chrome/browser/preferences/android/README.md - experimental/chromium/src - Git at Google

 # Storing preferences

 This guide is intended for developers of Chrome for Android who need to read
 and/or write small amounts of data from Java to a persistent key-value store.

 ## SharedPreferencesManager

 [`SharedPreferencesManager`][0] is a lightweight wrapper around Android
 [SharedPreferences][1] to handle additional key management logic in Chrome. It
 supports reading and writing simple key-value pairs to a file that is saved
 across app sessions.

 ## PrefService

 [`PrefService`][2] is a JNI bridge providing access to a native Chrome
 [PrefService][3] instance associated. This interface can be used to read and
 write prefs once they're registered through the `PrefRegistry` and exposed to
 Java by way of a `java_cpp_strings` build target such as [this one][4].

 ## FAQ

 **Should I use SharedPreferences or PrefService?**

 Ask yourself the following questions about the preference to be stored:

 * Will the preference need to be accessed from native C++ code?
 * Should the preference be configured as syncable, so that its state can be
   managed by Chrome Sync at Backup and Restore?
 * Does the preference need a managed policy setting?

 If the answer to one or more of the above questions is Yes, then the preference
 should be stored in PrefService. If the answer to all of the above questions is
 No, then SharedPreferences should be preferred.

 **What if the PrefService type I need to access is not supported by
 PrefService (i.e. double, Time, etc.)?**

 If a base value type is supported by PrefService, then PrefService should
 be extended to support it once it's needed.

 **How do I access a PrefService pref associated with local state rather than
 browser profile?**

 Most Chrome for Android preferences should be associated with a specific
 profile. If your preference should instead be associated with [local state][5]
 (for example, if it is related to the First Run Experience), then you should not
 use PrefService and should instead create your own feature-specific JNI
 bridge to access the correct PrefService instance (see [`first_run_utils.cc`][6]).

 [0]: https://source.chromium.org/chromium/chromium/src/+/master:chrome/browser/preferences/android/java/src/org/chromium/chrome/browser/preferences/SharedPreferencesManager.java
 [1]: https://developer.android.com/reference/android/content/SharedPreferences
 [2]: https://source.chromium.org/chromium/chromium/src/+/master:components/prefs/android/java/src/org/chromium/components/prefs/PrefService.java
 [3]: https://chromium.googlesource.com/chromium/src/+/master/services/preferences/README.md
 [4]: https://source.chromium.org/chromium/chromium/src/+/master:chrome/browser/preferences/BUILD.gn;drc=4ae1b7be67cd9b470ebcc90f2747a9f31f155b00;l=28
 [5]: https://www.chromium.org/developers/design-documents/preferences#TOC-Introduction
 [6]: https://source.chromium.org/chromium/chromium/src/+/master:chrome/browser/first_run/android/first_run_utils.cc
	# Storing preferences

	This guide is intended for developers of Chrome for Android who need to read
	and/or write small amounts of data from Java to a persistent key-value store.

	## SharedPreferencesManager

	[`SharedPreferencesManager`][0] is a lightweight wrapper around Android
	[SharedPreferences][1] to handle additional key management logic in Chrome. It
	supports reading and writing simple key-value pairs to a file that is saved
	across app sessions.

	## PrefService

	[`PrefService`][2] is a JNI bridge providing access to a native Chrome
	[PrefService][3] instance associated. This interface can be used to read and
	write prefs once they're registered through the `PrefRegistry` and exposed to
	Java by way of a `java_cpp_strings` build target such as [this one][4].

	## FAQ

	Should I use SharedPreferences or PrefService?

	Ask yourself the following questions about the preference to be stored:

	* Will the preference need to be accessed from native C++ code?
	* Should the preference be configured as syncable, so that its state can be
	managed by Chrome Sync at Backup and Restore?
	* Does the preference need a managed policy setting?

	If the answer to one or more of the above questions is Yes, then the preference
	should be stored in PrefService. If the answer to all of the above questions is
	No, then SharedPreferences should be preferred.

	**What if the PrefService type I need to access is not supported by
	PrefService (i.e. double, Time, etc.)?**

	If a base value type is supported by PrefService, then PrefService should
	be extended to support it once it's needed.

	**How do I access a PrefService pref associated with local state rather than
	browser profile?**

	Most Chrome for Android preferences should be associated with a specific
	profile. If your preference should instead be associated with [local state][5]
	(for example, if it is related to the First Run Experience), then you should not
	use PrefService and should instead create your own feature-specific JNI
	bridge to access the correct PrefService instance (see [`first_run_utils.cc`][6]).

	[0]: https://source.chromium.org/chromium/chromium/src/+/master:chrome/browser/preferences/android/java/src/org/chromium/chrome/browser/preferences/SharedPreferencesManager.java
	[1]: https://developer.android.com/reference/android/content/SharedPreferences
	[2]: https://source.chromium.org/chromium/chromium/src/+/master:components/prefs/android/java/src/org/chromium/components/prefs/PrefService.java
	[3]: https://chromium.googlesource.com/chromium/src/+/master/services/preferences/README.md
	[4]: https://source.chromium.org/chromium/chromium/src/+/master:chrome/browser/preferences/BUILD.gn;drc=4ae1b7be67cd9b470ebcc90f2747a9f31f155b00;l=28
	[5]: https://www.chromium.org/developers/design-documents/preferences#TOC-Introduction
	[6]: https://source.chromium.org/chromium/chromium/src/+/master:chrome/browser/first_run/android/first_run_utils.cc