Thursday Feb 12, 2015

Introduction to custom Cordova plugin development

Oracle Mobile Application Framework (MAF) v2.1.0 uses Cordova version 3.6.3 on Android and 3.7.0 on iOS to provide access to native device functionality.  The MAF 2.1.0 extension to JDeveloper 12.1.3 enables you to easily include any of the hundreds of published 3rd party Cordova plugins into your MAF app.

But what if you can’t find a suitable 3rd party plugin? You could elect to write your own, which, depending on the functionality required, may not be as difficult as you think.

In this post I’ll provide an introduction to developing a Cordova plugin by creating a very simple plugin for each of Android and iOS.

How does a Cordova plugin work?

In a nutshell, Cordova provides a bridge between JavaScript and native code, enabling you to write native code that gets exposed to your app via a common JavaScript interface.

Each method exposed by a plugin’s JavaScript interface is mapped to a method in the plugin’s native code via the Cordova bridge, which also enables you to pass parameters back and forth between the JavaScript and native methods.

What comprises a Cordova plugin?

A Cordova plugin typically consists of:

  • Native code for each supported platform
  • A common JavaScript interface
  • A manifest file called plugin.xml

The conventional structure for a Cordova plugin supporting both Android and iOS is:

  - Plugin top-level folder
     - plugin.xml
     - src/
        - android/
           - <Java source code>
        - ios/
           - <Objective-C source code>
     - www/
        - <JavaScript interface>

Ideally, community-published plugins also include release notes, author and license information, and a README file.  

A plugin may also include additional native resources and these are identified in the plugin.xml manifest file. This manifest file is read by the plugman command-line tool, which is used by the Cordova command-line interface and also by the MAF extension for JDeveloper.

In some rare cases, a plugin may be created that simply executes some native code on initialization and requires no JavaScript interface.

For more detailed information about the plugin.xml manifest file, refer to the Cordova Plugin Specification.

How do I create my own custom Cordova plugin?

To create your own custom Cordova plugin, you must write:

  • JavaScript that provides the interface for calling your plugin from within a Cordova-based app, such as a MAF app.
  • Native code that provides the functionality you need.  Since MAF supports both Android and iOS, you should write native code for both platforms.
  • A plugin.xml manifest file that defines your plugin and how plugman should incorporate it into a MAF app (or any Cordova-based app).

What tools do I need to create my own custom Cordova plugin?

You really only need a text editor to create your own custom Cordova plugin, which is all I’ve used to create the custom plugin described in this post.

For more complex plugins, you may wish to develop and test the plugin’s native code in each platform’s native IDE, which means downloading and installing the Android Studio and/or Apple’s Xcode.

You don’t need Cordova installed to develop a Cordova plugin.  Once you have developed your Cordova plugin, you can incorporate it directly into your MAF app for testing. However, if you wish to test your plugin within a Cordova app, you must download and install Cordova using the Cordova Command-Line Interface.

How do I write the plugin’s JavaScript interface?

We start with the JavaScript interface since it provides a common interface to both the Android and iOS native code.  This interface effectively defines what is required in the native code.

The JavaScript interface must call the cordova.exec method to invoke a native plugin method, as follows: 

cordova.exec(successCallback, failureCallback, service, action, [args]);

This call invokes the action method on the service class on the native side, passing the arguments in the optional args array.  If the native code completes successfully, the successCallback function is executed, along with any return parameters.  If the native code fails, the failureCallback function is executed, with an optional error parameter.  For more information on JavaScript callback functions, refer to this helpful blog post by Michael Vollmer.

Let’s create a very simple plugin that displays a native popup dialog.  Thus plugin shall present one method that takes 3 parameters – title, message and button label – and shall return the result in the ‘success’ callback. No ‘failure’ callback will be implemented. The service class shall be named “Alert” and we shall call the sole method “alert”. 

The following JavaScript defines the interface:

module.exports = {
  alert: function(title, message, buttonLabel, successCallback) {
    cordova.exec(successCallback,
                 null, // No failure callback
                 "Alert",
                 "alert",
                 [title, message, buttonLabel]);
  }
};

The call to module.exports exports the JavaScript function alert as part of the JavaScript module that will be defined in the plugin manifest file, plugin.xml

Your app will call this alert JavaScript function, which will invoke the alert method on the Alert class in the plugin’s native code.

Save this JavaScript into a file called alert.js, within a www subfolder of your plugin’s top-level folder.

How do I write the plugin’s native code?

Android

Based on the JavaScript interface, we must define a class called Alert in a Java source file called Alert.java.  Let’s take a look at the Alert.java source file:

package com.acme.plugin.alert;

import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.content.DialogInterface;
import org.apache.cordova.CallbackContext;
import org.apache.cordova.CordovaInterface;
import org.apache.cordova.CordovaPlugin;
import org.apache.cordova.CordovaWebView;
import org.apache.cordova.PluginResult;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class Alert extends CordovaPlugin {
  protected void pluginInitialize() {
  }

  public boolean execute(String action, JSONArray args, CallbackContext callbackContext)
      throws JSONException {
    if (action.equals("alert")) {
      alert(args.getString(
0), args.getString(1), args.getString(2), callbackContext);
      return true;
    }
    return false;
  }

  private synchronized void alert(final String title,
                                  final String message,
                                  final String buttonLabel,
                                  final CallbackContext callbackContext) {
    new AlertDialog.Builder(cordova.getActivity())
    .setTitle(title)
    .setMessage(message)
    .setCancelable(
false)
    .setNeutralButton(buttonLabel,
new AlertDialog.OnClickListener() {
      public void onClick(DialogInterface dialogInterface, int which) {
        dialogInterface.dismiss();
        callbackContext.sendPluginResult(
new PluginResult(PluginResult.Status.OK, 0));
      }
    })
    .create()
    .show();
  }
}

The Alert class should be part of a package that will be referenced in the manifest file, plugin.xml.

The Alert class must extend the CordovaPlugin class, the definition of which you can find here.

The Alert class must override the execute method, since this will be called each time the JavaScript cordova.exec method is called, providing the name of the plugin method, the input parameters and a callback context.  The execute method should return true if a valid action was passed in, otherwise false.

Once the code has completed, it should return a result and optional return parameters to the calling JavaScript by invoking the sendPluginResult method on the callbackContext object.   Returning a result of PluginResult.Status.OK will cause the JavaScript ‘success’ callback to be executed.  Any other result (apart from PluginResult.Status.NO_RESULT) will cause the JavaScript ‘failure’ callback to be executed.

In our plugin, a ‘success’ result is returned when the user taps the button on the popup dialog and a value of 0 is returned.

The Alert class may override the pluginInitialize method if any initialization logic is required when the plugin is first constructed.

Save this code into a file called Alert.java, within a src/android subfolder of your plugin’s top-level folder.

For more detailed information on aspects such a threading and event handling, refer to the Cordova page Android Plugins.

iOS

For our example, we must define a class called Alert in an Objective-C source file called Alert.m and corresponding header file Alert.h

Let’s take a look at the Alert.h header file:

#import <Cordova/CDV.h>

@interface Alert : CDVPlugin <UIAlertViewDelegate> {}
- (void)alert:(CDVInvokedUrlCommand*)command;
@end

@interface
MyAlertView : UIAlertView {}
@property (nonatomic, copy) NSString* callbackId;
@end

The Alert class must be a sub-class of CDVPlugin, the definition of which you can find here.

The Alert class must provide an alert method, since this will be called each time the plugin’s JavaScript alert method executes the cordova.exec method.

Save this code into a file called Alert.h, within a src/ios subfolder of your plugin’s top-level folder.

Let’s take a look at the Alert.m source file:

#import "Alert.h"

@implementation Alert
- (void)pluginInitialize
{
}

- (void)alert:(CDVInvokedUrlCommand*)command
{
  NSString* callbackId = command.callbackId;
  NSString* title = [command argumentAtIndex:
0];
  NSString* message = [command argumentAtIndex:
1];
  NSString* button = [command argumentAtIndex:
2];

  MyAlertView *alert = [[MyAlertView alloc]
                        initWithTitle:title
                        message:message
                        delegate:
self
                        cancelButtonTitle:button
                        otherButtonTitles:
nil];
                        alert.callbackId = callbackId;
  [alert show];
}

- (void)alertView:(UIAlertView*)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
  MyAlertView* myAlertView = (MyAlertView*)alertView;
  CDVPluginResult* result = [CDVPluginResult resultWithStatus:CDVCommandStatus_OK
                             messageAsInt:
0];
  [
self.commandDelegate sendPluginResult:result callbackId:myAlertView.callbackId];
}
@end

@implementation
MyAlertView
@synthesize callbackId;
@end

The alert method receives the input parameters and a callback id.

Once the code has completed, it should return a result and optional return parameters to the calling JavaScript by invoking the sendPluginResult method on the commandDelegate object. Returning a result of CDVCommandStatus_OK will cause the JavaScript ‘success’ callback to be executed. Any other result will cause the JavaScript ‘failure’ callback to be executed.

In our plugin, a ‘success’ result is returned when the user taps the button on the popup dialog and a value of 0 is returned.

The Alert class may implement the pluginInitialize method if any initialization logic is required when the plugin is first constructed.

Save this code into a file called Alert.m, within a src/ios subfolder of your plugin’s top-level folder.

For more detailed information on aspects such a threading and event handling, refer to the Cordova page iOS Plugins.

How do I write the plugin’s manifest file (plugin.xml)?

The manifest file, called plugin.xml, is an XML document that defines the plugin and tells plugman how to incorporate the plugin into your MAF app (or any Cordova-based app) for each platform it supports.

The Cordova Plugin Specification is comprehensive, but we will focus on the manifest file used for our “Alert” plugin:

<?xml version="1.0" encoding="UTF-8"?>
<plugin 
xmlns="http://apache.org/cordova/ns/plugins/1.0"
        id="com.acme.plugin.alert"
        version="0.0.1">

  <name>
Alert</name>
  <description>
A Cordova plugin that displays an alert popup dialog</description>

  <engines>
    <engine
name="cordova" version=">=3.6.0" />
  </engines>

  <js-module
src="www/alert.js" name="Alert">
    <clobbers
target="Alert" />
  </js-module>

  <!-- android -->
  <platform name="android">
    <config-file
target="res/xml/config.xml"
parent="/*">
      <feature name="Alert">
        <param name="android-package" value="com.acme.plugin.alert.Alert" />
      </feature>
    </config-file>
    <source-file src="src/android/Alert.java" target-dir="src/com/acme/plugin/alert" />
  </platform>

  <!-- ios -->
  <platform name="ios">
    <config-file target="config.xml" parent="/*">
      <feature name="Alert">
        <param name="ios-package" value="Alert" />
      </feature>
    </config-file>
    <header-file src="src/ios/Alert.h" />
    <source-file src="src/ios/Alert.m" />
  </platform>

</plugin>

The plugin element must contain the plugin’s XML namespace (xmlns), id and version.

The name and description elements should always be defined.  If you intend to publish your plugin for public use, you should include additional elements such as those identifying the author, license, keywords and repository.

The child elements of the engines element define which version(s) of the Cordova framework the plugin supports.  Since this plugin has been developed based on Cordova 3.6.0 documentation and will be tested within a MAF 2.1.0 app, we should set the minimum required Cordova version to 3.6.0.

The JavaScript interface is defined by including a js-module tag for each JavaScript file.  Any file defined here is automatically copied into your MAF app and injected into any HTML using a <script> tag so that you don’t have to specifically add this tag yourself, or include the JavaScript as content in your AMX features.  The clobbers tag indicates that the module shall be inserted into the window object as Alert, so your MAF app code should call the JavaScript method Alert.alert to execute the plugin’s alert method.

If your plugin has a dependency on another Cordova plugin, you can define this using a dependency tag.  Since our plugin does not have any dependencies, there is no such tag defined.

The platform tag is used to define the platforms that are supported by the plugin.  Within each platform tag, you specify the native source files, changes required to configuration files, any additional native resources or frameworks and any platform-specific JavaScript files.

For Android, it is important to specify the full package name of the plugin as the value for the android-package parameter, for example “com.acme.plugin.alert.Alert”, and to specify the target-dir for any source files (since this indicates the location to which the source file should be copied and it must match the package name), for example “src/com/acme/plugin/alert”.

Save this XML into a file called plugin.xml, within your plugin’s top-level folder.

Conclusion

We have now developed a custom Cordova plugin that can be incorporated into a MAF 2.1.0 app, or any app based on Cordova 3.6.0 or above.  In a follow-up post [Edit: here], I’ll describe how to integrate this plugin into a MAF app.

For developers looking for more detailed information about how to create a Cordova plugin, refer to the Cordova Plugin Development Guide, which contains specific guides for each native platform.

Thursday Jan 30, 2014

New Enhancement Released for iOS7+Android Native Look & Feel and Xcode 5 Support

Hi, everyone:

It has been a while since a blog article was published last.  While the bloggers took a little time off during the holidays, the product development team has been hard at work to release a new ADF Mobile "Patch" (Patch 5) that adds some significant new functionality, in addition to numerous bug fixes.  You can find the release note for the new patch here.

To download, you would simply need to start JDeveloper 11.1.2.4, and select menu item Help->Check For Updates->Official Oracle Extension and Updates, and select ADF Mobile.  It should have version number 11.1.2.4.39.64.62.

For any customers who have received one off patch through the BLR process, please note that one-off patches obtained through the BLR process are not automatically rolled into this overall patch.  Therefore, please work with your Oracle Support representative to request a new BLR patch for this latest patch.

We will focus on two specific enhancements in this article:

  • New iOS7 and Android Native Look and Feel (mobileAlta Skin)
  • Xcode 5 support

mobileAlta Skin for Native iOS 7 and Android Look and Feel

With iOS7, Apple introduced a new look and feel that gives the iOS user interface a cleaner and more stream-lined look and feel  Gone are a lot of the three-dimensional and gradient effect in the user interface and icons, and replaced by simple and modern "skins" to complement the iOS device hardware.  With the latest ADF Mobile patch, we introduced a new mobileAlta skin that, when running on iOS devices, would closely match the standard look and feel of the iOS7 look and feel.

Here is what the HR application looks like with the old (mobileFusionFX) skin:

The updated skin on the iPhone now looks like:

As for Android, as many of you noticed, the look and feel of the ADF Mobile skin has always more resembled that of the iOS than Android.  Android did not introduce a more formal UI standard until Android 4.x, and is still evolving.  Nevertheless, it has evolved to a look and feel that's very distinctive from the iOS UI.  Many of you have reported this issue to us, and we listened.  When rendered on Android devices, mobileAlta skin would also introduce a more Android look and feel. 

Here is the new Android native look-and-feel:

How to Apply the New Look and Feel

To apply the new look and feel, you simply need to edit the adfmf-config.xml file, and change the skin family as follows:

<skin-family>mobileFusionFX</skin-family>

to 

<skin-family>mobileAlta</skin-family>

 That's it.  If you have over-written out of box ADF Mobile CSS styles or added your own CSS classes, please test the application thoroughly and ensure the new style is compatible with the customized classes.  Color, coordinates, and icon references may have changed, and thorough UI testing is needed to ensure there is no unexpected side-effects.


Xcode 5 support

With the latest patch, you will need to use Xcode5 to deploy the iOS version of the ADF Mobile application.  Only Xcode 5 is supported.  This complies with the latest Apple guideline due to take effect on February 1, 2014, where all apps submitted to the AppStore must be compiled with Xcode5 and optimized for iOS 7.

Update to the latest Xcode requires downloading and installing Xcode 5, and then configure the location of the Xcode 5 in JDeveloper - Tools - Preferences - ADF Mobile.  

While JDeveloper's integration with Xcode 5 did not change, Xcode 5 itself introduced a number of changes.  The most prominent change is around how Provisioning Profiles and Developer Accounts are managed.  Previously Provisioning Profiles and Developer Accounts are accessed and managed through the Organizer utility that's accessed through menu item Windows - Organizer.  Now it is managed through the Xcode Preferences dialog box accessed with menu item Xcode - Preferences, and then select the "Accounts" tab.  You will then see your Apple Developer account information displayed.  When you click on the "View Details..." button, you will then see the list of certificates and provisioning profiles assigned to you.  Therefore, when you need to verify the Provisioning Profiles, you will need to access this dialog box.  You can still double click on the .mobileprovision file to install the Provisioning Profiles, but must use this functionality to see it.

Please consult Apple documentation for details of how to use this new functionality.

There had been some blog article published that references the old "Organizer" functionality.  These blog articles would be updated over time.  

Thanks,

ADF Mobile Product Management Team 

About

This blog is is dedicated to announcements,tips and tricks and other items related to developing, integrating, securing, and managing mobile applications using Oracle's Mobile Platform. It is created and maintained by the Oracle Mobile product development team.

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