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Android 多个Activity之间共享类(数据)——Application Context

 
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多个Activity中经常使用同一变量时,使用Bundle则每次调用Activity都要设置。在android中想在整个应用中不同Activity多次重复使用相同的变量时利用使用Application context可以方便的实现。

1、新建一个保存数据的类,继承自Application

package activity.com;

import android.app.Application;

public  class  MyApp  extends  Application{
	
	  private String myState="start";

	  public String getState(){
	    return myState;
	  }
	  public void setState(String s){
	    myState = s;
	  }
}
2、在其它两个Activity中分别调用

package activity.com;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class FirstActivity extends Activity {

	private TextView myTextView = null;
	private Button myButton = null;	
    	MyApp myApp;
    
	@Override
	public void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);
		setContentView(R.layout.first);
		
		myTextView = (TextView) findViewById(R.id.myTextView);
		myTextView.setText("This is first TextView");
		
		myButton = (Button) findViewById(R.id.myButton);
		myButton.setText("First Button");
		myButton.setOnClickListener(new myOnClickListener());
		
		myApp=(MyApp) getApplication();
	}

	class myOnClickListener implements View.OnClickListener {

		@Override
		public void onClick(View v) {
			String state = myApp.getState();		
			Log.d("TEMP", "First获取数据:"+state);
			myApp.setState("First");
			Log.d("TEMP", "First更改数据为数据:"+"First");

			Intent intent = new Intent();
			intent.setClass(FirstActivity.this, SecondActivity.class);
			FirstActivity.this.startActivity(intent);
		}
	}
}
package activity.com;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class SecondActivity extends Activity{
	private Button myButton2 = null;	
	private TextView myTextView2 = null;
	MyApp myApp;
	
	@Override
	public void onCreate(Bundle savedInstanceState){		
		super.onCreate(savedInstanceState);
		
		setContentView(R.layout.second);
		System.out.println("2->1");
		myTextView2 =(TextView)findViewById(R.id.myTextView2);
		myTextView2.setText("This is second TextView");
		
		System.out.println("2->2");
		myButton2 = (Button)findViewById(R.id.myButton2) ;
		myButton2.setText("Second Button");
		myButton2.setOnClickListener(new myOnClickListener());
		
		System.out.println("2->3");
		myApp=(MyApp) getApplication();
	}
	
	class myOnClickListener implements View.OnClickListener {

		@Override
		public void onClick(View v) {
			String state = myApp.getState();		
			Log.d("TEMP", "Second获取数据:"+state);
			myApp.setState("Second");
			Log.d("TEMP", "Second更改数据为数据:"+"Second");
			
		}
	}
}

3、AndroidManifest.xml中的设置:

application的name标签中添加MyApplication,如下:

 <application android:icon="@drawable/icon" android:label="@string/app_name" android:name=".MyApp">

4、变量在一个Activity中改变后,在其它Activity中可以获取改变后的值

04-25 04:32:23.361: DEBUG/TEMP(1130): First获取数据:start
04-25 04:32:23.361: DEBUG/TEMP(1130): First更改数据为数据:First
04-25 04:32:30.891: DEBUG/TEMP(1130): Second获取数据:First
04-25 04:32:30.891: DEBUG/TEMP(1130): Second更改数据为数据:Second
04-25 04:32:36.743: DEBUG/TEMP(1130): First获取数据:Second
04-25 04:32:36.743: DEBUG/TEMP(1130): First更改数据为数据:First
04-25 04:32:39.883: DEBUG/TEMP(1130): Second获取数据:First
04-25 04:32:39.883: DEBUG/TEMP(1130): Second更改数据为数据:Second

操作如图:



代码下载地址:http://download.csdn.net/detail/love254443233/4254731

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