com.codename1.javascript.JSFunction Maven / Gradle / Ivy
/*
* Copyright (c) 2012, Steve Hannah/Codename One and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Codename One designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Codename One through http://www.codenameone.com/ if you
* need additional information or have any questions.
*/
package com.codename1.javascript;
import com.codename1.ui.BrowserComponent;
/**
* The JSFunction interface allows you to implement functions in Java that can
* be called from Javascript. You can assign any JSFunction object to be a member
* method of an existing JSObject via the {@link JSObject#set(String,Object) JSObject.set()} method. Then the function
* can be called from javascript just like any other Javascript method. JSFunction
* methods are called asynchronously from Javascript to prevent deadlocks. If you
* require a return value to Javascript, you can do that by passing a callback
* function which is called by the JSFunction with some parameters.
*
*
* NOTE: The {@link com.codename1.javascript } package is now
* deprecated. The preferred method of Java/Javascript interop is to use {@link BrowserComponent#execute(java.lang.String) }, {@link BrowserComponent#execute(java.lang.String, com.codename1.util.SuccessCallback) },
* {@link BrowserComponent#executeAndWait(java.lang.String) }, etc.. as these
* work asynchronously (except in the XXXAndWait() variants, which use
* invokeAndBlock() to make the calls synchronously.
*
* The following example, adds a camera object to the Javascript environment
* that has a capture() method, which can be used to capture images using the
* device's camera:
*
*
* // Create a new Javascript object "camera"
* final JSObject camera = (JSObject)ctx.get("{}");
*
* // Create a capture() method on the camera object
* // as a JSFunction callback.
* camera.set("capture", new JSFunction(){
*
* public void apply(JSObject self, final Object[] args) {
* Display.getInstance().capturePhoto(new ActionListener(){
*
* public void actionPerformed(ActionEvent evt) {
*
* String imagePath = (String)evt.getSource();
*
* // Get the callback function that was provided
* // from javascript
* JSObject callback = (JSObject)args[0];
*
* ctx.call(
* callback, // The function
* camera, // The "this" object
* new Object[]{"file://"+imagePath} // Parameters
* );
* }
*
* });
* }
*
* });
*
*
* // Add the camera object to the top-level window object
* ctx.set("window.camera", camera);
*
*
* We can then capture photos directly from Javascript using a function similar to the following:
*
* camera.capture(function(url){
* if ( url == null ){
* // No image was captured
* return;
* }
*
* // Fetch the preview <img> tag.
* var image = document.getElementById('preview-image');
* // Set the preview URL to the image that was taken.
* image.src = url;
* });
*