android 全局变量Application类使用

一 新建一个class 继承Application类

package com.application.kzp.example.applicationclasstest;

import android.app.Application;

public class MyApplication extends Application {

private String value;

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

public void setValue(String value) {
this.value = value;
}

public String getValue() {
return value;
}
}

二 MainActivity.java

package com.application.kzp.example.applicationclasstest;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;public class MainActivity extends AppCompatActivity {MyApplication app;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);app= (MyApplication) getApplication();app.setValue("改变了");Intent intent=new Intent(MainActivity.this,Main2Activity.class);startActivity(intent);finish();}}

三 Main2Activity.java

package com.application.kzp.example.applicationclasstest;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.widget.TextView;public class Main2Activity extends AppCompatActivity {MyApplication app;TextView textView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main2);app= (MyApplication) getApplication();textView= (TextView) findViewById(R.id.text);String value=app.getValue();textView.setText(value);}}

<?xml version="1.0" encoding="utf-8"?><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:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"android:paddingBottom="@dimen/activity_vertical_margin"tools:context="com.application.kzp.example.applicationclasstest.Main2Activity"><TextViewandroid:id="@+id/text"android:layout_width="wrap_content"android:layout_height="wrap_content" /></RelativeLayo4000ut>

这样我们就设置了一个全局变量value

运行就可以看到效果，也可以自己添加一个按钮再跳转页面那样效果更明显