Java tutorial
/* * Copyright 2011 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ package com.google.gwt.sample.mobilewebapp.presenter.task; import com.google.gwt.sample.mobilewebapp.client.ClientFactory; import com.google.gwt.sample.mobilewebapp.client.event.ActionEvent; import com.google.gwt.sample.mobilewebapp.client.event.ActionNames; import com.google.gwt.sample.mobilewebapp.client.ui.SoundEffects; import com.google.gwt.sample.mobilewebapp.shared.TaskProxy; import com.google.gwt.sample.mobilewebapp.shared.TaskRequest; import com.google.gwt.user.client.Window; import com.google.gwt.user.client.ui.Widget; import com.google.web.bindery.event.shared.EventBus; import com.google.web.bindery.requestfactory.shared.Receiver; import com.google.web.bindery.requestfactory.shared.Request; import com.google.web.bindery.requestfactory.shared.ServerFailure; import java.util.Set; import java.util.logging.Logger; import javax.validation.ConstraintViolation; /** * Drives a {@link TaskEditView} to fetch and edit a given task, or to create a * new one. */ public class TaskEditPresenter implements TaskEditView.Presenter { private static final Logger log = Logger.getLogger(TaskEditPresenter.class.getName()); private final ClientFactory clientFactory; /** * Indicates whether the activity is editing an existing task or creating a * new task. */ private boolean isEditing; /** * The current task being edited, provided by RequestFactory. */ private TaskProxy editTask; /** * The ID of the current task being edited. */ private final Long taskId; /** * The request used to persist the modified task. */ private Request<Void> taskPersistRequest; private EventBus eventBus; /** * For creating a new task. */ public TaskEditPresenter(ClientFactory clientFactory) { this.taskId = null; this.clientFactory = clientFactory; clientFactory.getTaskEditView().setPresenter(this); } /** * For editing an existing task. */ public TaskEditPresenter(ClientFactory clientFactory, TaskProxy readOnlyTask) { /* * TODO surely we can find a way to show the read-only values while waiting * for the async fetch */ this.taskId = readOnlyTask.getId(); this.clientFactory = clientFactory; clientFactory.getTaskEditView().setPresenter(this); } @Override public Widget asWidget() { return getView().asWidget(); } public void deleteTask() { if (isEditing) { doDeleteTask(); } else { doCancelTask(); } } @Override public String mayStop() { if ((eventBus != null && editTask != null) && getView().getEditorDriver().isDirty()) { return "Are you sure you want to discard these changes?"; } return null; } public void saveTask() { // Flush the changes into the editable task. TaskRequest context = (TaskRequest) clientFactory.getTaskEditView().getEditorDriver().flush(); /* * Create a persist request the first time we try to save this task. If a * request already exists, reuse it. */ if (taskPersistRequest == null) { taskPersistRequest = context.persist().using(editTask); } // Fire the request. taskPersistRequest.fire(new Receiver<Void>() { @Override public void onConstraintViolation(Set<ConstraintViolation<?>> violations) { handleConstraintViolations(violations); } @Override public void onSuccess(Void response) { editTask = null; // Notify the user that the task was updated. TaskEditPresenter.this.notify("Task Saved"); // Return to the task list. ActionEvent.fire(eventBus, ActionNames.TASK_SAVED); } }); } public void start(EventBus eventBus) { this.eventBus = eventBus; getView().setNameViolation(null); // Prefetch the sounds used in this activity. SoundEffects.get().prefetchError(); // Hide the 'add' button in the shell. // TODO(rjrjr) Ick! clientFactory.getShell().setAddButtonVisible(false); if (taskId == null) { startCreate(); } else { startEdit(); } } @Override public void stop() { eventBus = null; clientFactory.getTaskEditView().setLocked(false); } /** * Cancel the current task. */ private void doCancelTask() { ActionEvent.fire(eventBus, ActionNames.EDITING_CANCELED); } /** * Delete the current task. */ private void doDeleteTask() { if (editTask == null) { return; } // Delete the task in the data store. final TaskProxy toDelete = this.editTask; clientFactory.getRequestFactory().taskRequest().remove().using(toDelete).fire(new Receiver<Void>() { @Override public void onFailure(ServerFailure error) { Window.alert("An error occurred on the server while deleting this task: \"." + error.getMessage() + "\"."); } @Override public void onSuccess(Void response) { onTaskDeleted(); } }); } private TaskEditView getView() { return clientFactory.getTaskEditView(); } /** * Handle constraint violations. */ private void handleConstraintViolations(Set<ConstraintViolation<?>> violations) { // Display the violations. getView().getEditorDriver().setConstraintViolations(violations); // Play a sound. SoundEffects.get().playError(); } /** * Notify the user of a message. * * @param message the message to display */ private void notify(String message) { // TODO Add notification pop-up log.fine("Tell the user: " + message); } /** * Called when a task has been successfully deleted. */ private void onTaskDeleted() { // Notify the user that the task was deleted. notify("Task Deleted"); // Return to the task list. ActionEvent.fire(eventBus, ActionNames.TASK_SAVED); } private void startCreate() { isEditing = false; getView().setEditing(false); TaskRequest request = clientFactory.getRequestFactory().taskRequest(); editTask = request.create(TaskProxy.class); getView().getEditorDriver().edit(editTask, request); } private void startEdit() { isEditing = true; getView().setEditing(true); // Lock the display until the task is loaded. getView().setLocked(true); clientFactory.getRequestFactory().taskRequest().findTask(this.taskId).fire(new Receiver<TaskProxy>() { @Override public void onConstraintViolation(Set<ConstraintViolation<?>> violations) { getView().setLocked(false); getView().getEditorDriver().setConstraintViolations(violations); } @Override public void onFailure(ServerFailure error) { getView().setLocked(false); doCancelTask(); super.onFailure(error); } @Override public void onSuccess(TaskProxy response) { // Early exit if we have already stopped. if (eventBus == null) { return; } // Task not found. if (response == null) { Window.alert("The task with id '" + taskId + "' could not be found." + " Please select a different task from the task list."); doCancelTask(); return; } // Show the task. editTask = response; getView().getEditorDriver().edit(response, clientFactory.getRequestFactory().taskRequest()); getView().setLocked(false); } }); } }