For developers who have an understanding of how to use the Cordova CLI and make use of plugins, there are a few things you may want to consider researching next to build better, more performant Cordova applications. The following document offers advice on various topics relating to best practices, testing, upgrades, and other topics, but is not meant to be prescriptive. Consider this your launching point for your growth as a Cordova developer. Also, if you see something that can be improved, please contribute!
This guide contains the following topics:
Using a SPA can help you organize your application in a more efficient manner, but it also has specific benefits for Cordova applications. A Cordova application must wait for the deviceready event to fire before any plugins may be used. If you do not use a SPA, and your user clicks to go from one page to another, you will have to wait for deviceready to fire again before you make use of a plugin. This is easy to forget as your application gets larger.
Even if you choose not to use Cordova, creating a mobile application without using a single page architecture will have serious performance implications. This is because navigating between pages will require scripts, assets, etc., to be reloaded. Even if these assets are cached, there will still be performance issues.
Examples of SPA libraries you can use in your Cordova applications are:
And many, many, more.
One of the biggest mistakes a new Cordova developer can make is to assume that the performance they get on a desktop machine is the same they will get on a mobile device. While our mobile devices have gotten more powerful every year, they still lack the power and performance of a desktop. Mobile devices typically have much less RAM and a GPU that is a far cry from their desktop (or even laptop) brethren. A full list of tips here would be too much, but here are a few things to keep in mind (with a list of longer resources at the end for further research).
Click versus Touch - The biggest and simplest mistake you can make is to use click events. While these "work" just fine on mobile, most devices impose a 300ms delay on them in order to distinguish between a touch and a touch "hold" event. Using
touchend, will result in a dramatic improvement - 300ms doesn't sound like much, but it can result in jerky UI updates and behavior. You should also consider the fact that “touch” events are not supported on non-webkit browsers, see CanIUse. In order to deal with these limitations, you can checkout various libraries like HandJS and Fastouch.
Networks Suck - Ok, networks don't always suck, but the latency of mobile networks, even good mobile networks, is far worse than you probably think. A desktop app that slurps down 500 rows of JSON data, every 30 seconds, will be both slower on a mobile device as well as a battery hog. Keep in mind that Cordova apps have multiple ways to persist data in the app (LocalStorage and the file system for example). Cache that data locally and be cognizant of the amount of data you are sending back and forth. This is an especially important consideration when your application is connected over a cellular network.
Additional Performance Articles and Resources
See the previous tip about networks. Not only can you be on a slow network, it is entirely possible for your application to be completely offline. Your application should handle this in an intelligent manner. If your application does not, people will think your application is broken. Given how easy it is to handle (Cordova supports listening for both an offline and online event), there is absolutely no reason for your application to not respond well when run offline. Be sure to test (see the Testing section below) your application and be sure to test how your application handles when you start in one state and then switch to another.
Note that the online and offline events, as well as the Network Connection API is not perfect. You may need to rely on using an XHR request to see if the device is truly offline or online. At the end of the day, be sure add some form of support for network issues - in fact, the Apple store (and probably other stores) will reject apps that don’t properly handle offline/online states. For more discussion on this topic, see "Is This Thing On?"
If your existing project was created using Cordova 3.x, you can upgrade the project by issuing the following:
cordova platform update platform-name ios, android, etc.
If your existing project was created under a version prior to Cordova 3.x, it would probably be best to create a new Cordova 3.x project, and then copy your existing project’s code and assets to the new project. Typical steps:
Regardless of the project's prior version, it is absolutely critical that you read up on what was changed in the updated version, as the update may break your code. The best place to find this information will be in the release notes published both in the repositories and on the Cordova blog. You will want to test your app thoroughly in order to verify that it is working correctly after you perform the update.
Note: some plugins may not be compatible with the new version of Cordova. If a plugin is not compatible, you may be able to find a replacement plugin that does what you need, or you may need to delay upgrading your project. Alternatively, alter the plugin so that it does work under the new version and contribute back to the community.
As of Cordova 3.4, there is no mechanism for upgrading changed plugins using a single command. Instead, remove the plugin and add it back to your project, and the new version will be installed:
cordova plugin rm com.some.plugin cordova plugin add com.some.plugin
Be sure to check the updated plugin's documentation, as you may need to adjust your code to work with the new version. Also, double check that the new version of the plugin works with your project’s version of Cordova.
Always test your apps to ensure that installing the new plugin has not broken something that you did not anticipate.
If your project has a lot of plugins that you need updated, it might save time to create a shell or batch script that removes and adds the plugins with one command.
Testing your applications is super important. The Cordova team uses Jasmine but any web friendly unit testing solution will do.
It’s not uncommon to use desktop browsers and device simulators/emulators when developing a Cordova application. However, it is incredibly important that you test your app on as many physical devices as you possibly can:
It is, of course, impossible to test on every possible device on the market. For this reason, it’s wise to recruit many testers who have different devices. Although they won’t catch every problem, chances are good that they will discover quirks and issues that you would never find alone.
Tip: It is possible on Android Nexus devices to easily flash different versions of Android onto the device. This simple process will allow you to easily test your application on different levels of Android with a single device, without voiding your warranty or requiring you to “jailbreak” or “root” your device. The Google Android factory images and instructions are located at: https://developers.google.com/android/nexus/images#instructions
Debugging Cordova requires some setup. Unlike a desktop application, you can't simply open dev tools on your mobile device and start debugging, luckily there are some great alternatives.
Virtually the same as the Safari version, this works with Android only but can be used from any desktop operating system. It requires a minimum of Android 4.4 (KitKat), minimum API level of 19, and Chrome 30+ (on the desktop). Once connected, you get the same Chrome Dev Tools experience for your mobile applications as you do with your desktop applications. Even better, the Chrome Dev Tools have a mirror option that shows your app running on the mobile device. This is more than just a view - you can scroll and click from dev tools and it updates on the mobile device. More details on Chrome Remote Debugging may be found here: https://developers.google.com/chrome/mobile/docs/debugging
It is possible to use Chrome Dev Tools to inspect iOS apps, through a WebKit proxy: https://github.com/google/ios-webkit-debug-proxy/
Ripple is a desktop based emulator for Cordova projects. Essentially it lets you run a Cordova application in your desktop application and fake various Cordova features. For example, it lets you simulate the accelerometer to test shake events. It fakes the camera API by letting you select a picture from your hard drive. Ripple lets you focus more on your custom code rather than worrying about Cordova plugins. You can find out more about Ripple here: http://ripple.incubator.apache.org/
Weinre creates a local server that can host a remote debug client for your Cordova applications. After you've installed and started it up, you copy a line of code into your Cordova application and then restart it. You can then open a dev tool panel on your desktop to work with the application. Weinre is not quite as fancy as Chrome and Safari Remote debugging but has the benefit of working with a much greater range of operating systems and platforms. More information may be found here: http://people.apache.org/~pmuellr/weinre/docs/latest/
Building a Cordova application that looks nice on mobile can be a challenge, especially for developers. Many people chose to use a UI framework to make this easier. Here is a short list of options you may want to consider.
When building your user interface, it is important to think about all platforms that you are targeting and the differences between the user’s expectations. For example, an Android application that has an iOS-style UI will probably not go over well with users. This sometimes is even enforced by the various application stores. Because of this, it is important that you respect the conventions of each platform and therefore are familiar with the various Human Interface Guidelines:
Although browser engines become more and more standards complaint, we still live in a prefixed world (-webkit and -ms.) The following article is valuable when developing UI’s in for cross browser apps: http://blogs.windows.com/windows_phone/b/wpdev/archive/2012/11/15/adapting-your-webkit-optimized-site-for-internet-explorer-10.aspx
Here are a few ways to keep up to date with Cordova.
The following links are the best places to get help for Cordova: