Android初级教程Activity小案例（计算器乘法运算）

首先设置两个布局文件，一个布局文件进行输入数据，获取加法运算；另一个布局文件进行显示最终结果。Activity1启动Activity2，并传递计算结果值给Activity2.

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/factorOne"
    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" 
    />
<EditText 
	android:id="@+id/factorTwo"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
	/>
<Button
	android:id="@+id/calculate"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
	/>
</LinearLayout>

页面展示：

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>

界面展示：

activity03活动：

package mars.activity03;

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;
//1.在Activity03当中，要声明四个控件
//2.要为其中的两个控件设置显示的值
//3.创建一个监听器类，监听按钮按下的动作
//4.将监听器类的对象，绑定在按钮对象上
public class Activity03 extends Activity {
    /** Called when the activity is first created. */
	private EditText factorOne ;
	private EditText factorTwo;
	private TextView symbol;
	private Button calculate;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //根据控件的ID来取得代表控件的对象
        factorOne = (EditText)findViewById(R.id.factorOne);
        factorTwo = (EditText)findViewById(R.id.factorTwo);
        symbol = (TextView)findViewById(R.id.symbol);
        calculate = (Button)findViewById(R.id.calculate);
        //为symbol和calculate设置显示的值
//        symbol.setText("乘以");
//        calculate.setText("计算");
        symbol.setText(R.string.symbol);//这里通过引用的方式，去String文件中引用。保证了业务逻辑、视图、引用资源分开
        calculate.setText(R.string.calculate);
        //将监听器的对象绑定到按钮对象上面
        calculate.setOnClickListener(new CalculateListener());
    }
    //当客户点击MENU按钮的时候，调用该方法
    @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);
	}
    //当客户点击菜单当中的某一个选项时，会调用该方法
	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		if(item.getItemId() == 1){
			finish();
		}
		return super.onOptionsItemSelected(item);
	}
	class CalculateListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			//取得两个EditText控件的值
			String factorOneStr = factorOne.getText().toString();
			String factorTwoStr = factorTwo.getText().toString();
			//将这两个值存放到Intent对象当中
			Intent intent = new Intent();
			intent.putExtra("one",factorOneStr);
			intent.putExtra("two",factorTwoStr);
			intent.setClass(Activity03.this, ResultActivity.class);
			//使用这个Intent对象来启动ResultActivity
			Activity03.this.startActivity(intent);
		}
    }
}

resultActivity:

package mars.activity03;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
//1.接受从Activity03当中所传递的值
//2.计算两个值的积
//3.将计算的结果显示在Activity上
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);
		//得到Intent对象当中的值 
		Intent intent = getIntent();
		String factorOneStr = intent.getStringExtra("one");
		String factorTwoStr = intent.getStringExtra("two");
		int factorOneInt = Integer.parseInt(factorOneStr);
		int factorTwoInt = Integer.parseInt(factorTwoStr);
		//计算两个值的积
		int result = factorOneInt * factorTwoInt;
		resultView.setText(result + "");
	}

}

String.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="hello">Hello World, Activity03!</string>
    <string name="app_name">activity03</string>
    <string name="resultLabel">result</string>
    <string name="symbol">乘以</string>
    <string name="calculate">计算</string>
    <string name="exit">退出</string>
    <string name="about">关于</string>
</resources>

最后再看一下配置文件：活动都要进行注册，并且设置Activity03为主活动

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="mars.activity03"
      android:versionCode="1"
      android:versionName="1.0">
    <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/resultLabel"/><!--这里使ResultActivity标题栏显示result-->
    </application>
    <uses-sdk android:minSdkVersion="4" />

</manifest> 

运行结果：