在我們使用android編寫程式的時候，少不了想利用全域性變數，但是面嚮物件語言和過程語言區別很大，不再是include就可以的。這裡我寫了使用全域性變數的兩種方法：

1.使用application來儲存全域性變量                                                             

這裡沒有太多理論性的東西，無非就是一些實際操作。

1.1定義Data類繼承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;
	}
	@Override
	public void onCreate(){
		b = "hello";
		super.onCreate();
	}
}
 

1.2在manifest.xml中宣告application

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

1.3建立兩個Activity

MainActivity.class

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

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執行程式
   

說明：程式首先進入MainActivity.class中，獲取Data中變數b的值，顯示圖1所示的介面hello，單擊button後app.setB("no_hello")， 修改變數b的值。

           跳轉到secondActivity.class，獲取Data中變數b的值，顯示圖2所示的介面no_hello，單擊button後app.setB("hello")， 修改變數b的值。

           跳轉回MainActivity.class……  迴圈

2.使用普通的類Data.class來儲存全域性變量                                                             

方法和上面差不多。

1.1 定義Data.class

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建立兩個Activity

MainActivity.class

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

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執行程式
                     

說明：程式首先進入MainActivity.class中，獲取Data中變數b的值，顯示圖1所示的介面feiyangxiaomi，單擊button後app.setB("no_feiyangxiaomi")， 修改變數b的值。

           跳轉到secondActivity.class，獲取Data中變數b的值，顯示圖2所示的介面no_feiyangxiaomi，單擊button後app.setB("feiyangxiaomi")， 修改變數b的值。

           跳轉回MainActivity.class……  迴圈

3.總結                                                                                        

    兩種方法我測試的都可以的，大多數人應該更會偏向於第一種，畢竟Application是android專門提供的應用入口，並且執行週期貫穿整個程式執行。