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我是 Android 应用程序开发的新手，我尝试编写我的第一个简单应用程序以尝试在活动之间发送数据。代码已编译，我尝试在虚拟设备上启动它，但就像标题所说的那样，它停止了。

这是 logcat 输出：

     08-16 22:44:22.729: D/AndroidRuntime(800): Shutting down VM
     08-16 22:44:22.749: W/dalvikvm(800): threadid=1: thread exiting with uncaught exception          (group=0x414c4700)
     08-16 22:44:22.829: E/AndroidRuntime(800): FATAL EXCEPTION: main
     08-16 22:44:22.829: E/AndroidRuntime(800): java.lang.RuntimeException: Unable to    instantiate activity ComponentInfo{com.example.Testapp/com.example.Testapp.FirstActivity}:   java.lang.NullPointerException
     08-16 22:44:22.829: E/AndroidRuntime(800):     at    android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at  android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at android.os.Handler.dispatchMessage(Handler.java:99)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at android.os.Looper.loop(Looper.java:137)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at andr     oid.app.ActivityThread.main(ActivityThread.java:5103)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at java.lang.reflect.Method.invokeNative(Native Method)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at  java.lang.reflect.Method.invoke(Method.java:525)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
      08-16 22:44:22.829: E/AndroidRuntime(800):    at dalvik.system.NativeStart.main(Native Method)
      08-16 22:44:22.829: E/AndroidRuntime(800): Caused by: java.lang.NullPointerException
      08-16 22:44:22.829: E/AndroidRuntime(800):    at     android.app.Activity.findViewById(Activity.java:1853)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at com.example.Testapp.FirstActivity.<init>(FirstActivity.java:12)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at java.lang.Class.newInstanceImpl(Native Method)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at java.lang.Class.newInstance(Class.java:1130)
     08-16 22:44:22.829: E/AndroidRuntime(800):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
08-16 22:44:22.829: E/AndroidRuntime(800):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128)
08-16 22:44:22.829: E/AndroidRuntime(800):  ... 11 more
08-16 22:45:14.220: I/Process(800): Sending signal. PID: 800 SIG: 9
08-16 22:45:29.609: D/AndroidRuntime(903): Shutting down VM
08-16 22:45:29.619: W/dalvikvm(903): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
08-16 22:45:29.679: E/AndroidRuntime(903): FATAL EXCEPTION: main
08-16 22:45:29.679: E/AndroidRuntime(903): java.lang.RuntimeException: Unable to instantiate     activity ComponentInfo{com.example.Testapp/com.example.Testapp.FirstActivity}: java.lang.NullPointerException
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137)
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.os.Handler.dispatchMessage(Handler.java:99)
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.os.Looper.loop(Looper.java:137)
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.app.ActivityThread.main(ActivityThread.java:5103)
08-16 22:45:29.679: E/AndroidRuntime(903):  at java.lang.reflect.Method.invokeNative(Native Method)
08-16 22:45:29.679: E/AndroidRuntime(903):  at     java.lang.reflect.Method.invoke(Method.java:525)
08-16 22:45:29.679: E/AndroidRuntime(903):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
08-16 22:45:29.679: E/AndroidRuntime(903):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-16 22:45:29.679: E/AndroidRuntime(903):  at dalvik.system.NativeStart.main(Native Method)
08-16 22:45:29.679: E/AndroidRuntime(903): Caused by: java.lang.NullPointerException
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.app.Activity.findViewById(Activity.java:1853)
08-16 22:45:29.679: E/AndroidRuntime(903):  at com.example.Testapp.FirstActivity.<init>(FirstActivity.java:12)
08-16 22:45:29.679: E/AndroidRuntime(903):  at java.lang.Class.newInstanceImpl(Native Method)
08-16 22:45:29.679: E/AndroidRuntime(903):  at java.lang.Class.newInstance(Class.java:1130)
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
08-16 22:45:29.679: E/AndroidRuntime(903):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128)
08-16 22:45:29.679: E/AndroidRuntime(903):  ... 11 more

谁能告诉我这个日志引用了什么错误以及我应该在哪里寻找来解决这个问题。

一切顺利

4

1 回答 1

1

谁能告诉我这个日志引用了什么错误以及我应该在哪里寻找来解决这个问题。

这第一行除了之后

FATAL EXCEPTION: main
 08-16 22:44:22.829: E/AndroidRuntime(800): java.lang.RuntimeException: Unable to    instantiate activity ComponentInfo{com.example.Testapp/com.example.Testapp.FirstActivity}:   java.lang.NullPointerException

Caused by: java.lang.NullPointerException

告诉我们有一个NPE. 然后，如果我们找到引用您的项目的第一行，它将告诉我们行号

at com.example.Testapp.FirstActivity.<init>(FirstActivity.java:12)

null第 12 行有东西FirstActivity。View最有可能在膨胀之前实例化 alayout但可能是关于任何事情。

如果您无法弄清楚某事是什么/为什么是null，请在第 12 行附近发布这些行。

于 2013-08-16T20:35:01.733 回答