When I run the app, the build is successful but the app is crashing. Please help me with that. Below is the error I'm receiving in the run tab

Question

D/AndroidRuntime: Shutting down VM E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.hello, PID: 26685 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.hello/com.example.hello.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference at com.example.hello.MainActivity.loadRecyclerViewData(MainActivity.java:93) at com.example.hello.MainActivity.onCreate(MainActivity.java:42) at android.app.Activity.performCreate(Activity.java:7136) at android.app.Activity.performCreate(Activity.java:7127) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)  at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)  at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)  at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)  at android.os.Handler.dispatchMessage(Handler.java:106)  at android.os.Looper.loop(Looper.java:193)  at android.app.ActivityThread.main(ActivityThread.java:6669)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)  E/Volley: [1025] NetworkDispatcher.processRequest: Unhandled exception java.lang.ClassCastException: sun.net.www.protocol.file.FileURLConnection cannot be cast to java.net.HttpURLConnection java.lang.ClassCastException: sun.net.www.protocol.file.FileURLConnection cannot be cast to java.net.HttpURLConnection at com.android.volley.toolbox.HurlStack.createConnection(HurlStack.java:189) at com.android.volley.toolbox.HurlStack.openConnection(HurlStack.java:207) at com.android.volley.toolbox.HurlStack.executeRequest(HurlStack.java:88) at com.android.volley.toolbox.BasicNetwork.performRequest(BasicNetwork.java:123) at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:131) at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:111) at com.android.volley.NetworkDispatcher.run(NetworkDispatcher.java:90) I/Process: Sending signal. PID: 26685 SIG: 9

Answer 1

When you are setting layout manager RecyclerView instance is null:

ava.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)