Methods to manipulate folders and files on the SD card

Folder creation

　　　　　　　　File file = Environment.getExternalStorageDirectory();
　　　　　　　　File file_0 = new File(file, "file_demo");
　　　　　　　　　　if (!file_0.exists()) {
　　　　　　　　　　　　　　file_0.mkdirs();
　　　　　　　　　　　}

When you create a folder, you need to < uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" / > Permissions,

Otherwise, the following error will be reported:

ApplicationContext   Unable to create external files directory

It is recommended to use mkdirs () to create a folder, rather than mkdir (), because the former can create a parent folder at the same time, if it does not exist, while the latter cannot.

File creation

                     File file = Environment.getExternalStorageDirectory();
                      File file_0 = new File(file, "pic");
                         if (!file_0.exists()) {
                                file_0.mkdirs();
                         }
                      try {
                          File pic = new File(file_0, "pic.png");
                      InputStream is = getResources().openRawResource(
                                                            R.drawable.ic_launcher);
                      OutputStream os = new FileOutputStream(pic);
                      byte[] data = new byte[is.available()];
                      is.read(data);
                      os.write(data);
                      is.close();
                      os.close();
                      } catch (FileNotFoundException e) {
                         // TODO Auto-generated catch block
                      e.printStackTrace();
                      } catch (IOException e) {
                       // TODO Auto-generated catch block
                             e.printStackTrace();
                      }

The file name created cannot have the. Suffix, otherwise the following error will be reported:

java.io.FileNotFoundException:/mnt/sdcard/pic/pic.png (Is a directory)

At the same time, it is better to add the following permissions when reading and writing to the folder:

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