基於android N MTK釋放的原始碼
本文主要講解如何在 IncallUI 的notification 上面不停地更新顯示當前已通話多長時間，從而達到和incallUI通話介面上的通話時間一致。

主要思路

1. 我們需要知道通話建立時的時間，即call 的狀態從 INCOMING或者DIALING 轉變成ACTIVE的時候
2. 時間每秒鐘都會發生變化，所以我們就需要不停的更新notification的介面，我們這裡是不停的建立和notify同一個notification，已到達更新時間的效果
3. 我們需要CallTimer執行緒不停的幫我們計算時間，並控制介面的更新

程式碼實現

這裡是在原始碼incallUI目錄下的StatusBarNotifier.java中修改

....省略部分程式碼
    //震動時長，這裡為不振動
    private static final long[] IN_CALL_VIBRATE_PATTERN_NULL = new long[] {0, 0, 0};
    //執行緒隔多久執行一次已ms為單位，這裡為1S
    private static final long CALL_TIME_UPDATE_INTERVAL_MS = 1000;

    //我們需要獲取一些全域性的變數，已到達不停的建立notification並更新同一個notification的UI
    private CallTimer mCallTimer;
    private
 
 Notification.Builder mCopyBuilder;
    private int  mCopyCallState;
    private ContactCacheEntry mCopyContactInfo;
    private int mCopyNotificationType; //當前notification的ID,通過這個ID我們可以一直更新同一個notification並且只會彈出一次
    private Bitmap mCopyLargeIcon;

    public StatusBarNotifier(Context context, ContactInfoCache contactInfoCache) {
        .......省略部分程式碼
        //StatusBarNotifier初始化的時候就建立CallTimer物件，用來計算時間和更新UI
 

        mCallTimer = new CallTimer(new Runnable() {
            @Override
            public void run() {
                updateCallTime(); //更新UI的函式
            }
        });
    }

    @Override
    public void onStateChange(InCallState oldState, InCallState newState, CallList callList) {
        if (callList.getActiveCall() == null || callList.getActiveCall().getState() != Call.State.ACTIVE){
            //當通話結束時需要取消計算時間的執行緒
            mCallTimer.cancel();
        }
    }

    //系統構建notification的方法
    private void buildAndSendNotification(Call originalCall, ContactCacheEntry contactInfo) {
        ....省略部分程式碼
        else if (callState == Call.State.ACTIVE && !mIsCallUiShown) {
            //儲存一個公共的變數到全部變數裡面，方便後面構造新的notification並重新整理
            copyInfoFromHeadsUpView(builder, callState, contactInfo, notificationType, largeIcon);
            //下面是計算顯示的時間
            final long callStart = call.getConnectTimeMillis();
            final long duration = System.currentTimeMillis() - callStart;
            //建立一個HeadsUpView顯示在notification上面
            RemoteViews inCall = createInCallHeadsUpView(duration / 1000, largeIcon);
            builder.setContent(inCall);
            builder.setCustomHeadsUpContentView(inCall);
            //系統原生的方法最後notify通知
            fireNotification(builder, callState, contactInfo, notificationType);
            //開始我們的計時執行緒
            mCallTimer.start(CALL_TIME_UPDATE_INTERVAL_MS);
        }

        .....省略部分程式碼
    }

    private RemoteViews createInCallHeadsUpView(Long callDuration, Bitmap contactAvatar) {
        RemoteViews headsUpView = new RemoteViews(mContext.getPackageName(), R.layout.in_call_headsup);
        if (null != contactAvatar) {
            headsUpView.setImageViewBitmap(R.id.in_call_hu_avatar, contactAvatar);
        }
        //格式化時間
        String callTimeElapsed = DateUtils.formatElapsedTime(callDuration);
        headsUpView.setTextViewText(R.id.in_call_hu_elapsedTime, callTimeElapsed);
        return headsUpView;
    }

    /*according the mCallTimer to update time data*/
    public void updateCallTime() {
        Call call = CallList.getInstance().getActiveCall();
        final long callStart = call.getConnectTimeMillis();
        final long duration = System.currentTimeMillis() - callStart;
        RemoteViews inCall = createInCallHeadsUpView(duration / 1000, mCopyLargeIcon);
        mCopyBuilder.setContent(inCall);
        mCopyBuilder.setCustomHeadsUpContentView(inCall);
        Notification notification = mCopyBuilder.build();
        notification.vibrate = IN_CALL_VIBRATE_PATTERN_NULL;
        mNotificationManager.notify(mCopyNotificationType, notification);

    }

    /*Change local variables  to global variables*/
    private void copyInfoFromHeadsUpView(Notification.Builder builder, int callState, ContactCacheEntry contactInfo,
                          int notificationType, Bitmap largeIcon){
        mCopyBuilder = builder;
        mCopyCallState = callState;
        mCopyContactInfo = contactInfo;
        mCopyNotificationType = notificationType;
        mCopyLargeIcon = largeIcon;
    }

........省略部分程式碼

CallTimer原始碼如下

package com.android.incallui;

import com.google.common.base.Preconditions;

import android.os.Handler;
import android.os.SystemClock;

/**
 * Helper class used to keep track of events requiring regular intervals.
 */
public class CallTimer extends Handler {
    private Runnable mInternalCallback;
    private Runnable mCallback;
    private long mLastReportedTime;
    private long mInterval;
    private boolean mRunning;

    public CallTimer(Runnable callback) {
        Preconditions.checkNotNull(callback);

        mInterval = 0;
        mLastReportedTime = 0;
        mRunning = false;
        mCallback = callback;
        mInternalCallback = new CallTimerCallback();
    }

    public boolean start(long interval) {
        if (interval <= 0) {
            return false;
        }

        // cancel any previous timer
        cancel();

        mInterval = interval;
        mLastReportedTime = SystemClock.uptimeMillis();

        mRunning = true;
        periodicUpdateTimer();

        return true;
    }

    public void cancel() {
        removeCallbacks(mInternalCallback);
        mRunning = false;
    }

    private void periodicUpdateTimer() {
        if (!mRunning) {
            return;
        }

        final long now = SystemClock.uptimeMillis();
        long nextReport = mLastReportedTime + mInterval;
        while (now >= nextReport) {
            nextReport += mInterval;
        }

        postAtTime(mInternalCallback, nextReport);
        mLastReportedTime = nextReport;

        // Run the callback
        mCallback.run();
    }

    private class CallTimerCallback implements Runnable {
        @Override
        public void run() {
            periodicUpdateTimer();
        }
    }
}