Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2015 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.jface.preference; import org.eclipse.swt.SWT; import org.eclipse.swt.events.SelectionAdapter; import org.eclipse.swt.events.SelectionEvent; import org.eclipse.swt.layout.GridData; import org.eclipse.swt.widgets.Button; import org.eclipse.swt.widgets.Composite; import org.eclipse.swt.widgets.Control; import org.eclipse.swt.widgets.Label; /** * A field editor for a boolean type preference. */ public class BooleanFieldEditor extends FieldEditor { /** * Style constant (value <code>0</code>) indicating the default layout where * the field editor's check box appears to the left of the label. */ public static final int DEFAULT = 0; /** * Style constant (value <code>1</code>) indicating a layout where the field * editor's label appears on the left with a check box on the right. */ public static final int SEPARATE_LABEL = 1; /** * Style bits. Either <code>DEFAULT</code> or <code>SEPARATE_LABEL</code>. */ private int style; /** * The previously selected, or "before", value. */ private boolean wasSelected; /** * The checkbox control, or <code>null</code> if none. */ private Button checkBox = null; /** * Creates a new boolean field editor */ protected BooleanFieldEditor() { } /** * Creates a boolean field editor in the given style. * * @param name * the name of the preference this field editor works on * @param labelText * the label text of the field editor * @param style * the style, either <code>DEFAULT</code> or * <code>SEPARATE_LABEL</code> * @param parent * the parent of the field editor's control * @see #DEFAULT * @see #SEPARATE_LABEL */ public BooleanFieldEditor(String name, String labelText, int style, Composite parent) { init(name, labelText); this.style = style; createControl(parent); } /** * Creates a boolean field editor in the default style. * * @param name * the name of the preference this field editor works on * @param label * the label text of the field editor * @param parent * the parent of the field editor's control */ public BooleanFieldEditor(String name, String label, Composite parent) { this(name, label, DEFAULT, parent); } @Override protected void adjustForNumColumns(int numColumns) { if (style == SEPARATE_LABEL) { numColumns--; } ((GridData) checkBox.getLayoutData()).horizontalSpan = numColumns; } @Override protected void doFillIntoGrid(Composite parent, int numColumns) { String text = getLabelText(); switch (style) { case SEPARATE_LABEL: getLabelControl(parent); numColumns--; text = null; //$FALL-THROUGH$ default: checkBox = getChangeControl(parent); GridData gd = new GridData(); gd.horizontalSpan = numColumns; checkBox.setLayoutData(gd); if (text != null) { checkBox.setText(text); } } } /** * Returns the control responsible for displaying this field editor's label. * This method can be used to set a tooltip for a * <code>BooleanFieldEditor</code>. Note that the normal pattern of * <code>getLabelControl(parent).setToolTipText(tooltipText)</code> does not * work for boolean field editors, as it can lead to duplicate text (see bug * 259952). * * @param parent * the parent composite * @return the control responsible for displaying the label * * @since 3.5 */ public Control getDescriptionControl(Composite parent) { if (style == SEPARATE_LABEL) { return getLabelControl(parent); } return getChangeControl(parent); } @Override protected void doLoad() { if (checkBox != null) { boolean value = getPreferenceStore().getBoolean(getPreferenceName()); checkBox.setSelection(value); wasSelected = value; } } @Override protected void doLoadDefault() { if (checkBox != null) { boolean value = getPreferenceStore().getDefaultBoolean(getPreferenceName()); checkBox.setSelection(value); wasSelected = value; } } @Override protected void doStore() { getPreferenceStore().setValue(getPreferenceName(), checkBox.getSelection()); } /** * Returns this field editor's current value. * * @return the value */ public boolean getBooleanValue() { return checkBox.getSelection(); } /** * Returns the change button for this field editor. * * @param parent * The Composite to create the receiver in. * * @return the change button */ protected Button getChangeControl(Composite parent) { if (checkBox == null) { checkBox = new Button(parent, SWT.CHECK | SWT.LEFT); checkBox.setFont(parent.getFont()); checkBox.addSelectionListener(new SelectionAdapter() { @Override public void widgetSelected(SelectionEvent e) { boolean isSelected = checkBox.getSelection(); valueChanged(wasSelected, isSelected); wasSelected = isSelected; } }); checkBox.addDisposeListener(event -> checkBox = null); } else { checkParent(checkBox, parent); } return checkBox; } @Override public int getNumberOfControls() { switch (style) { case SEPARATE_LABEL: return 2; default: return 1; } } @Override public void setFocus() { if (checkBox != null) { checkBox.setFocus(); } } @Override public void setLabelText(String text) { super.setLabelText(text); Label label = getLabelControl(); if (label == null && checkBox != null) { checkBox.setText(text); } } /** * Informs this field editor's listener, if it has one, about a change to * the value (<code>VALUE</code> property) provided that the old and new * values are different. * * @param oldValue * the old value * @param newValue * the new value */ protected void valueChanged(boolean oldValue, boolean newValue) { setPresentsDefaultValue(false); if (oldValue != newValue) { fireStateChanged(VALUE, oldValue, newValue); } } /* * @see FieldEditor.setEnabled */ @Override public void setEnabled(boolean enabled, Composite parent) { // Only call super if there is a label already if (style == SEPARATE_LABEL) { super.setEnabled(enabled, parent); } getChangeControl(parent).setEnabled(enabled); } }