为什么我的Java代码总是在AndroidStudio中将信号强度打印为零

我对编码非常陌生,这是我第一次使用TelephonyManager.我不知道为什么当我按下此代码中的按钮时,TextView只输出零.我需要它来打印信号强度.该应用程序可以编译并运行,并且具有权限,因此我现在没有想法.
谢谢,麻烦您了.

package com.example.vitaliy_2.signalminer11;
import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.telephony.PhoneStateListener;
import android.telephony.SignalStrength;
import android.telephony.TelephonyManager;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class Menu extends AppCompatActivity{
TextView cdmaSignal;
Button cellButt;
String cap;
TelephonyManager tm;
MMPSL mm;
float sigstr;
int permissionCheck;
@RequiresApi(api = Build.VERSION_CODES.N)
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_menu);
cdmaSignal = (TextView) findViewById(R.id.cdmaSignal);
cellButt = (Button) findViewById(R.id.cellButt);
mm = new MMPSL();
tm = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
tm.listen(mm,PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);
permissiOnCheck= ContextCompat.checkSelfPermission(Menu.this,
Manifest.permission.READ_PHONE_STATE);
cap = Float.toString(sigstr);
String nmp = "Permission required for the continued function of the phone signal monitor ";
if(permissionCheck != PackageManager.PERMISSION_GRANTED){
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.READ_PHONE_STATE)) {
} else {
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.READ_PHONE_STATE},
1);
}
cdmaSignal.setText(nmp);
}
}
public void clkFrSgnl(View view){
cdmaSignal.setText(cap);
// tts = Integer.toString(gs.signal);
//gsmSignal.setText(tts);
}
class MMPSL extends PhoneStateListener{
@Override
public void onSignalStrengthsChanged(SignalStrength signalStrength) {
super.onSignalStrengthsChanged(signalStrength);
sigstr = signalStrength.getCdmaDbm();
sigstr = (2 * sigstr) - 113;
}
}
}


这是xml文件


xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_menu"
android:layout_
android:layout_
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:cOntext="com.example.vitaliy_2.signalminer11.Menu">
android:layout_
android:layout_
android:text="@string/cell_signal_CDMA"
android:textAlignment="center"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:id="@+id/cdmaSignal"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
android:text="@string/get_signal_CDMA"
android:layout_
android:layout_
android:layout_alignParentBottom="true"
android:layout_centerHorizOntal="true"
android:id="@+id/cellButt"
android:OnClick="clkFrSgnl" />



从我过去所做的事情来看,andoroid：onClick函数足以满足按钮和代码中的需要.视图类被调用.

解决方法:

public void clkFrSgnl(View view){
cap = Float.toString(sigstr);
cdmaSignal.setText(cap);
}