android 中的全局变量问题

关于android中是否可以使用全局变量，当然可以。做Java的人肯定都用过全局变量了
，使用方法无非是定义一个静态变量，public类型，这样在其他类中就可以直接调用了，
android中也可以这样使用。但是，android中这样使用全局变量是不是最符合android的架构呢
在国外的论坛里找到了下面的解决办法：
The more general problem you are encountering is how to save stateacross several Activities 
and all parts of your application. A staticvariable (for instance, a singleton) is 
a common Java way of achievingthis. I have found however, that a more elegant way in 
Android is toassociate your state with the Application context.


--如想在整个应用中使用，在java中一般是使用静态变量，而在android中有个更优雅的方式是使用Application context。</strong><br />

As you know, each Activity is also a Context,
which is informationabout its execution environment in the broadest sense. 
Your applicationalso has a context, and Android guarantees
that it will exist as asingle instance across your application
--每个Activity 都是Context，其包含了其运行时的一些状态，android保证了其是single instance的。

The way to do this is to create your own subclass of android.app.Application,and then specify that class in the application tag in your manifest.Now Android will automatically create an instance of that class andmake it available for your entire application. You can access it fromany context using the Context.getApplicationContext() method (Activityalso provides a method getApplication() which has the exact sameeffect):<br />
--方法是创建一个属于你自己的android.app.Application的子类，
然后在manifest中申明一下这个类，这是android就为此建立一个全局可用的实例，
你可以在其他任何地方使用Context.getApplicationContext()方法获取这个实例，
进而获取其中的状态（变量）。
请看如下demo
public class MyApplication extends Application{
    private int num;
    @Override
    public void onCreate() {
     // TODO Auto-generated method stub
     super.onCreate();
     setNum(10);
    }
 public int getNum() {
  return num;
 }

 public void setNum(int num) {
  this.num = num;
 }
     
}
public class MainActivity extends Activity {
    /** Called when the activity is first created. */
 private static final String TAG="---------MainActivity--------";
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        MyApplication myApp=(MyApplication)getApplication();
        Log.i(TAG,String.valueOf(myApp.getNum()));
    }
}
在AndroidMenifest.xml配置如下：
....
 <application android:name=".MyApplication" android:icon="@drawable/icon" android:label="@string/app_name">
.....
这样即可实现全局变量。

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