accident d'application Andriod et donne la tentative d'erreur d'invoquer la méthode virtuelle sur un objet null référence

Question

Je suis en train de faire une application comme Twitter et mon application se bloque en raison de l'erreur suivante:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

Ceci est mon LoginActivity code:

package com.ghayoorshan.nestedlayout1; 
import android.content.Intent; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.widget.TextView; 
import android.view.View.OnClickListener; 

public class LoginActivity extends AppCompatActivity { 

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

     TextView registerScreen = (TextView) findViewById(R.id.link_to_register); 
     // Button button = (Button)findViewById(R.id.link_to_register); 
     // Listening to register new account link 
     registerScreen.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 
     // Switching to Register screen 
       Intent i = new Intent(getApplicationContext(), RegisterActivity.class); 
       startActivity(i); 
      } 
     }); 
    } 
} 

l'erreur se produit dans la ligne suivante:

registerScreen.setOnClickListener(new View.OnClickListener()... 

Logcat:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ghayoorshan.nestedlayout1/com.ghayoorshan.nestedlayout1.LoginActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference            
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2552) 
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2618) 
     at android.app.ActivityThread.-wrap11(ActivityThread.java) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1474) 
     at android.os.Handler.dispatchMessage(Handler.java:111) 
     at android.os.Looper.loop(Looper.java:207) 
     at android.app.ActivityThread.main(ActivityThread.java:5701) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:888) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:749) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference 
     at com.ghayoorshan.nestedlayout1.LoginActivity.onCreate(LoginActivity.java:18) 
     at android.app.Activity.performCreate(Activity.java:6294) 
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1113) 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2505) 
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2618) 
     at android.app.ActivityThread.-wrap11(ActivityThread.java) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1474) 
     at android.os.Handler.dispatchMessage(Handler.java:111) 
     at android.os.Looper.loop(Looper.java:207) 
     at android.app.ActivityThread.main(ActivityThread.java:5701) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:888) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:749) 
03-04 02:41:33.060 24340-24340/com.ghayoorshan.nestedlayout1 I/Process: Sending signal. PID: 24340 SIG: 9 

Quelle est la cause de l'erreur?

Answer 1

Votre mise en page xml "activity_login.xml" ne contient pas TextView avec l'ID link_to_register ou son ID serait différent. Vérifiez "activity_login.xml" pour trouver le problème exact.

Answer 2

@Passiondroid ceci est mon code XML je pense que tout est ici

<!-- Link to Registration Screen --> 
      <TextView android:id="@+id/link_to_register" 
       android:layout_width="fill_parent" 
       android:layout_height="wrap_content" 
       android:layout_marginTop="40dip" 
       android:layout_marginBottom="40dip" 
       android:text="New to Twitter? Register here" 
       android:gravity="center" 
       android:textSize="20dip" 
       android:textColor="#0b84aa"/>