小弟我这个是错哪里啦?

我这个是错哪里啦???
main.xml

<?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_width="fill_parent"
android:layout_height="50dp"
android:background="@android:color/darker_gray"
android:orientation="horizontal" 
>
<EditText 
android:id="@+id/editText1"
android:layout_width="90dp"
android:layout_height="40dp"/>
<TextView
android:layout_width="10dp"
android:layout_height="wrap_content"
android:text=" + " />
<EditText 
android:id="@+id/editText2"
android:layout_width="90dp"
android:layout_height="40dp"/>
<TextView
android:layout_width="10dp"
android:layout_height="wrap_content"
android:text=" = " />
<EditText 
android:id="@+id/editText3"
android:layout_width="90dp"
android:layout_height="40dp"/>
</LinearLayout>


<Button
android:id="@+id/mainButton"
android:layout_width="match_parent"
android:layout_height="wrap_content" 
android:text="提交到第二个activity"
>
</Button>

</LinearLayout>


other.xml

<?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"
android:background="@android:color/darker_gray" >

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#FF0000"
android:id="@+id/text" />
<EditText
android:layout_width="fill_parent"
android:layout_height="30dp"
android:background="#0000FF"
android:id="@+id/editTextResult" />
<Button 
android:id="@+id/otherButton"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="提交计算结果回前台" 
/>

</LinearLayout>

mainacitivity.class

package com.test;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
private EditText one,two,three;
private Button button;
private final int REQUESTCODE=1;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
one=(EditText)findViewById(R.id.editText1);
two=(EditText)findViewById(R.id.editText2);
three=(EditText)findViewById(R.id.editText3);
button=(Button)findViewById(R.id.mainButton);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(MainActivity.this, "在main点击按钮了..", Toast.LENGTH_SHORT).show();
Intent intent=new Intent(MainActivity.this,OtherActivity.class);
int one_=Integer.valueOf(one.getText().toString());
int two_=Integer.valueOf(two.getText().toString());
intent.putExtra("one", one_);
intent.putExtra("two", two_);
startActivityForResult(intent, REQUESTCODE);;

}
});

}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(requestCode==REQUESTCODE){
if(resultCode==2){
int three_=data.getIntExtra("three", 0);
three.setText(three_);//这行报错
}
}
}
}

otheractivity.class

package com.test;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;


public class OtherActivity extends Activity {
private TextView textView;
private EditText editText;
private Button button;
private int one,two;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.other);
Intent intent=getIntent();
one=intent.getIntExtra("one", 0);
two=intent.getIntExtra("two", 0);
editText=(EditText)findViewById(R.id.editTextResult);
button=(Button)findViewById(R.id.otherButton);
textView=(TextView)findViewById(R.id.text);
textView.setText(one+" + "+two+" = ?");
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent=new Intent(OtherActivity.this,MainActivity.class);
intent.putExtra("three", one+two);
setResult(2, intent);
finish();
}
});
}
}


清单文件


<P><?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="<A href="http://schemas.android.com/apk/res/android">http://schemas.android.com/apk/res/android</A>"