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Difference between revisions of "E4/Doc/Preferences"
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== Implementation == | == Implementation == | ||
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| + | In the most common case, e4 permits preference retrieval through dependency injection. By specifying an injection with a @Preference qualifier key, the qualifier's corresponding preference value is retrieved and injected. | ||
| + | |||
| + | For example, in the following Java code, | ||
| + | <source lang="java"> | ||
| + | |||
| + | public class LoginWindow | ||
| + | |||
| + | @Inject @Preference(MyPrefConstants.DEFAULT_USERNAME) String username; | ||
| + | |||
| + | public LoginWindow(){ | ||
| + | getUserNameInput.setText(username); | ||
| + | } | ||
| + | |||
| + | </source> | ||
Revision as of 13:13, 16 March 2010
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The ability for users to customize application features according to their individual requirements is often useful. Eclipse e4 provides a mechanism to persist and retrieve these customizations, known as preferences, within a range of scopes.
In the most common case, a user preference is simply a key-value pair that is associated with an Eclipse instance. For example, the preference that specifies that a user would like to have a tool tip displayed on startup could be stored as "showToolTip=true".
Relevant Terms
- Key - A key is a unique string identifier for a preference setting.
- Value - A value is the current preference setting associated with a key, within a specific scope.
- Eclipse instance - An Eclipse instance is synonymous with a workspace. In the context of preferences, an instance scope is valid while using a specific workspace.
Motivation
Although managing preferences within a variety of scopes can become complex, e4 has streamlined the most common, "80-percent" case. In this default scenario, preferences reside within the scope of an Eclipse instance. This means that when a user switches workspaces, a new set corresponding preferences are applied.
For situations where greater control of preference behaviour is necessary, e4 provides mechanisms to specify a range of scopes and listen for changes to preferences. For example, a user may want to apply a preference to all workspaces within a single Eclipse install, to a plugin or set of plugins, or to a set of projects within a plugin. Eclipse e4 permits this flexibility of scope, and enables cascading preferences through the chaining of scopes in any order.
Applicability
The applications of preferences are many:
- UI customization: fonts, window & pane properties, and colors
- Installation settings: locations of resources, working directories
- Application settings: internationalization selections, program parameters
Implementation
In the most common case, e4 permits preference retrieval through dependency injection. By specifying an injection with a @Preference qualifier key, the qualifier's corresponding preference value is retrieved and injected.
For example, in the following Java code,
public class LoginWindow @Inject @Preference(MyPrefConstants.DEFAULT_USERNAME) String username; public LoginWindow(){ getUserNameInput.setText(username); }