android使用全局变量的两种方法

来源：互联网发布：linux方面的知识编辑：程序博客网时间：2024/06/02 03:52

android使用全局变量的两种方法

在我们使用Android编写程序的时候，少不了想利用全局变量，但是面向对象语言和过程语言区别很大，不再是include就可以的。这里我写了使用全局变量的两种方法：

1.使用application来保存全局变量

这里没有太多理论性的东西，无非就是一些实际操作。

1.1定义Data类继承Application Data.class

[java] view plain copy

print?

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;
}
@Override
public void onCreate(){
b = ”hello”;
super.onCreate();
}
}

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;    }    @Override    public void onCreate(){        b = "hello";        super.onCreate();    }}

1.2在manifest.xml中声明application

[java] view plain copy

print?

android:name=“com.animator1.Data” >

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

1.3创建两个Activity

MainActivity.class

[java] view plain copy

print?

public class MainActivity extends Activity {
@Override
protected 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() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
app.setB(”no_hello”);
txtview.setText(app.getB());
Intent intent = new Intent(MainActivity.this, secondActivity.class);
startActivity(intent);
}
});
}
}

public class MainActivity extends Activity {    @Override    protected 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() {            @Override            public void onClick(View v) {                // TODO Auto-generated method stub                app.setB("no_hello");                txtview.setText(app.getB());                Intent intent = new Intent(MainActivity.this, secondActivity.class);                startActivity(intent);            }        });    }}

secondActivity.class

[java] view plain copy

print?

public class secondActivity extends Activity{
@Override
protected 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() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
app.setB(”hello”);
txtview.setText(app.getB());
Intent intent = new Intent(secondActivity.this, MainActivity.class);
startActivity(intent);
}
});
}
}

public class secondActivity extends Activity{    @Override    protected 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() {            @Override            public void onClick(View v) {                // TODO Auto-generated method stub                              app.setB("hello");                txtview.setText(app.getB());                Intent intent = new Intent(secondActivity.this, MainActivity.class);                startActivity(intent);            }        });    }}

1.4运行程序

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

2.使用普通的类Data.class来保存全局变量

方法和上面差不多。

1.1 定义Data.class

[java] view plain copy

print?

public class Data{
private static String a =“feiyangxiaomi”;
public static String getA() {
return a;
}
public static void setA(String a) {
Data.a = a;
}
}

public class Data{    private static String a ="feiyangxiaomi";    public static String getA() {        return a;    }    public static void setA(String a) {        Data.a = a;    }}

1.2创建两个Activity

MainActivity.class

[java] view plain copy

print?

public class MainActivity extends Activity {
@Override
protected 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);
txtview.setText(Data.getA());
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Data.setA(”no_feiyangxiaomi”);
Intent intent = new Intent(MainActivity.this, secondActivity.class);
startActivity(intent);
}
});
}
}

public class MainActivity extends Activity {    @Override    protected 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);        txtview.setText(Data.getA());        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                // TODO Auto-generated method stub                Data.setA("no_feiyangxiaomi");                Intent intent = new Intent(MainActivity.this, secondActivity.class);                startActivity(intent);            }        });    }}

secondActivity.class

[java] view plain copy

print?

public class secondActivity extends Activity{
@Override
protected 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);
txtview.setText(Data.getA());
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Data.setA(”feiyangxiaomi”);
Intent intent = new Intent(secondActivity.this, MainActivity.class);
startActivity(intent);
}
});
}
}

public class secondActivity extends Activity{    @Override    protected 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);        txtview.setText(Data.getA());        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                // TODO Auto-generated method stub                              Data.setA("feiyangxiaomi");                Intent intent = new Intent(secondActivity.this, MainActivity.class);                startActivity(intent);            }        });    }}

1.3运行程序

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feiyangxiaomi，单击button后app.setB(“no_feiyangxiaomi”)，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_feiyangxiaomi，单击button后app.setB(“feiyangxiaomi”)，修改变量b的值。

跳转回MainActivity.class…… 循环

3.总结

两种方法我测试的都可以的，大多数人应该更会偏向于第一种，毕竟Application是android专门提供的应用入口，并且运行周期贯穿整个程序运行。

document.getElementById("bdshell_js").src = "http://bdimg.share.baidu.com/static/js/shell_v2.js?cdnversion=" + Math.ceil(new Date()/3600000)

    <div id="digg" articleid="9966215">        <dl id="btnDigg" class="digg digg_enable" onclick="btndigga();">             <dt>顶</dt>            <dd>17</dd>        </dl>        <dl id="btnBury" class="digg digg_enable" onclick="btnburya();">              <dt>踩</dt>            <dd>0</dd>                       </dl>    </div> <div class="tracking-ad" data-mod="popu_222"><a href="javascript:void(0);" target="_blank">&nbsp;</a>   </div><div class="tracking-ad" data-mod="popu_223"> <a href="javascript:void(0);" target="_blank">&nbsp;</a></div><script type="text/javascript">            function btndigga() {                $(".tracking-ad[data-mod='popu_222'] a").click();            }            function btnburya() {                $(".tracking-ad[data-mod='popu_223'] a").click();            }        </script>

上一篇第3.3.2节动画
下一篇第3.3.4节创建高级图形之surfaceView（一）

<div style="clear:both; height:10px;"></div>

阅读全文

0 0