Question

我想用我的Android应用程序从URL下载文件，但出现错误：

2019-03-25 09:28:05.133 7481-7511/info.androidhive.recyclerview E/Error:: /storage/emulated/0/2011.kml (Permission denied)

该链接工作正常，因为如果我在浏览器中将其打开，则会下载文件。我尝试添加权限：

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

但是问题仍然存在。

FileDownloadClass看起来像这样：

package info.androidhive.recyclerview;

import android.os.AsyncTask;
import android.os.Environment;
import android.util.Log;

import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;

class DownloadFileFromURL extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Bar Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
       // showDialog(progress_bar_type);
    }

    /**
     * Downloading file in background thread
     * */
    @Override
    protected String doInBackground(String... f_url) {
        int count;
        try {
            URL url = new URL(f_url[0]);
            URLConnection conection = url.openConnection();
            conection.connect();

            // this will be useful so that you can show a tipical 0-100%
            // progress bar
            int lenghtOfFile = conection.getContentLength();

            // download the file
            InputStream input = new BufferedInputStream(url.openStream(),
                    8192);

            // Output stream
            OutputStream output = new FileOutputStream(Environment
                    .getExternalStorageDirectory().toString()
                    + "/2011.kml");

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                // After this onProgressUpdate will be called
                publishProgress("" + (int) ((total * 100) / lenghtOfFile));

                // writing data to file
                output.write(data, 0, count);
            }

            // flushing output
            output.flush();

            // closing streams
            output.close();
            input.close();

        } catch (Exception e) {
            Log.e("Error: ", e.getMessage());
        }

        return null;
    }

    /**
     * Updating progress bar
     * */
    protected void onProgressUpdate(String... progress) {
        // setting progress percentage
      //  pDialog.setProgress(Integer.parseInt(progress[0]));
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    @Override
    protected void onPostExecute(String file_url) {
        // dismiss the dialog after the file was downloaded
       // dismissDialog(progress_bar_type);

    }

}

我错了什么？我需要哪个权限？

Answer 1

您应该使用以下方法检查用户是否已授予外部存储权限：

if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
    Log.v(TAG,"Permission is granted");
    //File write logic here
    return true;
}

否则，您需要要求用户向您的应用授予权限：

ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);

当然，这些仅用于棉花糖设备，因此您需要检查您的应用程序是否在棉花糖上运行：

if (Build.VERSION.SDK_INT >= 23) {
      //do your check here
 }

还要确保您的活动实现了OnRequestPermissionResult

整个权限如下：

public  boolean isStoragePermissionGranted() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
                == PackageManager.PERMISSION_GRANTED) {
            Log.v(TAG,"Permission is granted");
            return true;
        } else {

            Log.v(TAG,"Permission is revoked");
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
            return false;
        }
    }
    else { //permission is automatically granted on sdk<23 upon installation
        Log.v(TAG,"Permission is granted");
        return true;
    }
}

权限结果回调：

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if(grantResults[0]== PackageManager.PERMISSION_GRANTED){
        Log.v(TAG,"Permission: "+permissions[0]+ "was "+grantResults[0]);
        //resume tasks needing this permission
    }
}

请点击该链接以获取详细信息：Run time permissons

Android Studio从URL许可下载文件被拒绝错误

1 个答案: