我已经从 master 分支下载了整个源代码 https://android.googlesource.com/platform/frameworks/base/+/master ，并试图破译来电的事件链。

我假设 ACTION_ANSWER Intent 已启动，但除此之外不知道之前或之后发生了什么。

有人能帮忙吗？

最佳答案

让我们先看看 CallNotifier :

/** * Phone app module that listens for phone state changes and various other * events from the telephony layer, and triggers any resulting UI behavior * (like starting the Ringer and Incoming Call UI, playing in-call tones, * updating notifications, writing call log entries, etc.) */

此处理程序响应的消息之一是:CallStateMonitor.PHONE_NEW_RINGING_CONNECTION :

case CallStateMonitor.PHONE_NEW_RINGING_CONNECTION:
    log("RINGING... (new)");
    onNewRingingConnection((AsyncResult) msg.obj);
    mSilentRingerRequested = false;
    break;

onNewRingingConnection(AsyncResult)最终(一般情况下)调用 ringAndNotifyOfIncomingCall(Connection c) :

private void ringAndNotifyOfIncomingCall(Connection c) {
    if (PhoneUtils.isRealIncomingCall(c.getState())) {
        mRinger.ring();
    } else {
        if (VDBG) log("- starting call waiting tone...");
            if (mCallWaitingTonePlayer == null) {
                mCallWaitingTonePlayer = new InCallTonePlayer(
                                         InCallTonePlayer.TONE_CALL_WAITING);
                mCallWaitingTonePlayer.start();
            }
    }

    // CallModeler.onNewRingingConnection(Connection)
    mCallModeler.onNewRingingConnection(c);
}

CallModeler.onNewRingingConnection(Connection) ( Link ) 通知附加的监听器:

for (int i = 0; i < mListeners.size(); ++i) {
    mListeners.get(i).onIncoming(call);
}

这些监听器实现了CallModeler.Listener界面。 CallHandlerServiceProxy就是这样一个听众，它的 onIncoming(Call)回调触发 CallHandlerServiceProxy.processIncoming(Call) :

private void processIncoming(Call call) {
    ....
    // ICallHandlerService
    mCallHandlerServiceGuarded.onIncoming(call,
                   RejectWithTextMessageManager.loadCannedResponses());
    ....
}

CallHandlerService定义一个 ICallHandlerService.Stub成员及其onIncoming(Call, List<String>)方法看起来像:

@Override
public void onIncoming(Call call, List<String> textResponses) {
    ....
    mMainHandler.sendMessage(mMainHandler.obtainMessage(
                   ON_UPDATE_CALL_WITH_TEXT_RESPONSES, incomingCall));
    ....
}

这就是mMainHandler拉手箱ON_UPDATE_CALL_WITH_TEXT_RESPONSES :

case ON_UPDATE_CALL_WITH_TEXT_RESPONSES:
    AbstractMap.SimpleEntry<Call, List<String>> entry
                   = (AbstractMap.SimpleEntry<Call, List<String>>) msg.obj;
    Log.i(TAG, "ON_INCOMING_CALL: " + entry.getKey());

    // CallList
    mCallList.onIncoming(entry.getKey(), entry.getValue());
    break;

CallList保留实现 CallList.Listener 的监听器列表，并触发他们的 onIncomingCall(Call)来自其 CallList.onIncoming(Call, List<String>) 的事件方法。

现在，让我们看看InCallPresenter :

/** * Takes updates from the CallList and notifies the InCallActivity (UI) * of the changes. * Responsible for starting the activity for a new call and finishing the activity when all calls * are disconnected. * Creates and manages the in-call state and provides a listener pattern for the presenters * that want to listen in on the in-call state changes. * TODO: This class has become more of a state machine at this point. Consider renaming. */

InCallPresenter工具 CallList.Listener接口(interface)，并负责启动InCallActivity为所有电话相关操作提供 UI。以下评论(摘自 InCallPresenter.startOrFinishUi(InCallState))将上述事件链整合在一起:

/* A new Incoming call means that the user needs to be notified of the
   the call (since it wasn't them who initiated it).  We do this 
   through full  screen notifications and happens indirectly through {@link 
   StatusBarListener}. The process for incoming calls is as follows:

   1) CallList          - Announces existence of new INCOMING call
   2) InCallPresenter   - Gets announcement and calculates that the new 
                          InCallState should be set to INCOMING.
   3) InCallPresenter   - This method is called to see if we need to 
                          start or finish the app given the new state.
   4) StatusBarNotifier - Listens to InCallState changes. InCallPresenter 
                          calls StatusBarNotifier explicitly to issue a 
                          FullScreen Notification that will either start the
                          InCallActivity or show the user a top-level 
                          notification dialog if the user is in 
                          an immersive app. That notification can also start 
                          the InCallActivity.         
   5) InCallActivity    - Main activity starts up and at the end of its 
                          onCreate will call InCallPresenter::setActivity() 
                          to let the presenter know that start-up is complete.
                  [ AND NOW YOU'RE IN THE CALL. voila! ] */

我希望这能回答您的问题，或者至少能告诉您去哪里寻找。请随时纠正我忽略/误解的任何内容。

关于android - 来电时系统级会发生什么情况？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21054077/