permission.WRITE_EXTERNAL_STORAGE);
            if(permissionCheck == PackageManager.PERMISSION_GRANTED){


            output = new FileOutputStream(xmlFile);
            byte data[] = new byte[4096];
            long total = 0;
            int count;
            while ((count = input.read(data)) != -1) {
                // allow canceling with back button
                if (isCancelled()) {
                    input.close();
                    return null;
                }
                total += count;
                // publishing the progress....
                if (fileLength > 0) // only if total length is known
                    publishProgress((int) (total * 100 / fileLength));
                output.write(data, 0, count);

            }
            }else{
               Log.d("Permission check",""+permissionCheck);
            }

            saveFiles = context.fileList();
            String s = "";
            for (String element : saveFiles) {
                s += " " + element;
            }

            ris = "Server returned HTTP " + connection.getResponseCode();
        } catch (Exception e) {
            return e.toString();
        } finally {
            try {
                if (output != null)
                    output.close();
                if (input != null)
                    input.close();
            } catch (IOException ignored) {
            }

            if (connection != null)
                connection.disconnect();
        }
        return ris;
    }
}

我认为清单上的所有许可都可以：

 <uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.USE_CREDENTIALS" />
<!-- To retrieve the account name (email) as part of sign-in: -->
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<!-- To auto-complete the email text field in the login form with the user's emails -->
<uses-permission android:name="android.permission.READ_PROFILE" />
<uses-permission android:name="android.permission.READ_CONTACTS" />

---

最终我找到了解决方案：我在要打开的文件路径中添加了file://

Uri path = Uri.parse("file:///"+Environment
                    .getExternalStorageDirectory().toString()
                    + "/YOURFILE.pdf");

---

原始文件有多少字节？下载的ond.Figures有多少字节！

risultato=downloadTask.execute（param）.get（）；

.Bad code。不要使用.get（）方法。而是在onPostExecute（）中处理doInBackground（）的结果.Act normal。我尝试在onPostExecute中处理结果，但没有任何更改。请求返回HTTP 200。我尝试使用文件资源管理器查找该文件，但在我的设备上找不到。这怎么可能？我尝试检查（file.exists（））是否返回false。但安卓棒棒糖的相同代码是可以的。

Uri path = Uri.parse("file:///"+Environment
                    .getExternalStorageDirectory().toString()
                    + "/YOURFILE.pdf");