Android下訊號強度顯示和訊號重新整理時間

android介面UI訊號顯示是通過RIL對通訊模組發送AT命令來實現的，如AT+CSQ，我們查看一般可以通過 logcat -b radio來擷取一些RIL的即時資訊

那麼訊號顯示隔多長時間在在介面上重新整理？

frameworks/base/telephony/java/com/android/internal/telephony/ServiceStateTracker.java

    /** Signal strength poll rate. */
  protected static final int POLL_PERIOD_MILLIS = 120 * 1000; 

它的訊號重新整理時間為2分鐘，也就是說從我開機到訊號顯示大概需要2分鐘的時間，這顯示太長了

 protected static final int POLL_PERIOD_MILLIS = 12 * 1000;

我們可以將其改為12秒

那麼訊號在介面上的顯示的訊號強度又是 如何擷取的呢？

frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/StatusBarPolicy.java

        if (!isCdma()) {                                                   //GSM訊號強度的擷取
            int asu = mSignalStrength.getGsmSignalStrength();

            // ASU ranges from 0 to 31 - TS 27.007 Sec 8.5
            // asu = 0 (-113dB or less) is very weak
            // signal, its better to show 0 bars to the user in such cases.
            // asu = 99 is a special case, where the signal strength is unknown.
            if (asu <= 2 || asu == 99) iconLevel = 0;            
            else if (asu >= 12) iconLevel = 4;
            else if (asu >= 8)  iconLevel = 3;
            else if (asu >= 5)  iconLevel = 2;
            else iconLevel = 1;

            // Though mPhone is a Manager, this call is not an IPC
            if (mPhone.isNetworkRoaming()) {
                iconList = sSignalImages_r[mInetCondition];
            } else {
                iconList = sSignalImages[mInetCondition];
            }
        } else {
            iconList = sSignalImages[mInetCondition];

            // If 3G(EV) and 1x network are available than 3G should be //當有3G和1X(電信2.5G)網路的時候會顯示EVDO網路
            // displayed, displayed RSSI should be from the EV side.           
            // If a voice call is made then RSSI should switch to 1x.                   //打電話的時候走的是1X網路，
            if ((mPhoneState == TelephonyManager.CALL_STATE_IDLE) && isEvdo()){
                iconLevel = getEvdoLevel();
                if (false) {
                    Slog.d(TAG, "use Evdo level=" + iconLevel + " to replace Cdma Level=" + getCdmaLevel());
                }
            } else {
                iconLevel = getCdmaLevel();
            }
        }
        mPhoneSignalIconId = iconList[iconLevel];
        mService.setIcon("phone_signal", mPhoneSignalIconId, 0);
    }

    private int getCdmaLevel() {                                                //CDMA訊號顯示
        final int cdmaDbm = mSignalStrength.getCdmaDbm();
        final int cdmaEcio = mSignalStrength.getCdmaEcio();
        int levelDbm = 0;
        int levelEcio = 0;

        if (cdmaDbm >= -75) levelDbm = 4;
        else if (cdmaDbm >= -85) levelDbm = 3;
        else if (cdmaDbm >= -95) levelDbm = 2;
        else if (cdmaDbm >= -100) levelDbm = 1;
        else levelDbm = 0;

        // Ec/Io are in dB*10
        if (cdmaEcio >= -90) levelEcio = 4;
        else if (cdmaEcio >= -110) levelEcio = 3;
        else if (cdmaEcio >= -130) levelEcio = 2;
        else if (cdmaEcio >= -150) levelEcio = 1;
        else levelEcio = 0;

        return (levelDbm < levelEcio) ? levelDbm : levelEcio;
    }

    private int getEvdoLevel() {                                             //EVDO網路顯示 CDMA2000 3G訊號顯示（例如電信天翼3G）
        int evdoDbm = mSignalStrength.getEvdoDbm();
        int evdoSnr = mSignalStrength.getEvdoSnr();
        int levelEvdoDbm = 0;
        int levelEvdoSnr = 0;

        if (evdoDbm >= -65) levelEvdoDbm = 4;
        else if (evdoDbm >= -75) levelEvdoDbm = 3;
        else if (evdoDbm >= -90) levelEvdoDbm = 2;
        else if (evdoDbm >= -105) levelEvdoDbm = 1;
        else levelEvdoDbm = 0;

        if (evdoSnr >= 7) levelEvdoSnr = 4;
        else if (evdoSnr >= 5) levelEvdoSnr = 3;
        else if (evdoSnr >= 3) levelEvdoSnr = 2;
        else if (evdoSnr >= 1) levelEvdoSnr = 1;
        else levelEvdoSnr = 0;

        return (levelEvdoDbm < levelEvdoSnr) ? levelEvdoDbm : levelEvdoSnr;
    }

很多android手機訊號並非很好，他們可以通過修改上面一段讓介面顯示的訊號維持在某個地區內，當然每個模組的訊號取值 RSSI值並不是全部遵循上面這段代碼的分級標準，需對應相應的AT手冊進行修改。