Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2016 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.jface.resource.JFaceResources; import org.eclipse.core.runtime.Assert; import org.eclipse.swt.SWT; import org.eclipse.swt.events.FocusAdapter; import org.eclipse.swt.events.FocusEvent; import org.eclipse.swt.events.KeyAdapter; import org.eclipse.swt.events.KeyEvent; import org.eclipse.swt.graphics.GC; import org.eclipse.swt.graphics.Point; import org.eclipse.swt.layout.GridData; import org.eclipse.swt.widgets.Composite; import org.eclipse.swt.widgets.Text; /** * A field editor for a string type preference. * <p> * This class may be used as is, or subclassed as required. * </p> */ public class StringFieldEditor extends FieldEditor { /** * Validation strategy constant (value <code>0</code>) indicating that * the editor should perform validation after every key stroke. * * @see #setValidateStrategy */ public static final int VALIDATE_ON_KEY_STROKE = 0; /** * Validation strategy constant (value <code>1</code>) indicating that * the editor should perform validation only when the text widget * loses focus. * * @see #setValidateStrategy */ public static final int VALIDATE_ON_FOCUS_LOST = 1; /** * Text limit constant (value <code>-1</code>) indicating unlimited * text limit and width. */ public static int UNLIMITED = -1; /** * Cached valid state. */ private boolean isValid; /** * Old text value. * @since 3.4 this field is protected. */ protected String oldValue; /** * The text field, or <code>null</code> if none. */ Text textField; /** * Width of text field in characters; initially unlimited. */ private int widthInChars = UNLIMITED; /** * Text limit of text field in characters; initially unlimited. */ private int textLimit = UNLIMITED; /** * The error message, or <code>null</code> if none. */ private String errorMessage; /** * Indicates whether the empty string is legal; * <code>true</code> by default. */ private boolean emptyStringAllowed = true; /** * The validation strategy; * <code>VALIDATE_ON_KEY_STROKE</code> by default. */ private int validateStrategy = VALIDATE_ON_KEY_STROKE; /** * Creates a new string field editor */ protected StringFieldEditor() { } /** * Creates a string field editor. * Use the method <code>setTextLimit</code> to limit the text. * * @param name the name of the preference this field editor works on * @param labelText the label text of the field editor * @param width the width of the text input field in characters, * or <code>UNLIMITED</code> for no limit * @param strategy either <code>VALIDATE_ON_KEY_STROKE</code> to perform * on the fly checking (the default), or <code>VALIDATE_ON_FOCUS_LOST</code> to * perform validation only after the text has been typed in * @param parent the parent of the field editor's control * @since 2.0 */ public StringFieldEditor(String name, String labelText, int width, int strategy, Composite parent) { init(name, labelText); widthInChars = width; setValidateStrategy(strategy); isValid = false; errorMessage = JFaceResources.getString("StringFieldEditor.errorMessage");//$NON-NLS-1$ createControl(parent); } /** * Creates a string field editor. * Use the method <code>setTextLimit</code> to limit the text. * * @param name the name of the preference this field editor works on * @param labelText the label text of the field editor * @param width the width of the text input field in characters, * or <code>UNLIMITED</code> for no limit * @param parent the parent of the field editor's control */ public StringFieldEditor(String name, String labelText, int width, Composite parent) { this(name, labelText, width, VALIDATE_ON_KEY_STROKE, parent); } /** * Creates a string field editor of unlimited width. * Use the method <code>setTextLimit</code> to limit the text. * * @param name the name of the preference this field editor works on * @param labelText the label text of the field editor * @param parent the parent of the field editor's control */ public StringFieldEditor(String name, String labelText, Composite parent) { this(name, labelText, UNLIMITED, parent); } @Override protected void adjustForNumColumns(int numColumns) { GridData gd = (GridData) textField.getLayoutData(); gd.horizontalSpan = numColumns - 1; // We only grab excess space if we have to // If another field editor has more columns then // we assume it is setting the width. gd.grabExcessHorizontalSpace = gd.horizontalSpan == 1; } /** * Checks whether the text input field contains a valid value or not. * * @return <code>true</code> if the field value is valid, * and <code>false</code> if invalid */ protected boolean checkState() { boolean result = false; if (emptyStringAllowed) { result = true; } if (textField == null) { result = false; } else { String txt = textField.getText(); result = (txt.trim().length() > 0) || emptyStringAllowed; } // call hook for subclasses result = result && doCheckState(); if (result) { clearErrorMessage(); } else { showErrorMessage(errorMessage); } return result; } /** * Hook for subclasses to do specific state checks. * <p> * The default implementation of this framework method does * nothing and returns <code>true</code>. Subclasses should * override this method to specific state checks. * </p> * * @return <code>true</code> if the field value is valid, * and <code>false</code> if invalid */ protected boolean doCheckState() { return true; } /** * Fills this field editor's basic controls into the given parent. * <p> * The string field implementation of this <code>FieldEditor</code> * framework method contributes the text field. Subclasses may override * but must call <code>super.doFillIntoGrid</code>. * </p> */ @Override protected void doFillIntoGrid(Composite parent, int numColumns) { getLabelControl(parent); textField = getTextControl(parent); GridData gd = new GridData(); gd.horizontalSpan = numColumns - 1; if (widthInChars != UNLIMITED) { GC gc = new GC(textField); try { Point extent = gc.textExtent("X");//$NON-NLS-1$ gd.widthHint = widthInChars * extent.x; } finally { gc.dispose(); } } else { gd.horizontalAlignment = GridData.FILL; gd.grabExcessHorizontalSpace = true; } textField.setLayoutData(gd); } @Override protected void doLoad() { if (textField != null) { String value = getPreferenceStore().getString(getPreferenceName()); textField.setText(value); oldValue = value; } } @Override protected void doLoadDefault() { if (textField != null) { String value = getPreferenceStore().getDefaultString(getPreferenceName()); textField.setText(value); } valueChanged(); } @Override protected void doStore() { getPreferenceStore().setValue(getPreferenceName(), textField.getText()); } /** * Returns the error message that will be displayed when and if * an error occurs. * * @return the error message, or <code>null</code> if none */ public String getErrorMessage() { return errorMessage; } @Override public int getNumberOfControls() { return 2; } /** * Returns the field editor's value. * * @return the current value */ public String getStringValue() { if (textField != null) { return textField.getText(); } return getPreferenceStore().getString(getPreferenceName()); } /** * Returns this field editor's text control. * * @return the text control, or <code>null</code> if no * text field is created yet */ protected Text getTextControl() { return textField; } /** * Returns this field editor's text control. * <p> * The control is created if it does not yet exist * </p> * * @param parent the parent * @return the text control */ public Text getTextControl(Composite parent) { if (textField == null) { textField = new Text(parent, SWT.SINGLE | SWT.BORDER); textField.setFont(parent.getFont()); switch (validateStrategy) { case VALIDATE_ON_KEY_STROKE: textField.addKeyListener(new KeyAdapter() { @Override public void keyReleased(KeyEvent e) { valueChanged(); } }); textField.addFocusListener(new FocusAdapter() { // Ensure that the value is checked on focus loss in case we // missed a keyRelease or user hasn't released key. // See https://bugs.eclipse.org/bugs/show_bug.cgi?id=214716 @Override public void focusLost(FocusEvent e) { valueChanged(); } }); break; case VALIDATE_ON_FOCUS_LOST: textField.addKeyListener(new KeyAdapter() { @Override public void keyPressed(KeyEvent e) { clearErrorMessage(); } }); textField.addFocusListener(new FocusAdapter() { @Override public void focusGained(FocusEvent e) { refreshValidState(); } @Override public void focusLost(FocusEvent e) { valueChanged(); clearErrorMessage(); } }); break; default: Assert.isTrue(false, "Unknown validate strategy");//$NON-NLS-1$ } textField.addDisposeListener(event -> textField = null); if (textLimit > 0) {//Only set limits above 0 - see SWT spec textField.setTextLimit(textLimit); } } else { checkParent(textField, parent); } return textField; } /** * Returns whether an empty string is a valid value. * * @return <code>true</code> if an empty string is a valid value, and * <code>false</code> if an empty string is invalid * @see #setEmptyStringAllowed */ public boolean isEmptyStringAllowed() { return emptyStringAllowed; } @Override public boolean isValid() { return isValid; } @Override protected void refreshValidState() { isValid = checkState(); } /** * Sets whether the empty string is a valid value or not. * * @param b <code>true</code> if the empty string is allowed, * and <code>false</code> if it is considered invalid */ public void setEmptyStringAllowed(boolean b) { emptyStringAllowed = b; } /** * Sets the error message that will be displayed when and if * an error occurs. * * @param message the error message */ public void setErrorMessage(String message) { errorMessage = message; } @Override public void setFocus() { if (textField != null) { textField.setFocus(); } } /** * Sets this field editor's value. * * @param value the new value, or <code>null</code> meaning the empty string */ public void setStringValue(String value) { if (textField != null) { if (value == null) { value = "";//$NON-NLS-1$ } oldValue = textField.getText(); if (!oldValue.equals(value)) { textField.setText(value); valueChanged(); } } } /** * Sets this text field's text limit. * * @param limit the limit on the number of character in the text * input field, or <code>UNLIMITED</code> for no limit */ public void setTextLimit(int limit) { textLimit = limit; if (textField != null) { textField.setTextLimit(limit); } } /** * Sets the strategy for validating the text. * <p> * Calling this method has no effect after <code>createPartControl</code> * is called. Thus this method is really only useful for subclasses to call * in their constructor. However, it has public visibility for backward * compatibility. * </p> * * @param value either <code>VALIDATE_ON_KEY_STROKE</code> to perform * on the fly checking (the default), or <code>VALIDATE_ON_FOCUS_LOST</code> to * perform validation only after the text has been typed in */ public void setValidateStrategy(int value) { Assert.isTrue(value == VALIDATE_ON_FOCUS_LOST || value == VALIDATE_ON_KEY_STROKE); validateStrategy = value; } /** * Shows the error message set via <code>setErrorMessage</code>. */ public void showErrorMessage() { showErrorMessage(errorMessage); } /** * 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. * <p> * This hook is <em>not</em> called when the text is initialized * (or reset to the default value) from the preference store. * </p> */ protected void valueChanged() { setPresentsDefaultValue(false); boolean oldState = isValid; refreshValidState(); if (isValid != oldState) { fireStateChanged(IS_VALID, oldState, isValid); } String newValue = textField.getText(); if (!newValue.equals(oldValue)) { fireValueChanged(VALUE, oldValue, newValue); oldValue = newValue; } } /* * @see FieldEditor.setEnabled(boolean,Composite). */ @Override public void setEnabled(boolean enabled, Composite parent) { super.setEnabled(enabled, parent); getTextControl(parent).setEnabled(enabled); } }