If you don't need to send broadcasts across applications, consider using * this class with {@link android.support.v4.content.LocalBroadcastManager} instead * of the more general facilities described below. This will give you a much * more efficient implementation (no cross-process communication needed) and allow * you to avoid thinking about any security issues related to other applications * being able to receive or send your broadcasts. * *
You can either dynamically register an instance of this class with
* {@link Context#registerReceiver Context.registerReceiver()}
* or statically publish an implementation through the
* {@link android.R.styleable#AndroidManifestReceiver <receiver>}
* tag in your AndroidManifest.xml.
*
*
Note: * If registering a receiver in your * {@link android.app.Activity#onResume() Activity.onResume()} * implementation, you should unregister it in * {@link android.app.Activity#onPause() Activity.onPause()}. * (You won't receive intents when paused, * and this will cut down on unnecessary system overhead). Do not unregister in * {@link android.app.Activity#onSaveInstanceState(android.os.Bundle) Activity.onSaveInstanceState()}, * because this won't be called if the user moves back in the history * stack. * *
There are two major classes of broadcasts that can be received:
*Even in the case of normal broadcasts, the system may in some * situations revert to delivering the broadcast one receiver at a time. In * particular, for receivers that may require the creation of a process, only * one will be run at a time to avoid overloading the system with new processes. * In this situation, however, the non-ordered semantics hold: these receivers still * cannot return results or abort their broadcast.
* *Note that, although the Intent class is used for sending and receiving * these broadcasts, the Intent broadcast mechanism here is completely separate * from Intents that are used to start Activities with * {@link Context#startActivity Context.startActivity()}. * There is no way for a BroadcastReceiver * to see or capture Intents used with startActivity(); likewise, when * you broadcast an Intent, you will never find or start an Activity. * These two operations are semantically very different: starting an * Activity with an Intent is a foreground operation that modifies what the * user is currently interacting with; broadcasting an Intent is a background * operation that the user is not normally aware of. * *
The BroadcastReceiver class (when launched as a component through * a manifest's {@link android.R.styleable#AndroidManifestReceiver <receiver>} * tag) is an important part of an * application's overall lifecycle.
* *Topics covered here: *
* *For information about how to use this class to receive and resolve intents, read the * Intents and Intent Filters * developer guide.
*Receivers used with the {@link Context} APIs are by their nature a * cross-application facility, so you must consider how other applications * may be able to abuse your use of them. Some things to consider are: * *
The Intent namespace is global. Make sure that Intent action names and * other strings are written in a namespace you own, or else you may inadvertantly * conflict with other applications. *
When you use {@link Context#registerReceiver(BroadcastReceiver, IntentFilter)}, * any application may send broadcasts to that registered receiver. You can * control who can send broadcasts to it through permissions described below. *
When you publish a receiver in your application's manifest and specify
* intent-filters for it, any other application can send broadcasts to it regardless
* of the filters you specify. To prevent others from sending to it, make it
* unavailable to them with android:exported="false".
*
When you use {@link Context#sendBroadcast(Intent)} or related methods, * normally any other application can receive these broadcasts. You can control who * can receive such broadcasts through permissions described below. Alternatively, * starting with {@link android.os.Build.VERSION_CODES#ICE_CREAM_SANDWICH}, you * can also safely restrict the broadcast to a single application with * {@link Intent#setPackage(String) Intent.setPackage} *
None of these issues exist when using * {@link android.support.v4.content.LocalBroadcastManager}, since intents * broadcast it never go outside of the current process. * *
Access permissions can be enforced by either the sender or receiver * of a broadcast. * *
To enforce a permission when sending, you supply a non-null
* permission argument to
* {@link Context#sendBroadcast(Intent, String)} or
* {@link Context#sendOrderedBroadcast(Intent, String, BroadcastReceiver, android.os.Handler, int, String, Bundle)}.
* Only receivers who have been granted this permission
* (by requesting it with the
* {@link android.R.styleable#AndroidManifestUsesPermission <uses-permission>}
* tag in their AndroidManifest.xml) will be able to receive
* the broadcast.
*
*
To enforce a permission when receiving, you supply a non-null
* permission when registering your receiver -- either when calling
* {@link Context#registerReceiver(BroadcastReceiver, IntentFilter, String, android.os.Handler)}
* or in the static
* {@link android.R.styleable#AndroidManifestReceiver <receiver>}
* tag in your AndroidManifest.xml. Only broadcasters who have
* been granted this permission (by requesting it with the
* {@link android.R.styleable#AndroidManifestUsesPermission <uses-permission>}
* tag in their AndroidManifest.xml) will be able to send an
* Intent to the receiver.
*
*
See the Security and Permissions * document for more information on permissions and security in general. * * *
A BroadcastReceiver object is only valid for the duration of the call * to {@link #onReceive}. Once your code returns from this function, * the system considers the object to be finished and no longer active. * *
This has important repercussions to what you can do in an * {@link #onReceive} implementation: anything that requires asynchronous * operation is not available, because you will need to return from the * function to handle the asynchronous operation, but at that point the * BroadcastReceiver is no longer active and thus the system is free to kill * its process before the asynchronous operation completes. * *
In particular, you may not show a dialog or bind to a service from * within a BroadcastReceiver. For the former, you should instead use the * {@link android.app.NotificationManager} API. For the latter, you can * use {@link android.content.Context#startService Context.startService()} to * send a command to the service. * * *
A process that is currently executing a BroadcastReceiver (that is, * currently running the code in its {@link #onReceive} method) is * considered to be a foreground process and will be kept running by the * system except under cases of extreme memory pressure. * *
Once you return from onReceive(), the BroadcastReceiver is no longer * active, and its hosting process is only as important as any other application * components that are running in it. This is especially important because if * that process was only hosting the BroadcastReceiver (a common case for * applications that the user has never or not recently interacted with), then * upon returning from onReceive() the system will consider its process * to be empty and aggressively kill it so that resources are available for other * more important processes. * *
This means that for longer-running operations you will often use * a {@link android.app.Service} in conjunction with a BroadcastReceiver to keep * the containing process active for the entire time of your operation. */ public abstract class BroadcastReceiver { private PendingResult mPendingResult; private boolean mDebugUnregister; /** * State for a result that is pending for a broadcast receiver. Returned * by {@link BroadcastReceiver#goAsync() goAsync()} * while in {@link BroadcastReceiver#onReceive BroadcastReceiver.onReceive()}. * This allows you to return from onReceive() without having the broadcast * terminate; you must call {@link #finish()} once you are done with the * broadcast. This allows you to process the broadcast off of the main * thread of your app. * *
Note on threading: the state inside of this class is not itself * thread-safe, however you can use it from any thread if you properly * sure that you do not have races. Typically this means you will hand * the entire object to another thread, which will be solely responsible * for setting any results and finally calling {@link #finish()}. */ public static class PendingResult { /** @hide */ public static final int TYPE_COMPONENT = 0; /** @hide */ public static final int TYPE_REGISTERED = 1; /** @hide */ public static final int TYPE_UNREGISTERED = 2; final int mType; final boolean mOrderedHint; final boolean mInitialStickyHint; final IBinder mToken; int mResultCode; String mResultData; Bundle mResultExtras; boolean mAbortBroadcast; boolean mFinished; /** @hide */ public PendingResult(int resultCode, String resultData, Bundle resultExtras, int type, boolean ordered, boolean sticky, IBinder token) { mResultCode = resultCode; mResultData = resultData; mResultExtras = resultExtras; mType = type; mOrderedHint = ordered; mInitialStickyHint = sticky; mToken = token; } /** * Version of {@link BroadcastReceiver#setResultCode(int) * BroadcastReceiver.setResultCode(int)} for * asynchronous broadcast handling. */ public final void setResultCode(int code) { checkSynchronousHint(); mResultCode = code; } /** * Version of {@link BroadcastReceiver#getResultCode() * BroadcastReceiver.getResultCode()} for * asynchronous broadcast handling. */ public final int getResultCode() { return mResultCode; } /** * Version of {@link BroadcastReceiver#setResultData(String) * BroadcastReceiver.setResultData(String)} for * asynchronous broadcast handling. */ public final void setResultData(String data) { checkSynchronousHint(); mResultData = data; } /** * Version of {@link BroadcastReceiver#getResultData() * BroadcastReceiver.getResultData()} for * asynchronous broadcast handling. */ public final String getResultData() { return mResultData; } /** * Version of {@link BroadcastReceiver#setResultExtras(Bundle) * BroadcastReceiver.setResultExtras(Bundle)} for * asynchronous broadcast handling. */ public final void setResultExtras(Bundle extras) { checkSynchronousHint(); mResultExtras = extras; } /** * Version of {@link BroadcastReceiver#getResultExtras(boolean) * BroadcastReceiver.getResultExtras(boolean)} for * asynchronous broadcast handling. */ public final Bundle getResultExtras(boolean makeMap) { Bundle e = mResultExtras; if (!makeMap) return e; if (e == null) mResultExtras = e = new Bundle(); return e; } /** * Version of {@link BroadcastReceiver#setResult(int, String, Bundle) * BroadcastReceiver.setResult(int, String, Bundle)} for * asynchronous broadcast handling. */ public final void setResult(int code, String data, Bundle extras) { checkSynchronousHint(); mResultCode = code; mResultData = data; mResultExtras = extras; } /** * Version of {@link BroadcastReceiver#getAbortBroadcast() * BroadcastReceiver.getAbortBroadcast()} for * asynchronous broadcast handling. */ public final boolean getAbortBroadcast() { return mAbortBroadcast; } /** * Version of {@link BroadcastReceiver#abortBroadcast() * BroadcastReceiver.abortBroadcast()} for * asynchronous broadcast handling. */ public final void abortBroadcast() { checkSynchronousHint(); mAbortBroadcast = true; } /** * Version of {@link BroadcastReceiver#clearAbortBroadcast() * BroadcastReceiver.clearAbortBroadcast()} for * asynchronous broadcast handling. */ public final void clearAbortBroadcast() { mAbortBroadcast = false; } /** * Finish the broadcast. The current result will be sent and the * next broadcast will proceed. */ public final void finish() { if (mType == TYPE_COMPONENT) { final IActivityManager mgr = ActivityManagerNative.getDefault(); if (QueuedWork.hasPendingWork()) { // If this is a broadcast component, we need to make sure any // queued work is complete before telling AM we are done, so // we don't have our process killed before that. We now know // there is pending work; put another piece of work at the end // of the list to finish the broadcast, so we don't block this // thread (which may be the main thread) to have it finished. // // Note that we don't need to use QueuedWork.add() with the // runnable, since we know the AM is waiting for us until the // executor gets to it. QueuedWork.singleThreadExecutor().execute( new Runnable() { @Override public void run() { if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG, "Finishing broadcast after work to component " + mToken); sendFinished(mgr); } }); } else { if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG, "Finishing broadcast to component " + mToken); sendFinished(mgr); } } else if (mOrderedHint && mType != TYPE_UNREGISTERED) { if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG, "Finishing broadcast to " + mToken); final IActivityManager mgr = ActivityManagerNative.getDefault(); sendFinished(mgr); } } /** @hide */ public void setExtrasClassLoader(ClassLoader cl) { if (mResultExtras != null) { mResultExtras.setClassLoader(cl); } } /** @hide */ public void sendFinished(IActivityManager am) { synchronized (this) { if (mFinished) { throw new IllegalStateException("Broadcast already finished"); } mFinished = true; try { if (mResultExtras != null) { mResultExtras.setAllowFds(false); } if (mOrderedHint) { am.finishReceiver(mToken, mResultCode, mResultData, mResultExtras, mAbortBroadcast); } else { // This broadcast was sent to a component; it is not ordered, // but we still need to tell the activity manager we are done. am.finishReceiver(mToken, 0, null, null, false); } } catch (RemoteException ex) { } } } void checkSynchronousHint() { // Note that we don't assert when receiving the initial sticky value, // since that may have come from an ordered broadcast. We'll catch // them later when the real broadcast happens again. if (mOrderedHint || mInitialStickyHint) { return; } RuntimeException e = new RuntimeException( "BroadcastReceiver trying to return result during a non-ordered broadcast"); e.fillInStackTrace(); Log.e("BroadcastReceiver", e.getMessage(), e); } } public BroadcastReceiver() { } /** * This method is called when the BroadcastReceiver is receiving an Intent * broadcast. During this time you can use the other methods on * BroadcastReceiver to view/modify the current result values. This method * is always called within the main thread of its process, unless you * explicitly asked for it to be scheduled on a different thread using * {@link android.content.Context#registerReceiver(BroadcastReceiver, * IntentFilter, String, android.os.Handler)}. When it runs on the main * thread you should * never perform long-running operations in it (there is a timeout of * 10 seconds that the system allows before considering the receiver to * be blocked and a candidate to be killed). You cannot launch a popup dialog * in your implementation of onReceive(). * *
If this BroadcastReceiver was launched through a <receiver> tag, * then the object is no longer alive after returning from this * function. This means you should not perform any operations that * return a result to you asynchronously -- in particular, for interacting * with services, you should use * {@link Context#startService(Intent)} instead of * {@link Context#bindService(Intent, ServiceConnection, int)}. If you wish * to interact with a service that is already running, you can use * {@link #peekService}. * *
The Intent filters used in {@link android.content.Context#registerReceiver} * and in application manifests are not guaranteed to be exclusive. They * are hints to the operating system about how to find suitable recipients. It is * possible for senders to force delivery to specific recipients, bypassing filter * resolution. For this reason, {@link #onReceive(Context, Intent) onReceive()} * implementations should respond only to known actions, ignoring any unexpected * Intents that they may receive. * * @param context The Context in which the receiver is running. * @param intent The Intent being received. */ public abstract void onReceive(Context context, Intent intent); /** * This can be called by an application in {@link #onReceive} to allow * it to keep the broadcast active after returning from that function. * This does not change the expectation of being relatively * responsive to the broadcast (finishing it within 10s), but does allow * the implementation to move work related to it over to another thread * to avoid glitching the main UI thread due to disk IO. * * @return Returns a {@link PendingResult} representing the result of * the active broadcast. The BroadcastRecord itself is no longer active; * all data and other interaction must go through {@link PendingResult} * APIs. The {@link PendingResult#finish PendingResult.finish()} method * must be called once processing of the broadcast is done. */ public final PendingResult goAsync() { PendingResult res = mPendingResult; mPendingResult = null; return res; } /** * Provide a binder to an already-running service. This method is synchronous * and will not start the target service if it is not present, so it is safe * to call from {@link #onReceive}. * * @param myContext The Context that had been passed to {@link #onReceive(Context, Intent)} * @param service The Intent indicating the service you wish to use. See {@link * Context#startService(Intent)} for more information. */ public IBinder peekService(Context myContext, Intent service) { IActivityManager am = ActivityManagerNative.getDefault(); IBinder binder = null; try { service.setAllowFds(false); binder = am.peekService(service, service.resolveTypeIfNeeded( myContext.getContentResolver())); } catch (RemoteException e) { } return binder; } /** * Change the current result code of this broadcast; only works with * broadcasts sent through * {@link Context#sendOrderedBroadcast(Intent, String) * Context.sendOrderedBroadcast}. Often uses the * Activity {@link android.app.Activity#RESULT_CANCELED} and * {@link android.app.Activity#RESULT_OK} constants, though the * actual meaning of this value is ultimately up to the broadcaster. * *
This method does not work with non-ordered broadcasts such * as those sent with {@link Context#sendBroadcast(Intent) * Context.sendBroadcast}
* * @param code The new result code. * * @see #setResult(int, String, Bundle) */ public final void setResultCode(int code) { checkSynchronousHint(); mPendingResult.mResultCode = code; } /** * Retrieve the current result code, as set by the previous receiver. * * @return int The current result code. */ public final int getResultCode() { return mPendingResult != null ? mPendingResult.mResultCode : 0; } /** * Change the current result data of this broadcast; only works with * broadcasts sent through * {@link Context#sendOrderedBroadcast(Intent, String) * Context.sendOrderedBroadcast}. This is an arbitrary * string whose interpretation is up to the broadcaster. * *This method does not work with non-ordered broadcasts such * as those sent with {@link Context#sendBroadcast(Intent) * Context.sendBroadcast}
* * @param data The new result data; may be null. * * @see #setResult(int, String, Bundle) */ public final void setResultData(String data) { checkSynchronousHint(); mPendingResult.mResultData = data; } /** * Retrieve the current result data, as set by the previous receiver. * Often this is null. * * @return String The current result data; may be null. */ public final String getResultData() { return mPendingResult != null ? mPendingResult.mResultData : null; } /** * Change the current result extras of this broadcast; only works with * broadcasts sent through * {@link Context#sendOrderedBroadcast(Intent, String) * Context.sendOrderedBroadcast}. This is a Bundle * holding arbitrary data, whose interpretation is up to the * broadcaster. Can be set to null. Calling this method completely * replaces the current map (if any). * *This method does not work with non-ordered broadcasts such * as those sent with {@link Context#sendBroadcast(Intent) * Context.sendBroadcast}
* * @param extras The new extra data map; may be null. * * @see #setResult(int, String, Bundle) */ public final void setResultExtras(Bundle extras) { checkSynchronousHint(); mPendingResult.mResultExtras = extras; } /** * Retrieve the current result extra data, as set by the previous receiver. * Any changes you make to the returned Map will be propagated to the next * receiver. * * @param makeMap If true then a new empty Map will be made for you if the * current Map is null; if false you should be prepared to * receive a null Map. * * @return Map The current extras map. */ public final Bundle getResultExtras(boolean makeMap) { if (mPendingResult == null) { return null; } Bundle e = mPendingResult.mResultExtras; if (!makeMap) return e; if (e == null) mPendingResult.mResultExtras = e = new Bundle(); return e; } /** * Change all of the result data returned from this broadcasts; only works * with broadcasts sent through * {@link Context#sendOrderedBroadcast(Intent, String) * Context.sendOrderedBroadcast}. All current result data is replaced * by the value given to this method. * *This method does not work with non-ordered broadcasts such * as those sent with {@link Context#sendBroadcast(Intent) * Context.sendBroadcast}
* * @param code The new result code. Often uses the * Activity {@link android.app.Activity#RESULT_CANCELED} and * {@link android.app.Activity#RESULT_OK} constants, though the * actual meaning of this value is ultimately up to the broadcaster. * @param data The new result data. This is an arbitrary * string whose interpretation is up to the broadcaster; may be null. * @param extras The new extra data map. This is a Bundle * holding arbitrary data, whose interpretation is up to the * broadcaster. Can be set to null. This completely * replaces the current map (if any). */ public final void setResult(int code, String data, Bundle extras) { checkSynchronousHint(); mPendingResult.mResultCode = code; mPendingResult.mResultData = data; mPendingResult.mResultExtras = extras; } /** * Returns the flag indicating whether or not this receiver should * abort the current broadcast. * * @return True if the broadcast should be aborted. */ public final boolean getAbortBroadcast() { return mPendingResult != null ? mPendingResult.mAbortBroadcast : false; } /** * Sets the flag indicating that this receiver should abort the * current broadcast; only works with broadcasts sent through * {@link Context#sendOrderedBroadcast(Intent, String) * Context.sendOrderedBroadcast}. This will prevent * any other broadcast receivers from receiving the broadcast. It will still * call {@link #onReceive} of the BroadcastReceiver that the caller of * {@link Context#sendOrderedBroadcast(Intent, String) * Context.sendOrderedBroadcast} passed in. * *This method does not work with non-ordered broadcasts such * as those sent with {@link Context#sendBroadcast(Intent) * Context.sendBroadcast}
*/ public final void abortBroadcast() { checkSynchronousHint(); mPendingResult.mAbortBroadcast = true; } /** * Clears the flag indicating that this receiver should abort the current * broadcast. */ public final void clearAbortBroadcast() { if (mPendingResult != null) { mPendingResult.mAbortBroadcast = false; } } /** * Returns true if the receiver is currently processing an ordered * broadcast. */ public final boolean isOrderedBroadcast() { return mPendingResult != null ? mPendingResult.mOrderedHint : false; } /** * Returns true if the receiver is currently processing the initial * value of a sticky broadcast -- that is, the value that was last * broadcast and is currently held in the sticky cache, so this is * not directly the result of a broadcast right now. */ public final boolean isInitialStickyBroadcast() { return mPendingResult != null ? mPendingResult.mInitialStickyHint : false; } /** * For internal use, sets the hint about whether this BroadcastReceiver is * running in ordered mode. */ public final void setOrderedHint(boolean isOrdered) { // Accidentally left in the SDK. } /** * For internal use to set the result data that is active. @hide */ public final void setPendingResult(PendingResult result) { mPendingResult = result; } /** * For internal use to set the result data that is active. @hide */ public final PendingResult getPendingResult() { return mPendingResult; } /** * Control inclusion of debugging help for mismatched * calls to {@ Context#registerReceiver(BroadcastReceiver, IntentFilter) * Context.registerReceiver()}. * If called with true, before given to registerReceiver(), then the * callstack of the following {@link Context#unregisterReceiver(BroadcastReceiver) * Context.unregisterReceiver()} call is retained, to be printed if a later * incorrect unregister call is made. Note that doing this requires retaining * information about the BroadcastReceiver for the lifetime of the app, * resulting in a leak -- this should only be used for debugging. */ public final void setDebugUnregister(boolean debug) { mDebugUnregister = debug; } /** * Return the last value given to {@link #setDebugUnregister}. */ public final boolean getDebugUnregister() { return mDebugUnregister; } void checkSynchronousHint() { if (mPendingResult == null) { throw new IllegalStateException("Call while result is not pending"); } // Note that we don't assert when receiving the initial sticky value, // since that may have come from an ordered broadcast. We'll catch // them later when the real broadcast happens again. if (mPendingResult.mOrderedHint || mPendingResult.mInitialStickyHint) { return; } RuntimeException e = new RuntimeException( "BroadcastReceiver trying to return result during a non-ordered broadcast"); e.fillInStackTrace(); Log.e("BroadcastReceiver", e.getMessage(), e); } }