Android example source code file (HeadsetObserver.java)

This example Android source code file (HeadsetObserver.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

android, bit_headset, bit_headset_no_mic, content, context, filereader, handler, headset_name_path, headsetobserver, headsets_with_mic, intent, io, log, media, os, override, photo, powermanager, string, supported_headsets

The HeadsetObserver.java Android example source code

/*
 * Copyright (C) 2008 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 com.android.server;

import android.app.ActivityManagerNative;
import android.content.Context;
import android.content.Intent;
import android.os.Handler;
import android.os.Message;
import android.os.PowerManager;
import android.os.PowerManager.WakeLock;
import android.os.UEventObserver;
import android.util.Slog;
import android.media.AudioManager;

import java.io.FileReader;
import java.io.FileNotFoundException;

/**
 * <p>HeadsetObserver monitors for a wired headset.
 */
class HeadsetObserver extends UEventObserver {
    private static final String TAG = HeadsetObserver.class.getSimpleName();
    private static final boolean LOG = true;

    private static final String HEADSET_UEVENT_MATCH = "DEVPATH=/devices/virtual/switch/h2w";
    private static final String HEADSET_STATE_PATH = "/sys/class/switch/h2w/state";
    private static final String HEADSET_NAME_PATH = "/sys/class/switch/h2w/name";

    private static final int BIT_HEADSET = (1 << 0);
    private static final int BIT_HEADSET_NO_MIC = (1 << 1);
    private static final int SUPPORTED_HEADSETS = (BIT_HEADSET|BIT_HEADSET_NO_MIC);
    private static final int HEADSETS_WITH_MIC = BIT_HEADSET;

    private int mHeadsetState;
    private int mPrevHeadsetState;
    private String mHeadsetName;

    private final Context mContext;
    private final WakeLock mWakeLock;  // held while there is a pending route change

    public HeadsetObserver(Context context) {
        mContext = context;
        PowerManager pm = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
        mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "HeadsetObserver");
        mWakeLock.setReferenceCounted(false);

        startObserving(HEADSET_UEVENT_MATCH);

        init();  // set initial status
    }

    @Override
    public void onUEvent(UEventObserver.UEvent event) {
        if (LOG) Slog.v(TAG, "Headset UEVENT: " + event.toString());

        try {
            update(event.get("SWITCH_NAME"), Integer.parseInt(event.get("SWITCH_STATE")));
        } catch (NumberFormatException e) {
            Slog.e(TAG, "Could not parse switch state from event " + event);
        }
    }

    private synchronized final void init() {
        char[] buffer = new char[1024];

        String newName = mHeadsetName;
        int newState = mHeadsetState;
        mPrevHeadsetState = mHeadsetState;
        try {
            FileReader file = new FileReader(HEADSET_STATE_PATH);
            int len = file.read(buffer, 0, 1024);
            newState = Integer.valueOf((new String(buffer, 0, len)).trim());

            file = new FileReader(HEADSET_NAME_PATH);
            len = file.read(buffer, 0, 1024);
            newName = new String(buffer, 0, len).trim();

        } catch (FileNotFoundException e) {
            Slog.w(TAG, "This kernel does not have wired headset support");
        } catch (Exception e) {
            Slog.e(TAG, "" , e);
        }

        update(newName, newState);
    }

    private synchronized final void update(String newName, int newState) {
        // Retain only relevant bits
        int headsetState = newState & SUPPORTED_HEADSETS;
        int newOrOld = headsetState | mHeadsetState;
        int delay = 0;
        // reject all suspect transitions: only accept state changes from:
        // - a: 0 heaset to 1 headset
        // - b: 1 headset to 0 headset
        if (mHeadsetState == headsetState || ((newOrOld & (newOrOld - 1)) != 0)) {
            return;
        }

        mHeadsetName = newName;
        mPrevHeadsetState = mHeadsetState;
        mHeadsetState = headsetState;

        if (headsetState == 0) {
            Intent intent = new Intent(AudioManager.ACTION_AUDIO_BECOMING_NOISY);
            mContext.sendBroadcast(intent);
            // It can take hundreds of ms flush the audio pipeline after
            // apps pause audio playback, but audio route changes are
            // immediate, so delay the route change by 1000ms.
            // This could be improved once the audio sub-system provides an
            // interface to clear the audio pipeline.
            delay = 1000;
        } else {
            // Insert the same delay for headset connection so that the connection event is not
            // broadcast before the disconnection event in case of fast removal/insertion
            if (mHandler.hasMessages(0)) {
                delay = 1000;
            }
        }
        mWakeLock.acquire();
        mHandler.sendMessageDelayed(mHandler.obtainMessage(0,
                                                           mHeadsetState,
                                                           mPrevHeadsetState,
                                                           mHeadsetName),
                                    delay);
    }

    private synchronized final void sendIntents(int headsetState, int prevHeadsetState, String headsetName) {
        int allHeadsets = SUPPORTED_HEADSETS;
        for (int curHeadset = 1; allHeadsets != 0; curHeadset <<= 1) {
            if ((curHeadset & allHeadsets) != 0) {
                sendIntent(curHeadset, headsetState, prevHeadsetState, headsetName);
                allHeadsets &= ~curHeadset;
            }
        }
    }

    private final void sendIntent(int headset, int headsetState, int prevHeadsetState, String headsetName) {
        if ((headsetState & headset) != (prevHeadsetState & headset)) {
            //  Pack up the values and broadcast them to everyone
            Intent intent = new Intent(Intent.ACTION_HEADSET_PLUG);
            intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
            int state = 0;
            int microphone = 0;

            if ((headset & HEADSETS_WITH_MIC) != 0) {
                microphone = 1;
            }
            if ((headsetState & headset) != 0) {
                state = 1;
            }
            intent.putExtra("state", state);
            intent.putExtra("name", headsetName);
            intent.putExtra("microphone", microphone);

            if (LOG) Slog.v(TAG, "Intent.ACTION_HEADSET_PLUG: state: "+state+" name: "+headsetName+" mic: "+microphone);
            // TODO: Should we require a permission?
            ActivityManagerNative.broadcastStickyIntent(intent, null);
        }
    }

    private final Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            sendIntents(msg.arg1, msg.arg2, (String)msg.obj);
            mWakeLock.release();
        }
    };
}