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This installs the app on your device. The syntax of the command is: adb uninstall com. The creators of Android added their own middleware, libraries, and APIs to the Linux kernel to develop the framework. This means that it includes a command-line interface that will look familiar to Linux users. The shell interface will have many of the same tools developers are used to, but not all of them.
Additionally, the tools themselves may be different, and likely won t support every operation you expect. For instance, the ls -l command works, but ls -x does not. I suggest you look in that folder to familiarize yourself with the commands that are available. Some frequently used commands that are not available include more, less, cp, and file. Some common tools that are included are ls, ps, and rm. It contains not just the standard command-line tools, but also a variety of additional tools designed specifically for Android development like monkey, logcat, dumpstate, etc.
You may get frustrated by the limitations of the Android shell, especially if you are used to the more feature-rich options available in full Linux distributions. You should spend some time learning how to use these tools effectively; they may be limited, but they still are still very useful. You can use ADB to access the command shell of a device directly. You can issue commands as one-line executables, or interact with the shell interactively by issuing a series of commands.
Interactive mode Interactive mode allows you to execute more than one command successively on the device. To start interactive shell mode, type: adb shell 20 Chapter 2: Essential Tools. The example belows shows accessing the shell, using common Linux commands to navigate the directory structure, reading the contents of a file, and finally, exiting the shell back to the command prompt. To do this, type the command you want to execute after the shell keyword.
Some useful commands can dump huge amounts of information about the system, including service status, system statistics, and error logs. You may want to collect these statistics if you are trying to analyze trends or specific details about your application.
For example, adb shell dumpsys alarm will output details about all the alarms currently registered on the system. This output is quite verbose, and contains a lot of key information from the system kernel, including Android Debug Bridge ADB It can be useful, especially when trying to debug hardware issues, or when writing software that interacts directly with the system hardware. This information is useful when interacting with the networking stack.
Some of the information available in this log includes time of events, a listing of commands used by the system to communicate, SMS information, IP information, and cellular network data. Using the Activity Manager Shell access allows much more granular access to the device. You can use this to start applications or even single activities in a controlled way.
This can be very useful if you need to test different entry points to an application that may be hard to simulate by stepping through the UI.
Use the Activity Manager to launch a specific screen with a specific set of Intent parameters. An example of starting an activity named com.
It is worth becoming familiar with these additional features, as they provide a lot of useful and important functionality. Some functionality worth highlighting includes: Modify network configuration options like port forwarding example: adb forward tcp tcp Access your device as the root user example: adb shell su Restart the device in alternate modes, such as recovery mode example: adb reboot recovery View system logs, such as the radio or event buffers example: adb logcat -b events Show kernel debug info example: adb shell dmesg Examine system utilization example: adb shell tail top 22 Chapter 2: Essential Tools.
Activity Manager example There is a lot of other functionality we aren t able to cover. For a complete list of all available commands and their parameters, type adb -help without any additional arguments to get a listing of all options. To do so, stop the existing ADB process, and then restart it by issuing the following two commands in order: 1.
If you would like to learn more about the advanced capabilities of this tool, there are a few excellent resources. Command Reference The command reference on the official Android page has a listing of all the commands and their options. Embedded Android Book This book by Karim Yaghmour contains in-depth explanations relating to the internals of the ADB tool and using it to control embedded environments.
Because there is such a large variety available for Android at the time of this writing, there are over 3, devices supported in the Google Play Store , this can be particularly challenging. It is necessary to test your app to ensure it runs well on the majority of devices; you also need to test out a few different screen sizes. You may also need to account for different hardware capabilities, including OS levels, existence of sensors, amount of memory, or CPU.
Fortunately, ADT provides tools that make handling these challenges easier. I ll describe how to test on real devices, and also how to use emulators when the devices you need aren t available. Using a Physical Device for Development For many activities, it s important not to rely completely on an emulator, but to check your app on an actual device.
For instance, this is particularly useful when you are testing advanced graphics rendering, utilizing location services, or making use of advanced sensors. It is not strictly necessary to own an Android device to develop for Android see Using Hardware Acceleration on page 33 for details , but it is a common and simple way to start testing with minimal effort.
This section will go through the steps required to use an Android device as a development aid. If you don t already have a device, it is easy to acquire a cheap used handset; check Craigslist or ebay for older devices.
Capabilities and Limitations As I mentioned, there are reasons to use a physical device instead of an emulator. Here is an overview of the most important capabilities and limitations: Using multitouch on a screen.
Having access to actual location data, in multiple locations and when in motion. Using advanced sensors, such as a compass, gyroscope, or barometer. Limitations Certain core services of a phone might be locked down by the device manufacturer or service provider.
It might be difficult to change networking parameters or access resources as the root user. Testing on a device, particularly if it is one you rely on, could mess up your phone. Simulating distant locations is a no-go for example, if you want to test a location in Egypt and your device is in Belize. In order to configure a device, enable the option in the Settings app on the device.
To do this, open the Settings app, then select Applications Development. The result should look like Figure Using an Emulator for Development We all agree that it is necessary to test Android apps on a variety of different devices and hardware. As it is practically impossible to own every physical device, you will need to use an emulator to check configurations of hardware you don t have. Some of the important reasons to use emulators include: Testing on different hardware configurations Validating on different versions of the Android OS Simulating load or other stress tests Viewing your UI on various screen sizes and resolutions 26 Chapter 3: Configuring Devices and Emulators.
Enable USB debugging on a physical device Supported Features The emulator included in the standard toolkit is feature-rich, however there are some constraints. Supported features Simulating telephony, including latency and connectivity Simulating text messaging Using an Emulator for Development It allows you to specify hardware and software options that will be used by the emulator to model an actual device. The easiest way is to use the graphical AVD manager.
It is also possible to configure AVDs from the command line by passing configuration parameters to the android tool. For the most part, you will likely want to use the graphical tool, as it is simple to use. You would use the command-line option when working with scripts or other noninteractive operations for instance, if you are creating emulator images on a build server, or using a batch operation to test your code on multiple device configurations. Start it by clicking on the icon or running the android tool from the command line.
The first time you launch it, you will see something similar to Figure The screen will display a list of existing emulator configurations.
You will be able to create, edit, repair, start, or see details of the various AVDs you have configured. You will then use this simple form to set the various configuration options necessary.
Android Virtual Devices They will be used to define the specific hardware parameters you wish to emulate. The options include: Name Identifies your current configuration image. This can be anything you like, but you should choose a name that lets you identify the specific options offered by the AVD. I usually name these according to the device I am trying to emulate, e. Device Allows you to select a preconfigured image based on a variety of common devices. Target Specifies the version of the platform the device will run.
The tool will allow you to specify only those platforms that you have downloaded to your environment. In other words, if you have not used the SDK Manager Chapter 1 to install the API you wish to use, you will not be able to create an emulator running that version. See Using Hardware Acceleration on page 33 for information on how to enable it. Snapshot Enabling this feature gives you the ability to save and restore an emulator s state to a snapshot file.
This can be useful for saving the state of an emulator, allowing you to quickly boot to a specific state, avoiding lengthy boot times. For more information, see Using the Emulator on page Skin Allows you to specify a particular screen size and resolution.
It provides a set of standard screen configurations for a particular platform, or you can specify custom values. Creating AVDs from the command line It can be useful to generate AVD images from the command line when you are scripting or using an environment where employing the GUI isn t practical. To create AVDs using this method, you need to pass command-line parameters to the android tool. To create an AVD, run the android create avd command and include parameters that specify the particular configurations.
Required parameters are a name for the AVD and the system image that should run on the emulator when it is invoked. If you want, you can also specify other options, such as SD card size, OS platform, skin, or a specific location in which to store user data files. This directory contains the AVD configuration files, the user data image, the SD card image if configured , and any other relevant files.
This file contains the location of the directory containing the AVD files. The default location of this directory is: Android Virtual Devices It is also possible to specify a different location for a specific AVD by including -p path as an option when you create the AVD. If you do set a custom location for the. I will describe a few of the most common ones you will likely want to set for each emulator you create. If you want to learn about all the available options, this AVD Command Reference is an excellent source.
The default value is 96, which is quite low. I suggest increasing this value substantially to improve emulator performance. I generally set it to , but you can set it higher if your hardware can support it. Keyboard support Defines whether the device will support the physical keyboard on your computer. I always set this to yes, because it makes interacting with the device easier. You will be able to use your computer keyboard to interact directly with the Android OS, which makes typing much easier than trying to use the onscreen keyboard with your mouse.
Camera support Defines whether your emulator will support camera functionality. If your app requires a camera, make sure to set this value, as the default is no. You can specify if your emulator will support front, back, or both cameras. GPS support Will allow your device to support location functionality. The default for this is yes, so you will need to change it only if you specifically want to disable this functionality.
Cache partition size This value is used by the Google Play Store to determine whether a device can download an app from the market. It is worth testing with a variety of settings to make sure your app will work on 32 Chapter 3: Configuring Devices and Emulators.
Advanced Emulator Configuration Working with the emulator can be frustrating. Some of the most common tasks like starting or deploying an app can take a long time. There are a few simple things you can do to make it faster, including using VM hardware acceleration, eliminating unnecessary functionality, and dedicating a CPU core to the emulator. Using it can improve performance significantly, but there are also limitations to consider.
Benefits Key benefits of HAXM include: Improved emulator performance, in particular, quicker startup and shorter deploy times. Better performance of graphics-intensive applications, particularly those that make use of OpenGL.
Better use of native hardware: if your development computer is robust, using HAXM will allow you to use it to its full potential. The performance characteristics of the emulator are not the same as you would find in the real world, because most current Android devices use different ARM-based processors.
Advanced Emulator Configuration Installing the HAXM software It is not enough to just download the tool; you also need to install it. You need to launch the installer process and accept the license agreement to complete the installation. In order to use this functionality on Linux, you also need to install the KVM software package. Instructions for this vary based on the particular version of the OS being used. You will see additional options for using the Intel-based system for your emulator.
Do not select the Snapshot option. Snapshots are not supported for emulators with graphics acceleration enabled. Validating that HAXM is running After you have installed all the correct components and started your correctly configured AVD, you can easily validate that everything is running correctly. If it is, a notification indicating success is displayed in the console during startup Figure Generally this isn t something you need to see, and it s preferable not to waste precious seconds while it displays.
You can disable the boot animation by adding the -no-boot-anim option to your AVD start command. For example: emulator -avd myavd. This prevents it from contending for a CPU with other resource-intensive processes such as Eclipse. To do this, start the Windows Task Manager, select the Processes tab, right-click on the running emulator process, and click on Set Affinity option. Then you will be able to check or uncheck the CPU processor core s on which you want to run the application see Figure Finally, click OK to finish the setup.
Dedicating a core to the emulator 38 Chapter 3: Configuring Devices and Emulators. Now we ll discuss their use. An emulator is a very powerful tool that makes testing easier and allows the developer to simulate a variety of things that would be difficult to accomplish under realworld conditions. For instance, if you are writing a mapping application, you might need to test locations all over the world, and it would be impractical although quite a bit of fun to actually travel to each of these locations.
It eliminates the need to have physical devices to represent each configuration that you need to test. For instance, you will use emulators to mock various screen sizes and memory configurations. This chapter describes how to use the emulator to effectively test various parameters. For the most part, emulators and physical devices interact with the ADT tools in the exact same way.
In other words, the operations we discuss in this chapter perform the same way on an emulator as they will on a physical device. In most cases, a physical device is more limited, because options such as changing network configurations are locked down by the service provider. You will likely use many different combinations of physical devices and emulators to test thoroughly.
You can run as many different emulators and devices as you like. It is common for a developer to have many different emulator and physical devices running at the same time, then use each of them throughout the test cycle. It is worth noting that the emulator doesn t support certain actions, such as simulating accelerometer activity, or simulating some sensor activity such as the magnetometer. This tool is also used to start the emulator instances as well.
It provides options to control runtime parameters of the emulators you created. To start it from within Eclipse, click the icon from the main toolbar. Or start it from the command line with the following command: android avd When you launch the AVD Manager, you will see a screen similar to Figure This screen displays a list of all the AVDs you have configured on your system, and some options for managing them.
To start an emulator, select a particular AVD and click the Start button. AVD Manager tool You are then presented with a secondary screen Figure that has a variety of options specific to running an emulator instance.
Using them allows you to change the size, performance, and data of your emulator. Scale factor This allows you to adjust the size of the emulator on your computer screen. To specify a particular screen size, place a checkmark in the Scale Factor box.
Next, click the? Enter the resolution and size of your display. Then type a number in the Screen Size box. Your emulator will be started with the screen size you entered. Snapshot This lets you save an emulator s state to a snapshot file and restore it later. This can be useful if you would like to preconfigure an emulator to start in a particular state every time, or would like to avoid the lengthy boot process when starting from scratch. This is a great way to speed up the time to boot an emulator, and will save a lot of time.
Emulator boot times can be reduced from many minutes to just seconds. Starting an emulator from the command line It s not absolutely necessary to use the AVD Manager to start an emulator. You can also start it from the command line. This is useful when using scripts, or if you would like to run an emulator without the overhead of Eclipse. There are a variety of configuration options you can use when starting an emulator this way. There are options relating to networking, graphics acceleration, sensor abilities, and more.
To see a complete list of options, type: emulator -help Using the Emulator For example, you could start an emulator with graphics acceleration turned on and boot animation disabled two good options you can use to improve performance. This would look like: emulator -avd Nexus7 -gpu on -no-boot-anim Using snapshots to improve performance The snapshot is a view of your emulator including all data, the current UI being displayed, or any other sensor or data currently being used.
This snapshot can be very useful if you wish to start your emulator with a certain configuration or state multiple times. In order to use snapshots with a particular AVD, it needs to be configured appropriately. Reread Creating AVDs on page 28 to review how to do this. You will notice three options in the snapshot section of the launch configuration tool. Wipe user data Refreshes your emulator image to remove all data and resets it to a clean configuration just as if it were started for the very first time.
Launch from snapshot Allows you to restore your emulator to the state it was in when the last snapshot was taken. If there is no snapshot in memory, this option is not enabled. Save to snapshot Triggers the system to save a snapshot of the current state of the emulator when you close it.
I use snapshots as a way to save a clean emulator that I can recover quickly. I save a snapshot the first time I start the emulator, right after it has completed the boot sequence. We’d love to hear your app’s favorite response. We regularly upgrade and create new features that are useful for you.
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You can try again with the new version. Shows all the TODO comments sprinkled throughout your project s code. Here you can examine the results of any find command that you execute. If your project is Maven-based, interact with this panel to perform Maven activities.
If you re utilizing the new Gradle build system, you can find the tools necessary to interact with Gradle here. At times, the Android Studio IDE may encounter an unexpected error or have important events that need to be visible to you, the developer. This panel will show you these events. The final area, which is of utmost importance, is the status bar at the bottom of Android Studio, shown in Figure This is where the majority of status updates will occur when background processes run.
Some of these background processes include updating indices on the files, Maven or Gradle background processing, and event errors. The rightmost box shows the IDE s memory usage. The Android Studio status bar Toolbars Android Studio ships with a highly customizable toolbar that is easily accessible from the top of the display. The default toolbar that ships with Android Studio is shown in Figure The default toolbar in Android Studio Table describes each set of tools from left to right.
Navigate forward and backward in the most recent files that you ve accessed or edited recently. These buttons are some of the most common buttons that you will use in Android Studio, as they allow you to build, run, debug, and attach to a running Android process for debugging. Where you can go for help in using Android Studio. Useful Actions in Android Studio In addition to the various panels and toolbars, Android Studio has a wide feature set that is accessible via the top menu and various contextual menus.
Table shows a few of the common actions that you ll want to familiarize yourself with. At times, you may want to customize Android Studio. You can do this by accessing the Preferences through the Android Studio Preferences menu. Some options you can edit are the theme of the IDE, font sizes, keymap, toolbars, and many other options. An Android project is comprised of modules and libraries, and at times you may need to edit the settings for these modules and libraries.
To do so, you ll need to enter the project structure by visiting the File Project Structure menu. Although the default windows that ship with Android Studio are usually sufficient for day-to-day Android development, there may come a time when you need to get into the gritty details of the IDE. To explore the various other windows that are available to you such as file structure, commander, VCS changes, etc. Anytime you re unaware of the actions you can perform in the IDE, simply right-click the area in which you would like to see the various options.
Android Studio will present you with the array of options if available that are possible in the given context of the IDE panel in which you re working. Navigation shortcuts are used for navigating around your code base at the speed of light. Master the shortcuts in Table and you ll increase your productivity immensely. Almost all of your files are located in the src directory.
The new file structure is in place in order to support the new Gradle build system. A Tour Around the New Structure As noted, the new file structure puts the majority of your files in the src folder, as shown in Figure The files in this folder are the source files for your project. These are the files you ll be editing the majority of the time.
This file structure provides more flexibility and will eventually provide the ability to provide multiple build variants different types of builds with the same project. Everything in your project will still behave the same for the most part. The New Structure of an Android Project An example of the Android folder structure in Android Studio Build variants are not implemented at the time of this writing. All three of these commands are available via the Run menu or the main toolbar in Android Studio, as shown in Figures and The Attach Debugger to Android Process item is at the very bottom of this long menu and has been removed from this screenshot for brevity.
The Run menu Figure The toolbar run actions To run an Android app on the currently connected device, select Run from the Run menu or press the Run button in the toolbar. This command will build the Android application and deploy it to the currently attached device. To debug an Android app on the currently connected device, select Debug from the Run menu or click the debug icon in the toolbar.
This command will build the Android app and deploy it to the currently attached device, and attach the debugger to it. At this point, if any breakpoints are set, Android Studio will stop execution so that you can inspect your runtime environment for debugging.
Another wildly useful tool is the Attach Debugger to Android Process command. This is mainly used when you need to start your app and navigate through a series of steps before attaching the debugger at a particular execution point perhaps right before you click a button or before you navigate to a new screen.
This tool allows you to quickly flow through your app and then set the breakpoint, instead of having the debugger running the entire time. To attach the debugger to your currently running app, install the app with the run command as outlined earlier and then select Run Attach Debugger to Android Process or press the Attach Debugger to Android Process icon in the toolbar. Creating New Android Components A very common task during Android development is to create new components for the app.
Creating New Android Components Layout Designer lets you arrange Views on the screen by dragging and dropping, while Layout Preview lets you see how your screen looks while you are editing your XML resources.
I ll provide a brief introduction to both tools in this section. Layout Designer When you first open an Android layout file, you ll see the Android designer with the Design tab selected, as shown in Figure The other tab is Text, which allows you to hop into the XML that defines the layout. I will cover that in the next section. Select one of the controls from the palette and drag it to the layout. Once the control is in place, you can edit the various properties of the control by selecting the control and editing the properties on the right, as shown in Figure Layout Designer automatically creates the underlying XML code that represents the layout you created.
The component tree shows you how the layout is organized in a hierarchical fashion. You can also right-click and choose Go To Definition. This will open the Text tab of the layout designer and you are navigated to the XML snippet that defines that control. I highly advise you to peruse the various options in the designer, as it is a very powerful tool.
If you love graphical editors, the Layout Designer is great for whipping up a user interface quickly. However, some of us love to get as close to the metal as possible, and in order to do that you need to edit the XML.
Layout Preview As soon as you enter the XML layout, you will notice that the control palette, component tree, property editor, and drag-and-drop designer are gone and replaced with a slew of XML code and a layout preview.
This is shown in Figure The preview shown here is the Layout Preview tool. You can turn this panel on and off by selecting the Preview button on the right side of the screen. This panel is shown only when the XML editor is in use.
As an example, if you change a TextView or Button to a bold font style, the Layout Preview will show the bolded text. If you like being closer to the XML, this is the view for you. I often hop back and forth between the Layout Designer and Layout Preview tools during my day-to-day Android development.
Layout Designer and Layout Preview Follow these steps: 1. Select your module and click Next. Either supply the path to your keystore that you re currently using for your Android application, or create a new keystore.
Optional Once your keystore values are provided, click Remember Password and Android Studio will keep track of your entered password in a local password database so you don t have to enter it again. You will be required to provide a master password for this password database, so be sure you remember this password.
Tools like LastPass. The remember password feature is very useful if you create or maintain a lot of Android applications. Click Next. At this point you can define the destination for your APK.
You can also specify whether you d like to run ProGuard described in ProGuard on page , and where the ProGuard configuration file is located. Click Finish and your APK will be generated in the destination folder.
Android Studio ships with support for Maven and Gradle right out of the box. This is great considering that in Eclipse you had to use a plug-in that was often buggy and not entirely reliable. Given that Android Studio ships with support for both tools, you can easily work with projects that use either technology via a panel in Android Studio.
Simply start Android Studio and open the pom. Android Studio walks you through the Maven project import process. Once the import is complete, you can open pom. The Maven panel is now populated with various options, as shown in Figure Figure The Maven panel expanded Once the Maven panel is expanded, you will be able to explore the lifecycle, various plug-ins, and dependencies. To refresh the Maven project, click the refresh icon in the top right of the panel.
This loads all of the dependencies, plug-ins, etc. To execute a lifecycle goal, simply select it and then press the play button in the top part of the panel. I recommend that you explore the panel and its options, because you can configure Maven and perform various other actions within it. Interacting with Maven and Gradle One way is to execute and build the task you want through the Maven panel.
Finally, you can build through the Build menu. I prefer to build through the Build menu because Android Studio caches the files and only builds off of changesets, so I m not running through an entire Android Maven build every time which can be very time consuming. Interacting with Gradle As with Maven, projects that use the Gradle build system are very easy to work with in Android Studio.
There are a couple of panels that you should be familiar with. These panels include the Gradle panel and the Build Variants panel as shown in Figures and Once your project is loaded, you can open the Gradle panel and interact with the various tasks.
You can also open the build. I recommend that you use the Build menu to build your application because it is the simplest way.
If for any reason your application Gradle files become out of sync with your Android application, you can select the Sync Project with Gradle Files option from the toolbar, as shown in Figure This will update your project with the settings defined in the Gradle file. These integrations allow you to perform VCS operations commit, pull, push, update, etc.
Once it is set up, you will be able to perform various VCS commands for all the files in Android Studio. Migrating from Eclipse Although Android Studio is not ready for prime time yet, it will be shortly and I m sure a lot of folks are going to be moving to Android Studio from Eclipse. When the time comes for you to make the move, you can easily export your project from Eclipse using the Gradle export tool, and import it into Android Studio.
The Android team has written an easy-to-follow guide on how to migrate from Eclipse. Android Studio Tips and Tricks Android Studio is packed with great keyboard shortcuts that allow you to be much more productive than previous Android development environments except for IntelliJ, which is what Android Studio is based on.
In this section, I m going to show you some of the most common keyboard shortcuts that you ll use on a daily basis while developing Android applications. Refactoring and Code Generation Many of the important code refactoring options available in Eclipse see Refactor Menu on page 70 are also available in Android Studio.
I advise you to review the Refactor This option in Table as well as the other options in the Refactor menu in Android Studio. Learning common refactorings, such as generating getters and setters, will save you valuable time and ensure the code you generate is standardscompliant.
Having used IntelliJ for Android for the last two years, I can honestly say I m twice as fast at developing Android applications and I ve become a better developer because of it. I believe that Android Studio will be an extension of that same strength and I hope you feel the same way about it after you use it for a while. I will update these tutorials as Android Studio evolves, so I encourage you to check it out if you would like to learn more.
Logs from the system and various apps are output to a series of buffers, which can then be filtered with the logcat command. If you have experience working with Log4J or the java. You can review output from many different systems in a single location and filter it to view information relevant to your application.
It is worth getting a good understanding of all the options, as this tool will make your life much easier. Android logs pretty much everything in the system to a common log file. Information about garbage collection, various system activities, and app output are all sent to the same file.
This provides a central location to gather a broad range of information in a single place. It is also important to note that this single file is shared by all apps installed on the device. Therefore, you should be careful not to output sensitive information to the logs.
You can use the Proguard utility to obfuscate your code and hide certain details. It can also be used to remove log statements when packaging your app for release details about using this tool can be found in ProGuard on page Viewing the Logcat File To view the entire log file without any filters , issue the command: adb logcat This outputs a very verbose log, which includes information about all processes on the system.
Anatomy of a Log Message Each log message includes a variety of metadata that can be used to filter the output. Log tag Defines a process or ID associated with a message. Log message The content being reported.
Reading logcat output Each line in the logcat contains a variety of important information. I want to highlight what they mean, so you can understand where to find relevant information in the statement.
The first statement we will look at is one generated from the system remember both system and custom messages are output to the same file. This log statement was marked to be output when the Info level is being output. It tells us which system in this case, Activity Manager was responsible for generating this message. This is a unique identifier assigned to an application during runtime, and can be a great way to filter messages.
Displayed com. In this case, the message tells us that an activity was started, and how many milliseconds it took to be created. We can look at another statement; this time, it is output as a result of a statement I placed in my code.
You can see the output from a custom statement looks exactly like a system message and contains the same information. A tag I created to keep track of user interaction events. The user entered a value: value from the call is: Tracks that the user entered into a form field. There is a lot of information in the logcat, which can be difficult to manage.
Next I will discuss some strategies for generating and filtering logs that will make this easier. Filtering Based on Logging Level It is possible to filter logging output based on the severity of a message. Log messages are displayed based on their debug priority. You can specify a minimum level, and the output will be filtered to include only messages with that level or higher.
It is important to know the different log levels. You want to ensure that the level you are viewing is appropriate for the type of message you are looking for. Refer to Table for a breakdown of the log levels. This means that any logs you create with the D level will not be output in your production app. Therefore, it is safest to use this level for most of your log statements, in order to make sure that sensitive data doesn t accidentally get output into the field.
Using Tags to Filter Output It is possible to apply filter expressions from logcat so you see only the messages that are most interesting to you.
The filter expressions have the format tag:level. You can apply more than one filter at a time to isolate the specific information you need.
The procedure for finding messages of interest to you, therefore, is to create custom tags in your Java code and filter using these tags. The syntax for this follows: Log. You can apply as many different filter expressions to your logcat command as you need to fine-tune what is being displayed.
For certain content such as the radio or events , output will be left in an alternative buffer instead of the default one. To see the additional log messages, start logcat with the -b option and specify the alternate buffer you wish to view. For example, to view the radio buffer, enter: adb logcat -b radio Predefined Output Formats Log messages include a variety of metadata fields, such as level, time, process ID, application, tag, and the error text.
There are a variety of predefined output formats that can be specified in order to include the specific metadata field you want to see in the display. You can do this by including the -v option and one of these predefined output formats. For example, to generate output data in the time format, enter: adb logcat -v time Logcat Viewer in Eclipse In the standard Java perspective in Eclipse, you will notice a logcat tab in the collection of tabs on the bottom of the screen see Figure This tool allows you to navigate the logcat of the currently connected device using some additional UI assistance.
Logcat To make things easier, you can create an exclusion filter to exclude common system information that you don t want to see.
To create a filter: 1. Select the plus icon icon to create a new filter. Specify a Filter Name. The Logcat tool Logcat Example Logcat is a very powerful Android feature, but it can be hard to find what you need in it sometimes due to the amount of information that is output to the common log.
Let s step through a simple example to demonstrate how to filter verbose system logs to find the information you want and get a better understanding of your code output. For this example, I created code that takes an input value from the user in US dollars and sends this value to a web service, which returns the value in Euros.
Finally, the value is converted to a custom formatted style and displayed on the user interface. Determining areas to monitor It is important to think about the specific characteristics of the code you are logging. You want to separate your logic into distinct areas which will be represented with custom tags. This will make it easy to concentrate on specific areas because you will be able to isolate log statements based on functionality. In this case, there are a few 94 Chapter 7: Testing Your Code.
The areas I want to monitor include: User Interface Check the values entered by the user, check the values actually displayed on the screen, monitor when the user presses a button, etc. Formatting Check the algorithm I use to format the values for my application. AsyncTasks Track a call through the lifecycle of this code. Then I use this tag in my code e. That way, I can easily look at a particular subsystem even across multiple activities, by filtering for that particular tag.
Then I put log statements in my code and use the custom tags as appropriate. As the following printout shows, this output can contain a lot of information and be difficult to understand. The following output is what you would see from a single execution of our currency conversion workflow. The application may be doing too much work on its main thread.
To do this, I use the custom tags I created to view the specific categories I want to see. Because only the information I care about is displayed, it is much easier to understand the specific operations I am interested in. For instance, if I wanted to see only information related to user interactions, I could filter based on the UI tag.
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