java - 将 MainActivity.java 移动到子文件夹中后执行失败

Question

我目前正在开发我的 Android 项目。就像标题所示，我将 MainActivity.java 文件移动到我的 Activitys 包中，我这样做是因为我的一个 friend 出于概述的原因建议我这样做。现在，在启动、构建和安装工程 finde 后，我收到以下错误代码。

我的项目可以查看:https://github.com/SchoolGuy/GCFunde

02-17 19:39:24.890  16607-16607/de.noname.enno.gcfunde E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: de.noname.enno.gcfunde, PID: 16607
    java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
            at android.widget.AbsListView.obtainView(AbsListView.java:2483)
            at android.widget.ListView.makeAndAddView(ListView.java:1864)
            at android.widget.ListView.fillDown(ListView.java:698)
            at android.widget.ListView.fillFromTop(ListView.java:759)
            at android.widget.ListView.layoutChildren(ListView.java:1673)
            at android.widget.AbsListView.onLayout(AbsListView.java:2271)
            at android.view.View.layout(View.java:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            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:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            at android.support.design.widget.CoordinatorLayout.layoutChild(CoordinatorLayout.java:1034)
            at android.support.design.widget.CoordinatorLayout.onLayoutChild(CoordinatorLayout.java:744)
            at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
            at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1180)
            at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:757)
            at android.view.View.layout(View.java:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1043)
            at android.view.View.layout(View.java:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
            at android.view.View.layout(View.java:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            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:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
            at android.view.View.layout(View.java:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            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:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
            at android.view.View.layout(View.java:15695)
            at android.view.ViewGroup.layout(ViewGroup.java:4981)
            at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2209)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1943)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1126)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6041)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:792)
            at android.view.Choreographer.doCallbacks(Choreographer.java:596)
            at android.view.Choreographer.doFrame(Choreographer.java:557)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:778)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:155)
            at android.app.ActivityThread.main(ActivityThread.java:5727)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1029)
            at com.android.internal.os.
02-17 19:39:28.163  16607-16607/de.noname.enno.gcfunde D/Process﹕ killProcess, pid=16607
02-17 19:39:28.173  16607-16607/de.noname.enno.gcfunde D/Process﹕ com.android.internal.os.RuntimeInit$UncaughtHandler.uncaughtException:138 java.lang.ThreadGroup.uncaughtException:693 java.lang.ThreadGroup.uncaughtException:690

如果你能帮助我，那就太好了。顺便说一句，我正在使用 IntelliJ 15.0.2，并且我已经做了“无效缓存并重新启动”。据我所知，我认为问题不直接出现在我的类(class)中。

提前致谢，学校_guy

Answer 1

这似乎是一个 ListView 问题 - 可能您的 getView 方法返回 null 而不是实际的 View 对象。检查您的 ListAdapter 实现，并确保永远不会在 public View getView(intposition, View ConvertView, ViewGroupparent) 方法中返回 null。

正如我从 GeocacheListAdapter.java 中的代码中看到的，if 语句是错误的 - 检查应该是 if (convertView == null) 而不是 if(convertView != null)

if (convertView == null) {
            Holder holder = new Holder();
            convertView = layoutInflater.inflate(R.layout.row_layout, null);
            //...
}