Android does not insert SD file writing and reading methods

When developing Android, you may encounter one of the following scenarios:
You want to download the application to the root directory of the current application, not the SD card.
Then, the file can be accessed by the application or other applications at any time, that is, the file can be read globally.

In this case, you can use the local file output stream of the context for file writing.
Be sure to grant the write and read permissions to the file. Otherwise, an error will be reported when the file is read.
FileOutputStream fos = context. openFileOutput (saveFileName,
Context. MODE_WORLD_WRITEABLE
| Context. MODE_WORLD_READABLE );
Then, you can use context. openFileInput to obtain the input stream.
You can also use context. getFileStreamPath (name) to obtain its File instance. For example, this method is particularly useful when you want to download an Apk to a local device and open it.

Finally, add the permission statement in the configuration file.