Android9.0 开启关闭移动数据流程

@DcTracker.java
public void setUserDataEnabled(boolean enable) {
      Message msg = obtainMessage(DctConstants.CMD_SET_USER_DATA_ENABLE);
      msg.arg1 = enable ? 1 : 0;
      if (DBG) log("setDataEnabled: sendMessage: enable=" + enable);
      sendMessage(msg);
}
调用打开/关闭数据接口后，DcTracker给自己发送msg(DctConstants.CMD_SET_USER_DATA_ENABLE)，在handleMessage中处理调用onSetUserDataEnable，这里是具体的打开/关闭数据的操作。打开操作是onTrySetupData(),关闭操作是onCleanUpAllConnections()
private void onSetUserDataEnabled(boolean enabled) {
      if (mDataEnabledSettings.isUserDataEnabled() != enabled) {
         mDataEnabledSettings.setUserDataEnabled(enabled);
         if (!getDataRoamingEnabled() && mPhone.getServiceState().getDataRoaming()) {
            if (enabled) {
                  notifyOffApnsOfAvailability(Phone.REASON_ROAMING_ON);
            } else {
                  notifyOffApnsOfAvailability(Phone.REASON_DATA_DISABLED);
            }
         }

         mPhone.notifyUserMobileDataStateChanged(enabled);

         // TODO: We should register for DataEnabledSetting's data enabled/disabled event and
         // handle the rest from there.
         if (enabled) {
            reevaluateDataConnections();
            onTrySetupData(Phone.REASON_DATA_ENABLED);//打开数据流量
         } else {
            onCleanUpAllConnections(Phone.REASON_DATA_SPECIFIC_DISABLED);//关闭数据流量
         }
      }
}

private boolean onTrySetupData(String reason) {
      if (DBG) log("onTrySetupData: reason=" + reason);
      setupDataOnConnectableApns(reason);
      return true;
}

//此方法的作用为增加一个标志位，目的是连接失败时总是尝试重新连接
private void setupDataOnConnectableApns(String reason) {
      setupDataOnConnectableApns(reason, RetryFailures.ALWAYS);
}

private void setupDataOnConnectableApns(String reason, RetryFailures retryFailures) {

      ...

      for (ApnContext apnContext : mPrioritySortedApnContexts) {
         if (VDBG) log("setupDataOnConnectableApns: apnContext " + apnContext);

         if (apnContext.getState() == DctConstants.State.FAILED
                  || apnContext.getState() == DctConstants.State.SCANNING) {
            if (retryFailures == RetryFailures.ALWAYS) {
                  apnContext.releaseDataConnection(reason);
            } else if (apnContext.isConcurrentVoiceAndDataAllowed() == false &&
                     mPhone.getServiceStateTracker().isConcurrentVoiceAndDataAllowed()) {
                  // RetryFailures.ONLY_ON_CHANGE - check if voice concurrency has changed
                  apnContext.releaseDataConnection(reason);
            }
         }
         if (apnContext.isConnectable()) {
            log("isConnectable() call trySetupData");
            apnContext.setReason(reason);
            trySetupData(apnContext);
         }
      }
}
遍历mPrioritySortedApnContexts，尝试每一种apn是否可连接，可连接就调用trySetupData(apnContext);进行实际连接操作。
mPrioritySortedApnContexts中的数值为，DcTracker初始化时构造方法调用initApnContexts()，生成的apn对象保存到mPrioritySortedApnContexts。

来源：oschina

链接：https://my.oschina.net/u/2288619/blog/3175432

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