Requests that your app makes to the network are a major cause of battery drain because they turn on power-consuming cellular or Wi-Fi radios. Beyond the power needed to send and receive packets, these radios expend extra power just turning on and keeping awake. Something as simple as a network request every 15 seconds can keep the mobile radio on continuously and quickly use up battery power.
There are three general types of regular updates:
- User-initiated. Performing an update based on some user behavior, such as a pull-to-refresh gesture.
- App-initiated. Performing an update on a recurring basis.
- Server-initiated. Performing an update in response to a notification from a server.
This topic looks at each of these and discusses additional ways they can be optimized to reduce battery drain.
Optimize user-initiated requests
User-initiated requests typically occur in response to some user behavior. For example, an app used to read the latest news articles may allow the user to perform a pull-to-refresh gesture to check for new articles. You can use the following techniques to respond to user-initiated requests while optimizing network use.
Throttle user requests
You may want to disregard some user-initiated requests if there is no need for them, such as multiple pull-to-refresh gestures over a short period of time to check for new data while the current data is still fresh. Acting on each request could waste a significant amount of power by keeping the radio awake. A more efficient approach is to throttle the user-initiated requests so that only one request can be made over a period of time, reducing how often the radio is used.
Use a cache
By caching your app’s data, you’re creating a local copy of the information that your app needs to reference. Your app can then access the same local copy of the information multiple times without having to open a network connection to make new requests.
You should cache data as aggressively as possible, including static resources and on-demand downloads such as full-size images. You can use HTTP cache headers to ensure that your caching strategy doesn’t result in your app displaying stale data. For more information on caching network responses, see Avoid redundant downloads.
On Android 11 and higher, your app can use the same large datasets that other apps use for use cases such as machine learning and media playback. When your app needs to access a shared dataset, it can first check for a cached version before attempting to download a new copy. To learn more about shared datasets, see Access shared datasets.
Use greater bandwidth to download more data less often
When connected over a wireless radio, higher bandwidth generally comes at the price of higher battery cost, meaning that 5G typically consumes more energy than LTE, which is in turn more expensive than 3G.
This means that while the underlying radio state varies based on the radio technology, generally speaking the relative battery impact of the state change tail-time is greater for higher bandwidth radios. For more information on tail-time, see The radio state machine.
At the same time, the higher bandwidth means you can prefetch more aggressively, downloading more data over the same time. Perhaps less intuitively, because the tail-time battery cost is relatively higher, it's also more efficient to keep the radio active for longer periods during each transfer session to reduce the frequency of updates.
For example, if an LTE radio has double the bandwidth and double the energy cost of 3G, you should download four times as much data during each session—or potentially as much as 10MB. When downloading this much data, it's important to consider the effect of your prefetching on the available local storage and flush your prefetch cache regularly.
You can use the
ConnectivityManager to register
a listener for the default network, and the
TelephonyManager to register
a PhoneStateListener to
determine the current device connection type. Once the connection type is known,
you can modify your prefetching routines accordingly:
Kotlin
val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
val tm = getSystemService(Context.TELEPHONY_SERVICE) as TelephonyManager
private var hasWifi = false
private var hasCellular = false
private var cellModifier: Float = 1f
private val networkCallback = object : ConnectivityManager.NetworkCallback() {
// Network capabilities have changed for the network
override fun onCapabilitiesChanged(
network: Network,
networkCapabilities: NetworkCapabilities
) {
super.onCapabilitiesChanged(network, networkCapabilities)
hasCellular = networkCapabilities
.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)
hasWifi = networkCapabilities
.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)
}
}
private val phoneStateListener = object : PhoneStateListener() {
override fun onPreciseDataConnectionStateChanged(
dataConnectionState: PreciseDataConnectionState
) {
cellModifier = when (dataConnectionState.networkType) {
TelephonyManager.NETWORK_TYPE_LTE or TelephonyManager.NETWORK_TYPE_HSPAP -> 4f
TelephonyManager.NETWORK_TYPE_EDGE or TelephonyManager.NETWORK_TYPE_GPRS -> 1/2f
else -> 1f
}
}
private class NetworkState {
private var defaultNetwork: Network? = null
private var defaultCapabilities: NetworkCapabilities? = null
fun setDefaultNetwork(network: Network?, caps: NetworkCapabilities?) = synchronized(this) {
defaultNetwork = network
defaultCapabilities = caps
}
val isDefaultNetworkWifi
get() = synchronized(this) {
defaultCapabilities?.hasTransport(TRANSPORT_WIFI) ?: false
}
val isDefaultNetworkCellular
get() = synchronized(this) {
defaultCapabilities?.hasTransport(TRANSPORT_CELLULAR) ?: false
}
val isDefaultNetworkUnmetered
get() = synchronized(this) {
defaultCapabilities?.hasCapability(NET_CAPABILITY_NOT_METERED) ?: false
}
var cellNetworkType: Int = TelephonyManager.NETWORK_TYPE_UNKNOWN
get() = synchronized(this) { field }
set(t) = synchronized(this) { field = t }
private val cellModifier: Float
get() = synchronized(this) {
when (cellNetworkType) {
TelephonyManager.NETWORK_TYPE_LTE or TelephonyManager.NETWORK_TYPE_HSPAP -> 4f
TelephonyManager.NETWORK_TYPE_EDGE or TelephonyManager.NETWORK_TYPE_GPRS -> 1 / 2f
else -> 1f
}
}
val prefetchCacheSize: Int
get() = when {
isDefaultNetworkWifi -> MAX_PREFETCH_CACHE
isDefaultNetworkCellular -> (DEFAULT_PREFETCH_CACHE * cellModifier).toInt()
else -> DEFAULT_PREFETCH_CACHE
}
}
private val networkState = NetworkState()
private val networkCallback = object : ConnectivityManager.NetworkCallback() {
// Network capabilities have changed for the network
override fun onCapabilitiesChanged(
network: Network,
networkCapabilities: NetworkCapabilities
) {
networkState.setDefaultNetwork(network, networkCapabilities)
}
override fun onLost(network: Network?) {
networkState.setDefaultNetwork(null, null)
}
}
private val telephonyCallback = object : TelephonyCallback(), TelephonyCallback.PreciseDataConnectionStateListener {
override fun onPreciseDataConnectionStateChanged(dataConnectionState: PreciseDataConnectionState) {
networkState.cellNetworkType = dataConnectionState.networkType
}
}
connectivityManager.registerDefaultNetworkCallback(networkCallback)
telephonyManager.registerTelephonyCallback(telephonyCallback)
private val prefetchCacheSize: Int
get() {
return when {
hasWifi -> MAX_PREFETCH_CACHE
hasCellular -> (DEFAULT_PREFETCH_CACHE * cellModifier).toInt()
else -> DEFAULT_PREFETCH_CACHE
}
}
}
Java
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
TelephonyManager tm =
(TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
private boolean hasWifi = false;
private boolean hasCellular = false;
private float cellModifier = 1f;
private ConnectivityManager.NetworkCallback networkCallback = new ConnectivityManager.NetworkCallback() {
@Override
public void onCapabilitiesChanged(
@NonNull Network network,
@NonNull NetworkCapabilities networkCapabilities
) {
super.onCapabilitiesChanged(network, networkCapabilities);
hasCellular = networkCapabilities
.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR);
hasWifi = networkCapabilities
.hasTransport(NetworkCapabilities.TRANSPORT_WIFI);
}
};
private PhoneStateListener phoneStateListener = new PhoneStateListener() {
@Override
public void onPreciseDataConnectionStateChanged(
@NonNull PreciseDataConnectionState dataConnectionState
) {
switch (dataConnectionState.getNetworkType()) {
case (TelephonyManager.NETWORK_TYPE_LTE |
TelephonyManager.NETWORK_TYPE_HSPAP):
cellModifier = 4;
Break;
case (TelephonyManager.NETWORK_TYPE_EDGE |
TelephonyManager.NETWORK_TYPE_GPRS):
cellModifier = 1/2.0f;
Break;
default:
cellModifier = 1;
Break;
}
}
};
cm.registerDefaultNetworkCallback(networkCallback);
tm.listen(
phoneStateListener,
PhoneStateListener.LISTEN_PRECISE_DATA_CONNECTION_STATE
);
public int getPrefetchCacheSize() {
if (hasWifi) {
return MAX_PREFETCH_SIZE;
}
if (hasCellular) {
return (int) (DEFAULT_PREFETCH_SIZE * cellModifier);
}
return DEFAULT_PREFETCH_SIZE;
}
Optimize app-initiated requests
App-initiated requests typically occur on a schedule, such as an app that sends logs or analytics to a backend service. When dealing with app-initiated requests, consider the priority of those requests, whether they can be batched together, and whether they can be deferred until the device is charging or connected to an unmetered network. These requests can be optimized with careful scheduling and by using libraries such as WorkManager.
Batch network requests
On a mobile device, the process of turning on the radio, making a connection, and keeping the radio awake uses a large amount of power. For this reason, processing individual requests at random times can consume significant power and reduce battery life. A more efficient approach is to queue a set of network requests and process them together. This allows the system to pay the power cost of turning on the radio just once, and still get all the data requested by an app.
Use WorkManager
You can use the WorkManager library to perform work on an efficient schedule
that considers whether specific conditions are met, such as network availability
and power status. For example, suppose you have a
Worker subclass called
DownloadHeadlinesWorker that retrieves the latest news headlines. This worker
can be scheduled to run every hour, provided the device is connected to an
unmetered network and device’s battery isn’t low, with a custom retry strategy
if there are any problems retrieving the data, as shown below:
Kotlin
val constraints = Constraints.Builder()
.setRequiredNetworkType(NetworkType.UNMETERED)
.setRequiresBatteryNotLow(true)
.build()
val request =
PeriodicWorkRequestBuilder<DownloadHeadlinesWorker>(1, TimeUnit.HOURS)
.setConstraints(constraints)
.setBackoffCriteria(BackoffPolicy.LINEAR, 1L, TimeUnit.MINUTES)
.build()
WorkManager.getInstance(context).enqueue(request)
Java
Constraints constraints = new Constraints.Builder()
.setRequiredNetworkType(NetworkType.UNMETERED)
.setRequiresBatteryNotLow(true)
.build();
WorkRequest request = new PeriodicWorkRequest.Builder(DownloadHeadlinesWorker.class, 1, TimeUnit.HOURS)
.setBackoffCriteria(BackoffPolicy.LINEAR, 1L, TimeUnit.MINUTES)
.build();
WorkManager.getInstance(this).enqueue(request);
In addition to WorkManager, the Android platform provides several other tools to help you create an efficient schedule for completing networking tasks, such as polling. To learn more about using these tools, see the Guide to background processing.
Optimize server-initiated requests
Server-initiated requests typically occur in response to a notification from a server. For example, an app used to read the latest news articles may receive a notification about a new batch of articles that fit the user’s personalization preferences, which it then downloads.
Send server updates with Firebase Cloud Messaging
Firebase Cloud Messaging (FCM) is a lightweight mechanism used to transmit data from a server to a particular app instance. Using FCM, your server can notify your app running on a particular device that there is new data available for it.
Compared to polling, where your app must regularly ping the server to query for new data, this event-driven model allows your app to create a new connection only when it knows there is data to download. The model minimizes unnecessary connections and reduces latency when updating information within your app.
FCM is implemented using a persistent TCP/IP connection. This minimizes the number of persistent connections and allows the platform to optimize bandwidth and minimize the associated impact on battery life.