Android app crashes when launched in debug mode

Debugging an Android app can be a frustrating experience, especially when the app crashes immediately upon launch in debug mode. This frustrating scenario can halt your development workflow and leave you scratching your head. This post will delve into common causes of these debug-mode crashes, provide actionable solutions, and equip you with the tools to prevent them in the future. We’ll explore everything from corrupted data and conflicting dependencies to issues with the debugger itself. Let’s get your app back on track!

NullPointerExceptions: The Usual Suspect

NullPointerExceptions are frequent culprits in Android crashes. They occur when your code attempts to access a member of an object that is currently null. In debug mode, certain initialization processes might differ, making these exceptions more apparent. Thorough logging and utilizing the debugger’s breakpoints can help pinpoint the exact line of code causing the issue. Often, a simple null check can prevent the crash.

For example, imagine accessing a TextView before it’s properly inflated in your Activity’s onCreate() method. In release mode, this might go unnoticed due to optimization, but debug mode can expose such issues, leading to an immediate crash. Always double-check that your views are initialized before interacting with them.

Conflicting Dependencies: A Recipe for Disaster

Modern Android development relies heavily on external libraries. However, incorporating these dependencies can sometimes lead to conflicts, particularly in debug mode where different build configurations can clash. Ensure your Gradle file correctly defines dependency versions and resolves any conflicts using tools like dependency trees.

A classic example is including two libraries that rely on different versions of the same underlying library. This can result in unpredictable behavior and crashes during debugging. Carefully manage your dependencies and use tools provided by Android Studio to identify and resolve conflicts.

Debugger Issues: When the Helper Becomes the Problem

Ironically, the debugger itself can sometimes be the source of crashes. Outdated debugger versions or misconfigurations can introduce instability. Ensure your Android Studio and debugger are up-to-date. Consider disabling certain debugger features temporarily to identify if the debugger is contributing to the problem.

Sometimes, specific breakpoints or watch expressions can interfere with the application’s normal execution flow. Experimenting with different breakpoint types or removing watch expressions can help isolate the problem.

Corrupted Data and Caches: Starting Fresh

Corrupted application data or caches can also trigger crashes, especially during debug sessions. Clearing the app’s data and cache, or even uninstalling and reinstalling the app, can resolve issues stemming from corrupted data. This is a simple yet often effective solution to try before diving into more complex debugging procedures.

For instance, a corrupted SharedPreferences file can lead to unexpected behavior and crashes. Clearing the app’s data eliminates this potential issue and allows the app to start with a clean slate. This is a crucial step in diagnosing crashes related to persistent data.

Proactive Debugging Techniques

Implement robust logging throughout your codebase.
Utilize the debugger effectively, setting breakpoints and stepping through code execution.

Analyzing Crash Reports

Utilize tools like Logcat to capture crash logs.
Learn to decipher stack traces to identify the source of the crash.
Use online resources and forums to find solutions to common crash scenarios.

“Effective debugging is not just about fixing bugs, but about preventing them.” - Steve McConnell

Case Study: A development team struggled with an app that consistently crashed in debug mode when launching a specific activity. After thorough investigation using the debugger and analyzing crash logs, they discovered a conflict between two libraries used for image loading. Resolving the dependency conflict eliminated the crash.

Learn more about dependency management.Infographic Placeholder: [Insert infographic visualizing common causes of Android debug mode crashes and their solutions.]

External Resources:

Featured Snippet Optimized Paragraph: To fix Android app crashes in debug mode, start by checking for NullPointerExceptions, resolving dependency conflicts, and ensuring your debugger is up-to-date. Clearing app data and caches can also help. Remember, thorough logging and effective use of the debugger are crucial for identifying the root cause of crashes.

FAQ

Q: Why does my app only crash in debug mode?

A: Debug mode often exposes issues masked in release builds due to optimizations and different build configurations. This can lead to crashes related to null pointers, dependencies, or the debugger itself.

By understanding the common causes of debug mode crashes and applying the strategies outlined in this post, you can significantly improve your debugging workflow and create more stable Android applications. Remember to leverage the powerful tools available in Android Studio, stay updated with best practices, and don’t be afraid to seek help from the vast Android development community.

Explore related topics such as advanced debugging techniques, performance optimization, and error handling to further enhance your Android development skills. Now, go forth and conquer those crashes!

Question & Answer :
When I run in debug mode the app crashes, but when I just run it normally it works. I think the problem happens when the debugger is attached.

Log:

A/art: art/runtime/jdwp/jdwp_event.cc:661] Check failed: Thread::Current() != GetDebugThread() (Thread::Current()=0x7f44a18400, GetDebugThread()=0x7f44a18400) Expected event thread A/art: art/runtime/runtime.cc:422] Runtime aborting... A/art: art/runtime/runtime.cc:422] Aborting thread: A/art: art/runtime/runtime.cc:422] "JDWP" prio=5 tid=4 WaitingForDebuggerSend A/art: art/runtime/runtime.cc:422] | group="" sCount=0 dsCount=0 obj=0x12c60280 self=0x7f44a18400 A/art: art/runtime/runtime.cc:422] | sysTid=24137 nice=0 cgrp=default sched=0/0 handle=0x7f4b904450 A/art: art/runtime/runtime.cc:422] | state=R schedstat=( 132066712 16401043 106 ) utm=9 stm=2 core=3 HZ=100 A/art: art/runtime/runtime.cc:422] | stack=0x7f4b80a000-0x7f4b80c000 stackSize=1005KB A/art: art/runtime/runtime.cc:422] | held mutexes= "abort lock" A/art: art/runtime/runtime.cc:422] native: #00 pc 000000000047e2cc /system/lib64/libart.so (_ZN3art15DumpNativeStackERNSt3__113basic_ostreamIcNS0_11char_traitsIcEEEEiP12BacktraceMapPKcPNS_9ArtMethodEPv+220) A/art: art/runtime/runtime.cc:422] native: #01 pc 000000000047e2c8 /system/lib64/libart.so (_ZN3art15DumpNativeStackERNSt3__113basic_ostreamIcNS0_11char_traitsIcEEEEiP12BacktraceMapPKcPNS_9ArtMethodEPv+216) A/art: art/runtime/runtime.cc:422] native: #02 pc 0000000000452434 /system/lib64/libart.so (_ZNK3art6Thread9DumpStackERNSt3__113basic_ostreamIcNS1_11char_traitsIcEEEEbP12BacktraceMap+480) A/art: art/runtime/runtime.cc:422] native: #03 pc 00000000004403ac /system/lib64/libart.so (_ZNK3art10AbortState10DumpThreadERNSt3__113basic_ostreamIcNS1_11char_traitsIcEEEEPNS_6ThreadE+56) A/art: art/runtime/runtime.cc:422] native: #04 pc 0000000000440228 /system/lib64/libart.so (_ZNK3art10AbortState4DumpERNSt3__113basic_ostreamIcNS1_11char_traitsIcEEEE+668) A/art: art/runtime/runtime.cc:422] native: #05 pc 0000000000433bfc /system/lib64/libart.so (_ZN3art7Runtime5AbortEPKc+148) A/art: art/runtime/runtime.cc:422] native: #06 pc 00000000000e597c /system/lib64/libart.so (_ZN3art10LogMessageD2Ev+1592) A/art: art/runtime/runtime.cc:422] native: #07 pc 00000000002f8458 /system/lib64/libart.so (_ZN3art4JDWP9JdwpState24AcquireJdwpTokenForEventEm+624) A/art: art/runtime/runtime.cc:422] native: #08 pc 00000000002f7b1c /system/lib64/libart.so (_ZN3art4JDWP9JdwpState29SendRequestAndPossiblySuspendEPNS0_9ExpandBufENS0_17JdwpSuspendPolicyEm+248) A/art: art/runtime/runtime.cc:422] native: #09 pc 00000000002fcb08 /system/lib64/libart.so (_ZN3art4JDWP9JdwpState16PostClassPrepareEPNS_6mirror5ClassE+1380) A/art: art/runtime/runtime.cc:422] native: #10 pc 0000000000124a9c /system/lib64/libart.so (_ZN3art11ClassLinker11DefineClassEPNS_6ThreadEPKcmNS_6HandleINS_6mirror11ClassLoaderEEERKNS_7DexFileERKNS9_8ClassDefE+804) A/art: art/runtime/runtime.cc:422] native: #11 pc 0000000000381d04 /system/lib64/libart.so (_ZN3artL25DexFile_defineClassNativeEP7_JNIEnvP7_jclassP8_jstringP8_jobjectS7_S7_+344) A/art: art/runtime/runtime.cc:422] native: #12 pc 00000000001dd40c /system/framework/arm64/boot-core-libart.oat (???) A/art: art/runtime/runtime.cc:422] at dalvik.system.DexFile.defineClassNative(Native method) A/art: art/runtime/runtime.cc:422] at dalvik.system.DexFile.defineClass(DexFile.java:296) A/art: art/runtime/runtime.cc:422] at dalvik.system.DexFile.loadClassBinaryName(DexFile.java:289) A/art: art/runtime/runtime.cc:422] at dalvik.system.DexPathList.findClass(DexPathList.java:418) A/art: art/runtime/runtime.cc:422] at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:54) A/art: art/runtime/runtime.cc:422] at com.android.tools.fd.runtime.IncrementalClassLoader$DelegateClassLoader.findClass(IncrementalClassLoader.java:90) A/art: art/runtime/runtime.cc:422] at com.android.tools.fd.runtime.IncrementalClassLoader.findClass(IncrementalClassLoader.java:62) A/art: art/runtime/runtime.cc:422] at java.lang.ClassLoader.loadClass(ClassLoader.java:380) A/art: art/runtime/runtime.cc:422] at java.lang.ClassLoader.loadClass(ClassLoader.java:367) A/art: art/runtime/runtime.cc:422] at java.lang.ClassLoader.loadClass(ClassLoader.java:367) A/art: art/runtime/runtime.cc:422] at java.lang.ClassLoader.loadClass(ClassLoader.java:312) A/art: art/runtime/runtime.cc:422] Dumping all threads without appropriate locks held: thread list lock mutator lock

For me, it occurred when I have a breakpoint in a nested function. In my case, it was within Runnable.run() {}. Not sure if it happens in other nested functions.

Example:

public class TouchEvent { public boolean HandleEvent(MotionEvent Event) { new Runnable() { @Override public void run() { int i=5; i++; }}; } }

If there is a breakpoint on any line inside the run() func, it crashes with the error A/art: art/runtime/jdwp/jdwp_event.cc:661] Check failed: Thread::Current() != GetDebugThread() (Thread::Current()=0x########, GetDebugThread()=0x########) Expected event thread .

This error occurs the first time the class is encountered, NOT when the breakpoint is hit. So it occurred for me when I stepped into a line that had new TouchEvent();, before any of the TouchEvent’s code was run (before the constructor).

The solution is to remove the break point (and put it elsewhere).

Edit:

Forgot to mention, it seems to be tied to API25, but has been reported for API26 and API27 too.

Edit:

Another solution is to disabled Instant Run, but please give @toobsco42 credit for that below.