Question

尝试创建有助于下载文件的应用。我单击下载按钮，然后出现进度栏。它显示进度。然后进度条结束，我收到ENOENT错误：

E/Error:: /storage/emulated/0/logo.png: open failed: EACCES (Permission denied) E/BitmapFactory: Unable to decode stream: java.io.FileNotFoundException: /storage/emulated/0/logo.png: open failed: ENOENT (No such file or directory)

无法理解此代码的问题，我在模拟器和真实设备上对其进行了测试。

public class DownloadProgress extends AppCompatActivity {

    Button btnShowProgress;
    private ProgressDialog pDialog;

    ImageView my_image;

    public static final int progress_bar_type = 0;

    private static String file_url = "http://idsp.ak.gov.ng/images/logo.png";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        btnShowProgress = (Button) findViewById(R.id.btnProgressBar);

        my_image = (ImageView) findViewById(R.id.my_image);

        btnShowProgress.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v){

                new DownloadFileFromURL().execute(file_url);
            }
        });
    }

    @Override
    protected Dialog onCreateDialog(int id){
        switch (id){
            case progress_bar_type:
                pDialog = new ProgressDialog(this);
                pDialog.setMessage("Downloading file. Please wait...");
                pDialog.setIndeterminate(false);
                pDialog.setMax(100);
                pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
                pDialog.setCancelable(true);
                pDialog.show();
                return pDialog;
            default:
                return null;
        }
    }

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

       @Override
       protected void onPreExecute(){
           super.onPreExecute();
           showDialog(progress_bar_type);
       }

       @Override
       protected  String doInBackground(String... f_url){
           int count;
           try{
               URL url = new URL(f_url[0]);
               URLConnection connection = url.openConnection();
               connection.connect();

               int lenghtOfFile = connection.getContentLength();

               InputStream input = new BufferedInputStream(url.openStream(), 8192);

               String storageDir = Environment.getExternalStorageDirectory().getAbsolutePath();
               String fileName = "/logo.png";
               File imageFile = new File(storageDir+fileName);
               OutputStream output = new FileOutputStream(imageFile);

               byte data[] = new byte[1024];
               long total = 0;

               while((count = input.read(data)) != -1){
                   total += count;

                   publishProgress(""+(int)((total*100)/lenghtOfFile));

                   output.write(data, 0, count);
               }
               output.flush();

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

           return null;
       }

       protected void onProgressUpdate(String... progress){
           pDialog.setProgress(Integer.parseInt(progress[0]));
       }

       @Override
       protected void onPostExecute(String file_url){
           dismissDialog(progress_bar_type);

           String imagePath = Environment.getExternalStorageDirectory() + "/logo.png";
           my_image.setImageDrawable(Drawable.createFromPath(imagePath));
       }
   }
}

感谢您阅读这篇文章！

Answer 1

根据您的问题：

/storage/emulated/0/logo.png: open failed: EACCES (Permission denied)

是您遇到问题的主要原因。

从Android 6.0（API级别23）开始，您不仅应该声明

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

{p> AndroidManifest.xml中的权限，以及request it in run time中的权限：

如果您的应用需要危险许可，则必须检查您是否每次执行需要执行的操作时都要获得该许可该许可。从Android 6.0（API级别23）开始，用户可以随时撤消任何应用程序的权限，即使该应用程序定位到较低的API级别。因此，即使该应用昨天使用了相机，不能认为它今天仍然具有该权限。

看看DownloadManager-这是处理长时间运行的HTTP下载的系统服务。

下载文件时出现ENOENT错误

1 个答案: