智能手机中显示信号强度格数

在Android4.0的系统中，手机中显示信号强度格数的代码在

frameworks\base\telephony\java\android\telephony\SignalStrength.java

getLevel( )函数，该函数是主要用来获取信号的强度。

public int getLevel() {
        int level;

        if (isGsm) {
            level = getLteLevel();
            if (level == SIGNAL_STRENGTH_NONE_OR_UNKNOWN) {
                level = getGsmLevel();
            }
        } else {
            int cdmaLevel = getCdmaLevel();
            int evdoLevel = getEvdoLevel();
            if (evdoLevel == SIGNAL_STRENGTH_NONE_OR_UNKNOWN) {
                /* We don't know evdo, use cdma */
                level = cdmaLevel;
            } else if (cdmaLevel == SIGNAL_STRENGTH_NONE_OR_UNKNOWN) {
                /* We don't know cdma, use evdo */
                level = evdoLevel;
            } else {
                /* We know both, use the lowest level */
                //level = cdmaLevel < evdoLevel ? cdmaLevel : evdoLevel;
                level = cdmaLevel > evdoLevel ? cdmaLevel : evdoLevel;
            }
        }
        if (DBG) log("getLevel=" + level);
        return level;
    }

getCdmaLevel( )获取CdmaLevel，同样也有getEvdoLevel( )函数，在上一个函数中，通过比较Evdo和Cdma的强度，来最终确定信号的显示强度，也就是我们在通知栏里看到的信号格数。

public int getCdmaLevel() {
        final int cdmaDbm = getCdmaDbm();
        final int cdmaEcio = getCdmaEcio();
        int levelDbm;
        int levelEcio;

        if (cdmaDbm >= -75) levelDbm = SIGNAL_STRENGTH_GREAT;
        else if (cdmaDbm >= -85) levelDbm = SIGNAL_STRENGTH_GOOD;
        else if (cdmaDbm >= -95) levelDbm = SIGNAL_STRENGTH_MODERATE;
        else if (cdmaDbm >= -100) levelDbm = SIGNAL_STRENGTH_POOR;
        else levelDbm = SIGNAL_STRENGTH_NONE_OR_UNKNOWN;

        // Ec/Io are in dB*10
        if (cdmaEcio >= -90) levelEcio = SIGNAL_STRENGTH_GREAT;
        else if (cdmaEcio >= -110) levelEcio = SIGNAL_STRENGTH_GOOD;
        else if (cdmaEcio >= -130) levelEcio = SIGNAL_STRENGTH_MODERATE;
        else if (cdmaEcio >= -150) levelEcio = SIGNAL_STRENGTH_POOR;
        else levelEcio = SIGNAL_STRENGTH_NONE_OR_UNKNOWN;

        int level = (levelDbm < levelEcio) ? levelDbm : levelEcio;
        if (DBG) log("getCdmaLevel=" + level + ",cdmaDbm=" + cdmaDbm + ",cdmaEcio=" +cdmaEcio);
        return level;
    }