Android中打电话的数据流程分析

1.所有流程的起点是从拨号后按下拨号键开始，此步的代码在/android sourcecode/packages/contacts/src/com/android/contacts/目录的twelvekeydialer.java文件中，相关代码如下：

dialbuttonpressed() {
.........
final string number = mdigits.gettext().tostring();
startactivity(newdialnumberintent(number));
mdigits.gettext().clear();
finish();
}

代码中newdialnumberintent()方法定义如下：

private intent newdialnumberintent(string number) {
final intent intent = new intent(intent.action_call_privileged, uri.fromparts("tel", number, null));
.............
}

从newdialnumberintent的定义可以看出，当拨号键按下以后，twelvekeydial会启动一个特定的组件，该组件的action为：action_call_privileged,经过查找，该action启动的组件是目下：/android sourcecode/packeges/phone/的一个文件，在该文件下的androidmenifest.xml中可以查到:“action_call_privileged”启动的activity的名字是：privilegedoutgoingcallbroadcast,但是我们到/android sourcecode/packeges/phone/src/....目下并找不到该文件，因为该文件在androidmenifest.xml中标记有点特殊：
<activity-alias />,这个标签的意思是这个activity是另一个activity的别名，真实的activity在标签中用“android:targetactivity = outgoingcallbroadcast”标出，所以 “action_call_privileged”启动的 privilegedoutgoingcallbroadcast 所对应的真实“身份”是 “outgoingcallbroadcast”。

2.这个时候电话的数据已经流到outgoingcallbroadcast.java中了。
在outgoingcallbroadcast.java的oncreate()方法中有：

<pre class=java name="code">protected void oncreate(bundle icicle) {
.......
intent intent = getintent();
........
string action = intent.getaction();
.......
final boolean emergencynum = (number != null) && phonenumutils.isemergencynumber(number);//判断号码是否是紧急号码
.......
if (intent.action_call_privileged.equals(action)) ｛
action = emergencynum ? intent.action_call_emergency : intent.action_call;
intent.setaction(action);
}
.......
intent.setclass(this, incallscreen.class);
startactivity(intent);
}</pre><p></p>
<pre></pre>
在这个方法中，判断如果所收到的action是“action_call_privileged”，那么根据所输入的号码是否是紧急号码进行转换，如果是紧急号码，则action ＝ intent.action_call_emergency,否则action ＝ intent.action_call,并启动转换activity ：incallscreen.java
<p></p>
<p>3. incallscreen.java依然在目录/packeges/phone/src/com/android/phone下。</p>
<p>incallscreen的oncreate中调用initincallscreen初始化打电话界面，并调用registerforphonestates注册电话状态监听.<br>
</p>
<p>在onnewintent()方法中有：</p>
<p><pre class=java name="code">protected void onnewintent(intent intent) {
..........
string action = intent.getaction();
..........
else if (action.equals(intent.action_call) || action.equals(intent.action_call_emergency)) {
..........
incallinitstatus status = placecall(intent);
}
}
//placecall
private incallinitstatus placecall(intent intent) {
..............
int callstatus = phoneutils.placecall(........);
}</pre>incallscreen.java中的placecall方法调用phoneutils.java文件的placecall方法。<br>
<p></p>
<p>4. phoneutils.java依然在目录/packeges/phone/src/com/android/phone下。</p>
<p><pre class=java name="code">public static int placecall(...) {
connection connection;
connection = phoneapp.getinstance().mcm.dial(phone, numbertodial);
}</pre>继续追踪，在phoneapp.java中发现，mcm是callmanager.java类的一个对象，而callmanager.java是属于frameworks层的，所以，这个时候数据流已经进入frameworks.<p></p>
<p>5. 进入/frameworks/base/telephony/java/com/android/internal/telephony目录。</p>
<p>在callmanager.java的dial()方法中，有：</p>
<p><pre class=java name="code"><span style="background-color: rgb(255,255,255); font-family: arial, verdana, sans-serif; white-space: normal"></span><pre class=java name="code">public connection dial(phone phone, string dialnumber) throws callstateexception {
phone basephone = getphonebase(phone);
connection result;
<span style="color: #3333ff">result = basephone.dial(dialstring);</span>
........
}
private static phone getphonebase(phone phone) {
if (phone instanceof phoneproxy) {
<span style="color: #ff0000">return phone.getforegroundcall().getphone();</span>
}
return phone;
}</pre><p></p>
<pre></pre>
<pre class=java name="code"><span style="background-color: rgb(255,255,255); font-family: arial, verdana, sans-serif; white-space: normal">继续追踪会发现：</span></pre><pre class=java name="code"><span style="background-color: rgb(255,255,255); font-family: arial, verdana, sans-serif; white-space: normal">phonebase.java抽象类实现了接口phone.java,而gsmphone.java又实现了抽象类phonebase,所以:</span></pre>
<p></p>
<p>上述代码中：phone.getforegroundcall()实际相当于gsmphone对象执行了getforegroundcall()方法。</p>
<p>6. 继续追踪gsmphone.java,该类位于/frameworks/base/telephony/java/com/android/internal/telephony/gsm/下。</p>
<p><pre class=java name="code">gsmphone.java：
gsmcalltracker mct;
public gsmcall getforegroundcall() {
return mct.foregroundcall;
}</pre>可以看出getforegroundcall()函数继续调用gsmcalltracker.java的foregroundcall属性。<p></p>
<p>7.gsmcalltracker.java位于/frameworks/base/telephony/java/com/android/internal/telephony/gsm/下.</p>
<p><pre class=cpp name="code">gsmcalltracker.java:
gsmcall foregroundcall = new gsmcall(this);</pre><p></p>
<p>打开gsmcall.java,找到getphone()方法，发现：</p>
<p><pre class=java name="code">gsmcalltracker owner;
public phone getphone() {
return owner.phone;
}</pre><p></p>
<p>而在gsmcalltracker.java中有如下声明：</p>
<p><pre class=cpp name="code">gsmphone phone;</pre><p></p>
<p><span style="color: #ff0000">到此，我们得出一下结论：第5部分标记红色的代码所返回的就是gsmphone的对象，</span><span style="color: #3333ff">进一步可以得出，第5部分蓝色标记的代码即是调用了gsmphone对象的dial方法。</span></p>
<p>8. 在gsmphone.java中：</p>
<p><pre class=java name="code">gsmcalltracker mct;
public connection dial(string dialstring) throws callstateexception {
return dial(dialstring, null);
}
public connection dial(string dialstring, uusinfo uusinfo) throws callstateexception {
.......
mct.dial(.......);
}</pre><p></p>
<p>继续调用gsmcalltracker.java中的dial()方法：</p>
<p><pre class=cpp name="code">gsmcalltracker.java：
gsmcalltracker(gsmphone phone) {
cm = phone.mcm;
}
connection dial(string dialstring, int clirmode, uusinfo uusinfo) {
<span style="color: #ff0000">cm.dial(........);</span>
}</pre>追踪mcm,发现 :<p></p>
<p>public commandsinterface mcm;</p>
<p>所以gsmcalltracker持有commandsinterface对象，即ril.java类的对象，所以"cm.dial(....)"即是调用ril类对象的dial()方法。</p>
<p>9. ril.java</p>
<p>boss出现。</p>
<p>ril对象负责把客户端的通话请求按照一定的格式发送给"rild"socket,至此，请求过程完毕。</p>
</pre>