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我正在 Android Studio 中开发一个应用程序，由于某种原因，它不断抛出错误“不幸的是，MyApp 已停止”。这只发生在我运行应用程序，在它运行时对代码进行更改，然后尝试再次运行它时。如果我停止“运行”任务并重新启动它，我不会收到此错误。

这是日志：

06-14 15:54:06.213 25752-25752/com.myapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.myapp, PID: 25752
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp/com.myapp.activity_host}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.myapp.MB_item.getItemId()' on a null object reference
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
  at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4077)
  at android.app.ActivityThread.-wrap15(ActivityThread.java)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1350)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:148)
  at android.app.ActivityThread.main(ActivityThread.java:5417)
  at java.lang.reflect.Method.invoke(Native Method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.myapp.MB_item.getItemId()' on a null object reference
  at com.myapp.BT_screen_menuButtons$override.onCreateView(MB_screen_menuButtons.java:119)
  at com.myapp.BT_screen_menuButtons$override.access$dispatch(MB_screen_menuButtons.java)
  at com.myapp.BT_screen_menuButtons.onCreateView(MB_screen_menuButtons.java:0)
  at android.app.Fragment.performCreateView(Fragment.java:2220)
  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:973)
  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1148)
  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1130)
  at android.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1953)
  at android.app.FragmentController.dispatchActivityCreated(FragmentController.java:152)
  at android.app.Activity.performCreateCommon(Activity.java:6232)
  at android.app.Activity.performCreate(Activity.java:6239)
  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
  at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4077) 
  at android.app.ActivityThread.-wrap15(ActivityThread.java) 
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1350) 
  at android.os.Handler.dispatchMessage(Handler.java:102) 
  at android.os.Looper.loop(Looper.java:148) 
  at android.app.ActivityThread.main(ActivityThread.java:5417) 
  at java.lang.reflect.Method.invoke(Native Method) 
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

为什么代码只会在后续启动时表现不同，而不是在我最初运行应用程序时？

附加代码：

这是引发错误的行（MB_screen_menuButtons.java 的第 119 行）。screenData.getItemId() 显然是传递空值的位置，但我不明白为什么它只会在即时运行更新期间为空。

debugger.showIt(fragmentName + ":onCreateView JSON itemId: \"" + screenData.getItemId() + "\" itemType: \"" + screenData.getItemType() + "\" itemNickname: \"" + screenData.getItemNickname() + "\"");
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1 回答 1

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这似乎是Instant Run与您的代码中的某些内容不兼容的问题 - 可能是生成代码的库。

您可以禁用 Instant Run，它应该可以解决此问题：

首选项 > 构建、执行、部署 > 即时运行 > 取消选中“启用即时运行”

如果您想保留即时运行，您可以取消选中“重新启动代码更改活动”

Preferences > Build, Execution, Deployment > Instant Run > 取消选中“Restart Activity on Code Changes”

于 2016-06-16T17:45:41.130 回答