Each button sets the background color to either Red, White or Blue and saves the setting to Shared Preferences. It also does not notify you if an error has occurred when saving. Calling apply causes the change to be stored to the in-memory SharedPreferences right away, with final persistence to file happening asynchronously. So what's the difference? Calling commit applies the change immediately. If you look at the Developer documentation, there's another method: editor.apply() Ĭalling apply accomplishes the same thing in the long run (assuming no errors occur). mit() įor our purposes, mit() is the preferred method for saving SharedPreference values to file. Once you have called the putX() method for any data you want to persist (where X = the data type), you must finally commit those changes to file using the commit() method. SharedPreferences.Editor editor = prefs.edit() You then use this editor to "put" items into Shared Preferences. As with retrieving data, there's a corresponsing method for each data type: String colorString To save something to the application's shared preferences, you must first get an instance of the preferences Editor. String colorString = prefs.getString("color", "red") Writing To Shared Preferences The first parameter in the method call is the data's key, and the second value is the default value to return if no item exists for the given key: // get String To read a stored value, you use the method call corresponding to the type of data being retrieves. Once you have an instance, you can use it to read and write data to file. To get an instance of an application's Shared Prefences, you use the Preference Manager: SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this) Reading From Shared Preferences Shared Preferences are best suited for persisting small bits of data.like preferences (thus the name). Because of the manner in which data is stored in Shared Preferences, this technique can be only used to save primitive data type: booleans, floats, ints, longs, and strings. Values are stored as key/value pairs in XML format in the application's built-in data space. Shared Preferences are Singletons, which means that the same instance is accessible to all activities in the app. One of the ways to accomplish file persistence is by using something called Shared Preferences. This lesson will focus on the first two options. On these occassions, you have three options: There are many occasions where you might need your application to save data on the device. As with any Java application, when an Android application stops running, items created at run-time in memory for that program are no longer available. Sometimes we need to store values for later use. Using Intent extras to pass data works great as long as the values you pass don't need to persist once your app closes.
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