Попытка вызвать виртуальный метод 'void android.widget.Button.setOnClickListener

Question

enter image description here Когда я открываю приложение для Android, он выходит из строя. Вот код:

import android.Manifest; 
 
import android.content.Intent; 
 
import android.content.pm.PackageManager; 
 
import android.location.Location; 
 
import android.location.LocationListener; 
 
import android.location.LocationManager; 
 
import android.os.Build; 
 
import android.provider.Settings; 
 
import android.support.v4.app.ActivityCompat; 
 
import android.support.v7.app.AppCompatActivity; 
 
import android.os.Bundle; 
 
import android.view.View; 
 
import android.widget.Button; 
 
import android.widget.TextView; 
 

 

 
public class MainActivity extends AppCompatActivity { 
 

 
    private Button requestButton; 
 
    private TextView coordinateText; 
 
    private LocationManager locationManager; 
 
    private LocationListener locationListener; 
 
    private Button buttonMap; 
 
    private Button buttonCurrentLocation; 
 

 

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

 
     //reference requestButton 
 
     requestButton = (Button) findViewById(R.id.requestButton); 
 
     //reference coordText 
 
     coordinateText = (TextView) findViewById(R.id.coordinateText); 
 

 
     // Creating button object for buttonMap 
 
     buttonMap = (Button) findViewById(R.id.buttonMap); 
 

 
     //Create a button object for buttonCurrentLocation 
 
     buttonCurrentLocation = (Button) findViewById(R.id.buttonCurrentLocation); 
 

 
     //Action listener for buttonMap 
 
     buttonMap.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View v) { 
 
       Intent intent1 = new Intent(getApplicationContext(), MapsActivity.class); 
 
       startActivity(intent1); 
 
      } 
 

 
     }); 
 

 
     // Action listener for buttonCurrentLocation 
 
     buttonCurrentLocation.setOnClickListener(new View.OnClickListener() { 
 
      public void onClick(View v) { 
 

 
       Intent i = new Intent(getApplicationContext(), GPSShow.class); 
 
       startActivity(i); 
 

 
       } 
 

 
     }); 
 

 

 
     //Initialize locationManager 
 
     locationManager = (LocationManager) getSystemService(LOCATION_SERVICE); 
 
     //Initialize locationListener 
 
     locationListener = new LocationListener() { 
 
      @Override 
 
      public void onLocationChanged(Location location) { 
 
       coordinateText.append("\n" + location.getLatitude() + " " + location.getLongitude()); 
 

 
      } 
 

 
      @Override 
 
      public void onStatusChanged(String provider, int status, Bundle extras) { 
 

 
      } 
 

 
      @Override 
 
      public void onProviderEnabled(String provider) { 
 

 
      } 
 

 
      @Override 
 
      public void onProviderDisabled(String provider) { 
 
       Intent intent2 = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS); 
 
       startActivity(intent2); 
 

 
      } 
 
     }; 
 
     if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 
 
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
 
       requestPermissions(new String[]{ 
 
         Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.INTERNET 
 

 
       }, 10); 
 
      } 
 
      return; 
 
     } else { 
 
      configureButton(); 
 
     } 
 

 

 
    } 
 

 
    //OUTSIDE ONCREATE METHOD 
 

 

 
    public void onRequestPermissionResult(int requestCode, String[] permissions, int[] grantResults) { 
 

 
     switch (requestCode) { 
 
      case 10: 
 
       if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) 
 
        configureButton(); 
 
       return; 
 
     } 
 

 
    } 
 

 
    private void configureButton() { 
 
     requestButton.setOnClickListener(new View.OnClickListener() { 
 
      public void onClick(View view) { 
 
       locationManager.requestLocationUpdates("gps", 5000, 0, locationListener); 
 

 
      } 
 
     }); 
 

 
    } 
 

 

 
}

Вот это LogCat:

01-15 17:10:18.088 2340-2340/com.example.matt.palt E/AndroidRuntime: FATAL EXCEPTION: main 
 
                    Process: com.example.matt.palt, PID: 2340 
 
                    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.matt.palt/com.example.matt.palt.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference 
 
                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) 
 
                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
 
                     at android.app.ActivityThread.-wrap11(ActivityThread.java) 
 
                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
 
                     at android.os.Handler.dispatchMessage(Handler.java:102) 
 
                     at android.os.Looper.loop(Looper.java:148) 
 
                     at android.app.ActivityThread.main(ActivityThread.java:5417) 
 
                     at java.lang.reflect.Method.invoke(Native Method) 
 
                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
 
                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
 
                     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference 
 
                     at com.example.matt.palt.MainActivity.configureButton(MainActivity.java:124) 
 
                     at com.example.matt.palt.MainActivity.onCreate(MainActivity.java:103) 
 
                     at android.app.Activity.performCreate(Activity.java:6237) 
 
                     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) 
 
                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) 
 
                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)  
 
                     at android.app.ActivityThread.-wrap11(ActivityThread.java)  
 
                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)  
 
                     at android.os.Handler.dispatchMessage(Handler.java:102)  
 
                     at android.os.Looper.loop(Looper.java:148)  
 
                     at android.app.ActivityThread.main(ActivityThread.java:5417)  
 
                     at java.lang.reflect.Method.invoke(Native Method)  
 
                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)  
 
                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)  
 
01-15 17:10:20.435 2340-2340/com.example.matt.palt I/Process: Sending signal. PID: 2340 SIG: 9

В первый раз я побежал приложения он работает нормально.

Похоже, что проблема заключается в requestButton. Я пробовал искать решение, но не могу найти его.

Main XML file and other XML file

Answer 1

R.id.buttonMap не найден, в результате нуль из findViewById (R.id.buttonMap).

ID buttonMap должен находиться в файле activity_main xml. Это не.

Answer 2

От logcat его ясно, что кнопка requestButton имеет значение null. Кажется, ваш Java-код прав, и проблема в вашем макете. ID requestButton не совсем то же самое в вашем XML-файле. Соответствует вашему xml с кодом Java