Java tutorial
// -*- mode: java; c-basic-offset: 2; -*- // Copyright 2009-2011 Google, All Rights reserved // Copyright 2011-2012 MIT, All rights reserved // Released under the Apache License, Version 2.0 // http://www.apache.org/licenses/LICENSE-2.0 package com.google.appinventor.client.widgets.properties; import static com.google.appinventor.client.Ode.MESSAGES; import com.google.gwt.event.dom.client.BlurEvent; import com.google.gwt.event.dom.client.BlurHandler; import com.google.gwt.event.dom.client.ClickEvent; import com.google.gwt.event.dom.client.ClickHandler; import com.google.gwt.event.dom.client.FocusEvent; import com.google.gwt.event.dom.client.FocusHandler; import com.google.gwt.event.dom.client.KeyCodes; import com.google.gwt.event.dom.client.KeyPressEvent; import com.google.gwt.event.dom.client.KeyPressHandler; import com.google.gwt.event.dom.client.KeyUpEvent; import com.google.gwt.event.dom.client.KeyUpHandler; import com.google.gwt.event.logical.shared.ValueChangeEvent; import com.google.gwt.event.logical.shared.ValueChangeHandler; import com.google.gwt.user.client.Window; import com.google.gwt.user.client.ui.TextBoxBase; /** * Property editor base for text box editors. * */ public class TextPropertyEditorBase extends PropertyEditor { /** * Thrown to indicate that text input is invalid. */ public static class InvalidTextException extends Exception { public InvalidTextException(String message) { super(message); } } // This is the GWT object that supports the property editor // It can be TextBoxBase object, currently in App Inventor only // TextBox and TextArea protected TextBoxBase textEdit; private boolean hasFocus; /** * Creates a new instance of the property editor. */ public TextPropertyEditorBase(final TextBoxBase widget) { textEdit = widget; textEdit.addKeyPressHandler(new KeyPressHandler() { @Override public void onKeyPress(KeyPressEvent event) { handleKeyPress(event.getCharCode()); } }); textEdit.addKeyUpHandler(new KeyUpHandler() { @Override public void onKeyUp(KeyUpEvent event) { handleKeyUp(event.getNativeKeyCode()); } }); textEdit.addValueChangeHandler(new ValueChangeHandler() { @Override public void onValueChange(ValueChangeEvent event) { validateText(); } }); // NOTE(lizlooney) - The following handlers for focus, blur, and click are needed to workaround // a bug with WebKit browsers (chrome and safari) where clicking in the TextBox causes it to // gain focus, but then immediately lose focus (blur). To work around the problem, we keep // track of whether the TextBox has focus using a FocusHandler and a BlurHandler. Then, we use // a ClickHandler and if we get a ClickEvent and the TextBox does not have focus, we explicitly // call setFocus. textEdit.addFocusHandler(new FocusHandler() { @Override public void onFocus(FocusEvent event) { hasFocus = true; } }); textEdit.addBlurHandler(new BlurHandler() { @Override public void onBlur(BlurEvent event) { hasFocus = false; // Calling validateText here means that we will save the changed property value (if it is // valid) when this property editor loses focus (for example, when the user clicks on // another property editor). validateText(); } }); textEdit.addClickHandler(new ClickHandler() { @Override public void onClick(ClickEvent event) { if (!hasFocus) { textEdit.setFocus(true); } } }); initWidget(textEdit); //kludge for now fix this with instanceOf? setHeight("2em"); } @Override protected void onUnload() { // onUnload is called immediately before a widget becomes detached from the browser's document. // Calling validateText here means that we will save the changed property value (if it is // valid) when the user clicks on another component. validateText(); super.onUnload(); } @Override protected void updateValue() { textEdit.setText(property.getValue()); } private void handleKeyPress(char keyCode) { if (keyCode == KeyCodes.KEY_ENTER || keyCode == KeyCodes.KEY_TAB) { // Pressing <tab>, <enter> or <return> will surrender focus. textEdit.cancelKey(); textEdit.setFocus(false); } else if (!validateKeyCode(keyCode)) { textEdit.cancelKey(); } } private void handleKeyUp(int keyCode) { if (keyCode == KeyCodes.KEY_ESCAPE) { // Pressing <esc> will reset the content of the editor to the previous property value as well // as surrender focus. updateValue(); // Restore previous property value. textEdit.cancelKey(); textEdit.setFocus(false); } } /* * Validates the text in the textEdit and if it is valid, sets the property * value to the text. */ private void validateText() { String text = textEdit.getText(); try { validate(text); property.setValue(text); } catch (InvalidTextException e) { String error = e.getMessage(); if (error == null || error.isEmpty()) { error = MESSAGES.malformedInputError(); } Window.alert(error); updateValue(); // Restore previous property value. } } /** * Validates the given key code. * * <p/>The implementation here does no validation. Subclasses may override * this method to provide actual validation. * * @param keyCode key code to validate * @return true if the keycode is allowed, false if it is not allowed. */ protected boolean validateKeyCode(char keyCode) { return true; } /** * Validates the given text. Throw an InvalidTextException if the text is * invalid. * * <p/>The implementation here does no validation. Subclasses may override * this method to provide actual validation. * * @param text input string to validate * @throws InvalidTextException if the text is invalid */ protected void validate(String text) throws InvalidTextException { } }