External storage

1. Determine whether the SDK is available

 if ((Environment.MEDIA_MOUNTED).equals(Environment.getExternalStorageState())){
                            Toast.makeText(getApplicationContext(),"sdk可用" ,Toast.LENGTH_LONG).show();
                        }

2. Get external storage path String path = Environment.getExternalStorageDirectory (). GetPath (); Obsolete
   FileOutputStream fileOutputStream = new FileOutputStream (new File (path, "c.txt"));
3. Permissions but still will refuse permission errors It is said that Android 6.0 and above need to dynamically add permissions

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Get the total size of the
sdk Environment.getExternalStorageDirectory (). GetTotalSpace () Get the free space of the sdk