The Android SDK provides most of the tools that you need to debug your applications. You need
a JDWP-compliant debugger if you want to be able to do things such as step through code,
view variable values, and pause execution of an application. If you are using Eclipse, a
JDWP-compliant debugger is already included and there is no setup required. If you are using
another IDE, you can use the debugger that comes with it and attach the debugger to a special
port so it can communicate with the application VMs on your devices. The main components that
comprise a typical Android debugging environment are:
- adb
adb acts as a middleman between a device and your development system. It provides various
device management capabilities, including moving and syncing files to the emulator, running a
UNIX shell on the device or emulator, and providing a general means to communicate with
connected emulators and devices.- Dalvik Debug Monitor
Server
- DDMS is a graphical program that communicates with your devices through
adb. DDMS can
capture screenshots, gather thread and stack information, spoof incoming calls and SMS
messages, and has many other features.
- Device or
Android Virtual Device
- Your application must run in a device or in an AVD so that it can be debugged. An
adb device
daemon runs on the device or emulator and provides a means for the adb host daemon to
communicate with the device or emulator.
- JDWP debugger
- The Dalvik VM (Virtual Machine) supports the JDWP protocol to allow debuggers to attach to
a VM. Each application runs in a VM and exposes a unique port that you can attach a debugger to
via DDMS. If you want to debug multiple applications, attaching to each port might become
tedious, so DDMS provides a port forwarding feature that can forward a specific VM's debugging
port to port 8700. You can switch freely from application to application by highlighting it in the
Devices tab of DDMS. DDMS forwards the appropriate port to port 8700. Most modern Java IDEs include a JDWP debugger,
or you can use a command line debugger such as
jdb.
Debugging Environment
Figure 1 shows how the various debugging tools work together in a typical
debugging environment.
Additional Debugging Tools
In addition to the main debugging tools, the Android SDK provides additional tools to help you
debug and profile your applications:
- Heirarchy Viewer
and layoutopt
- Graphical programs that let you debug and profile user interfaces.
- Traceview
- A graphical viewer that displays trace file data for method calls and times saved by your
application, which can help you profile the performance of your application.
- Dev Tools
Android application
- The Dev Tools application included in the emulator system image exposes several settings
that provide useful information such as CPU usage and frame rate. You can also transfer the
application to a hardware device.
Debugging Tips
While debugging, keep these helpful tips in mind to help you figure out common problems with your
applications:
- Dump the stack trace
- To obtain a stack dump from emulator, you can log
in with
adb shell, use ps to find the process you
want, and then kill -3. The stack trace appears in the log file.
- Display useful info on the emulator screen
- The device can display useful information such as CPU usage or highlights
around redrawn areas. Turn these features on and off in the developer settings
window as described in
Debugging with the Dev Tools App.
- Get application and system state information from the emulator
- You can access dumpstate information from the
adb shell commands. See
dumpsys and
dumpstate on the adb topic page.
- Get wireless connectivity information
- You can get information about wireless connectivity using DDMS.
From the Device menu, select Dump
radio state.
- Log trace data
- You can log method calls and other tracing data in an activity by calling
startMethodTracing(). See Profiling with Traceview and
dmtracedump for details.
- Log radio data
- By default, radio information is not logged to the system (it is a lot of
data). However, you can enable radio logging using the following commands:
adb shell
logcat -b radio
- Capture screenshots
- The Dalvik Debug Monitor Server (DDMS) can capture screenshots from the emulator. Select
Device > Screen capture.
- Use debugging helper classes
- Android provides debug helper classes such as
util.Log and Debug for your convenience.
See the Troubleshooting document
for answers to some common developing and debugging issues.
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