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| Field editors |
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| <H3> |
| Field editors</H3> |
| <P > |
| The implementation of a preference page is primarily SWT code. SWT code is |
| used to create the preference page controls, set the values of the controls, and |
| retrieve the values of the controls. The |
| <b><a href="../reference/api/org/eclipse/jface/preference/package-summary.html">org.eclipse.jface.preference</a></b> |
| package provides helper classes, called <b> field editors</b>, that create the widgets and implement the value setting |
| and retrieval code for the most common preference types. The platform provides field editors for displaying and updating |
| many value types, including booleans, colors, strings, integers, fonts, and file names.</P> |
| <P > |
| <b><a href="../reference/api/org/eclipse/jface/preference/FieldEditorPreferencePage.html"> FieldEditorPreferencePage</a></b> implements a |
| page that uses these field editors to display and store the preference values on the page. |
| Instead of creating SWT controls to fill its contents, a <b><a href="../reference/api/org/eclipse/jface/preference/FieldEditorPreferencePage.html"> FieldEditorPreferencePage</a></b> |
| subclass creates field editors to display the contents. All of the fields |
| on the page must be implemented as field editors. The following is a |
| snippet from the debug UI preferences page:</P> |
| <pre>protected void createFieldEditors() { |
| addField(new BooleanFieldEditor(IDebugUIConstants.PREF_BUILD_BEFORE_LAUNCH, |
| DebugPreferencesMessages.getString("DebugPreferencePage.auto_build_before_launch"), |
| SWT.NONE, getFieldEditorParent())); |
| ... |
| String[][] perspectiveNamesAndIds = getPerspectiveNamesAndIds(); |
| addField(new ComboFieldEditor(IDebugUIConstants.PREF_SHOW_DEBUG_PERSPECTIVE_DEFAULT, |
| DebugPreferencesMessages.getString("DebugPreferencePage.Default_perspective_for_Debug_2"), //$NON-NLS-1$ |
| perspectiveNamesAndIds, |
| getFieldEditorParent())); |
| ... |
| }</pre> |
| <P > |
| Each field editor is assigned the name of its corresponding preference key and the text label for the SWT |
| control that it will create. The kind of control created depends on the type of field editor. For example, a boolean field editor creates a checkbox.</P> |
| <P > |
| Since the preference page is associated with a preference store (specified in the |
| <b> doGetPreferenceStore</b> method), the code for storing the current values, |
| for initializing the control values from the preference store, and for restoring the controls to |
| their default values can all be implemented in the |
| <b><a href="../reference/api/org/eclipse/jface/preference/FieldEditorPreferencePage.html">FieldEditorPreferencePage</a></b>.</P> |
| <P > |
| The <b><a href="../reference/api/org/eclipse/jface/preference/FieldEditorPreferencePage.html"> FieldEditorPreferencePage</a></b> |
| will use a grid layout with one column as the default layout for field editor |
| widgets. For special layout requirements, you can override the <b>createContents</b> method.</P> |
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