Intent传值之通过Application传值

传值第五种方式:
 *     程序的全局变量application
 *     特点:1.一个程序application对象只能有一个
 *         2.application对象在程序启动时就创建
 *         3.通常用来存放全局变量

xml布局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/btn01"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="跳转到第二个页面"/>

</RelativeLayout>

myApplication.java

package com.example.day05_application_passvalue;

import android.app.Application;
import android.util.Log;
/**
 *
 *
 * @author my
 *
 */
//注意:需要在AndroidManifest.xml清单文件中注册自定义application
public class myApplication extends Application{

    private String TAG = "MainActivity";
    private String text = "呵呵呵呵";
    public String getTAG() {
        return TAG;
    }
    public void setTAG(String tAG) {
        TAG = tAG;
    }
    public String getText() {
        return text;
    }
    public void setText(String text) {
        this.text = text;
    }
    //重写onCreate()方法,application创建的时候调用
    @Override
    public void onCreate() {
        super.onCreate();
        Log.i(TAG, "MainActivity-->myApplication");
    }
}

MainActivity.java

package com.example.day05_application_passvalue;

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

public class MainActivity extends Activity {

    private Button btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn = (Button) findViewById(R.id.btn01);
        //获取Application对象
        myApplication  app = (myApplication)getApplication();
        //通过application对象获得值
        String text = app.getText();
        Log.i("MainActivity", text);
        //改变值
        app.setText("hahhah,值在Activity中被改变");
        /**
         * button点击事件,点击跳转到另一个页面
         */
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,Activity2.class);
                startActivity(intent);
            }
        });
    }
}

Activity2.java

package com.example.day05_application_passvalue;

import android.app.Activity;
import android.app.Application;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

public class Activity2 extends Activity{
    private TextView tv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout1);
        tv = (TextView) findViewById(R.id.text01);
        Log.i("MainActivity", "MainActity-->Activity2");
        myApplication app = (myApplication) getApplication();
        tv.setText(app.getText());
    }

}