android使用全局变量的方法

使用application来保存全局变量

1定义Data类继承Application Data.class

import android.app.Application;public class Data extends Application{private String b;public String getB(){return this.b;}public void setB(String c){this.b= c;}@Overridepublic void onCreate(){b = "hello";super.onCreate();}}

2在manifest.xml中声明application

android:name="com.animator1.Data" >

3创建两个Activity

MainActivity.class

public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);Button btn = (Button) this.findViewById(R.id.button1);final TextView txtview = (TextView) this.findViewById(R.id.main);final Data app = (Data)getApplication();txtview.setText(app.getB());btn.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubapp.setB("no_hello");txtview.setText(app.getB());Intent intent = new Intent(MainActivity.this, secondActivity.class);startActivity(intent);}});}}

secondActivity.class

public class secondActivity extends Activity{@Overrideprotected void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.second);Button btn = (Button) this.findViewById(R.id.button2);final TextView txtview = (TextView) this.findViewById(R.id.second);final Data app = (Data)getApplication();txtview.setText(app.getB());btn.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubapp.setB("hello");txtview.setText(app.getB());Intent intent = new Intent(secondActivity.this, MainActivity.class);startActivity(intent);}});}}

说明：程序首先进入MainActivity.class中，获取Data中变量b的值，显示图1所示的界面hello，单击button后app.setB("no_hello")，修改变量b的值。

跳转到secondActivity.class，获取Data中变量b的值，显示图2所示的界面no_hello，单击button后app.setB("hello")，修改变量b的值。

跳转回MainActivity.class…… 循环

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