Template:PT3 JAVA ANDROID AS

Language - Java

Android with Android Studio

Welcome to using Phidgets with Java! By using Java, you will have access to the complete Phidget22 API, including events.

Android Studio is a graphical IDE for Android java programs.

Creating A New Project

When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget Java libraries for Android Java.

To start, create a new project in Android Studio:

Creating A New Project

Once you have a new project, be sure to switch the side bar to Project view.

Creating A New Project

Next, download the Phidget22 Android Java libraries, extract the contents, and open the resulting folder.

Creating A New Project

Copy the .jar files into the app/libs/ folder of your project. If you are only going to use network Phidgets in your app, then you don't need to copy Phidget22usb.jar into your project.

Right click the jar files you just copied and select Add As Library.

Creating A New Project

Create a directory called jnilibs under app/src/main

Creating A New Project

Copy the remaining folders from the Phidget22 library (containing versions of libphidget22java.so) into the directory you just created.

Creating A New Project

To allow the use of the network and/or USB connections, the following lines must be added to your AndroidManifest.xml file:

<!-- Required for network access -->
<uses-permission android:name="android.permission.INTERNET" />

<!-- Required for USB access -->
<uses-feature android:name="android.hardware.usb.host" />

Finally, to import the Phidget22 library into your code, add the following line to the rest of your imports:

import com.phidget22.*;

The project now has access to Phidgets. Next, we'll walk through the steps for writing your own code.

Write Code

By following the instructions for your operating system and compiler above, you now have working examples and a project that is configured. This teaching section will help you understand how the examples were written so you can start writing your own code.

Your main reference for writing Android Java code will be:

● The Phidget22 API

● The Java example code

Write Code

Step One: Initialize and Open

You will need to declare your Phidget object in your code. For example, we can declare a digital input object like this:

DigitalInput device;

Next, we need to initialize the method(s) that the Android device can communicate with the Phidget. This is done either by enabling Network Server Discovery, and/or allowing direct USB connections as follows:

//Enable server discovery to list remote Phidgets
this.getSystemService(Context.NSD_SERVICE);
Net.enableServerDiscovery(ServerType.DEVICE_REMOTE);

//Allow direct USB connection of Phidgets
com.phidget22.usb.Manager.Initialize(this);

Write Code

To support remote (network) Phidgets on Android API versions earlier than API version 16, or to connect to Phidget Network Servers with passwords, you will need to add the specific server to your program:

//Add a specific network server to communicate with Phidgets remotely
Net.addServer("ServerName", "192.168.1.105", 5661, "password", 0);

After the connection methods are established, the Phidget object needs to be initialized and opened:

device = new DigitalInput();
device.open();

Write Code

Although we are not including it on this page, you should include error handling for all Phidget functions. Here is an example of the previous code with error handling:

try{
    device = new DigitalInput();
    device.open();
}catch (PhidgetException e) {
    e.printStackTrace();
}

For more information on error handling with Phidgets, see this page.

Write Code

Step Two: Wait for Attachment (plugging in) of the Phidget

Simply calling open does not guarantee you can use the Phidget immediately. To use a Phidget, it must be plugged in (attached). We can handle this by using event driven programming and tracking the attach events. Alternatively, we can modify our code so we wait for an attachment:

ch = new DigitalInput();
ch.open(5000); //wait for attach for 5 seconds, if not time out

Waiting for attachment will block indefinitely until a connection is made, or until the timeout value is exceeded.

Write Code

To use events, we have to modify our code:

ch = new DigitalInput();
device.addAttachListener(new AttachListener() {
    public void onAttach(final AttachEvent attachEvent) {
        AttachEventHandler handler = new AttachEventHandler(device);
        synchronized(handler)
        {
            runOnUiThread(handler);
            try {
                handler.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
});
ch.open();

Write Code

Next, we have to declare the function that will be called when an attach event is fired - in this case the function AttachEventHandler will be called.

class AttachEventHandler implements Runnable { 
    Phidget device;

    public AttachEventHandler(Phidget device) {
        this.device = device;
    }

    public void run() {
        TextView attachedTxt = (TextView) findViewById(R.id.attachedTxt);
        attachedTxt.setText("Attached");

        //notify that we're done
        synchronized(this)
        {
	    this.notify();
        }
    }
}

Write Code

Step Three: Do Things with the Phidget

We recommend the use of event driven programming when working with Phidgets. In a similar way to handling an attach event as described above, we can also add an event handler for a state change event:

ch = new DigitalInput();
device.addStateChangeListener(new DigitalInputStateChangeListener() {
	public void onStateChange(DigitalInputStateChangeEvent stateChangeEvent) {
        DigitalInputStateChangeEventHandler handler = 
            new DigitalInputStateChangeEventHandler(device, stateChangeEvent);
	runOnUiThread(handler);
    }
});
ch.open();

This code will connect a function and an event. In this case, the DigitalInputStateChangeEventHandler function will be called when there has been a change to the devices input.

Write Code

Next, we need to create the DigitalInputStateChangeEventHandler function itself:

class DigitalInputStateChangeEventHandler implements Runnable {
    Phidget device;
    DigitalInputStateChangeEvent stateChangeEvent;

    public DigitalInputStateChangeEventHandler(Phidget device,
       DigitalInputStateChangeEvent stateChangeEvent)
    {
        this.device = device;
        this.stateChangeEvent = stateChangeEvent;
    }

    public void run() {
        CheckBox stateBox = (CheckBox) findViewById(R.id.stateBox);
        stateBox.setChecked(stateChangeEvent.getState());
    }
}

If events do not suit your needs, you can also poll the device directly for data using code like this:

boolean state = ch.getState();

Write Code

Step Four: Close and Delete

At the end of your program, be sure to close your device.

ch.close();

Once the device is closed, to completely clean up after using Phidgets, you must uninitialize the USB connection as follows:

//Disable USB connection to Phidgets
com.phidget22.usb.Manager.Uninitialize();

What's Next?

Now that you've set up Phidgets in your programming environment, you should read our guide on Phidget Programming Basics to learn the fundamentals of programming with Phidgets.

Common Problems, Solutions and Workarounds

My Phidget Detached When I Rotated My Phone

You are likely using one of our examples, or handling the opening and closing of Phidgets in a similar way. In either case, chances are you are opening and closing Phidgets in your main activity. This is not recommended for practical applications, as the entire activity can be destroyed and re-created many times through its lifecycle due to configuration changes such as rotating the screen. This is a reality of the Android operating system, and must be addressed in whatever way best suits your application. A good option to keep your Phidgets connected would be to implement a Started Service or a Foreground Service, depending on your application, and open your Phidgets there.

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