Java Learning Lesson 16th, using File data storage (4 storage modes)

context.mode_private: Is the default mode of operation, which means that the file is private data and can only be accessed by the app itself , in which the contents of the original file are overwritten by the written content . If you want to append the newly written content to the original file. You can use Context.mode_append

context.mode_append: The mode checks whether the file exists, appends content to the file, or creates a new file.

context.mode_world_readable and context.mode_world_writeable

Used to control whether other apps have permission to read and write to the file.

Mode_world_readable: Indicates that the current file can be read by another application; Mode_world_writeable: Indicates that the current file can be written by another application.

If you want the file to be read and written by another app, you can pass in:

Openfileoutput ("Itcast.txt", context.mode_world_readable + context.mode_world_writeable);

Android has its own security model, and when the application (. apk) is installed, the system assigns him a userid, which requires a UserID match when the app is going to access other resources such as files. By default, any file created by the app, Sharedpreferences, should be private (in/data/data/<package name>/files) and other programs cannot access it.

Unless you specify context.mode_world_readable or context.mode_world_writeable at creation time, only such other programs can access them correctly .

Java Learning Lesson 16th, using File data storage (4 storage modes)