未连接蜂窝网络时，Android 仍会检测蜂窝信号强度

Question

我编写了一个小 Android 程序来检测蜂窝信号强度。我在手机中插入了一张过期的 SIM 卡，它在状态栏中显示零信号。但是，以下代码返回 Signal strength equals to 22。

public class WelcomeActivity extends AppCompatActivity {
    TelephonyManager telephonyManager;
    CustomPhoneStateListener customPhoneStateListener;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_welcome);

        customPhoneStateListener = new CustomPhoneStateListener();
        telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
        telephonyManager.listen(customPhoneStateListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);
    }

    @Override
    protected void onPause() {
        super.onPause();
        telephonyManager.listen(customPhoneStateListener, PhoneStateListener.LISTEN_NONE);
    }

    @Override
    protected void onResume() {
        super.onResume();
        telephonyManager.listen(customPhoneStateListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);
    }


    /* Phone State Listener */
    private class CustomPhoneStateListener extends PhoneStateListener {
        @Override
        public void onSignalStrengthsChanged(SignalStrength signalStrength) {
            super.onSignalStrengthsChanged(signalStrength);

            int strength = signalStrength.getGsmSignalStrength();
            Toast.makeText(getApplicationContext(), "Signal Strength: " + String.valueOf(strength), Toast.LENGTH_SHORT).show();
        }
    }
}

值 22 从何而来？如何检测蜂窝网络是否已连接？这个值真的靠谱吗？

从 Android documentation 开始，getGsmSignalStrength() 返回值 0 到 31 和 99。

Answer 1

我刚刚实现了n个运行代码：

package com.example.sanketprabhu.gsmsignalstrength;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.telephony.PhoneStateListener;
import android.telephony.SignalStrength;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity
    {
        TelephonyManager Tel;
        MyPhoneStateListener MyListener;

        @Override
        public void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            MyListener   = new MyPhoneStateListener();
            Tel       = ( TelephonyManager )getSystemService(Context.TELEPHONY_SERVICE);
            Tel.listen(MyListener ,PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);
        }

         @Override
        protected void onPause()
        {
            super.onPause();
            Tel.listen(MyListener, PhoneStateListener.LISTEN_NONE);
        }

          @Override
        protected void onResume()
        {
            super.onResume();
            Tel.listen(MyListener,PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);
        }

        public  class MyPhoneStateListener extends PhoneStateListener
        {
            /* Get the Signal strength from the provider, each tiome there is an update */
            @Override
            public void onSignalStrengthsChanged(SignalStrength signalStrength)
            {
                super.onSignalStrengthsChanged(signalStrength);
                Toast.makeText(getApplicationContext(), "Go to Firstdroid!!! GSM Cinr = " 
                        + String.valueOf(signalStrength.getGsmSignalStrength()), Toast.LENGTH_SHORT).show();
            }

        }

    }

它对我有用。

这里我附上了一些屏幕截图。

你是对的：0-31 和 99 的投注值

不幸的是，我在办公室信号强度低，但工作正常