![]() ![]() To conclude, reflection in Android is really slow. That’s a lot of time, especially taking into consideration that users expect an average app start time of 2s. Myntra sees similar problems: 1421ms for call Īs you can see, the library requires more than a second to initialize. Let’s take a look at how it can affect start time by analyzing some real apps on the Play store: More real-world examplesĪctiveAndroid is another library that uses reflection. Reduced, but the overhead is still quite significant. On a less powerful device only in Android 6.0 ART is the overhead Interestingly, Android 5.0 ART on a more powerfulĭevice actually makes reflection much slower than Android 4.1 Dalvik It’s evident that reflection in Android is excruciatingly slow - compare class for ( int i = 0 i < 10000 i ++) Īnd here are our results (all numbers are in ms, measured on our personalĭevices with real usage to make the results more faithful to real world): We will work with the class and repeat operations 10,000 times, like this: Class clazz = android. We’ve created a simple test to quantify how slow reflection is. From a performance point of view, this is catastrophic. The issue is that the library doesn’t process the annotations during build time, but instead parses and creates the REST client during runtime (with the help of reflection). It turns out that this library allows developers to configure a REST client with annotations. Let’s take a deeper look at why this is taking so long. Sure, on the surface this may not seem like much, but altogether, use of the method is causing ~600ms of start time delay. Here, it is invoked 5 times and takes ~81ms. Note that the getGenericInterfaces() method returns the types of the interfaces that this class directly implements. Check this out: lots of reflection calls, like: Looking further into the icicle graph, we see that the reason for such a lag lies in reflection. We see that the .jersey.UserClient constructor takes an entire 660ms to run. 660ms for call .jersey.UserClient constructor Here, reflection again causes a big bottleneck. They eventually fixed this delay with manually written custom typeĪ large photo-sharing platform. The help of NimbleDroid, our friends at NYTimesįound out that the reflective type adapters in Our first example involves NYTimes Android Intuitive way of understanding this is going through a couple of real-life Of significant slowdown within an Android application. To get our feet wet, well look at a very basic example that inspects the fields of a simple Java object at runtime. Yet it turns out that reflection can very often be the source Reflection is, of course, an extremely useful aspect of Java and Androidĭevelopment. The following examples (both written in Kotlin) show it. Starting from this post, we’ll describe these issues one by one.) Its possible to make private fields accessible using reflection. This is a relatively advanced feature and should be used only by developers who have a strong grasp of the fundamentals of the language. Discovered a handful of issues that significantly slow down many apps. Uses of Reflection Reflection is commonly used by programs which require the ability to examine or modify the runtime behavior of applications running in the Java virtual machine. ![]()
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