title: Problem in logout for my app. app keeps on crashing
body: <p>I'm trying to make a logout for my project. i want that whenever i click to logout image i intent to my login page again. For login i'm using Firebase. But i have write code for intent and whenever i'm running my app it's keeps crashing. <strong>Unfortunately, animation(name of my project) has stopped.</strong></p>
  
  <pre><code>import android.content.Intent;
  import android.graphics.drawable.AnimationDrawable;
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.view.View;
  import android.widget.ImageView;
  import android.widget.RelativeLayout;
  
  
  import com.google.firebase.auth.FirebaseAuth;
  
  
  public class dashboard extends AppCompatActivity {
      RelativeLayout myLayout;
      AnimationDrawable animationDrawable;
  
      ImageView imgauto,imgbud,imglimit,imgug,imgsignout;
      FirebaseAuth firebaseAuth;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_dashboard);
          timing(); ////////// animation
  
  
  
        imgauto = findViewById(R.id.autoimg);
          imgug = findViewById(R.id.ugimg);
         imglimit =findViewById(R.id.limitimg);
         imgsignout=findViewById(R.id.sign_out);
        imgauto.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               startActivity(new Intent(dashboard.this,view_rooms.class));
             }
          });
        imglimit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(dashboard.this,limit_rooms.class));
            }
        });
        imgug.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(dashboard.this,guidance_new.class));
            }
        });
          imgsignout.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View v) {
                  firebaseAuth.signOut();
                  finish();
                  startActivity(new Intent(dashboard.this,MainActivity.class));
              }
          });
      }
      private void timing(){
          myLayout=findViewById(R.id.dashboard);
          animationDrawable=(AnimationDrawable)myLayout.getBackground();
          animationDrawable.setEnterFadeDuration(2500);
          animationDrawable.setExitFadeDuration(2500);
          animationDrawable.start();
  
      }
  }
  </code></pre>
  
  <p>That's logcat:</p>
  
  <pre><code>05-25 13:04:27.429 8730-8730/com.example.animation E/AndroidRuntime: FATAL EXCEPTION: main
      java.lang.NullPointerException
          at com.example.animation.dashboard$4.onClick(dashboard.java:55)
          at android.view.View.performClick(View.java:4211)
          at android.view.View$PerformClick.run(View.java:17446)
          at android.os.Handler.handleCallback(Handler.java:725)
          at android.os.Handler.dispatchMessage(Handler.java:92)
          at android.os.Looper.loop(Looper.java:153)
          at android.app.ActivityThread.main(ActivityThread.java:5336)
          at java.lang.reflect.Method.invokeNative(Native Method)
          at java.lang.reflect.Method.invoke(Method.java:511)
          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
          at dalvik.system.NativeStart.main(Native Method)
  </code></pre>