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An Intel® XDK Debugging Tutorial

NOTE: the screenshots in this tutorial may vary from those you see in the Intel XDK that you are using and from the current versin of this demo application. Despite any such differences, the content of this tutorial still applies and can still be used to gain insight into how to use the Intel XDK to debug your Cordova application.

As the table on this page illustrates, there are many ways to debug a hybrid HTML5 app using the Intel XDK. In this article I’m going to go through just two of these options:

  1. using the Emulate tab

  2. using the Debug tab

Preparation

What you will need to follow this tutorial:

  • Android 4.0 (or higher) phone or tablet + USB cable

  • Intel App Preview installed on your Android device

  • Workstation running Linux, Windows 7+ or Mac OS X

  • The Intel XDK installed on your workstation

Download and unzip a copy of this “hello-cordova” sample app onto your workstation. Then, from the Intel XDK Projects tab (click PROJECTS in the upper-left corner of the Intel XDK window), choose Open an Intel XDK Project from the bottom of the list of projects. Navigate to the directory containing the unzipped “hello-cordova” project and select the hello-cordova.xdk file inside that directory.

The “hello-cordova” project should now be open in the Intel XDK. You can explore the source code using the Brackets code editor that is built into the Develop tab, or you can use your favorite source code editor to view the files outside of the Intel XDK. Start with the index.html file, it is the entry point into your application.

NOTE: some of the images in this tutorial may not precisely match what you see when using the app in the Emulate tab, in the Debug tab, in App Preview or when the app is built and installed on your device. Please ignore those differences, if what you see is close to the images shown in this tutorial your app is working correctly.

Using the Emulate Tab

The “hello-cordova” application is ready to run. Switching to the Emulate tab will start the app inside a simulated device. The Emulate tab does not simulate real devices, it primarily does the following three things:

See this doc page for more details about these limitations: https://software.intel.com/en-us/xdk/docs/intel-xdk-debug-and-test-overview#EmulateTab.

What the Emulate tab does do, very well, is make it easy to test and debug your basic application code (HTML, CSS and JavaScript). The fact that it simulates the “core” Cordova APIs means that it is possible to debug much of your device code without having to use a real device. You can do this quickly and easily with the builtin Chrome DevTools console that is included with the Emulate tab.

Start the Emulate tab by selecting it from the tabs at the top of the Intel XDK window. In its default configuration it will automatically refresh or restart your app whenever it detects changes to your project source files (i.e., whenever one of your project source files are saved to disk). You can change this behavior by selecting the Emulator settings icon on the toolbar (at the upper left, next to the “bug” icon) and selecting “Do nothing” in the settings dialog.

Try the Accelerometer (Motion) Simulator

Using your mouse, touch the “Accelerometer” button in the application’s viewport or simulated window. Make sure the Accelerometer panel to the left of the simulated device is showing, as in the picture below.

You can “grab” the small device in that panel with your mouse and move it up and down or left and right. As you do this you are simulating tilting the device; as if you were changing its physical orientation relative to the earth.

Notice that the numbers in the bottom of the Accelerometer pane (xAxis, yAxis, etc.) change as you tilt the device and will also appear on the simulated device screen. This is because the application is calling the Cordova navigator.accelerometer.* functions that are part of the Cordova device-motion plugin (which is included as part of the project by selecting Accelerometer from the Plugins section of the Projects tab).

If you want to inspect the accelerometer code, find the cordova-acc.js file inside the “hello-cordova” project.

NOTE: there is a known issue on some Android 5 devices where the accelerometer plugin does not work. This is an Apache Cordova problem that currently has no known solution. You will only see this problem when running on a real device. As an alternative you can use the deprecated Intel XDK accelerometer plugin or the HTML5 device orientation API.

Try the GeoLocation Simulator

For this step make sure you have selected one of the iOS devices (such as an Apple iPhone) from the Devices panel on the left side of the Emulate tab window. We are going to use an iOS device because its geolocation functions are easier to use in this simulation. The Android geolocation functions behave in a way that is more difficult to demonstrate.

Make sure the GeoLocation panel is showing to the right of the simulated device. Now select the “GeoFine” button, you should see some numbers appear in the geo fields on the display (you may have to scroll the device screen down to see all of the geo fields). If that is successful, push the “GeoWatch” button. Your simulated device screen should look something like the following:

While the “GeoWatch” function is active (signified by the green button), you can grab the map inside the GeoLocation panel to the right of the simulated device and move it around. As you do you will see the geo fields in the simulated device screen update to reflect the new location on the map. Likewise, as with the accelerometer exercise, the numbers below the map change to reflect your location on the map. You can also type numbers directly into those fields to effect the simulated geolocation.

If you want to inspect the code associated with the geolocation part of this app, find the cordova-geo.js file in the “hello-cordova” application’s project directory.

NOTE: some devices do not include GPS hardware or are built with very ineffective geolocation hardware. Android devices allow the user to control whether or not the GPS hardware is enabled. All devices allow users to block access to geolocation data (whether derived from GPS, wifi or mobile cell tower signal information). Be aware that all of these caveats mean that you may not always be able to get geolocation information from the device and your application should accommodate this condition.

Try the Compass Simulator

Push the “Compass” button to enable monitoring the compass feature of the “hello-cordova” app in the simulated device. The “Compass” button will turn green to indicate that the app is now watching the device’s compass data.

To effect the compass data returned by the Cordova Compass API, move the slider labeled Heading below the geolocation map, in the right-side panel. As you move the slider left and right you will see the yellow pointer in the center of the GeoLocation map rotate to indicate the relative direction of the compass, as specified by the Heading slider. Likewise, the compass field on the device’s simulated display will update to reflect the returned compass data.

Not all devices include the hardware necessary to provide compass heading data!

The code that is reading the compass data is located inside the cordova-acc.js file in the “hello-cordova” project directory.

NOTE: there is a known issue on some Android 5 devices where the compass feature does not work. This is an Apache Cordova problem that currently has no known solution. You will only see this problem when running on a real device. As an alternative you can use the HTML5 device orientation API.

Try to Debug some JavaScript, CSS and HTML

If you push the “Beep” button it will cause the simulated device to issue a short audio alert. You might have to turn up the volume of your workstation to hear the short beep. Notice that the button does not turn green, like the “Compass” or “GeoWatch” buttons did. This is because the Cordova API that is being used to issue this audio alert has no “watch” feature, it is a simple call to a function that generates the audio alert.

This is an easy function to test your JavaScript debugging skills. You’ll find the function associated with that button inside the app.js file in the “hello-cordova” project. The specific function you are looking for is called, appropriately, app.btnBeep(). It is a very simple function, so there’s not much debugging that can be done, but it will help you get started.

From the Emulate tab, push the “debug” icon in the toolbar (at the upper left of the Emulate tab window, see the image above). Pushing the “debug” icon will cause an instance of Chrome DevTools (CDT) to open on your screen.

See this image for an example of what a CDT window looks like:

If you have selected the Elements tab in the CDT window, and move your mouse over the HTML elements in the Elements panel, you will see the corresponding rendered elements highlighted on the simulated device display, just as if you were debugging a web page in Chrome and CDT. For example, similar to this image:

From here you can use CDT to monitor the many console.log() messages that have been included in the “hello-cordova” application. You can also select a specific HTML element and fine-tune the CSS associated with the application. Try a few things to see what happens. Don’t worry about breaking the app, changes you make in the CDT window are temporary and do not impact your actual source code files, so you can always get back to where you started by simply restarting the session with the “refresh” icon on the toolbar (the “refresh” icon is located to the left of the “debug” icon).

NOTE: each source code file includes a line of code similar to app.init.LOG = true ; (near the top of each file) that can be used to enable and disable console.log() messages within that module.

In order to debug JavaScript you need to select the Sources tab of CDT and find the source file of interest. In this case, we are going to set a breakpoint on the app.btnBeep() function, which is located in the app.js file. Once we locate that file in CDT we can set a breakpoint on the entry line of the app.btnBeep() function by double-clicking that line in the source code display. A breakpoints panel on the right side of the CDT window contains any breakpoints that have been set in our test application.

See the image below for an example (the image is slightly out of date, please find the app.js file and the app.btnBeep() function within that file):

Now push the “Beep” button on the simulated device. As soon as we enter the app.btnBeep() function we will encounter our breakpoint. This pauses the JavaScript execution, at the breakpoint.

This image shows the application just as we have encountered the JavaScript breakpoint (as noted above, the image is slightly out of date):

Notice the “Paused in debugger” alert at the top of the Emulate tab and the highlighted line of JavaScript code, where our breakpoint was placed.

From here you can inspect variables by hovering over them in the source panel (as shown below) and by using the JavaScript console.

To control execution following a break use the panel to the right of the of the source panel. The blue arrow causes execution of the application to resume (see the image below). Pushing the curved arrow that is jumping over a dot (to the right of the blue "resume" icon) causes your code to single-step. Try single-stepping through the function.

See the of Chrome DevTools pages on the Google Chrome developer site to learn more about debugging with CDT.

Using the Debug Tab with a Real Device

For a quick overview of the Debug tab requirements and features, see this article: https://software.intel.com/en-us/xdk/docs/intel-xdk-debug-and-test-overview#DebugTab. A more detailed explanation of the Debug tab can be found here: https://software.intel.com/en-us/xdk/docs/using-the-debug-tab.

Getting Started with the Debug Tab

Switch to the Debug tab to start debugging this same app on a real Android device attached to your workstation via a USB cable. If your device is ready for debugging the Debug tab will indicate that it can see a device in the upper left of the Debug tab’s toolbar, at the upper left of the window.

If your device does not appear, as shown above, follow the steps in this article to configure your device and workstation for Android USB debugging.

NOTE: the Debug tab can also be used with an iOS device, but does require that you have an Apple developer account in order to create the necessary certificates and provisioning files needed to debug an iOS app. To learn how to use USB debugging it is best to start with an Android device.

Installing the App Preview Debug Module

Once your device is recognized, you can load the “hello-cordova” application onto it by pushing either the “debug” or “run” icon on the toolbar, just to the right of the device selection pulldown. Pushing the “run” icon will load and run your app on the attached device. Pushing the “debug” icon will load and run your app and then start a copy of Chrome DevTools inside the Debug tab, similar to what you saw when using the Emulate tab.

In order to run your app on the device a special App Preview debug module must first be installed on your Android device. The Intel XDK will prompt you about this requirement and will lead you through the process of installing that debug module onto your device, if it is not already present, before it loads and starts your app.

Debugging Your App on a Real Device

After the Debug tab has started running your app on your device, and the CDT window is present, you can go through the same sequence of steps described in the Emulate tab in the first part of this article. Unlike the Emulate tab exercise, there are no simulation panels to effect the accelerometer, compass or geolocation data. Instead, you must interact with the attached device to see the data displayed by the app change. In other words, you must rotate and move the device to see any results, because your app is now running on a real device!

NOTE: that not all devices are guaranteed to include the hardware necessary to use all the features of this simple "hello-cordova" application. For example, it is quite common to encounter devices that do not include compass or GPS hardware. In that case the "Compass" button will not read any data and the precision of the GPS data may be quite low or non-existent. The precise capabilities of geolocation hardware in Android devices can vary widely. In addition, the ability to read geolocation data on a real device can also be restricted by the Android "Location" settings, or mode. For example, if a device includes GPS hardware but that GPS hardware has been disabled in the Android settings, it may result in no "fine" geolocation data being returned from the device, or the data may be identical to the "coarse" geolocation data results.

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