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Build and Run Your App

Android Studio sets up new projects to deploy to the Android Emulator or a connected device with just a few clicks. Once your app is installed, Instant Run allows you to push code changes without building a new APK.

To build and run your app, select Run > Run in the menu bar (or click Run in the toolbar). If it's the first time running the app, Android Studio asks you to select a deployment target as shown in figure 1. Simply select a device to install and run your app.

Figure 1. The Select Deployment Target dialog shows available devices

If the dialog says, "No USB devices or running emulators detected," then you need to set up and connect your device or launch an emulator by clicking a device listed under Available Virtual Devices. If there are no virtual devices listed, click Create New Virtual Device and follow the Virtual Device Configuration wizard (see Create and Manage Virtual Devices).

Note: You can also deploy your app in debug mode by clicking Debug . Running your app in debug mode allows you to set breakpoints in your code, examine variables and evaluate expressions at run time, and run debugging tools. To learn more, see Debug Your App.

Select and build a different module

If your project has multiple modules beyond the default app module, you can build a specific module as follows:

Android Studio builds the module using Gradle. Once the module is built, you can run and debug it if you've built a module for a new app or new device, or use it as a dependency if you've built a library or Google Cloud module.

To run a built app module:

Change the run/debug configuration

When you run your app for the first time, Android Studio uses a default run configuration. The run configuration specifies the module to run, package to deploy, activity to start, target device, emulator settings, logcat options, and more.

The default run/debug configuration launches the default project activity and uses the Select Deployment Target dialog for target device selection. If the default settings don't suit your project or module, you can customize the run/debug configuration, or even create a new one, at the project, default, and module levels. To edit a run/debug configuration, select Run > Edit Configurations. For more information, see Create and Edit Run/Debug Configurations.

Change the build variant

By default, Android Studio builds the debug version of your app, which is intended only for testing, when you click Run. You need to build the release version to prepare your app for public release.

To change the build variant Android Studio uses, select Build > Select Build Variant in the menu bar (or click Build Variants in the windows bar), and then select a build variant from the drop-down menu. By default, new projects are set up with a debug and release build variant.

Using product flavors, you can create additional build variants for different versions of your app, each having different features or device requirements. To find out more about build variants and product flavors, see Configure Your Build.

Generate APKs

To create an APK for your app, follow these steps:

  1. Select the build variant you want to build from the Build Variants window.
  2. Click Build > Build APK in the menu bar.

    To instead build the APK and immediately run it on a device, click Run in the toolbar.

All built APKs are saved in project-name/module-name/build/outputs/apk/. You can also locate the generated APKs by clicking the link in the pop-up dialog that appears once the build is complete, as shown in figure 2.

Figure 2. Click the link to locate the generated APK files.

Note: Before you can generate a release version of your app for public distribution, you must sign your APK.

Monitor the build process

You can view details about the build process by clicking View > Tool Windows > Gradle Console (or by clicking Gradle Console in the tool window bar). The console displays each task that Gradle executes in order to build your app, as shown in figure 3.

Figure 3. The Gradle Console in Android Studio.

If your build variants use product flavors, Gradle also invokes tasks to build those product flavors. To view the list of all available build tasks, click View > Tool Windows > Gradle (or click Gradle in the tool window bar).

If an error occurs during the build process, the Messages window appears to describe the issue. Gradle may recommend some command-line options to help you resolve the issue, such as --stacktrace or --debug. To use command-line options with your build process:

  1. Open the Settings or Preferences dialog:
    • On Windows or Linux, select File > Settings from the menu bar.
    • On Mac OSX, select Android Studio > Preferences from the menu bar.
  2. Navigate to Build, Execution, Deployment > Compiler.
  3. In the text field next to Command-line Options, enter your command-line options.
  4. Click OK to save and exit.

Gradle will apply these command-line options the next time you try building your app.

About Instant Run

In Android Studio 2.3 and higher, Instant Run significantly reduces the time it takes to update your app with code and resource changes. After deploying your app to a target device running Android 5.0 (API level 21) or higher, you can click Apply Changes to push certain code and resource changes to your running app without building a new APK—and, in some cases, without even restarting the current activity. The Run and Debug buttons are always available to you when you want to push your changes and force an app restart. However, you may find that using the Apply Changes button provides a faster workflow for most incremental changes to your app.

Tip: You can also press Control + F10 (or Control + Command + R on Mac) to apply changes with Instant Run.

The Apply Changes action is available only when you meet the following conditions:

For more information about enabling Instant Run, go to the section about configuring your project.

Instant Run pushes your changes by performing a hot swap, warm swap, or cold swap—the type of swap it performs depends on the type of change you made. When you click Apply Changes after making a code or resource change to your running app, Instant Run automatically determines the best way to push your change to the target device, as described in the following table.

Clicking Run (or Debug ) forces a cold swap and an app restart. If you make a change to the app manifest or a resource referenced by the manifest, Android Studio always pushes your changes with a full APK reinstall.

Code Change Apply Changes Behavior
  • Change implementation code of an existing method

Performs a hot swap: This is the fastest type of swap and makes changes visible much more quickly. Your application keeps running and a stub method with the new implementation is used the next time the method is called.

Hot swaps do not re-initialize objects in your running app. Before you see certain updates, you may need to either restart the current activity, by selecting Run > Restart Activity, or restart your app, by clicking Run (or Debug ). By default, Android Studio automatically restarts the current activity after performing a hot swap. If you do not want this behavior, you can disable automatic activity restarts.

  • Change or remove an existing resource
Performs a warm swap: This swap is still very fast, but Instant Run must restart the current activity when it pushes the changed resources to your app. Your app keeps running, but a small flicker may appear on the screen as the activity restarts—this is normal.
Structural code changes, such as:
  • Add, remove, or change:
    • an annotation
    • an instance field
    • a static field
    • a static method signature
    • an instance method signature
  • Change which parent class the current class inherits from
  • Change the list of implemented interfaces
  • Change a class's static initializer
  • Reorder layout elements that use dynamic resource IDs

Performs a cold swap: This swap is a bit slower because, although a new APK is not required, Instant Run must restart the whole app when it pushes structural code changes.

  • Change the app manifest
  • Change resources referenced by the app manifest
  • Change an Android system UI element, such as a widget or notification

When making changes to the app's manifest or resources referenced by the manifest, clicking Apply Changes redeploys a full build of your app with those changes. This is because certain information about the app, such as its name, app icon resources, and intent filters, are determined from the manifest when the APK is installed on the device.

If your build process automatically updates any part of the app manifest, such as automatically iterating versionCode or versionName, you will not be able to benefit from the full performance of Instant Run. When using Instant Run, you should disable automatic updates to any part in the app manifest in your debug build variants.

When updating an Android system UI element, such as a widget or notification, you need to click Run (or Debug ).

Note: If you need to restart your app after a crash, do not launch it from your target device. Restarting your app from your target device does not apply any of your code changes since the last cold swap or incremental build. To launch your app with all your recent changes, click Run (or Debug ) from Android Studio.

Disable automatic activity restart

When performing a hot swap, your app keeps running but Android Studio automatically restarts the current activity. To disable this default setting:

  1. Open the Settings or Preferences dialog:
    • On Windows or Linux, select File > Settings from the menu bar.
    • On Mac OSX, select Android Studio > Preferences from the menu bar.
  2. Navigate to Build, Execution, Deployment > Instant Run.
  3. Uncheck the box next to Restart activity on code changes.

If automatic activity restart is disabled, you can manually restart the current activity from the menu bar by selecting Run > Restart Activity.

Configure your project for Instant Run

Android Studio enables Instant Run by default for projects built using Android plugin for Gradle 2.3.0 and higher.

To update an existing project with the latest version of the plugin:

  1. Open the Settings or Preferences dialog.
  2. Navigate to Build, Execution, Deployment > Instant Run and click Update Project, as shown in figure 4.

    If the option to update the project does not appear, it’s already up-to-date with the latest Android plugin for Gradle. But make sure the box next to Enable Instant Run is checked.

    Figure 4. Updating the Android plugin for Gradle for an existing project.

To start using Instant Run, you also need to change the build variant to a debug version of your app and deploy it to a target device running Android 5.0 (API level 21) or higher. To learn about more techniques that speed up your build, read Optimize Your Build Speed

Exclude your project from Windows Defender

On Windows systems, Windows Defender may cause slowdowns while using Instant Run. If you are using Windows Defender, you should exclude your Android Studio project folder from Windows Defender malware scans.

Improve build times when using Crashlytics

If your version of the Fabric Gradle plugin is lower than 1.21.6, Crashlytics may cause slower build times. To improve build performance while developing your app, you can either update the plugin to the latest version or disable Crashlytics for your debug build variant.

Limitations of Instant Run

Instant Run is designed to speed up the build and deploy process in most situations. However, there are some aspects to using Instant Run that might affect its behavior and compatibility with your app. If you experience any other issues while using Instant Run, please enable extra logging and report a bug.

Apps don't launch on some physical devices

Some device manufacturers block apps from automatically launching after being installed on the device. When deploying your app to a physical device using Android Studio 2.3, this restriction breaks the intended behavior of Instant Run and causes the following error output: Error: Not found; no service started. To fix this issue, update Android Studio to 2.3.1 or higher.

Debug mode always uses cold swaps

On Android Studio 2.3, if you deploy your app by clicking Debug , pushing subsequent code changes by clicking Apply Changes always results in a cold swap. To learn more, go to issue #234401.

Deploying to multiple devices

Instant Run uses different techniques to perform hot, warm, and cold swaps that are specific to the API level of the target device. For this reason, while deploying an app to multiple devices at once, Android Studio temporarily turns off Instant Run.

Multidexing your app

If minSdkVersion is set to 21 or higher, Instant Run automatically configures your app for multidex. Because Instant Run only works with the debug version of your app, you may need to configure your app for multidex when deploying your release build variant.

Running instrumented tests and performance profilers

Instrumented tests load both the debug APK and a test APK into the same process on a test device, allowing control methods to override the normal lifecycle of the app and perform tests. While running or debugging instrumented tests, Android Studio does not inject the additional methods required for Instant Run and turns the feature off.

While profiling an app, you should disable Instant Run. There is a small performance impact when using Instant Run and a slightly larger impact when overriding methods with a hot swap. This performance impact could interfere with information provided by performance profiling tools. Additionally, the stub methods generated with each hot swap can complicate stack traces.

Using third-party plugins

Android Studio temporarily disables the Java Code Coverage Library (JaCoCo) and ProGuard while using Instant Run. Because Instant Run only works with debug builds, this does not affect your release build.

Certain third-party plugins that perform bytecode enhancement may cause issues with how Instant Run instruments your app. If you experience these issues, but want to continue using Instant Run, you should disable those plugins for your debug build variant. You can also help improve compatibility with third-party plugins by filing a bug.

Pushing changes to multi-process apps

Instant Run only instruments your app's main process in order to perform hot swaps and warm swaps. When pushing code changes to other app processes, such as changes to a method implementation or an existing resource, Instant Run performs a cold swap.

Launching your app in a Work profile

If you run your app with Instant Run and open your app using a Work profile (or other secondary profile), your app will crash because the instrumented DEX files used by Instant Run are accessible only from the primary profile's user space.

If you want to continue using Instant Run, just avoid opening your app with the Work profile and be sure your run configuration does not use the --user user_id flag.

If you need to use your app with the Work profile, we recommend you create a new run configuration that includes the --user user_id flag, specifying the Work profile user ID. You can find the user ID by executing adb shell pm list users from command line. When you use the --user flag, Android Studio disables Instant Run for only that deployment; Instant Run will work again when you switch to a configuration without the --user flag.

Disable Instant Run

To disable Instant Run:

  1. Open the Settings or Preferences dialog.
  2. Navigate to Build, Execution, Deployment > Instant Run.
  3. Uncheck the box next to Enable Instant Run.
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