Andriod App Absturz und gibt den Fehler Versuch virtuelle Methode auf ein Null-Objekt Verweis aufrufen

Question

Ich versuche, eine App wie Twitter und meine App abstürzt aufgrund der folgenden Fehler zu machen:

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

Das ist mein 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); 
      } 
     }); 
    } 
} 

der Fehler tritt in der folgenden Zeile:

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 

Was den Fehler verursacht?

Answer 1

Ihr Layout-XML "activity_login.xml" enthält kein TextView mit ID link_to_register oder seine ID wäre anders. Überprüfen Sie "activity_login.xml", um das genaue Problem zu finden.

Answer 2

@Passiondroid das ist mein XML-Code Ich denke, alles ist hier richtig

<!-- 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"/>