如何从Android PhoneStateListener返回值？

import android.telephony.PhoneStateListener;
import android.telephony.TelephonyManager;

public class MyPhoneStateListener extends PhoneStateListener {
    @Override
    public void onCallStateChanged(int state, String incomingNumber) {
        super.onCallStateChanged(state, incomingNumber);
        
        switch (state) {
            case TelephonyManager.CALL_STATE_IDLE:
                // 电话空闲状态
                break;
            case TelephonyManager.CALL_STATE_RINGING:
                // 电话响铃状态，有电话呼入
                break;
            case TelephonyManager.CALL_STATE_OFFHOOK:
                // 电话接通状态，正在通话中
                break;
        }
        
        // 处理呼入号码
        if (incomingNumber != null) {
            // 呼入号码不为空
        }
    }
}

import android.content.Context;
import android.telephony.TelephonyManager;

public class MainActivity extends AppCompatActivity {
    private TelephonyManager telephonyManager;
    private MyPhoneStateListener phoneStateListener;

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

        // 获取TelephonyManager实例
        telephonyManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);

        // 创建PhoneStateListener实例
        phoneStateListener = new MyPhoneStateListener();

        // 注册PhoneStateListener
        telephonyManager.listen(phoneStateListener, PhoneStateListener.LISTEN_CALL_STATE);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        // 取消注册PhoneStateListener
        telephonyManager.listen(phoneStateListener, PhoneStateListener.LISTEN_NONE);
    }
}