嘗試調用虛擬方法'int java.lang.String.hashCode（）'

我試圖從URL加載圖像到使用Volley庫的girdview。爲此，我正在關注this教程。當我運行我的項目時，它從服務器數據庫中收集所有URL，然後存儲在數組列表中。但不顯示圖像。我得到java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.hashCode()' on a null object reference錯誤。它甚至沒有指向我得到這個錯誤的任何代碼行數。見下面Logcat輸出：嘗試調用虛擬方法'int java.lang.String.hashCode（）'

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)

任何人都可以幫助我什麼是確切的問題，我該如何解決這個問題？

來源

2015-10-13 Ruchir

可能重複[什麼是空指針異常，以及如何解決它？]（http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how -do-i-fix-it） – Selvin

@Selvin No ..這不是重複什麼是空指針.... – Ruchir

你正在對空字符串調用#hashCode（）。 – nbokmans

獲取字符串值作爲空的，此實例說明String.hashcode（）錯誤

來源

2016-08-29 09:55:26

你應該檢查空值，你從服務器獲取數據的圖像。

來源

2016-10-04 12:46:30

嘗試調用虛擬方法'int java.lang.String.hashCode（）'

回答

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