启动新的activity安卓系统时出错

Question

我是Android开发的新手，在创建一个新的activity时遇到了一些问题。我想在单击按钮但应用程序崩溃时启动一个新的activity。以下是控制台和logcat中的内容：

logcat

null

03-11 00:21:08.639: D/AndroidRuntime(336): Shutting down VM
03-11 00:21:08.649: W/dalvikvm(336): threadid=1: thread exiting with uncaught exception (group=0x40015560)
03-11 00:21:08.659: E/AndroidRuntime(336): FATAL EXCEPTION: main
03-11 00:21:08.659: E/AndroidRuntime(336): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.src.vicnote/com.src.vicnote.MainActivity}: java.lang.NullPointerException
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.os.Looper.loop(Looper.java:123)
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.app.ActivityThread.main(ActivityThread.java:3683)
03-11 00:21:08.659: E/AndroidRuntime(336):  at java.lang.reflect.Method.invokeNative(Native Method)
03-11 00:21:08.659: E/AndroidRuntime(336):  at java.lang.reflect.Method.invoke(Method.java:507)
03-11 00:21:08.659: E/AndroidRuntime(336):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-11 00:21:08.659: E/AndroidRuntime(336):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-11 00:21:08.659: E/AndroidRuntime(336):  at dalvik.system.NativeStart.main(Native Method)
03-11 00:21:08.659: E/AndroidRuntime(336): Caused by: java.lang.NullPointerException
03-11 00:21:08.659: E/AndroidRuntime(336):  at com.src.vicnote.MainActivity.onCreate(MainActivity.java:26)
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-11 00:21:08.659: E/AndroidRuntime(336):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
03-11 00:21:08.659: E/AndroidRuntime(336):  ... 11 more
03-11 00:21:38.579: D/AndroidRuntime(365): Shutting down VM
03-11 00:21:38.579: W/dalvikvm(365): threadid=1: thread exiting with uncaught exception (group=0x40015560)
03-11 00:21:38.599: E/AndroidRuntime(365): FATAL EXCEPTION: main
03-11 00:21:38.599: E/AndroidRuntime(365): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.src.vicnote/com.src.vicnote.MainActivity}: java.lang.NullPointerException
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.os.Looper.loop(Looper.java:123)
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.app.ActivityThread.main(ActivityThread.java:3683)
03-11 00:21:38.599: E/AndroidRuntime(365):  at java.lang.reflect.Method.invokeNative(Native Method)
03-11 00:21:38.599: E/AndroidRuntime(365):  at java.lang.reflect.Method.invoke(Method.java:507)
03-11 00:21:38.599: E/AndroidRuntime(365):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-11 00:21:38.599: E/AndroidRuntime(365):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-11 00:21:38.599: E/AndroidRuntime(365):  at dalvik.system.NativeStart.main(Native Method)
03-11 00:21:38.599: E/AndroidRuntime(365): Caused by: java.lang.NullPointerException
03-11 00:21:38.599: E/AndroidRuntime(365):  at com.src.vicnote.MainActivity.onCreate(MainActivity.java:26)
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-11 00:21:38.599: E/AndroidRuntime(365):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
03-11 00:21:38.599: E/AndroidRuntime(365):  ... 11 more
Activity_Main
<pre><FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.src.vicnote.MainActivity"
tools:ignore="MergeRootFrame" /><code>
Fragment_Main
Java电码
http://pastebin.com/k8eawd2l
                




Answer 1

从它看起来是您设置内容视图

setContentView(R.layout.activity_main);

但是在activity_main.xml中没有您所提供的按钮，并且显示nullpointerexception,因为

newButton = (Button) findViewById(R.id.buttonNew);

是null，因为您提供信息中的实际按钮在

fragment_main.xml

所以你可以试试

setContentView(R.layout.fragment_main);