Android example source code file (Broadcaster.java)

This example Android source code file (Broadcaster.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

broadcaster, handler, message, registration

The Broadcaster.java Android example source code

/*
 * 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.os;

/** @hide */
public class Broadcaster
{
    public Broadcaster()
    {
    }

    /**
     *  Sign up for notifications about something.
     *
     *  When this broadcaster pushes a message with senderWhat in the what field,
     *  target will be sent a copy of that message with targetWhat in the what field.
     */
    public void request(int senderWhat, Handler target, int targetWhat)
    {
        synchronized (this) {
            Registration r = null;
            if (mReg == null) {
                r = new Registration();
                r.senderWhat = senderWhat;
                r.targets = new Handler[1];
                r.targetWhats = new int[1];
                r.targets[0] = target;
                r.targetWhats[0] = targetWhat;
                mReg = r;
                r.next = r;
                r.prev = r;
            } else {
                // find its place in the map
                Registration start = mReg;
                r = start;
                do {
                    if (r.senderWhat >= senderWhat) {
                        break;
                    }
                    r = r.next;
                } while (r != start);
                int n;
                if (r.senderWhat != senderWhat) {
                    // we didn't find a senderWhat match, but r is right
                    // after where it goes
                    Registration reg = new Registration();
                    reg.senderWhat = senderWhat;
                    reg.targets = new Handler[1];
                    reg.targetWhats = new int[1];
                    reg.next = r;
                    reg.prev = r.prev;
                    r.prev.next = reg;
                    r.prev = reg;

                    if (r == mReg && r.senderWhat > reg.senderWhat) {
                        mReg = reg;
                    }
                    
                    r = reg;
                    n = 0;
                } else {
                    n = r.targets.length;
                    Handler[] oldTargets = r.targets;
                    int[] oldWhats = r.targetWhats;
                    // check for duplicates, and don't do it if we are dup.
                    for (int i=0; i<n; i++) {
                        if (oldTargets[i] == target && oldWhats[i] == targetWhat) {
                            return;
                        }
                    }
                    r.targets = new Handler[n+1];
                    System.arraycopy(oldTargets, 0, r.targets, 0, n);
                    r.targetWhats = new int[n+1];
                    System.arraycopy(oldWhats, 0, r.targetWhats, 0, n);
                }
                r.targets[n] = target;
                r.targetWhats[n] = targetWhat;
            }
        }
    }
    
    /**
     * Unregister for notifications for this senderWhat/target/targetWhat tuple.
     */
    public void cancelRequest(int senderWhat, Handler target, int targetWhat)
    {
        synchronized (this) {
            Registration start = mReg;
            Registration r = start;
            
            if (r == null) {
                return;
            }
            
            do {
                if (r.senderWhat >= senderWhat) {
                    break;
                }
                r = r.next;
            } while (r != start);
            
            if (r.senderWhat == senderWhat) {
                Handler[] targets = r.targets;
                int[] whats = r.targetWhats;
                int oldLen = targets.length;
                for (int i=0; i<oldLen; i++) {
                    if (targets[i] == target && whats[i] == targetWhat) {
                        r.targets = new Handler[oldLen-1];
                        r.targetWhats = new int[oldLen-1];
                        if (i > 0) {
                            System.arraycopy(targets, 0, r.targets, 0, i);
                            System.arraycopy(whats, 0, r.targetWhats, 0, i);
                        }

                        int remainingLen = oldLen-i-1;
                        if (remainingLen != 0) {
                            System.arraycopy(targets, i+1, r.targets, i,
                                    remainingLen);
                            System.arraycopy(whats, i+1, r.targetWhats, i,
                                    remainingLen);
                        }
                        break;
                    }
                }
            }
        }
    }

    /**
     * For debugging purposes, print the registrations to System.out
     */
    public void dumpRegistrations()
    {
        synchronized (this) {
            Registration start = mReg;
            System.out.println("Broadcaster " + this + " {");
            if (start != null) {
                Registration r = start;
                do {
                    System.out.println("    senderWhat=" + r.senderWhat);
                    int n = r.targets.length;
                    for (int i=0; i<n; i++) {
                        System.out.println("        [" + r.targetWhats[i]
                                        + "] " + r.targets[i]);
                    }
                    r = r.next;
                } while (r != start);
            }
            System.out.println("}");
        }
    }

    /**
     * Send out msg.  Anyone who has registered via the request() method will be
     * sent the message.
     */
    public void broadcast(Message msg)
    {
        synchronized (this) {
        	if (mReg == null) {
        		return;
        	}
        	
            int senderWhat = msg.what;
            Registration start = mReg;
            Registration r = start;
            do {
                if (r.senderWhat >= senderWhat) {
                    break;
                }
                r = r.next;
            } while (r != start);
            if (r.senderWhat == senderWhat) {
                Handler[] targets = r.targets;
                int[] whats = r.targetWhats;
                int n = targets.length;
                for (int i=0; i<n; i++) {
                    Handler target = targets[i];
                    Message m = Message.obtain();
                    m.copyFrom(msg);
                    m.what = whats[i];
                    target.sendMessage(m);
                }
            }
        }
    }

    private class Registration
    {
        Registration next;
        Registration prev;

        int senderWhat;
        Handler[] targets;
        int[] targetWhats;
    }
    private Registration mReg;
}