how to switch to activity from listactivity using menu

my initial screen is basically from a listactivity which displays a list of records. i created a menu that should open a new window for entry but always force closes when i click it. below are my codes:

Guestbook.java (ListActivity)
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle item selection
        switch (item.getItemId()) {
        case R.id.mnuNew:
            //setContentView(R.layout.form);
            Intent mIntent  = new Intent(getApplicationContext(), Maintenance.class);
            startActivityForResult(mIntent, 0);

            //Toast.makeText(getApplicationContext(), "Test", Toast.LENGTH_SHORT).show();
            return true;
        default:
            return super.onOptionsItemSelected(item);
        }
    }

here is the code for Maintenance.class

package com.android.guestbook;

import android.app.Activity;
import android.os.Bundle;

public class Maintenance extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.form);
    }
}

is there something wrong with my code?

here is the logcat info.

02-06 07:02:29.617: INFO/ActivityManager(59): Starting activity: Intent { cmp=com.android.guestbook/.Maintenance }
02-06 07:02:29.956: DEBUG/AndroidRuntime(276): Shutting down VM
02-06 07:02:29.956: WARN/dalvikvm(276): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
02-06 07:02:30.107: ERROR/AndroidRuntime(276): FATAL EXCEPTION: main
02-06 07:02:30.107: ERROR/AndroidRuntime(276): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.guestbook/com.android.guestbook.Maintenance}: java.lang.RuntimeException: Binary XML file line #82: You must supply a layout_width attribute.
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.os.Looper.loop(Looper.java:123)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.app.ActivityThread.main(ActivityThread.java:4627)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at java.lang.reflect.Method.invokeNative(Native Method)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at java.lang.reflect.Method.invoke(Method.java:521)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at dalvik.system.NativeStart.main(Native Method)
02-06 07:02:30.107: ERROR/AndroidRuntime(276): Caused by: java.lang.RuntimeException: Binary XML file line #82: You must supply a layout_width attribute.
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.content.res.TypedArray.getLayoutDimension(TypedArray.java:491)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.view.ViewGroup$LayoutParams.setBaseAttributes(ViewGroup.java:3592)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.view.ViewGroup$MarginLayoutParams.<init>(ViewGroup.java:3672)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.widget.LinearLayout$LayoutParams.<init>(LinearLayout.java:1395)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.widget.LinearLayout.generateLayoutParams(LinearLayout.java:1321)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.widget.LinearLayout.generateLayoutParams(LinearLayout.java:45)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.view.LayoutInflater.rInflate(LayoutInflater.java:620)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.view.LayoutInflater.inflate(LayoutInflater.java:407)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.view.LayoutInflater.inflate(LayoutInflater.java:320)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.view.LayoutInflater.inflate(LayoutInflater.java:276)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:198)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.app.Activity.setContentView(Activity.java:1647)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at com.android.guestbook.Maintenance.onCreate(Maintenance.java:11)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
02-06 07:02:30.107: ERROR/AndroidRuntime(276):     ... 11 more
02-06 07:02:30.216: WARN/ActivityManager(59):   Force finishing activity com.android.guestbook/.Maintenance
02-06 07:02:30.267: WARN/ActivityManager(59):   Force finishing activity com.android.guestbook/.GuestBook

here is my form.xml for the Maintenance class.

> <?xml version="1.0" encoding="utf-8"?>
> <LinearLayout  
> xmlns:android="http://schemas.android.com/apk/res/android"
> android:layout_width="fill_parent"  
> android:layout_height="fill_parent"  
> android:orientation="vertical">
>     <LinearLayout         
>       android:layout_height="wrap_content"
>       android:layout_width="fill_parent">
>         <TextView 
>           android:layout_width="fill_parent" 
>           android:layout_height="wrap_content" 
>           android:text="@string/name" />
>     </LinearLayout>
>     <LinearLayout 
>       android:layout_height="wrap_content" 
>       android:layout_width="fill_parent">
>         <EditText 
>           android:inputType="textPersonName"
>           android:layout_width="fill_parent" 
>           android:layout_height="wrap_content" 
>           android:id="@+id/name" 
>           android:hint="Enter your name here" />
>     </LinearLayout>
>     <LinearLayout 
>       android:layout_height="wrap_content"
>       android:layout_width="fill_parent">
>         <TextView 
>           android:layout_width="wrap_content" 
>           android:layout_height="wrap_content" 
>           android:text="@string/email" />
>     </LinearLayout>
>     <LinearLayout 
>       android:layout_height="wrap_content" 
>       android:layout_width="fill_parent">
>         <EditText 
>           android:inputType="textEmailAddress"
>           android:layout_width="fill_parent" 
>           android:layout_height="wrap_content" 
>           android:id="@+id/email" 
>           android:hint="Enter your email here" />
>     </LinearLayout>
>     <LinearLayout 
>       android:layout_height="wrap_content" 
>       android:layout_width="开发者_开发技巧fill_parent">
>         <TextView 
>           android:layout_width="wrap_content" 
>           android:layout_height="wrap_content" 
>           android:text="@string/message" />
>     </LinearLayout>
>     <LinearLayout 
>       android:layout_height="wrap_content" 
>       android:layout_width="fill_parent">
>         <EditText 
>           android:inputType="textMultiLine"
>           android:layout_width="fill_parent" 
>           android:layout_height="wrap_content" 
>           android:id="@+id/message" 
>           android:hint="Enter your message here"></EditText>
>     </LinearLayout>
>     <LinearLayout 
>       android:layout_height="wrap_content" 
>       android:layout_width="fill_parent">
>         <Button 
>           android:onClick="onClick"
>           android:layout_weight="1"
>           android:layout_width="fill_parent" 
>           android:layout_height="wrap_content" 
>           android:id="@+id/submit" 
>           android:text="@string/submit" />
>         <Button 
>           android:onClick="onClick"
>           android:layout_weight="1"
>           android:layout_width="fill_parent" 
>           android:layout_height="wrap_content" 
>           android:id="@+id/cancel" 
>           android:text="@string/cancel" />
>     </LinearLayout>
>     <ListView
>       android:id="@+id/list" /> </LinearLayout>

Did you declare your Maintenance.class - Activity in your Manifest file?!

You need to put the <activity>-Tag in your AndroidManifest.xml between the <application>-Tag:

<application android:label="@string/app_name" android:icon="@drawable/icon" android:debuggable="true">
    <activity android:name=".activities.Guestbook"
        android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".activities.Maintenance "
        android:label="@string/app_name">
    </activity>

</application>

thanks to all your help i finally figured out what's wrong. checking the logcat it said some issue about the layout_width of my xml layout. so then i checked the xml and noticed that i had a listview without any layout_width property. once i took it off it started to work.

thanks again.

One error is that declare following two parameter of ListView widget at 82 line of form.xml.

android:layout_height=
android:layout_width=