Android起步--简单的乘法

在网上看了android的相关视频，本人也试着写了一些代码。现在我在这里贴出来，用来见证我学习android的历程。
先布局：
main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<EditText
	android:id="@+id/num1"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
/>
<TextView  
	android:id="@+id/symbol"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<EditText
	android:id="@+id/num2"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
/>
<Button
	android:id="@+id/buttonresult"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
/>
</LinearLayout>

result.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >

<TextView
	android:id="@+id/result"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
/>
</LinearLayout>

strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
	<string name="hello">Hello World, Activity03!</string>
	<string name="app_name">Activity03</string>
	<string name="symbol">乘以</string>
	<string name="buttonresult">计算</string>
	<string name="resultLable">result</string>
	<string name="exit">退出</string>
	<string name="about">关于</string>
	<style name="Text">
		<item name="android:textSize">18sp</item>
	</style>
	<style name="SpecialText" parent="@style/Text">
		<item name="android:textSize">18sp</item>
		<item name="android:textColor">#008</item>
	</style>
</resources>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="org.hs"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="4" />

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Activity03"
                  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=".ResultActivity" android:label="@string/resultLable"></activity>
    </application>
</manifest>

Activity03.java

package org.hs;

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

public class Activity03 extends Activity {
    /** Called when the activity is first created. */
    private EditText num1;
    private EditText num2;
    private TextView symbol;
    private Button buttonresult;
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        num1 = (EditText) findViewById(R.id.num1);
        num2 = (EditText) findViewById(R.id.num2);
        symbol = (TextView) findViewById(R.id.symbol);
        buttonresult = (Button) findViewById(R.id.buttonresult);
        
//        symbol.setText("乘以");
//        buttonresult.setText("计算");
        symbol.setText(R.string.symbol);
        buttonresult.setText(R.string.buttonresult);
        buttonresult.setOnClickListener(new CalculateListener());
    }
	
	
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
	
		menu.add(0,1,1,R.string.exit);
		menu.add(0,2,2,R.string.about);
		
		return super.onCreateOptionsMenu(menu);
	}
	
	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		//菜单响应
		super.onOptionsItemSelected(item);
		switch (item.getItemId()) {
		case 1:
			
			break;
		case 2:
			finish();
			break;
		default:
			break;
		}
		return true;
	}
	
	class CalculateListener implements OnClickListener{

		public void onClick(View v) {
			String num1Str = num1.getText().toString();//获取值
			String num2Str = num2.getText().toString();
			//将两个值存放在Intent对象中
			Intent intent=new Intent();
			intent.putExtra("one", num1Str);
			intent.putExtra("two", num2Str);
			intent.setClass(Activity03.this,ResultActivity.class );
			//使用这个Intent对象来启动ResultActivity
			Activity03.this.startActivity(intent);
		}
		
	}
}

ResultActivity.java

package org.hs;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

public class ResultActivity extends Activity {

	private TextView resultView;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.result);
		resultView = (TextView) findViewById(R.id.result);
		Intent intent = getIntent();
		String num1Str = intent.getStringExtra("one");
		String num2Str = intent.getStringExtra("two");
		int num1 = Integer.parseInt(num1Str);
		int num2 = Integer.parseInt(num2Str);
		int result = num1*num2;
		resultView.setText(result+"");//setText只接受字符串
	}
}