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启动Android新活动时出错

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我'm new in Android developing and I' m在创建新的 Activity 时遇到了一些问题 . 我想在点击 Button 但应用程序崩溃时启动新的 Activity . 以下是控制台和logcat中的内容：

LogCat

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 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/MainScreen"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.src.vicnote.MainActivity$PlaceholderFragment" >

<Button
android:id="@+id/buttonNew"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:text="New" />

</RelativeLayout>

Java code

http://pastebin.com/K8eAWD2L

java android eclipse android-intent android-activity

4 回答

  • 0

    从它看起来是你设置内容视图

    setContentView(R.layout.activity_main);

    但是在您提供的内容中，activity_main.xml中没有按钮，因为它显示的是nullpointerexception

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

    为null，因为您提供的信息中的实际按钮位于

    fragment_main.xml

    所以你可以尝试

    setContentView(R.layout.fragment_main);
    回复于
  • 0

    检查你的Manifest.xml并确保你有一些王者

    <activity android:name=".Mainfragment" />
    回复于
  • 0

    可能是xml中缺少的声明

    最有可能的

    R.id.buttonNew

    澄清一下：你的活动正在寻找一个名为buttonNew的按钮而没有找到它

    回复于
  • 1
    here you have to mention your button in fragment_main.xml and you have to set

    setContentView（）方法中的activity_main.xml然后如何才能找到你的按钮只需更改xml文件名 .

    如下：

    的setContentView（R.layout.fragment_main）;

    回复于

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