| // |
| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you 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. |
| // |
| |
| = DevFaqRequestProcessorTask |
| :jbake-type: wiki |
| :jbake-tags: wiki, devfaq, needsreview |
| :jbake-status: published |
| :keywords: Apache NetBeans wiki DevFaqRequestProcessorTask |
| :description: Apache NetBeans wiki DevFaqRequestProcessorTask |
| :toc: left |
| :toc-title: |
| :syntax: true |
| |
| === How can I operation occasionally on a background thread, but reschedule it if something happens to delay it? |
| |
| There are a lot of reasons you might want to reschedule a background operation. For example, you want to re-parse a file 3 seconds after the user stops typing, so you can show errors. But at 2 seconds she starts typing again. You don't want that task to run a second from now anymore. You can either cancel the task, or even simpler, call `task.schedule(3000)` every time a key is pressed. If it was already scheduled, it will be rescheduled for 3 seconds from now again. |
| |
| Or imagine you have the situation described in link:DevFaqRequestProcessor.asciidoc[the FAQ about RequestProcessor.getDefault()] - a node for a file needs to read the file after it is created to mark itself if the file has errors. `RequestProcessor.Task` makes this sort of thing easy. |
| |
| [source,java] |
| ---- |
| |
| public class FooDataNode extends DataNode implements PropertyChangeListener, Runnable { |
| private boolean error; |
| private static final RequestProcessor THREAD_POOL = new RequestProcessor("FooDataNode processor", 1); |
| private final RequestProcessor.Task task = THREAD_POOL.create(this); |
| |
| FooDataNode(FooDataObject obj) { |
| super(obj, Children.LEAF); |
| obj.addPropertyChangeListener(WeakListeners.propertyChange(this, obj)); |
| task.schedule(100); |
| } |
| |
| public void propertyChange(PropertyChangeEvent evt) { |
| DataObject obj = (DataObject) evt.getSource(); |
| if (DataObject.PROP_MODIFIED.equals(evt.getPropertyName()) && !obj.isModified()) { //file was saved |
| task.schedule(100); |
| } |
| } |
| |
| @Override |
| public String getHtmlDisplayName() { |
| return error ? "<font color=\"!nb.errorForeground\">" + getDisplayName() : null; |
| } |
| |
| public void run() { |
| boolean old = error; |
| error = doesTheFileHaveErrors(); |
| if (old != error) { |
| fireDisplayNameChange(null, null); |
| } |
| } |
| |
| private boolean doesTheFileHaveErrors() { |
| assert !EventQueue.isDispatchThread(); |
| //parse the file here |
| return true; //whatever the value should be |
| } |
| } |
| ---- |
| |
| === Apache Migration Information |
| |
| The content in this page was kindly donated by Oracle Corp. to the |
| Apache Software Foundation. |
| |
| This page was exported from link:http://wiki.netbeans.org/DevFaqRequestProcessorTask[http://wiki.netbeans.org/DevFaqRequestProcessorTask] , |
| that was last modified by NetBeans user Admin |
| on 2009-11-06T15:59:19Z. |
| |
| |
| *NOTE:* This document was automatically converted to the AsciiDoc format on 2018-02-07, and needs to be reviewed. |