android/content/BroadcastReceiver.java

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.content;

import android.app.ActivityManager;
import android.app.ActivityThread;
import android.app.IActivityManager;
import android.app.QueuedWork;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
import android.util.Slog;

/**
 * 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 declare an implementation with the
 * {@link android.R.styleable#AndroidManifestReceiver &lt;receiver&gt;}
 * tag in your <code>AndroidManifest.xml</code>.
 *
 * <div class="special reference">
 * <h3>Developer Guides</h3>
 * <p>For more information about using BroadcastReceiver, read the
 * <a href="{@docRoot}guide/components/broadcasts.html">Broadcasts</a> developer guide.</p></div>
 *
 */
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.
     *
     * <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
     * 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;
        final int mSendingUser;
        final int mFlags;

        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, int userId, int flags) {
            mResultCode = resultCode;
            mResultData = resultData;
            mResultExtras = resultExtras;
            mType = type;
            mOrderedHint = ordered;
            mInitialStickyHint = sticky;
            mToken = token;
            mSendingUser = userId;
            mFlags = flags;
        }

        /**
         * 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 = ActivityManager.getService();
                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.addFinisher() with the
                    // runnable, since we know the AM is waiting for us until the
                    // executor gets to it.
                    QueuedWork.queue(new Runnable() {
                        @Override public void run() {
                            if (ActivityThread.DEBUG_BROADCAST) Slog.i(ActivityThread.TAG,
                                    "Finishing broadcast after work to component " + mToken);
                            sendFinished(mgr);
                        }
                    }, false);
                } 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 = ActivityManager.getService();
                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, mFlags);
                    } 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, mFlags);
                    }
                } catch (RemoteException ex) {
                }
            }
        }

        /** @hide */
        public int getSendingUserId() {
            return mSendingUser;
        }

        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().
     *
     * <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. 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
     * 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 <em>not</em> change the expectation of being relatively
     * responsive to the broadcast, 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.
     *
     * <p>As a general rule, broadcast receivers are allowed to run for up to 10 seconds
     * before they system will consider them non-responsive and ANR the app.  Since these usually
     * execute on the app's main thread, they are already bound by the ~5 second time limit
     * of various operations that can happen there (not to mention just avoiding UI jank), so
     * the receive limit is generally not of concern.  However, once you use {@code goAsync}, though
     * able to be off the main thread, the broadcast execution limit still applies, and that
     * includes the time spent between calling this method and ultimately
     * {@link PendingResult#finish() PendingResult.finish()}.</p>
     *
     * <p>If you are taking advantage of this method to have more time to execute, it is useful
     * to know that the available time can be longer in certain situations.  In particular, if
     * the broadcast you are receiving is not a foreground broadcast (that is, the sender has not
     * used {@link Intent#FLAG_RECEIVER_FOREGROUND}), then more time is allowed for the receivers
     * to run, allowing them to execute for 30 seconds or even a bit more.  This is something that
     * receivers should rarely take advantage of (long work should be punted to another system
     * facility such as {@link android.app.job.JobScheduler}, {@link android.app.Service}, or
     * see especially {@link android.support.v4.app.JobIntentService}), but can be useful in
     * certain rare cases where it is necessary to do some work as soon as the broadcast is
     * delivered.  Keep in mind that the work you do here will block further broadcasts until
     * it completes, so taking advantage of this at all excessively can be counter-productive
     * and cause later events to be received more slowly.</p>
     *
     * @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-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 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 = ActivityManager.getService();
        IBinder binder = null;
        try {
            service.prepareToLeaveProcess(myContext);
            binder = am.peekService(service, service.resolveTypeIfNeeded(
                    myContext.getContentResolver()), myContext.getOpPackageName());
        } 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.
     *
     * <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) {
        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.
     *
     * <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) {
        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).
     *
     * <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) {
        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.
     *
     * <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
     * 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.
     *
     * <p><strong>This method does not work with non-ordered broadcasts such
     * as those sent with {@link Context#sendBroadcast(Intent)
     * Context.sendBroadcast}</strong></p>
     */
    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;
    }

    /** @hide */
    public int getSendingUserId() {
        return mPendingResult.mSendingUser;
    }

    /**
     * Control inclusion of debugging help for mismatched
     * calls to {@link 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);
    }
}