Android Application (全局变量)学习使用
Application概念理解
官方释义:
Base class for those who need to maintain global application state. You can provide your own implementation by specifying its name in your AndroidManifest.xml's <application> tag, which will cause that class to be instantiated for you when the process for your application/package is created.
There is normally no need to subclass Application. In most situation, static singletons can provide the same functionality in a more modular way. If your singleton needs a global context (for example to register broadcast receivers), the function to retrieve it can be given a Context which internally uses Context.getApplicationContext() when first constructing the singleton.
个人翻译:
Application类是为了那些需要保存全局变量设计的基本类。你可以在AndroidManifest.xml的<application>标签中指定名称进行自己的实现,这样的结果是:当你的application或者包被建立的时候将引起那个类被建立。
子类Application通常是没有必要的。大多数情况下,静态的单例可以通过更加模块化的方式提供相同的功能,如果你的单例需要一个全局的Context(例如注册一个广播接收器),当第一次构建单例时,程序内部使用Context.getApplication()方法可以返回一个Context(上下文)。
个人理解:
Application是用来保存全局变量的,并且是在package创建的时候就跟着存在了。所以当我们需要创建全局变量的时候,直接在Application中去实现。只需要调用Context的getApplicationContext或者Activity的getApplication方法来就可以获得一个Application对象。
接下来通过例子来看一下具体用法:
GlobalParameterApplication.java
[java]
package com.dt5000.ischool.util;
import android.app.Application;
import com.dt5000.ischool.bean.User;
/**
* @author: duanyr
* @创建时间: 2012-11-14 上午10:50:45
*
* 类说明:全局参数类
*/
public class GlobalParameterApplication extends Application {
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
[html] l.activity;
import android.app.Activity;
import com.dt5000.ischool.bean.User;
import com.dt5000.ischool.util.GlobalParameterApplication;
public class UserLoginActivity extends Activity {
@Override
protected void onStart() {
// TODO Auto-generated method stub
User user = new User();
user.setUserName("example");
GlobalParameterApplication gpa = (GlobalParameterApplication) getApplicationContext();
gpa.setUser(user);// 将User信息放入到Application
gpa.getUser();//取出User信息
super.onStart();
}
}
AndroidManifest.xml
[html]
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.dt5000.ischool.activity"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:maxSdkVersion="15" android:targetSdkVersion="8" />
<application
android:name="com.dt5000.ischool.util.GlobalParameterApplication"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@android:style/Theme.NoTitleBar" >
<activity
android:name=".WelcomeActivity"
android:label="@string/title_activity_welcome" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
注意:不用新建<application />,在原有基础上添加内容:android:name=".your_App_Name"
补充:移动开发 , Android ,