Android SDK reference

This reference guide documents all of the methods available in our Android SDK, and explains in detail how these methods work. If you want to dig even deeper, our SDKs are open source. To learn more, view the source on GitHub or the generated Javadocs. Additionally you can clone and run a sample application that uses this SDK.

Getting started

Building on top of our Getting Started guide, the following steps will get you started with using the LaunchDarkly SDK in your Android application.

To get started, declare a dependency on the LaunchDarkly Android SDK.

1implementation 'com.launchdarkly:launchdarkly-android-client-sdk:2.14.1'
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Once the SDK is installed, you'll want to create a single, shared instance of LDClient. You should specify your mobile key here so that your application will be authorized to connect to LaunchDarkly and retrieve flag values for your application and environment.

The following example shows the simplest way to create the client. It will block for up to 5 seconds until the latest feature flags have been retrieved from LaunchDarkly.

1LDConfig ldConfig = new LDConfig.Builder() 
2    .setMobileKey("YOUR_MOBILE_KEY") 
3    .build();
4
5LDUser user = new LDUser.Builder("user key")
6    .email("fake@example.com")
7    .build();
8
9LDClient ldClient = LDClient.init(this.getApplication(), ldConfig, user, 5);
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However, calling blocking code from the main thread in an Android app is not considered a best practice. The preferred method is shown below. It will allow you to use the client immediately. Flags from the previous launch of the app are stored on the device and retrieved for immediate use. The client will still connect in the background and continually update itself with the latest flags.

1LDClient ldClient = LDClient.init(this.getApplication(), ldConfig, user, 0);
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Using ldClient, you can check which variation a particular user should receive for a given feature flag.

1boolean showFeature = ldClient.boolVariation(flagKey, true);
2if (showFeature) {
3    // application code to show the feature
4}
5else {
6    // the code to run if the feature is off
7}
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Lastly, when your application is about to terminate, shut down ldClient. This ensures that the client releases any resources it is using, and that any pending analytics events are delivered to LaunchDarkly. If your application quits without this shutdown step, you may not see your requests and users on the dashboard, because they are derived from analytics events. This is something you only need to do once.

1ldClient.close();
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Customizing your client

You can also pass other custom parameters to the client with the configuration object:

1LDConfig ldConfig = new LDConfig.Builder()
2    .setMobileKey("YOUR_MOBILE_KEY")
3    .setConnectionTimeoutMillis(5000)
4    .setEventsFlushIntervalMillis(5000)
5    .build();
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Here, we've customized the client connect and flush interval parameters. For the full set of config options check out the Javadoc.

Users

Feature flag targeting and rollouts are all determined by the user you pass to your client. In our Android SDK, we use a builder pattern to make it easy to construct users. Here's an example:

1LDUser user = new LDUser.Builder("aa0ceb")
2    .email("fake@example.com")
3    .firstName("Jake")
4    .lastName("Fake")
5    .custom("group", "microsoft")
6    .build();
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Let's walk through this snippet. The first argument to the builder is the user's key. In this case we've used the hash "aa0ceb". The user key is the only mandatory user attribute. The key should also uniquely identify each user. You can use a primary key, an e-mail address, or a hash, as long as the same user always has the same key. We recommend using a hash if possible.

All of the other attributes (like firstName, email, and the custom attributes) are optional. The attributes you specify will automatically appear on our dashboard, meaning that you can start segmenting and targeting users with these attributes.

In addition to built-in attributes like names and e-mail addresses, you can pass us any of your own user data by passing custom attributes, like the groups attribute in the example above.

Custom attributes are one of the most powerful features of LaunchDarkly. They let you target users according to any data that you want to send to us, including organizations, groups, and account plans. Anything you pass to us becomes available instantly on our dashboard.

Private user attributes

You can optionally configure the Android SDK to treat some or all user attributes as private user attributes. Private user attributes can be used for targeting purposes, but are removed from the user data sent back to LaunchDarkly.

In the Android SDK you can define private attributes for the entire LaunchDarkly client. When creating the LDConfig object, you can call the setPrivateAttributeNames method, which which takes in a set of custom or built-in attributes as a parameter. If any user has a custom or built-in attribute named in this set, it will be removed before the user is sent to LaunchDarkly.

1HashSet<String> privateAttributes = new HashSet<>();
2privateAttributes.add("name");  // built-in attribute
3privateAttributes.add("group"); // custom attribute
4
5LDConfig ldConfig = new LDConfig.Builder()
6    .setPrivateAttributeNames(privateAttributes)
7    .build();
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You can also mark attributes as private when building the user object itself by using the private versions of the builder methods to set the attributes. For example:

1LDUser user = new LDUser.Builder("aa0ceb")
2    .email("fake@example.com")
3    .privateName("Jane")
4    .privateCustom("group", "microsoft")
5    .build();
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When this user is sent back to LaunchDarkly, the name and group attributes will be removed.

Anonymous users

You can also distinguish logged-in users from anonymous users in the SDK, as follows:

1LDUser user = new LDUser.Builder("user key")
2    .anonymous(true)
3    .build();
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You can leave the key parameter in the Builder null or make it an empty string and the client will automatically set it to a LaunchDarkly-specific device-unique string that is consistent between app restarts and device reboots.

Anonymous users work just like regular users, except that they won't appear on your Users page in LaunchDarkly. You also can't search for anonymous users on your Features page, and you can't search or autocomplete by anonymous user keys. This is actually a good thing, because it keeps anonymous users from polluting your Users page!

Variation

The variation method determines whether a flag is enabled or not for a specific user. In Android, there is a variation method for each type (e.g. boolVariation, stringVariation):

1boolean variationResult = ldClient.boolVariation(flagKey, false);
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variation calls take the feature flag key and a fallback value.

The fallback value will only be returned if an error is encountered. For example, the fallback value is served if the feature flag key doesn't exist or the user doesn't have a key specified.

The variation call will automatically create a user in LaunchDarkly if a user with that user key doesn't exist already. There's no need to create users ahead of time (but if you do need to, take a look at identify).

VariationDetail

The variationDetail methods (boolVariationDetail, etc.) work the same as variation, but also provide additional "reason" information about how a flag value was calculated (for instance, if the user matched a specific rule). You can examine the "reason" data programmatically; you can also view it with data export, if you are capturing detailed analytics events for this flag.

To learn more, read Evaluation reasons.

All flags

The allFlags method produces a map of feature flag keys to their values for a specific user.

1ldClient.allFlags();
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Track

The track method allows you to record actions your users take in your application. In LaunchDarkly, you can tie these events to goals in A/B tests. You can also attach custom JSON data to your event by passing an extra JsonElement parameter to track. Here's a simple example:

1ldClient.track("your-goal-key", data);
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Offline mode

In some situations, you might want to stop making remote calls to LaunchDarkly and switch to the last known values for your feature flags. offline mode lets you do this easily.

1LDConfig ldConfig = new LDConfig.Builder() 
2    .setMobileKey("YOUR_MOBILE_KEY") 
3    .setOffline(true)
4    .build();
5
6LDClient ldClient = LDClient.init(this.getApplication(), ldConfig, user);
7
8// Or to switch an already-instantiated client to offline mode:
9ldClient.setOffline();
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Flush

Internally, the LaunchDarkly SDK keeps an event buffer for track calls. These are flushed periodically in a background thread. In some situations (for example, if you're testing out the SDK in a simulator), you may want to manually call flush to request any queued events to be sent immediately. Note that this call is still non-blocking, so it will return before the events are actually sent.

1ldClient.flush();
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The flush interval is configurable. If you need to change the interval, you can do so via the configuration.

Changing the User Context

If your app is used by multiple users on a single device, you may want to change users and have separate flag settings for each user. To achieve this, the SDK will store the last 5 user contexts on a single device, with support for switching between different user contexts.

You can use the identify method to switch user contexts:

1LDUser updatedUser = new LDUser.Builder(user)
2    .email("fake2@example.com")
3    .build();
4
5ldClient.identify(updatedUser);
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The identify call will load any saved flag values for the new user and immediately trigger an update of the latest flags from LaunchDarkly.

identify returns a Future to indicate completion. If you want to be sure subsequent code is using the latest values from the server, you can wait on the future using get.

Real-Time Updates

The SDK maintains what variations a user should receive locally in cache. The SDK evaluates flags based on what it has cached locally. To keep the local cache in sync with your flag configurations in LaunchDarkly, the SDK uses both a streaming strategy and a polling strategy. The SDK is highly configurable, but the default SDK configuration has low latency updates, minimal data usage, and minimal battery drain. Here is the default behavior:

1. When the app is foregrounded a Server-Sent Events streaming connection is opened to LaunchDarkly. The initial payload from the streaming connection contains the variations your user receives. This streaming connection stays open and idles unless there are updates. This requires minimal data and battery to maintain. The streaming connection stays open as long as your app is in the foreground and is connected to the internet.
2. When the app is backgrounded, the stream connection terminates. The SDK polls for flag updates every hour (or another interval you configure) to stay in sync. This strategy has higher latency, but optimizes battery and data usage.
3. When the app is foregrounded, the SDK reconnects to the stream which sends the latest flag values.
4. When streaming, the SDK actively monitors the network availability. It avoids requests when the network is unavailable, and reconnects when the network becomes available again. When polling, the SDK checks for network connectivity at the current polling interval, only making the request if the check succeeds. When it reconnects, it automatically syncs its local cache with LaunchDarkly.

This configuration means that you will get near real-time updates for your feature flag values when the app is in the foreground, and maximum efficiency when backgrounded. See the "customizing your client" section above for information on how to change your configuration.

To perform real-time updates in your app, your app will need to register listeners to be notified of changes to a flag's value when it is updated:

1String flagKey = "yourFlagKey";
2
3FeatureFlagChangeListener listener = new FeatureFlagChangeListener() {
4    @Override
5    public void onFeatureFlagChange(String flagKey) {
6        boolean newValue = LDClient.get().boolVariation(flagKey, false);
7    }
8};
9
10LDClient.get().registerFeatureFlagListener(flagKey, listener);
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The flag key passed to onFeatureFlagChange is the key of the updated flag, allowing a single listener to be registered for multiple flags.

Similarly you can unregister listeners to disable them:

1LDClient.get().unregisterFeatureFlagListener(flagKey, listener);
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Additionally an update listener interface is provided for cases where you would like to be notified any time the flag cache is updated. The application provides a class implementing LDAllFlagsListener which provides the SDK with the method onChange. Whenever the SDK's flag cache is updated it will call the onChange method with a list of flag keys for flags that were updated during the update to the flag cache. If no flag values changed, this list will be empty.

1LDAllFlagsListener listener = new LDAllFlagsListener() {
2    @Override
3    public void onChange(List<String> flagKeys) {
4        // Get new values for flagKeys or other operations
5    }
6};
7
8// register all flags listener
9LDClient.get().registerAllFlagsListener(listener);
10// when done with all flags listener it should be unregistered
11LDClient.get().unregisterAllFlagsListener(listener);
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Multiple Environments

LaunchDarkly's Android SDK supports having multiple LDClient instances tied to separate mobile keys. This allows evaluating flags from multiple environments.

All LDClient instances will evaluate against the same LDUser. The mobile keys for additional environments are specified, along with identifying names, in a map passed to your LDConfig object.

1Map<String, String> otherKeys = new HashMap<String, String>();
2otherKeys.put("platform", "PLATFORM_MOBILE_KEY");
3otherKeys.put("core", "CORE_MOBILE_KEY");
4
5LDConfig ldConfig = new LDConfig.Builder()
6    .setMobileKey("MOBILE_KEY")
7    .setSecondaryMobileKeys(otherKeys)
8    .build();
9
10LDUser user = new LDUser.Builder("user key")
11    .email("fake@example.com")
12    .build();
13
14LDClient.init(this.getApplication(), ldConfig, user);
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To access the secondary mobile key instances, use the getForMobileKey method on LDClient. This method takes the identifier name assigned to your environment key in the secondaryMobileKeys map and returns the associated LDClient instance.

1LDClient coreInstance = LDClient.getForMobileKey("core");
2coreInstance.boolVariation("core-flag", false);
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As all the client instances use the same LDUser object, some calls will affect all instances.

1LDClient coreInstance = LDClient.getForMobileKey("core");
2
3// Calls affect all LDClient Instances
4coreInstance.identify(/*User Object*/);
5coreInstance.flush();
6coreInstance.setOffline();
7coreInstance.setOnline();
8coreInstance.close();
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Track calls, listeners, and flag evaluation are all tied to the client instance they are evaluated against.

Monitoring SDK Status

The Android SDK exposes some of its internal status through new APIs to allow your application to monitor the SDK's status. This is provided primarily as a mechanism for the application to determine how recently the internal flag cache has been updated with the most recent values, as well as diagnosing potential reasons for the flag cache to be out of date.

The SDK has seven connectivity states dependent on its configuration, application foreground state, network connectivity, as well as calls explicitly setting the client offline or online. A summary of these states is given below.

The SDK also internally stores a timestamp of the most recent successful and failed connections to LaunchDarkly, as well as information related to the most recent failed connection. The LDClient method getConnectionInformation() returns a structure allowing retrieval of these fields.

1LDClient ldClient = LDClient.get();
2ConnectionInformation connectionInfo = ldClient.getConnectionInformation();
3// One of the seven modes described above
4ConnectionInformation.ConnectionMode connectionMode =
5  connectionInfo.getConnectionMode();
6// Most recent successful flag cache update in millis from the epoch
7// Or null if flags have never been retrieved
8Long lastSuccess = connectionInfo.getLastSuccessfulConnection();
9// Most recent unsuccessful flag cache update attempt in millis from the epoch
10// Or null if flag update has never been attempted
11Long lastSuccess = connectionInfo.getLastFailedConnection();
12// Most recent failure or null
13LDFailure ldFailure = connectionInfo.getLastFailure();
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LDFailure is a LaunchDarklyException with an associated FailureType. It may include a .cause() propagated from an underlying exception associated with the update's failure. The cause itself should be considered unstable as it is dependent on internal implementation, though the mechanism to retrieve it will be maintained. The failure types are summarized below.

If matching on the FailureType, a default case should be used to handle any future cases provided. The UNEXPECTED_RESPONSE_CODE case indicates that the LDFailure is can be cast to a LDInvalidResponseCodeFailure for more information. This more specific failure includes a response code and whether the failure is considered retryable. An example is given below.

1LDClient ldClient = LDClient.get();
2ConnectionInformation connectionInfo = ldClient.getConnectionInformation();
3LDFailure ldFailure = connectionInfo.getLastFailure();
4if (ldFailure != null) {
5    Timber.d("Received failure with message %s", ldFailure.getMessage());
6    // Retrieve the failure type
7    LDFailure.FailureType failureType = ldFailure.getFailureType();
8    switch (failureType) {
9        case INVALID_RESPONSE_BODY:
10            Timber.d("Received invalid response body");
11            break;
12        case NETWORK_FAILURE:
13            Timber.d("Network failure, may have bad connection");
14            break;
15        case UNEXPECTED_STREAM_ELEMENT_TYPE:
16            Timber.d("Unexpected stream element, may require update");
17            break;
18        case UNEXPECTED_RESPONSE_CODE:
19            LDInvalidResponseCodeFailure responseCodeFailure =
20                (LDInvalidResponseCodeFailure) ldFailure;
21            int responseCode = responseCodeFailure.getResponseCode();
22            if (responseCodeFailure.isRetryable()) {
23                Timber.d("Received invalid response code %d", responseCode);
24            } else {
25                Timber.d("Received invalid response code %d, giving up", responseCode);
26            }
27            break;
28        case UNKNOWN_ERROR:
29        default:
30            Timber.d("Unknown error");
31            break;
32    }
33
34    Throwable cause = ldFailure.getCause();
35    if (cause != null) {
36        // Do something with underlying cause
37    }
38}
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A callback based interface is also provided to allow notifying the application when the ConnectionMode changes as well as whenever the LDFailure in ConnectionStatus changes. The application must provide a class instance implementing LDStatusListener to the SDK client instance method registerStatusListener to register the listeners with the SDK. A brief example is given below.

1class MainActivity extends Activity {
2    private LDClient ldClient;
3    private LDStatusListener ldStatusListener;
4
5    @Override
6    protected void onCreate(Bundle savedInstanceState) {
7        super.onCreate(savedInstanceState);
8        setContentView(R.layout.activity_main);
9
10        ldStatusListener = new LDStatusListener() {
11            @Override
12            public void onConnectionModeChanged(ConnectionInformation connectionInfo) {
13                // handle new connection info
14            }
15
16            @Override
17            public void onInternalFailure(LDFailure ldFailure) {
18                // handle failure
19            }
20        };
21
22        ldClient = LDClient.get();
23        ldClient.registerStatusListener(ldStatusListener);
24    }
25
26    @Override
27    protected void onDestroy() {
28        super.onDestroy();
29        ldClient.unregisterStatusListener(ldStatusListener);
30    }
31}
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Troubleshooting

The Android SDK makes heavy use of the Timber logging. Include Timber in your application to enable debug output or production logging. An example is shown below to enable debug output when the application is built with a debug configuration.

1if (BuildConfig.DEBUG) {
2    Timber.plant(new Timber.DebugTree());
3}
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