title: how to fix the issue in AS..? ScrollView.setOnScrollChangeListener
body: <pre><code>&lt;ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:id="@+id/scrollMenu"
      android:layout_height="wrap_content"&gt;
  
  
  
   @RequiresApi(api = Build.VERSION_CODES.P)
      private void initViews() {
          scrollMenu = findViewById(R.id.scrollMenu);
          scrollMenu.setOnScrollChangeListener(new View.OnScrollChangeListener() {
              @Override
              public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
  
              }
          });
  //        }
  </code></pre>
  
  <p>E/AndroidRuntime: FATAL EXCEPTION: main
      Process: com.dsmsoft.traccia.sampleui, PID: 12790
      java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dsmsoft.traccia.sampleui/com.dsmsoft.traccia.sampleui.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ScrollView.setOnScrollChangeListener(android.view.View$OnScrollChangeListener)' on a null object reference
          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
          at android.app.ActivityThread.-wrap11(Unknown Source:0)
          at ndroid.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
          at android.os.Handler.dispatchMessage(Handler.java:106)
          at android.os.Looper.loop(Looper.java:164)
          at android.app.ActivityThread.main(ActivityThread.java:6494)
          at java.lang.reflect.Method.invoke(Native Method)
          at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
       Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ScrollView.setOnScrollChangeListener(android.view.View$OnScrollChangeListener)' on a null object reference
          at com.dsmsoft.traccia.sampleui.MainActivity.initViews(MainActivity.java:25)
          at com.dsmsoft.traccia.sampleui.MainActivity.onCreate(MainActivity.java:19)
          at android.app.Activity.performCreate(Activity.java:7009)
          at android.app.Activity.performCreate(Activity.java:7000)
          at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
          at android.app.ActivityThread.-wrap11(Unknown Source:0) 
          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
          at android.os.Handler.dispatchMessage(Handler.java:106) 
          at android.os.Looper.loop(Looper.java:164) 
          at android.app.ActivityThread.main(ActivityThread.java:6494) 
          at java.lang.reflect.Method.invoke(Native Method) 
          at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 
  Process 12790 terminated.</p>