What is an apk crash and why does it happen?
Have you ever experienced an app that suddenly stops working, freezes, or closes unexpectedly on your Android device? If so, you have encountered an apk crash. An apk file is the package format that Android uses to distribute and install apps. An apk crash occurs when there is an unexpected exit caused by an unhandled exception or signal in the app's code.
There are many reasons why an app can crash on Android. Some of them are obvious, such as checking for a null value or an empty string, but others are more subtle, such as passing invalid arguments to an API or having complex multithreading interactions. Crashes can also happen due to external factors, such as low memory, network connectivity, device compatibility, or user actions.
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Crashes are not only frustrating for users, but also harmful for developers. They can affect your app's reputation, ratings, downloads, and revenue. Therefore, it is important to detect, diagnose, prevent, and fix apk crashes as soon as possible. In this article, we will show you how to do that using various tools and techniques.
How to detect and diagnose apk crashes
The first step in solving any problem is identifying it. To detect and diagnose apk crashes, you need to collect and analyze some information about the app's behavior and performance. Here are some ways you can do that:
Android vitals
Android vitals is a feature of Google Play Console that helps you monitor and improve your app's quality and stability. It measures several metrics related to crashes, such as:
Crash rate: The percentage of your daily active users who experienced any type of crash.
User-perceived crash rate: The percentage of your daily active users who experienced at least one crash while they were actively using your app.
Multiple crash rate: The percentage of your daily active users who experienced at least two crashes.
You can use Android vitals to see how your app's crash rate compares to other apps in your category, identify which device models or Android versions are more prone to crashes, and track the impact of your changes on your app's stability over time.
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Stack trace
A stack trace is a snapshot of the sequence of nested functions or methods that were executed before a crash occurred. It shows the name, location, and parameters of each function or method, as well as the line number where the error happened. A stack trace can help you pinpoint the exact cause of the crash and fix it accordingly.
You can view the stack trace of your app's crashes in several places, such as Android vitals, Firebase Crashlytics, Google Play Console Pre-launch report, or the app's crash report. A stack trace looks something like this:
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.example.myapp.MainActivity.onCreate(MainActivity.java:25) at android.app.Activity.performCreate(Activity.java:7136) at android.app.Activity.performCreate(Activity.java:7127) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893) ... 11 more
In this example, you can see that the crash was caused by a null pointer exception, which means that the app tried to access or modify an object that was null. You can also see that the error occurred in the onCreate method of the MainActivity class, at line 25, where the app tried to set the text of a TextView that was null.
Logcat
Logcat is a command-line tool that lets you view and filter the messages that your app and the system write to the log. A log message consists of a priority level, a tag, and a message. You can use log messages to print useful information about your app's state, such as variables, exceptions, or events. You can also use log messages to debug your app and find errors.
You can access logcat from Android Studio, Android Debug Bridge, or a terminal emulator. You can use various options and filters to customize the output of logcat and focus on the messages that are relevant to your app. A log message looks something like this:
D/MainActivity: onCreate: Hello World! E/MainActivity: onCreate: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
In this example, you can see that the app printed a debug message with the tag MainActivity and the message onCreate: Hello World! You can also see that the app printed an error message with the same tag and the message onCreate: java.lang.NullPointerException..., which is the same exception that caused the crash.
How to prevent and fix apk crashes
The next step in solving any problem is fixing it. To prevent and fix apk crashes, you need to write robust and reliable code that can handle different scenarios and edge cases. Here are some common causes of apk crashes and how to avoid or handle them:
Null pointer exceptions
A null pointer exception is one of the most frequent and notorious causes of apk crashes. It happens when you try to access or modify an object that is null, which means that it has no value or reference. For example, if you try to call a method on a null object, or access a field of a null object, you will get a null pointer exception.
To prevent null pointer exceptions, you need to check if an object is null before using it. You can use conditional statements, such as if-else or try-catch, to perform different actions depending on whether an object is null or not. For example:
TextView textView = findViewById(R.id.textView); if (textView != null) textView.setText("Hello World!"); else Log.e("MainActivity", "onCreate: textView is null");
In this example, you can see that the app checks if the textView object is null before calling the setText method on it. If it is not null, it sets the text to "Hello World!". If it is null, it logs an error message.
If you are using Kotlin, you can use some features that can help you avoid null pointer exceptions, such as:
Null safety: Kotlin distinguishes between nullable and non-null types, and does not allow you to assign or return null values for non-null types.
Safe call operator: Kotlin allows you to use the ? operator to call a method or access a property on a nullable object only if it is not null.
Elvis operator: Kotlin allows you to use the ?: operator to provide an alternative value or expression if a nullable object is null.
Let function: Kotlin allows you to use the let function to execute a block of code only if a nullable object is not null.
For example:
val textView: TextView? = findViewById(R.id.textView) textView?.setText("Hello World!") // Safe call operator textView?.setText("Hello World!") ?: Log.e("MainActivity", "onCreate: textView is null") // Elvis operator textView?.let it.setText("Hello World!") // Let function
Invalid arguments
An invalid argument is another common cause of apk crashes. It happens when you pass a value or an object to an API or a function that does not meet the expected requirements or conditions. For example, if you pass a negative number to a function that expects a positive number, or a null object to an API that expects a non-null object, you will get an invalid argument exception.
To prevent invalid argument exceptions, you need to check and validate the arguments before passing them to an API or a function. You can use conditional statements, such as if-else or try-catch, to perform different actions depending on whether the arguments are valid or not. For example:
public void setAge(int age) if (age > 0) this.age = age; else throw new IllegalArgumentException("Age must be positive");
In this example, you can see that the function checks if the age argument is positive before assigning it to the age field. If it is not positive, it throws an illegal argument exception with a message.
If you are using Kotlin, you can use some features that can help you avoid invalid argument exceptions, such as:
Preconditions: Kotlin provides some functions that allow you to check the validity of the arguments and throw an exception if they are not valid, such as check, require, assert, etc.
Data classes: Kotlin allows you to create data classes that automatically generate some useful methods and properties for your data objects, such as equals, hashCode, toString, copy, etc.
Data validation: Kotlin allows you to use some libraries that can help you validate your data objects and their properties, such as Kluent, Kotlin Validation, or Validated.
For example:
data class Person(val name: String, val age: Int) init require(name.isNotEmpty()) "Name must not be empty" require(age > 0) "Age must be positive"
In this example, you can see that the data class has an init block that checks the validity of the name and age properties using the require function. If they are not valid, it throws an illegal argument exception with a message.
Multithreading issues
A multithreading issue is another possible cause of apk crashes. It happens when you have multiple threads or processes that access or modify the same data or resource without proper synchronization or coordination. For example, if you have two threads that try to write to the same file at the same time, or one thread that tries to read from a file while another thread is deleting it, you will get a multithreading exception.
To prevent multithreading exceptions, you need to use synchronization and concurrency tools that can help you manage and control the access and modification of shared data or resources. Some of these tools are:
Locks: Locks are objects that allow only one thread to enter a critical section of code at a time. You can use locks to protect shared data or resources from concurrent access or modification by multiple threads.
Atomic variables: Atomic variables are variables that can be updated atomically, which means that they can be read and written in one indivisible operation. You can use atomic variables to avoid race conditions and ensure consistency and visibility of shared data across multiple threads.
Executors: Executors are objects that manage and execute tasks on different threads or processes. You can use executors to simplify the creation and management of threads and processes, and to handle their results and exceptions.
For example:
// Java Lock lock = new ReentrantLock(); AtomicInteger counter = new AtomicInteger(0); ExecutorService executor = Executors.newFixedThreadPool(4); Runnable task = () -> lock.lock(); try int count = counter.incrementAndGet(); System.out.println("Thread " + Thread.currentThread().getName() + " incremented counter to " + count); finally lock.unlock(); ; for (int i = 0; i
In this example, you can see that the app uses a lock to ensure that only one thread can increment the counter variable at a time. It also uses an atomic variable to ensure that the counter variable can be updated atomically. It also uses an executor to create and manage four threads that execute the task.
How to test and debug your app for apk crashes
The final step in solving any problem is verifying it. To test and debug your app for apk crashes, you need to reproduce and simulate different scenarios and conditions that can cause your app to crash. You also need to inspect and modify your app's state and behavior to find and fix any errors or bugs. Here are some ways you can do that:
Reproducing a crash
Reproducing a crash means recreating the exact situation and environment that caused the crash to happen. This can help you understand the root cause of the crash and verify if your solution works. There are different methods and tools you can use to reproduce a crash, such as:
User feedback: User feedback is the information that your users provide about their experience with your app, such as ratings, reviews, comments, or bug reports. You can use user feedback to identify the steps, actions, or inputs that led to the crash, as well as the device model, Android version, or app version that were involved.
Crash reports: Crash reports are the files that contain detailed information about the crash, such as the stack trace, the logcat output, the device state, or the app configuration. You can use crash reports to analyze the error message, the exception type, or the code location that caused the crash.
Testing tools: Testing tools are the software applications that allow you to create and run automated or manual tests on your app. You can use testing tools to simulate different user interactions, device configurations, network conditions, or system events that can trigger a crash.
For example:
Suppose you receive a user feedback that says: "The app crashes when I try to open a file from Google Drive". You also receive a crash report that says: "java.lang.SecurityException: Permission Denial: opening provider com.google.android.apps.docs.storagebackend.StorageBackendContentProvider from ProcessRecord... (pid=1234, uid=5678) requires com.google.android.apps.docs.storage.READ_METADATA or com.google.android.apps.docs.storage.READ_METADATA". You can use a testing tool, such as Espresso, to reproduce the crash by writing a test case that does the following:
// Espresso test case @Test fun openFileFromGoogleDrive() // Launch the app val activityScenario = ActivityScenario.launch(MainActivity::class.java) // Click on the open file button onView(withId(R.id.openFileButton)).perform(click()) // Select Google Drive as the source onView(withText("Google Drive")).perform(click()) // Select a file from Google Drive onView(withId(R.id.fileListView)).perform(actionOnItemAtPosition(0, click())) // Check if the app crashes assertThrows(SecurityException::class.java) activityScenario.getResult()
Testing tools
Testing tools are essential for ensuring your app's quality and stability. They can help you find and fix apk crashes before they affect your users. There are many testing tools available for Android developers, but here are some of the most popular ones:
Espresso
Espresso is a testing framework that allows you to write and run UI tests for your app. It provides a fluent API that lets you perform actions and assertions on UI elements with ease. It also handles synchronization issues between the test thread and the UI thread automatically. You can use Espresso to test your app's functionality, usability, accessibility, or performance.
Firebase Test Lab
Firebase Test Lab is a cloud-based service that allows you to test your app on real devices and emulators hosted by Google. It supports various testing frameworks, such as Espresso, Robolectric, or JUnit. You can use Firebase Test Lab to test your app across different device models, Android versions, screen sizes, orientations, locales, or network conditions.
LeakCanary
LeakCanary is a memory leak detection library that helps you find and fix memory leaks in your app. It monitors your app's heap and notifies you when an object is retained after it should have been garbage collected. It also provides a detailed analysis of the leak, including the reference chain, the size, and the type of the leaked object.
Debugging tools
Debugging tools are useful for inspecting and modifying your app's state and behavior during runtime. They can help you identify and resolve any errors or bugs in your code. There are many debugging tools available for Android developers , but here are some of the most popular ones:
Android Studio
Android Studio is the official integrated development environment (IDE) for Android development. It provides a rich set of features and tools that can help you debug your app, such as:
Code editor: The code editor allows you to write, edit, format, refactor, and navigate your code with ease. It also provides code completion, syntax highlighting, error checking, and quick fixes.
Layout editor: The layout editor allows you to design, preview, and modify your app's UI using drag-and-drop or XML. It also provides tools for creating and editing vector graphics, animations, and themes.
Debugger: The debugger allows you to attach to a running app and inspect its state and behavior. It also provides tools for setting breakpoints, stepping through code, evaluating expressions, and watching variables.
Profiler: The profiler allows you to monitor and analyze your app's performance and resource usage. It also provides tools for detecting and resolving memory leaks, CPU bottlenecks, network issues, and battery drain.
Android Debug Bridge
Android Debug Bridge (ADB) is a command-line tool that allows you to communicate with a device or an emulator. It supports various commands and options that can help you debug your app, such as:
adb devices: This command lists the devices or emulators that are connected to your computer.
adb install: This command installs an apk file on a device or an emulator.
adb uninstall: This command uninstalls an app from a device or an emulator.
adb shell: This command opens a shell on a device or an emulator.
adb logcat: This command displays the log messages from a device or an emulator.
adb pull: This command copies a file or a directory from a device or an emulator to your computer.
adb push: This command copies a file or a directory from your computer to a device or an emulator.
Breakpoints
Breakpoints are markers that you can set in your code to pause the execution of your app at a specific point. You can use breakpoints to inspect and modify the state and behavior of your app during runtime. You can also use breakpoints to perform various actions, such as:
Conditional breakpoints: Conditional breakpoints are breakpoints that are triggered only when a certain condition is met.
Logpoint breakpoints: Logpoint breakpoints are breakpoints that print a message to the log without pausing the execution of your app.
Exception breakpoints: Exception breakpoints are breakpoints that are triggered when an exception is thrown or caught by your app.
Method breakpoints: Method breakpoints are breakpoints that are triggered when a method is entered or exited by your app.
Conclusion
In this article, we have learned what an apk crash is and why it happens. We have also learned how to detect and diagnose apk crashes using Android vitals, stack trace, and logcat. We have also learned how to prevent and fix apk crashes using null pointer exceptions, invalid arguments, and multithreading issues. We have also learned how to test and debug your app for apk crashes using reproducing a crash, testing tools, debugging tools, and breakpoints.
We hope that this article has helped you understand how to deal with apk crashes and improve your app's quality and stability. If you have any feedback, questions, or suggestions, please feel free to leave them in the comments section below. Thank you for reading!
Frequently Asked Questions
What is the difference between an apk crash and an ANR?
An apk crash is when an app exits unexpectedly due to an unhandled exception or signal. An ANR (Application Not Responding) is when an app becomes unresponsive due to a long-running operation on the main thread. Both are indicators of poor app quality and stability, but they have different causes and solutions.
How can I prevent my app from crashing due to low memory?
You can prevent your app from crashing due to low memory by following some best practices, such as:
Avoiding memory leaks: Memory leaks are when objects are retained in memory after they are no longer needed. You can use tools like LeakCanary to detect and fix memory leaks in your app.
Managing bitmap memory: Bitmaps are images that consume a lot of memory. You can use tools like Glide or Picasso to load and cache bitmaps efficiently in your app.
Handling configuration changes: Configuration changes are when the device orientation, language, or screen size changes. These changes can cause your app to restart and lose its state. You can use tools like ViewModel or SavedStateHandle to preserve and restore your app's state across configuration changes.
Using the Android memory profiler: The Android memory profiler is a tool that allows you to monitor and analyze your app's memory usage. You can use it to identify memory allocation, deallocation, or garbage collection issues in your app.
How can I report a crash to the developer of an app?
You can report a crash to the developer of an app by following these steps:
Open the Google Play Store app on your device.
Search for the app that crashed and tap on it.
Scroll down to the bottom of the app's page and tap on "Send feedback".
Fill out the feedback form with the details of the crash, such as when it happened, what you were doing, and what error message you saw.
Tap on "Send" to submit your feedback.
This will send a crash report to the developer of the app, along with some information about your device and app version. The developer can use this information to diagnose and fix the crash.
How can I test my app for apk crashes on different devices and emulators?
You can test your app for apk crashes on different devices and emulators by using Firebase Test Lab. Firebase Test Lab is a cloud-based service that allows you to test your app on real devices and emulators hosted by Google. You can use Firebase Test Lab to test your app across different device models, Android versions, screen sizes, orientations, locales, or network conditions. You can also use Firebase Test Lab to run various testing frameworks, such as Espresso, Robolectric, or JUnit.
How can I debug my app for apk crashes using Android Studio?
You can debug your app for apk crashes using Android Studio by following these steps:
Connect your device or emulator to your computer.
Open your app project in Android Studio.
Select "Run" > "Debug" from the menu bar.
Select your device or emulator from the list of available devices.
Wait for your app to launch on your device or emulator.
Set breakpoints in your code where you want to pause the execution of your app.
Perform actions on your app that can cause a crash.
When a breakpoint is hit or a crash occurs, inspect and modify the state and behavior of your app using the debugger window.
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