安卓开发错误日志什么意思？

Question

2019-01-29 21:39:43.401 7638-7638/com.example.administrator.charge E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.administrator.charge, PID: 7638
    java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
        at com.example.administrator.charge.model.adapter.BookManageAdpter.getItemCount(BookManageAdpter.java:116)
        at android.support.v7.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:3722)
        at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:3219)
        at android.view.View.measure(View.java:22097)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6604)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:806)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:685)
        at android.view.View.measure(View.java:22097)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6604)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:141)
        at android.view.View.measure(View.java:22097)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6604)
        at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:400)
        at android.view.View.measure(View.java:22097)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6604)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at android.view.View.measure(View.java:22097)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6604)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:806)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:685)
        at android.view.View.measure(View.java:22097)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6604)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at com.android.internal.policy.DecorView.onMeasure(DecorView.java:727)
        at android.view.View.measure(View.java:22097)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2461)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1543)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1800)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1431)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6861)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1026)
        at android.view.Choreographer.doCallbacks(Choreographer.java:838)
        at android.view.Choreographer.doFrame(Choreographer.java:769)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1012)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6648)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)

Answer 1

  java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
        at com.example.administrator.charge.model.adapter.BookManageAdpter.getItemCount(BookManageAdpter.java:116)重点句

Answer 2

空指针问题，使用的时候先判断是否为null；
BookManageAdpter的getItemCount方法中，你现在应该是直接返回的list.size();改为return list == null ? 0 :list.size();

Answer 3

 java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference这句话重点，
BookManageAdpter.java:116在这个适配器里错误第116行，你的这个list.size()空指针，要给他写判断是否为null
不为空时做业务操作，空时不做业务操作或给提示不继续运行下面的代码

Answer 4

主要是空指针异常，应该是你的list里面没有值