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Android Debug Bridge

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Android Debug Bridge (adb) is a versatile command line tool that lets you communicate with an emulator instance or connected Android-powered device. It is a client-server program that includes three components:

• A client, which runs on your development machine. You can invoke a client from a shell by issuing an adb command. Other Android tools such as the ADT plugin and DDMS also create adb clients.
• A server, which runs as a background process on your development machine. The server manages communication between the client and the adb daemon running on an emulator or device.
• A daemon, which runs as a background process on each emulator or device instance.

You can find the adb tool in /platform-tools/ .

When you start an adb client, the client first checks whether there is an adb server process already running. If there isn’t, it starts the server process. When the server starts, it binds to local TCP port 5037 and listens for commands sent from adb clients—all adb clients use port 5037 to communicate with the adb server.

The server then sets up connections to all running emulator/device instances. It locates emulator/device instances by scanning odd-numbered ports in the range 5555 to 5585, the range used by emulators/devices. Where the server finds an adb daemon, it sets up a connection to that port. Note that each emulator/device instance acquires a pair of sequential ports — an even-numbered port for console connections and an odd-numbered port for adb connections. For example:

Emulator 1, console: 5554
Emulator 1, adb: 5555
Emulator 2, console: 5556
Emulator 2, adb: 5557
and so on.

As shown, the emulator instance connected to adb on port 5555 is the same as the instance whose console listens on port 5554.

Once the server has set up connections to all emulator instances, you can use adb commands to access those instances. Because the server manages connections to emulator/device instances and handles commands from multiple adb clients, you can control any emulator/device instance from any client (or from a script).

Enabling adb Debugging

In order to use adb with a device connected over USB, you must enable USB debugging in the device system settings, under Developer options.

On Android 4.2 and higher, the Developer options screen is hidden by default. To make it visible, go to Settings > About phone and tap Build number seven times. Return to the previous screen to find Developer options at the bottom.

On some devices, the Developer options screen may be located or named differently.

Note: When you connect a device running Android 4.2.2 or higher to your computer, the system shows a dialog asking whether to accept an RSA key that allows debugging through this computer. This security mechanism protects user devices because it ensures that USB debugging and other adb commands cannot be executed unless you’re able to unlock the device and acknowledge the dialog. This requires that you have adb version 1.0.31 (available with SDK Platform-tools r16.0.1 and higher) in order to debug on a device running Android 4.2.2 or higher.

For more information about connecting to a device over USB, read Using Hardware Devices.

Syntax

You can issue adb commands from a command line on your development machine or from a script. The usage is:

If there’s only one emulator running or only one device connected, the adb command is sent to that device by default. If multiple emulators are running and/or multiple devices are attached, you need to use the -d , -e , or -s option to specify the target device to which the command should be directed.

Commands

The table below lists all of the supported adb commands and explains their meaning and usage.

Table 1. Available adb commands

Category	Command	Description	Comments
Target Device	-d	Direct an adb command to the only attached USB device.	Returns an error if more than one USB device is attached.
	-e	Direct an adb command to the only running emulator instance.	Returns an error if more than one emulator instance is running.
	-s	Direct an adb command a specific emulator/device instance, referred to by its adb-assigned serial number (such as «emulator-5556»).	See Directing Commands to a Specific Emulator/Device Instance.
General	devices	Prints a list of all attached emulator/device instances.	See Querying for Emulator/Device Instances for more information.
	help	Prints a list of supported adb commands.
	version	Prints the adb version number.
Debug	logcat [option] [filter-specs]	Prints log data to the screen.
	bugreport	Prints dumpsys , dumpstate , and logcat data to the screen, for the purposes of bug reporting.
	jdwp	Prints a list of available JDWP processes on a given device.	You can use the forward jdwp: port-forwarding specification to connect to a specific JDWP process. For example: adb forward tcp:8000 jdwp:472 jdb -attach localhost:8000
Data	install	Pushes an Android application (specified as a full path to an .apk file) to an emulator/device.
pull	Copies a specified file from an emulator/device instance to your development computer.
push	Copies a specified file from your development computer to an emulator/device instance.
Ports and Networking	forward	Forwards socket connections from a specified local port to a specified remote port on the emulator/device instance.	Port specifications can use these schemes: tcp:
	ppp [parm].	Run PPP over USB. — the tty for PPP stream. For example dev:/dev/omap_csmi_ttyl . [parm]. — zero or more PPP/PPPD options, such as defaultroute , local , notty , etc. Note that you should not automatically start a PPP connection.
Scripting	get-serialno	Prints the adb instance serial number string.	See Querying for Emulator/Device Instances for more information.
	get-state	Prints the adb state of an emulator/device instance.
	wait-for-device	Blocks execution until the device is online — that is, until the instance state is device .	You can prepend this command to other adb commands, in which case adb will wait until the emulator/device instance is connected before issuing the other commands. Here’s an example: Note that this command does not cause adb to wait until the entire system is fully booted. For that reason, you should not prepend it to other commands that require a fully booted system. As an example, the install requires the Android package manager, which is available only after the system is fully booted. A command such as would issue the install command as soon as the emulator or device instance connected to the adb server, but before the Android system was fully booted, so it would result in an error.
Server	start-server	Checks whether the adb server process is running and starts it, if not.
	kill-server	Terminates the adb server process.
Shell	shell	Starts a remote shell in the target emulator/device instance.	See ADB Shell Commands for more information.
	shell [shellCommand]	Issues a shell command in the target emulator/device instance and then exits the remote shell.

Querying for Emulator/Device Instances

Before issuing adb commands, it is helpful to know what emulator/device instances are connected to the adb server. You can generate a list of attached emulators/devices using the devices command:

In response, adb prints this status information for each instance:

• Serial number — A string created by adb to uniquely identify an emulator/device instance by its console port number. The format of the serial number is — . Here’s an example serial number: emulator-5554
• State — The connection state of the instance may be one of the following:
  • offline — the instance is not connected to adb or is not responding.
  • device — the instance is now connected to the adb server. Note that this state does not imply that the Android system is fully booted and operational, since the instance connects to adb while the system is still booting. However, after boot-up, this is the normal operational state of an emulator/device instance.
  • no device — there is no emulator/device connected.

The output for each instance is formatted like this:

Here’s an example showing the devices command and its output:

Directing Commands to a Specific Emulator/Device Instance

If multiple emulator/device instances are running, you must specify a target instance when issuing adb commands. To do so, use the -s option in the commands. The usage for the -s option is:

As shown, you specify the target instance for a command using its adb-assigned serial number. You can use the devices command to obtain the serial numbers of running emulator/device instances. For example:

Note that, if you issue a command without specifying a target emulator/device instance while multiple devices are available, adb generates an error.

If you have multiple devices available (hardware or emulated), but only one is an emulator, simply use the -e option to send commands to the emulator. Likewise if there’s multiple devices but only one hardware device attached, use the -d option to send commands to the hardware device.

Installing an Application

You can use adb to copy an application from your development computer and install it on an emulator/device instance. To do so, use the install command. With the command, you must specify the path to the .apk file that you want to install:

For more information about how to create an .apk file that you can install on an emulator/device instance, see Building and Running

Note that, if you are using the Eclipse IDE and have the ADT plugin installed, you do not need to use adb (or aapt) directly to install your application on the emulator/device. Instead, the ADT plugin handles the packaging and installation of the application for you.

Forwarding Ports

You can use the forward command to set up arbitrary port forwarding — forwarding of requests on a specific host port to a different port on an emulator/device instance. Here’s how you would set up forwarding of host port 6100 to emulator/device port 7100:

You can also use adb to set up forwarding to named abstract UNIX domain sockets, as illustrated here:

Copying Files to or from an Emulator/Device Instance

You can use the adb commands pull and push to copy files to and from an emulator/device instance. Unlike the install command, which only copies an APK file to a specific location, the pull and push commands let you copy arbitrary directories and files to any location in an emulator/device instance.

To copy a file or directory (and its sub-directories) from the emulator or device, use

To copy a file or directory (and its sub-directories) to the emulator or device, use

In the commands, and refer to the paths to the target files/directory on your development machine (local) and on the emulator/device instance (remote). For example:

Stopping the adb Server

In some cases, you might need to terminate the adb server process and then restart it to resolve the problem (e.g., if adb does not respond to a command).

To stop the adb server, use the kill-server command. You can then restart the server by issuing any other adb command.

Wireless usage

adb is usually used over USB. However, it is also possible to use over Wi-Fi, as described here.

1. Connect Android device and adb host computer to a common Wi-Fi network accessible to both. We have found that not all access points are suitable; you may need to use an access point whose firewall is configured properly to support adb.
2. Connect the device with USB cable to host.
3. Make sure adb is running in USB mode on host.
4. Connect to the device over USB.
5. Restart host adb in tcpip mode.
6. Find out the IP address of the Android device: Settings -> About tablet -> Status -> IP address. Remember the IP address, of the form #.#.#.# .
7. Connect adb host to device:
8. Remove USB cable from device, and confirm you can still access device:

You’re now good to go!

If the adb connection is ever lost:

1. Make sure that your host is still connected to the same Wi-Fi network your Android device is.
2. Reconnect by executing the «adb connect» step again.
3. Or if that doesn’t work, reset your adb host: and then start over from the beginning.

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Debugging with Android Studio

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See also

Android Studio enables you to debug apps running on the emulator or on an Android device. With Android Studio, you can:

• Select a device to debug your app on.
• View the system log.
• Set breakpoints in your code.
• Examine variables and evaluate expressions at run time.
• Run the debugging tools from the Android SDK.
• Capture screenshots and videos of your app.

To debug your app, Android Studio builds a debuggable version of your app, connects to a device or to the emulator, installs the app and runs it. The IDE shows the system log while your app is running and provides debugging tools to filter log messages, work with breakpoints, and control the execution flow.

Run your App in Debug Mode

Figure 1. The Choose Device window enables you to select a physical Android device or a virtual device to debug your app.

To run your app in debug mode, you build an APK signed with a debug key and install it on a physical Android device or on the Android emulator. To set up an Android device for development, see Using Hardware Devices. For more information about the emulator provided by the Android SDK, see Using the Emulator.

To debug your app in Android Studio:

1. Open your project in Android Studio.
2. Click Debug in the toolbar.
3. On the Choose Device window, select a hardware device from the list or choose a virtual device.
4. Click OK. Your app starts on the selected device.

Figure 1 shows the Choose Device window. The list shows all the Android devices connected to your computer. Select Launch Emulator to use an Android virtual device instead. Click the ellipsis to open the Android Virtual Device Manager.

Android Studio opens the Debug tool window when you debug your app. To open the Debug window manually, click Debug . This window shows threads and variables in the Debugger tab, the device status in the Console tab, and the system log in the Logcat tab. The Debug tool window also provides other debugging tools covered in the following sections.

Figure 2. The Debug tool window in Android Studio showing the current thread and the object tree for a variable.

Attach the debugger to a running process

You don’t always have to restart your app to debug it. To debug an app that you’re already running:

1. Click Attach debugger to Android proccess.
2. In the Choose Process window, select the device and app you want to attach the debugger to.
3. To open the Debug tool window, click Debug .

Use the System Log

The system log shows system messages while you debug your app. These messages include information from apps running on the device. If you want to use the system log to debug your app, make sure your code writes log messages and prints the stack trace for exceptions while your app is in the development phase.

Write log messages in your code

To write log messages in your code, use the Log class. Log messages help you understand the execution flow by collecting the system debug output while you interact with your app. Log messages can tell you what part of your application failed. For more information about logging, see Reading and Writing Logs.

The following example shows how you might add log messages to determine if previous state information is available when your activity starts:

During development, your code can also catch exceptions and write the stack trace to the system log:

Note: Remove debug log messages and stack trace print calls from your code when you are ready to publish your app. You could do this by setting a DEBUG flag and placing debug log messages inside conditional statements.

View the system log

Both the Android DDMS (Dalvik Debug Monitor Server) and the Debug tool windows show the system log; however, the Android DDMS tool window lets you view only log messages for a particular process. To view the system log on the Android DDMS tool window:

1. Start your app as described in Run your App in Debug Mode.
2. Click Androidto open the Android DDMS tool window.
3. If the system log is empty in the Logcat view, click Restart.

Figure 4. The system log in the Android DDMS tool window.

The Android DDMS tool window gives you access to some DDMS features from Android Studio. For more information about DDMS, see Using DDMS.

The system log shows messages from Android services and other Android apps. To filter the log messages to view only the ones you are interested in, use the tools in the Android DDMS window:

• To show only log messages for a particular process, select the process in the Devices view and then click Only Show Logcat from Selected Process. If the Devices view is not available, click Restore Devices Viewon the right of the Android DDMS tool window. This button is only visible when you hide the Devices window.
• To filter log messages by log level, select a level under Log Level on the top of the Android DDMS window.
• To show only log messages that contain a particular string, enter the string in the search box and press Enter.

Work with Breakpoints

Breakpoints enable you to pause the execution of your app at a particular line of code, examine variables, evaluate expressions, and continue the execution line by line. Use breakpoints to determine the causes of run-time errors that you can’t fix by looking at your code only. To debug your app using breakpoints:

1. Open the source file in which you want to set a breakpoint.
2. Locate the line where you want to set a breakpoint and click on it.
3. Click on the yellow portion of the side bar to the left of this line, as shown in figure 5.
4. Start your app as described in Run your App in Debug Mode.

Android Studio pauses the execution of your app when it reaches the breakpoint. You can then use the tools in the Debug tool window to identify the cause of the error.

Figure 5. A red dot appears next to the line when you set a breakpoint.

View and configure breakpoints

To view all the breakpoints and configure breakpoint settings, click View Breakpoints on the left side of the Debug tool window. The Breakpoints window appears, as shown in figure 6.

Figure 6. The Breakpoints window lists all the current breakpoints and includes behavior settings for each.

The Breakpoints window lets you enable or disable each breakpoint from the list on the left. If a breakpoint is disabled, Android Studio does not pause your app when it hits that breakpoint. Select a breakpoint from the list to configure its settings. You can configure a breakpoint to be disabled at first and have the system enable it after a different breakpoint is hit. You can also configure whether a breakpoint should be disabled after it is hit. To set a breakpoint for any exception, select Exception Breakpoints in the list of breakpoints.

Debug your app with breakpoints

After you set breakpoints in your code, click Rerun to start the app again. When a breakpoint is hit, Android Studio pauses the app and highlights the breakpoint in the source code. The Debug tool window lets you examine variables and control the execution step by step:

To examine the object tree for a variable, expand it in the Variables view. If the Variables view is not visible, click Restore Variables View .

To evaluate an expression at the current execution point, click Evaluate Expression .

To advance to the next line in the code (without entering a method), click Step Over .

To advance to the first line inside a method call, click Step Into .

To advance to the next line outside the current method, click Step Out .

To continue running the app normally, click Resume Program .

Figure 7. The Variables view in the Debug tool window.

Track Object Allocation

Android Studio lets you track objects that are being allocated on the Java heap and see which classes and threads are allocating these objects. This allows you to see the list of objects allocated during a period of interest. This information is valuable for assessing memory usage that can affect application performance.

To track memory allocation of objects:

1. Start your app as described in Run Your App in Debug Mode.
2. Click Androidto open the Android DDMS tool window.
3. On the Android DDMS tool window, select the Devices | logcat tab.
4. Select your device from the dropdown list.
5. Select your app by its package name from the list of running apps.
6. Click Start Allocation Tracking
7. Interact with your app on the device.
8. Click Stop Allocation Tracking

Android Studio shows the objects that the system allocated with the following information:

• Allocation order
• Allocated class
• Allocation size
• Thread ID
• Allocation method, class, and line number
• Stack trace at the point of allocation

Figure 8. Object allocation tracking in Android Studio.

Analyze Runtime Metrics to Optimize your App

Even if your application does not generate runtime errors, this does not mean it is free of problems. You should also consider the following issues:

• Does your app use memory efficiently?
• Does your app generate unnecessary network traffic?
• What methods should you focus your attention on to improve the performance of your app?
• Does your app behave properly when the user receives a phone call or a message?

The Android Device Monitor is a stand-alone tool with a graphical user interface for serveral Android application debugging and analysis tools, including the Dalvik Debug Monitor Server (DDMS). You can use the Android Device Monitor to analyze memory usage, profile methods, monitor network traffic and simulate incoming calls and messages.

To open the Android Device Monitor from Android Studio, click Monitor on the toolbar. The Android Device Monitor opens in a new window.

For more information about the Android Device Monitor and DDMS, see Device Monitor and Using DDMS.

Capture Screenshots and Videos

Android Studio enables you to capture a screenshot or a short video of the device screen while your app is running. Screenshots and videos are useful as promotional materials for your app, and you can also attach them to bug reports that you send to your development team.

To take a screenshot of your app:

1. Start your app as described in Run your App in Debug Mode.
2. Click Androidto open the Android DDMS tool window.
3. Click Screen Captureon the left side of the Android DDMS tool window.
4. Optional: To add a device frame around your screenshot, enable the Frame screenshot option.
5. Click Save.

To take a video recording of your app:

1. Start your app as described in Run your App in Debug Mode.
2. Click Androidto open the Android DDMS tool window.
3. Click Screen Recordon the left side of the Android DDMS tool window.
4. Click Start Recording.
5. Interact with your app.
6. Click Stop Recording.
7. Enter a file name for the recording and click OK.

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