android N systemUI的VOLTE图标显示

    现在android N之后很多手机都支持VOLTE了，而android手机的VOLTE是独立于其他的网络的，但是对于VOLTE打开关闭对于用户直观的显示是如何操作的呢？也就是在状态栏上的显示如何更新：在SystemUI上VOLTE图标的显示是通过监听PhoneStateListener的状态来改变的，是在frameworks\base\packages\SystemUI\src\com\android\systemui\statusbar\policy\MobileSignalController.java中进行监听的，代码如下：

    class MobilePhoneStateListener extends PhoneStateListener {
        public MobilePhoneStateListener(int subId, Looper looper) {
            super(subId, looper);
        }

        @Override
        public void onSignalStrengthsChanged(SignalStrength signalStrength) {
            if (DEBUG) {
                Log.d(mTag, "onSignalStrengthsChanged signalStrength=" + signalStrength +
                        ((signalStrength == null) ? "" : (" level=" + signalStrength.getLevel())));
            }
            mSignalStrength = signalStrength;
            updateTelephony();
        }

        @Override
        public void onServiceStateChanged(ServiceState state) {
            if (DEBUG) {
                Log.d(mTag, "onServiceStateChanged voiceState=" + state.getVoiceRegState()
                        + " dataState=" + state.getDataRegState());
            }
            mServiceState = state;
            mDataNetType = state.getDataNetworkType();
            /// M: Support 4G+ icon.
            mDataNetType =
                NetworkTypeUtils.getDataNetTypeFromServiceState(mDataNetType, mServiceState);
            updateTelephony();
        }

        @Override
        public void onDataConnectionStateChanged(int state, int networkType) {
            if (DEBUG) {
                Log.d(mTag, "onDataConnectionStateChanged: state=" + state
                        + " type=" + networkType);
            }
            mDataState = state;
            mDataNetType = networkType;
            /// M: Support 4G+ icon.
            mDataNetType =
                NetworkTypeUtils.getDataNetTypeFromServiceState(mDataNetType, mServiceState);
            updateTelephony();
        }

        @Override
        public void onDataActivity(int direction) {
            if (DEBUG) {
                Log.d(mTag, "onDataActivity: direction=" + direction);
            }
            setActivity(direction);
        }

        @Override
        public void onCarrierNetworkChange(boolean active) {
            if (DEBUG) {
                Log.d(mTag, "onCarrierNetworkChange: active=" + active);
            }
            mCurrentState.carrierNetworkChangeMode = active;

            updateTelephony();
        }
    };

在以上的onServiceStateChanged与onDataConnectionStateChanged方法中SIM卡的数据状态发生变化时就会改变mDataNetType的值，然后通过updateTelephony（）方法来更新数据状态的变化而改变Systemui的网络状态的显示，updateTelephony（）更新VOLTE如下：

    private final void updateTelephony() {
 	........
        if (!mCurrentState.isOverwfc) {
            mCurrentState.volteIcon = mCurrentState.imsRegState == ServiceState.STATE_IN_SERVICE
                && isLteNetWork() ? NetworkTypeUtils.VOLTE_ICON : 0;
        }

        notifyListenersIfNecessary();
    }

而isLteNetWork()就算判断当前的网络状态是否为VOLTE：

    public boolean isLteNetWork() {
        return (mDataNetType == TelephonyManager.NETWORK_TYPE_LTE
            || mDataNetType == TelephonyManager.NETWORK_TYPE_LTEA);
    }

然后通过调用MobileSignalController.java的notifyListenersIfNecessary（）最后调用MobileSignalController.java的notifyListeners()方法 更新图标显示，代码如下：

    @Override
    public void notifyListeners(SignalCallback callback) {
        MobileIconGroup icons = getIcons();

 	........
        callback.setMobileDataIndicators(statusIcon, qsIcon, typeIcon, networkIcon, volteIcon,
                qsTypeIcon, activityIn, activityOut, dataContentDescription, description,
                icons.mIsWide, mSubscriptionInfo.getSubscriptionId());
        /** @ }*/

        /// M: update plmn label @{
        mNetworkController.refreshPlmnCarrierLabel();
        /// @}
    }

通过callback.setMobileDataIndicators（），去调用frameworks\base\packages\SystemUI\src\com\android\systemui\statusbar\SignalClusterView.java的setMobileDataIndicators方法：

    @Override
    public void setMobileDataIndicators(IconState statusIcon, IconState qsIcon, int statusType,
            int networkType, int volteIcon, int qsType, boolean activityIn, boolean activityOut,
            String typeContentDescription, String description, boolean isWide, int subId) {
        PhoneState state = getState(subId);
        if (state == null) {
            return;
        }
        state.mMobileVisible = statusIcon.visible && !mBlockMobile;
        state.mMobileStrengthId = statusIcon.icon;
        state.mMobileTypeId = statusType;
        state.mMobileDescription = statusIcon.contentDescription;
        state.mMobileTypeDescription = typeContentDescription;
        state.mIsMobileTypeIconWide = statusType != 0 && isWide;
        state.mNetworkIcon = networkType;
        state.mVolteIcon = volteIcon;

        /// M: Add for plugin features. @ {
        state.mDataActivityIn = activityIn;
        state.mDataActivityOut = activityOut;
        /// @ }

        apply();
    }

再通过apply（）方法调用setCustomizeViewProperty()方法：

private void setCustomizeViewProperty() {
            // Add for [Network Type on Statusbar], the place to set network type icon.
            setNetworkIcon();
            /// M: Add for volte icon.
            setVolteIcon();
        }

而通过setVolteIcon()方法显示：

        private void setVolteIcon() {
            if (mVolteIcon == 0) {
                mVolteType.setVisibility(View.GONE);
            } else {
                mVolteType.setImageResource(mVolteIcon);
                mVolteType.setVisibility(View.VISIBLE);
            }
            /// M: customize VoLTE icon. @{
            mStatusBarExt.setCustomizedVolteView(mVolteIcon, mVolteType);
            /// M: customize VoLTE icon. @}
        }
判断假如mVolteIcon是否为0,为0代表当前不是VOLTE，不为0代表当前为VOLTE状态。