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Merge "docs: changes to broadcast documentation" into nyc-mr1-dev

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This commit is contained in:
Mark Lu
2016-12-16 04:48:36 +00:00
committed by Android (Google) Code Review
parent 8cc9f081aa 33ec106d22
commit 7b22d549d4
2 changed files with 74 additions and 225 deletions
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292
core/java/android/content/BroadcastReceiver.java
View File

@ -27,189 +27,25 @@ import android.util.Log;
import android.util.Slog;
/**
* Base class for code that will receive intents sent by sendBroadcast().
*
* <p>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.
* Base class for code that receives and handles broadcast intents sent by
* {@link android.content.Context#sendBroadcast(Intent)}.
*
* <p>You can either dynamically register an instance of this class with
* {@link Context#registerReceiver Context.registerReceiver()}
* or statically publish an implementation through the
* or statically declare an implementation with the
* {@link android.R.styleable#AndroidManifestReceiver &lt;receiver&gt;}
* tag in your <code>AndroidManifest.xml</code>.
*
* <p><em><strong>Note:</strong></em>
* &nbsp;&nbsp;&nbsp;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.
*
* <p>There are two major classes of broadcasts that can be received:</p>
* <ul>
* <li> <b>Normal broadcasts</b> (sent with {@link Context#sendBroadcast(Intent)
* Context.sendBroadcast}) are completely asynchronous. All receivers of the
* broadcast are run in an undefined order, often at the same time. This is
* more efficient, but means that receivers cannot use the result or abort
* APIs included here.
* <li> <b>Ordered broadcasts</b> (sent with {@link Context#sendOrderedBroadcast(Intent, String)
* Context.sendOrderedBroadcast}) are delivered to one receiver at a time.
* As each receiver executes in turn, it can propagate a result to the next
* receiver, or it can completely abort the broadcast so that it won't be passed
* to other receivers. The order receivers run in can be controlled with the
* {@link android.R.styleable#AndroidManifestIntentFilter_priority
* android:priority} attribute of the matching intent-filter; receivers with
* the same priority will be run in an arbitrary order.
* </ul>
*
* <p>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.</p>
*
* <p>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.
*
* <p>The BroadcastReceiver class (when launched as a component through
* a manifest's {@link android.R.styleable#AndroidManifestReceiver &lt;receiver&gt;}
* tag) is an important part of an
* <a href="{@docRoot}guide/topics/fundamentals.html#lcycles">application's overall lifecycle</a>.</p>
*
* <p>Topics covered here:
* <ol>
* <li><a href="#Security">Security</a>
* <li><a href="#ReceiverLifecycle">Receiver Lifecycle</a>
* <li><a href="#ProcessLifecycle">Process Lifecycle</a>
* </ol>
*
* <div class="special reference">
* <h3>Developer Guides</h3>
* <p>For information about how to use this class to receive and resolve intents, read the
* <a href="{@docRoot}guide/topics/intents/intents-filters.html">Intents and Intent Filters</a>
* developer guide.</p>
* </div>
* <p>For more information about using BroadcastReceiver, read the
* <a href="{@docRoot}guide/components/broadcasts.html">Broadcasts</a> developer guide.</p></div>
*
* <a name="Security"></a>
* <h3>Security</h3>
*
* <p>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:
*
* <ul>
* <li><p>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 inadvertently
* conflict with other applications.
* <li><p>When you use {@link Context#registerReceiver(BroadcastReceiver, IntentFilter)},
* <em>any</em> application may send broadcasts to that registered receiver. You can
* control who can send broadcasts to it through permissions described below.
* <li><p>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 <code>android:exported="false"</code>.
* <li><p>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}
* </ul>
*
* <p>None of these issues exist when using
* {@link android.support.v4.content.LocalBroadcastManager}, since intents
* broadcast it never go outside of the current process.
*
* <p>Access permissions can be enforced by either the sender or receiver
* of a broadcast.
*
* <p>To enforce a permission when sending, you supply a non-null
* <var>permission</var> 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 &lt;uses-permission&gt;}
* tag in their <code>AndroidManifest.xml</code>) will be able to receive
* the broadcast.
*
* <p>To enforce a permission when receiving, you supply a non-null
* <var>permission</var> 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 &lt;receiver&gt;}
* tag in your <code>AndroidManifest.xml</code>. Only broadcasters who have
* been granted this permission (by requesting it with the
* {@link android.R.styleable#AndroidManifestUsesPermission &lt;uses-permission&gt;}
* tag in their <code>AndroidManifest.xml</code>) will be able to send an
* Intent to the receiver.
*
* <p>See the <a href="{@docRoot}guide/topics/security/security.html">Security and Permissions</a>
* document for more information on permissions and security in general.
*
* <a name="ReceiverLifecycle"></a>
* <h3>Receiver Lifecycle</h3>
*
* <p>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.
*
* <p>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.
*
* <p>In particular, you may <i>not</i> 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 name="ProcessLifecycle"></a>
* <h3>Process Lifecycle</h3>
*
* <p>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.
*
* <p>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.
*
* <p>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()}
@ -218,7 +54,7 @@ public abstract class BroadcastReceiver {
* 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.
*
*
* <p>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
@ -232,14 +68,14 @@ public abstract class BroadcastReceiver {
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;
final int mSendingUser;
final int mFlags;
int mResultCode;
String mResultData;
Bundle mResultExtras;
@ -259,7 +95,7 @@ public abstract class BroadcastReceiver {
mSendingUser = userId;
mFlags = flags;
}
/**
* Version of {@link BroadcastReceiver#setResultCode(int)
* BroadcastReceiver.setResultCode(int)} for
@ -331,7 +167,7 @@ public abstract class BroadcastReceiver {
mResultData = data;
mResultExtras = extras;
}
/**
* Version of {@link BroadcastReceiver#getAbortBroadcast()
* BroadcastReceiver.getAbortBroadcast()} for
@ -350,7 +186,7 @@ public abstract class BroadcastReceiver {
checkSynchronousHint();
mAbortBroadcast = true;
}
/**
* Version of {@link BroadcastReceiver#clearAbortBroadcast()
* BroadcastReceiver.clearAbortBroadcast()} for
@ -359,7 +195,7 @@ public abstract class BroadcastReceiver {
public final void clearAbortBroadcast() {
mAbortBroadcast = false;
}
/**
* Finish the broadcast. The current result will be sent and the
* next broadcast will proceed.
@ -397,14 +233,14 @@ public abstract class BroadcastReceiver {
sendFinished(mgr);
}
}
/** @hide */
public void setExtrasClassLoader(ClassLoader cl) {
if (mResultExtras != null) {
mResultExtras.setClassLoader(cl);
}
}
/** @hide */
public void sendFinished(IActivityManager am) {
synchronized (this) {
@ -412,7 +248,7 @@ public abstract class BroadcastReceiver {
throw new IllegalStateException("Broadcast already finished");
}
mFinished = true;
try {
if (mResultExtras != null) {
mResultExtras.setAllowFds(false);
@ -448,7 +284,7 @@ public abstract class BroadcastReceiver {
Log.e("BroadcastReceiver", e.getMessage(), e);
}
}
public BroadcastReceiver() {
}
@ -468,14 +304,15 @@ public abstract class BroadcastReceiver {
*
* <p><b>If this BroadcastReceiver was launched through a &lt;receiver&gt; tag,
* then the object is no longer alive after returning from this
* function.</b> 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}.
*
* function.</b> This means you should not perform any operations that
* return a result to you asynchronously. If you need to perform any follow up
* background work, schedule a {@link android.app.job.JobService} with
* {@link android.app.job.JobScheduler}.
*
* If you wish to interact with a service that is already running and previously
* bound using {@link android.content.Context#bindService(Intent, ServiceConnection, int) bindService()},
* you can use {@link #peekService}.
*
* <p>The Intent filters used in {@link android.content.Context#registerReceiver}
* and in application manifests are <em>not</em> guaranteed to be exclusive. They
* are hints to the operating system about how to find suitable recipients. It is
@ -483,7 +320,7 @@ public abstract class BroadcastReceiver {
* 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.
*/
@ -496,7 +333,7 @@ public abstract class BroadcastReceiver {
* 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}
@ -508,15 +345,20 @@ public abstract class BroadcastReceiver {
mPendingResult = null;
return res;
}
/**
* Provide a binder to an already-running service. This method is synchronous
* Provide a binder to an already-bound 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}.
*
*
* For peekService() to return a non null {@link android.os.IBinder} interface
* the service must have published it before. In other words some component
* must have called {@link android.content.Context#bindService(Intent, ServiceConnection, int)} on it.
*
* @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.
* @param service Identifies the already-bound service you wish to use. See
* {@link android.content.Context#bindService(Intent, ServiceConnection, int)}
* for more information.
*/
public IBinder peekService(Context myContext, Intent service) {
IActivityManager am = ActivityManagerNative.getDefault();
@ -538,13 +380,13 @@ public abstract class BroadcastReceiver {
* 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.
*
*
* <p class="note">This method does not work with non-ordered broadcasts such
* as those sent with {@link Context#sendBroadcast(Intent)
* Context.sendBroadcast}</p>
*
*
* @param code The new result code.
*
*
* @see #setResult(int, String, Bundle)
*/
public final void setResultCode(int code) {
@ -554,7 +396,7 @@ public abstract class BroadcastReceiver {
/**
* Retrieve the current result code, as set by the previous receiver.
*
*
* @return int The current result code.
*/
public final int getResultCode() {
@ -567,13 +409,13 @@ public abstract class BroadcastReceiver {
* {@link Context#sendOrderedBroadcast(Intent, String)
* Context.sendOrderedBroadcast}. This is an arbitrary
* string whose interpretation is up to the broadcaster.
*
*
* <p><strong>This method does not work with non-ordered broadcasts such
* as those sent with {@link Context#sendBroadcast(Intent)
* Context.sendBroadcast}</strong></p>
*
*
* @param data The new result data; may be null.
*
*
* @see #setResult(int, String, Bundle)
*/
public final void setResultData(String data) {
@ -584,7 +426,7 @@ public abstract class BroadcastReceiver {
/**
* 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() {
@ -599,13 +441,13 @@ public abstract class BroadcastReceiver {
* 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).
*
*
* <p><strong>This method does not work with non-ordered broadcasts such
* as those sent with {@link Context#sendBroadcast(Intent)
* Context.sendBroadcast}</strong></p>
*
*
* @param extras The new extra data map; may be null.
*
*
* @see #setResult(int, String, Bundle)
*/
public final void setResultExtras(Bundle extras) {
@ -617,11 +459,11 @@ public abstract class BroadcastReceiver {
* 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) {
@ -640,11 +482,11 @@ public abstract class BroadcastReceiver {
* {@link Context#sendOrderedBroadcast(Intent, String)
* Context.sendOrderedBroadcast}. All current result data is replaced
* by the value given to this method.
*
*
* <p><strong>This method does not work with non-ordered broadcasts such
* as those sent with {@link Context#sendBroadcast(Intent)
* Context.sendBroadcast}</strong></p>
*
*
* @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
@ -662,11 +504,11 @@ public abstract class BroadcastReceiver {
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() {
@ -679,10 +521,10 @@ public abstract class BroadcastReceiver {
* {@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
* call {@link #onReceive} of the BroadcastReceiver that the caller of
* {@link Context#sendOrderedBroadcast(Intent, String)
* Context.sendOrderedBroadcast} passed in.
*
*
* <p><strong>This method does not work with non-ordered broadcasts such
* as those sent with {@link Context#sendBroadcast(Intent)
* Context.sendBroadcast}</strong></p>
@ -691,7 +533,7 @@ public abstract class BroadcastReceiver {
checkSynchronousHint();
mPendingResult.mAbortBroadcast = true;
}
/**
* Clears the flag indicating that this receiver should abort the current
* broadcast.
@ -701,7 +543,7 @@ public abstract class BroadcastReceiver {
mPendingResult.mAbortBroadcast = false;
}
}
/**
* Returns true if the receiver is currently processing an ordered
* broadcast.
@ -709,7 +551,7 @@ public abstract class BroadcastReceiver {
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
@ -719,7 +561,7 @@ public abstract class BroadcastReceiver {
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.
@ -727,21 +569,21 @@ public abstract class BroadcastReceiver {
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;
}
/** @hide */
public int getSendingUserId() {
return mPendingResult.mSendingUser;
@ -761,19 +603,19 @@ public abstract class BroadcastReceiver {
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.

7
core/java/android/net/ConnectivityManager.java
View File

@ -87,6 +87,13 @@ public class ConnectivityManager {
* sent as an extra; it should be consulted to see what kind of
* connectivity event occurred.
* <p/>
* Apps targeting Android 7.0 (API level 24) and higher do not receive this
* broadcast if they declare the broadcast receiver in their manifest. Apps
* will still receive broadcasts if they register their
* {@link android.content.BroadcastReceiver} with
* {@link android.content.Context#registerReceiver Context.registerReceiver()}
* and that context is still valid.
* <p/>
* If this is a connection that was the result of failing over from a
* disconnected network, then the FAILOVER_CONNECTION boolean extra is
* set to true.