Android Studio：我曾经能够成功运行我的应用程序，但现在它无法再次运行。发生了什么？答案

【问题标题】：Android Studio: I was able to successfully run my app once but now it won't work again. What happened?Android Studio：我曾经能够成功运行我的应用程序，但现在它无法再次运行。发生了什么？
【发布时间】：2015-08-28 02:55:01
【问题描述】：

这是我第二次尝试运行我的应用时由 Android Studio 生成的错误。在我尝试运行它的时间之间我没有改变任何东西。第一次运行良好，但现在根本无法运行。

    Process: info.androidhive.materialdesign, PID: 5950
    java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.materialdesign/info.androidhive.materialdesign.activity.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            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:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
            at info.androidhive.materialdesign.activity.MainActivity.onCreate(MainActivity.java:63)
            at android.app.Activity.performCreate(Activity.java:5990)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            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:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

【问题讨论】：

标签： java android android-fragments android-studio

【解决方案1】：

我认为这解释了错误：

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
        at info.androidhive.materialdesign.activity.MainActivity.onCreate(MainActivity.java:63)

您是否再次检查过您的代码，例如进行一些调试？

【讨论】：

【解决方案2】：

我认为这不是 Android Studio 错误。您的适配器返回 null。将数据检查到适配器或循环的最大值中。当它应该是 '

【讨论】：