Volley Library を使用して、URL から girdview に画像を読み込もうとしています。このために、私はこのチュートリアルに従っています。プロジェクトを実行すると、サーバー データベースからすべての URL が収集され、arraylist に格納されます。ただし、画像は表示されません。そして、私はjava.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.hashCode()' on a null object referenceエラーが発生しています。このエラーが発生しているコードの行番号も指していません。以下の Logcat 出力を参照してください。
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.hashCode()' on a null object reference
at com.android.volley.Request.<init>(Request.java:136)
at com.android.volley.toolbox.ImageRequest.<init>(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)
正確な問題とは何か、これを解決するにはどうすればよいですか?