1. 生成application子类，类中包含需要全局的变量

public class MyApplication extends Application {  
        private String name;  
        public  String myname; 
        @Override 
        public void onCreate() {  
                super.onCreate();  
                setName(NAME); //初始化全局变量  
                myname="初始化";
        }  
        public String getName() {  
                return name;  
        }  
        public void setName(String name) {  
                this.name = name;  
        }  
        private static final String NAME = "MyApplication";  
} 

1. 在配置文件ApplicationManifest.xml中配置MyApplication。

<?xml version="1.0" encoding="utf-8"?>  
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
      package="com.hisoft.app" 
      android:versionCode="1" 
      android:versionName="1.0">  
    <application android:icon="@drawable/icon" android:label="@string/app_name" 
                 android:name=".MyApplication">  就是这儿，将我们以前一直用的默认Application给他设置成我们自己做的MyApplication  
        <activity android:name=".MyFirstActivity" 
                  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=".MySecondActivity"></activity>  
    </application>  
    <uses-sdk android:minSdkVersion="8" />  
 </manifest> 

1. 在Activity中声明该该类，并使用
   • 第一个Activity

public class MyFirstActivity extends Activity {  
        private MyApplication app;  
       @Override 
       public void onCreate(Bundle savedInstanceState) {  
            super.onCreate(savedInstanceState);  
            setContentView(R.layout.main);  
            app = (MyApplication) getApplication(); //获得我们的应用程序MyApplication  
            app.setName("is cool");  //OK，现在我们开始修改了  
            Intent intent = new Intent();  //更重要的是我们可以看在别的Activity中是拿到初始化的值，还是修改后的  
        intent.setClass(this, MySecondActivity.class);  
        startActivity(intent);  
    }  
} 

* 第二个Activity

public class MySecondActivity extends Activity {  
        private MyApplication app;  
         @Override 
        protected void onCreate(Bundle savedInstanceState) {  
                super.onCreate(savedInstanceState);  
                setContentView(R.layout.main);  
                app = (MyApplication) getApplication();  //获取应用程序  
                Log.e("MySecondActivity", app.getName()); //获取全局值  
        }          
}