キーボードを非表示にする

ボタンをクリックをしたとき、キーボードを非表示にする。

********************　　MainActivity.java　　********************
package jp.lesson.studyandroid;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.Button;
import android.widget.Toast;
import android.view.inputmethod.InputMethodManager;
public class MainActivity extends Activity {
   
    private EditText edit1, edit2;
    private Button btn1;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        edit1 = (EditText) findViewById(R.id.editText1);
        edit2 = (EditText) findViewById(R.id.editText2);
        btn1 = (Button) findViewById(R.id.button1);
        btn1.setOnClickListener(new View.OnClickListener() {
           
            public void onClick(View v) {
               
                InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
                imm.hideSoftInputFromWindow(v.getWindowToken(), 0);
                String s1 = edit1.getText().toString();
                String s2 = edit2.getText().toString();
                float f1 = Float.valueOf(s1);
                float f2 = Float.valueOf(s2);
                float f3;
                f3 = f1 + f2;
                /* トースト */
                Toast.makeText(getApplicationContext(), Float.toString(f3), Toast.LENGTH_LONG).show();
            }
        });
    }
   
}

********************　　activity_main.xml　　********************
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="vertical" >
        <EditText
            android:id="@+id/editText1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="numberDecimal" >
            <requestFocus />
        </EditText>
        <EditText
            android:id="@+id/editText2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="numberDecimal" />
        <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/btn" />
    </LinearLayout>

********************　　strings.xml　　********************
<resources>
    <string name="app_name">StudyAndroid</string>
    <string name="menu_settings">Settings</string>
    <string name="title_activity_main">MainActivity</string>
    <string name="btn">ボタン</string>
</resources>