高人帮看看,关于那个activtity打开新窗口-----快疯了..

想不到android开发,这么痛苦..
额就需要一个简单的功能,同一个包里,一个窗口(activtity)调到另一个窗口(activtity),
就像delphi里的loginForm.show;一句就行了.
可Eclipse确要一堆的代码,而且自己还是按书上来的,但竟然报错?高人请帮分析下,谢了.本人环境:
Eclipse 3.7
ADT 20
android 3.0代码如下(就2个文件):1.AndroidManifest.xml<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.roboschool"
    android:versionCode="1"
    android:versionName="1.0" >    <uses-sdk
        android:minSdkVersion="11" android:targetSdkVersion="15" />
    <uses-permission android:name="android.permission.INSTALL_PACKAGES" />    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".Main"
            android:label="@string/title_activity_login" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Login"
            android:label="@string/title_activity_main" >        </activity>
    </application></manifest>2.activity_login.xml<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@drawable/bg" >    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/editText1"
        android:layout_alignTop="@+id/editText4"
        android:layout_marginLeft="25dp"
        android:layout_toRightOf="@+id/editText4"
        android:text="Login" />
</RelativeLayout>3.login.javapackage com.example.roboschool;import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.support.v4.app.NavUtils;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;public class Login extends Activity {
private Button btn;    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        /*Button but=(Button)super.findViewById(R.id.button1);
        but.setText("Welcome back!");*/
        this.btn=(Button)super.findViewById(R.id.button1);
        this.btn.setOnClickListener(new OnClickListener()
        {
         @Override
            public void onClick(View v)
            {
                Intent it=new Intent(Login.this, Main.class);
                Login.this.startActivity(it);
               
            }
        });
      
    }
4.activity_main.xml<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">    <ImageButton
        android:id="@+id/imageButton1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="86dp"
        android:layout_marginTop="66dp"
        android:background="@drawable/icon1" /></RelativeLayout>5.main.javapackage com.example.roboschool;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;import android.app.Activity;
import android.view.Menu;
public class Main extends Activity {
private Button mybut=null;    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button mybut=(Button)super.findViewById(R.id.imageButton1); //出错的行,说找不到对象,我晕.真有的
        this.mybut.setOnClickListener(new OnClickListenerlmpl());
    }
    
    private class OnClickListenerlmpl implements OnClickListener
    {
     @Override
     public void onClick(View view)
     {
     Uri uri=Uri.parse("http://10.0.3.123");
     Intent it=new Intent();
     it.setAction(Intent.ACTION_VIEW);
     it.setData(uri);
     Main.this.startActivity(it);
    
     }
    
    }    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }    
}