title: Attempt to invoke virtual method 'int java.lang.String.hashCode()'
body: <p>I'm trying to load images from URL into girdview using Volley Library. For this I'm following <a href="http://www.101apps.co.za/index.php/articles/using-volley-to-download-cache-and-display-bitmaps.html" rel="noreferrer">this</a> tutorial. When I run my project, it collects all URLs from server database and then store in arraylist. But doesn't displays images. And I am getting <code>java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.hashCode()' on a null object reference</code> error. It doesn't even point to any line number of code where I'm getting this error. See below Logcat Output :</p>
  
  <pre><code>java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.hashCode()' on a null object reference
          at com.android.volley.Request.&lt;init&gt;(Request.java:136)
          at com.android.volley.toolbox.ImageRequest.&lt;init&gt;(ImageRequest.java:71)
          at com.android.volley.toolbox.ImageLoader.get(ImageLoader.java:219)
          at com.android.volley.toolbox.ImageLoader.get(ImageLoader.java:171)
          at com.android.volley.toolbox.NetworkImageView.loadImageIfNecessary(NetworkImageView.java:141)
          at com.android.volley.toolbox.NetworkImageView.onLayout(NetworkImageView.java:190)
          at android.view.View.layout(View.java:15596)
          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
          at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
          at android.view.View.layout(View.java:15596)
          at android.view.ViewGroup.layout(ViewGroup.java:4966)
          at android.widget.GridView.setupChild(GridView.java:1542)
          at android.widget.GridView.makeAndAddView(GridView.java:1436)
          at android.widget.GridView.makeRow(GridView.java:361)
          at android.widget.GridView.fillDown(GridView.java:302)
          at android.widget.GridView.fillFromTop(GridView.java:437)
          at android.widget.GridView.layoutChildren(GridView.java:1276)
          at android.widget.AbsListView.onLayout(AbsListView.java:2148)
          at android.view.View.layout(View.java:15596)
          at android.view.ViewGroup.layout(ViewGroup.java:4966)
          at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
          at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
          at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
          at android.view.View.layout(View.java:15596)
          at android.view.ViewGroup.layout(ViewGroup.java:4966)
          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
          at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
          at android.widget.ScrollView.onLayout(ScrollView.java:1502)
          at android.view.View.layout(View.java:15596)
          at android.view.ViewGroup.layout(ViewGroup.java:4966)
          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
          at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
          at android.view.View.layout(View.java:15596)
          at android.view.ViewGroup.layout(ViewGroup.java:4966)
          at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:494)
          at android.view.View.layout(View.java:15596)
          at android.view.ViewGroup.layout(ViewGroup.java:4966)
          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
          at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
          at android.view.View.layout(View.java:15596)
          at android.view.ViewGroup.layout(ViewGroup.java:4966)
          at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2072)
          at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1829)
          at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
          at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
          at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
          at android.view.Choreographer.doCallbacks(Choreographer.java:580)
          at android.view.Choreographer.doFrame(Choreographer.java:550)
          at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
          at android.os.Handler.handleCallback(Handler.java:739)
          at android.os.Handler.dispatchMessage(Handler.java:95)
          at android.os.Looper.loop(Looper.java:135)
          at android.app.ActivityThread.main(ActivityThread.java:5221)
          at java.lang.reflect.Method.invoke(Native Method)
          at java.lang.reflect.Method.invoke(Method.java:372)
          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
  </code></pre>
  
  <p>Can anybody help me what is the exact problem and how do I solve this ?</p>