如何在Android中检测信号强度？

Question

I want to send SMS when the signal strength is above 5 (I believe that is the minimum signal required to send an SMS). however, i want a reliable method to check this, so checking signal strength seems to be the best bet as it would also cover airplane mode.

An important constraint is that CellSignalStrength was added in API level 17, and need my code to work on API level 8 and above.

Answer 1

There is a thing - SignalStrength in android.telephony.SignalStrenght

The class contains methods to get various network strenght for example: getGsmSignalStrength() which gives you data in range 0-31 31 (99 is invalid)
For CDMA there are other methods like getCdmaDbm() which gives you values in dBm so you should convert them to your scale.
[EDIT]Example of use

telephonyManager = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);

final PhoneStateListener mListener = new PhoneStateListener() {
 @Override
 public void onSignalStrengthsChanged(SignalStrength sStrength) {
  //get your signals data
 }
};

// Register the listener for the telephony manager
telephonyManager.listen(mListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);