Android - Adding native UI elements

improve this page | report issue

Overview

While you can write hybrid application by using solely web technologies, IBM MobileFirst Platform Foundation also allows you to mix and match native code with web code as needed.

For example, use native UI controls or native elements, provide an animated native introduction screen, etc. To do so, you must take control of part of the application startup flow.

Prerequisite: This tutorial assumes working knowledge of native Android development.

This tutorial covers the following topics:

Taking control of the startup flow

When you create a hybrid application, MobileFirst Studio generates a main CordovaActivity class (appname.java) which handles various stages of the application startup flow.

The showSplashScreen method is called to display a simple splash screen while resources are being loaded. You can modify the location with any native introduction screen.

To initialize the MobileFirst framework and prepare web resources, the initializeWebFramework method is called.
As soon as the web framework finishes initializing and all resources are ready, the onInitWebFrameworkComplete method is called. The value of WLInitWebFrameworkResult can be checked and the application can be started.

Native SplashScreen sample

The NativeUIInHybrid project includes a hybrid application called NativeSplashScreen.

The application contains an InitiativeActivity activity. This activity is used to show a simple text view and a button as our customized splash screen:

In the onCreate method:

setContentView(R.layout.activity_initiative);
startAppBtn = (Button) findViewById(R.id.StartApp);
And in the onClickListener method:
startAppBtn.setOnClickListener(new View.OnClickListener() {
	public void onClick(View v) {
		setResult(Activity.RESULT_OK);
		finish();
	}
});
The text view and the button are also added to the activity layout file:
<TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/InitiativeActivityText" />
<Button
    	android:id="@+id/StartApp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="150dp"
        android:text="@string/InitiativeButtonText" />

It is also required to add an Intent to the MainActivity before the call to the initializeWebFramework method. The intent loads the newly created activity instead of opening the default MobileFirst splash screen.

WL.createInstance(this);</p>
<p>Intent intent = new Intent(this, InitiativeActivity.class);<br />
startActivity(intent);</p>
<p>WL.getInstance().initializeWebFramework(getApplicationContext(), this);

Sending actions from JavaScript to native code

In MobileFirst applications, commands are sent with parameters from the web view (via JavaScript) to an Android native class (written in Java).
You can use this feature to trigger native code to be run in the background, to update the native UI, to use native-only features, etc.

Step 1

In JavaScript, the following API is used:
WL.App.sendActionToNative("doSomething", {customData: 12345});

The doSomething parameter is an arbitrary action name to be used in the native side (see Step 2). The second parameter is a JSON object that contains any data.

Step 2

The native class to receive the action must implement the WLActionReceiver protocol:

public class ActionReceiver implements WLActionReceiver{
}

The WLActionReceiver protocol requires an onActionReceived method in which the action name can be checked for and perform any native code that the action needs:

public void onActionReceived(String action, JSONObject data){
	if (action.equals("doSomething")){
		// Write your code here...
	}
}

Step 3

For the action receiver to receive actions from the MobileFirst Web View, it must be registered. The registration can be done during the startup flow of the application to catch any actions early enough:

WL.getInstance().addActionReceiver(new ActionReceiver(this));

Sending actions from native code to JavaScript code

In MobileFirst applications, commands can be sent with parameters from native Android code to web view JavaScript code.
You can use this feature to receive responses from a native method, notify the web view when background code finished running, have a native UI control the content of the web view, etc.

Step 1

In Java, the following API is used:

JSONObject data = new JSONObject();
	data.put("someProperty", 12345);
	WL.getInstance().sendActionToJS("doSomething", data);

The doSomething parameter is an arbitrary action name to be used on the JavaScript side and the second parameter is an JSONObject instance that contains any data.

Step 2

A JavaScript function, which verifies the action name and implements any JavaScript code.

function actionReceiver(received){
  if (received.action == "doSomething" &amp;&amp; received.data.someProperty == "12345"){
    //perform required actions, e.g., update web user interface
  }
}

Step 3

For the action receiver to receive actions, it must first be registered. This should be done early enough in the JavaScript code so that the function handles those actions as early as possible.

WL.App.addActionReceiver ("MyActionReceiverId", actionReceiver);

The first parameter is an arbitrary name. It can be used later to remove an action receiver.

WL.App.removeActionReceiver("MyActionReceiverId");

SendAction sample

missing_alt

Overview

Download the NativeUIInHybrid project, which includes a hybrid application called SendAction.
This sample uses the MapView and the Google Maps services.

Note: This sample will NOT work without the following extra steps to install the MapView.

For more information about the MapView and Google Maps services, see the Google Map Android page at https://developers.google.com/maps/documentation/android/
This sample includes an additional FragmentActivity (DisplayMap) to display the requested map.

HTML

The HTML page shows the following elements:

  • A simple input field to enter an address
  • A button to trigger validation
  • An empty line to show potential error messages

<p>This is a MobileFirst WebView.</p>
<p>Enter a valid address (requires Internet connection):<br/><br />
    	<input type="text" name="address" id="address"/><br />
<input type="button" value="Display" id="displayBtn"/>
 </p><br />
 <p id="errorMsg" style="color:red;"></p>

JavaScript

When the button is clicked, the sendActionToNative method is called to send the address to the native code.

$('#displayBtn').on('click', function(){
	$('#errorMsg').empty();
	WL.App.sendActionToNative("displayAddress",
				{ address: $('#address').val()}
		);
	});

The code also registers an action receiver to display potential error messages from the native code.

WL.App.addActionReceiver ("MyActionReceiverId", function actionReceiver(received){
		if(received.action == 'displayError'){
			$('#errorMsg').html(received.data.errorReason);
		}
	});

Action receiver

A new class is required. It implements WLActionReceiver.
Before using this new class, call the addActionReceiver method to register ActionReceiver in the main activity after the initialization process is complete.

public void onInitWebFrameworkComplete(WLInitWebFrameworkResult result) {
	if (result.getStatusCode() == WLInitWebFrameworkResult.SUCCESS) {
		super.loadUrl(WL.getInstance().getMainHtmlFilePath());
	} else {
		handleWebFrameworkInitFailure(result);
	}
	WL.getInstance().addActionReceiver(new ActionReceiver(this));
}

The ActionReceiver class implements the onActionReceived method. This method is used to receive the address that was passed in the JavaScript code.

public void onActionReceived(String action, JSONObject data){
	if (action.equals("displayAddress")){
		try {
			mAddress = data.getString("address");
		} catch (JSONException e) {
			e.printStackTrace();
		}
		Intent intent = new Intent(parentActivity,DisplayMap.class);
		intent.putExtra("RECEIVED_ADDRESS", mAddress);
		parentActivity.startActivity(intent);
	}
}

Displaying the map

After the address parameter is received, a FragmentActivity instance is needed to display it.
This activity uses the GoogleMap services and the Google Geocoder to display the requested address on a map.

The address parameter needs to be sent to this activity in order to display the address in the map.

Shared session

When you use both JavaScript and native code in the same application, you might need to make HTTP requests to MobileFirst Server (connect, procedure invocation, etc.)

HTTP requests are explained in other tutorials (both for hybrid and native applications).
IBM Worklight 6.2 and IBM MobileFirst Platform Foundation 6.3 and later keep your session (cookies and HTTP headers) automatically synchronized between the JavaScript client and the native client.

Sample application

Click to download the Studio project.

Last modified on November 09, 2016