Android实现存储和实时更新和取出全局变量_activity全局变量记录一直更新

作者：寸_铁 | 2024-06-24 05:39:58

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activity全局变量记录一直更新

MaterialTest学习笔记（七）感谢郭神

Android实现存储和实时更新和取出全局变量

Android通过继承Application类，实现全局变量的存储更新与取出，可以解决用户登录状态，以及一些每个活动间都需要传递的变量。以及解决从Activity到Fragment，有Fragment到Activity的值得一系列传递。
效果图：
在这里插入图片描述

第一步，新建一个MyApplication类继承Application

package com.example.globalvariableuse;

import android.app.Application;
import android.content.Context;

public class MyApplication extends Application {
    private static Context context;
    private static MyApplication instance;
    //新建静态变量
    private static String Globalvariable;
    @Override
    public void onCreate() {
        super.onCreate();
        //获取去全局context
        context = getApplicationContext();
        //实例个人Application类
        instance = this ;
    }

    public static MyApplication getInstance() {
        return instance;
    }

    public static void setInstance(MyApplication instance) {
        MyApplication.instance = instance;
    }

    public static Context getContext() {
        return context;
    }

    public static void setContext(Context context) {
        MyApplication.context = context;
    }

    public static String getGlobalvariable() {
        return Globalvariable;
    }

    public static void setGlobalvariable(String globalvariable) {
        //这一步很重要
        MyApplication.Globalvariable = globalvariable;
    }
}
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第二步，添加name到AndroidManifest.xml文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.globalvariableuse">

    <application
    //添加注册应用，以便初始化自己的Application
        android:name=".MyApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".Main2Activity" />
        <activity android:name=".Main3Activity"></activity>
    </application>

</manifest>
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第三步，实际测试

新建三个空白Activity分别为,MainActivity.java,Main2Activity.java, MainActivity.java

修改activity_main.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
    <Button
        android:id="@+id/button_send_activity2"
        android:layout_weight="1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="设置一个页面2的跳转"/>
    <Button
        android:id="@+id/button_send_activity3"
        android:layout_width="wrap_content"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:text="设置一个页面3的跳转"/>

    </LinearLayout>
<EditText
    android:id="@+id/edit_input"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />
    <Button
        android:id="@+id/button_takeout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="取出输入的值，并赋给全局变量"/>
    <TextView
        android:id="@+id/text_response"
        android:layout_width="wrap_content"
        android:layout_marginTop="100dp"
        android:textStyle="bold"
        android:textColor="#F00"
        android:layout_height="wrap_content"
        />

</LinearLayout>
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修改activity_main2.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".Main2Activity">
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:id="@+id/button_send_activity1"
            android:layout_weight="1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="设置一个页面1的跳转"/>
        <Button
            android:id="@+id/button_send_activity3"
            android:layout_width="wrap_content"
            android:layout_weight="1"
            android:layout_height="wrap_content"
            android:text="设置一个页面3的跳转"/>

    </LinearLayout>
    <Button
        android:id="@+id/button_takeout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="取出全局变量值"/>
    <TextView
        android:id="@+id/text_response"
        android:layout_width="wrap_content"
        android:layout_marginTop="100dp"
        android:textStyle="bold"
        android:textColor="#F00"
        android:layout_height="wrap_content"
        />

</LinearLayout>
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修改activity_main3.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".Main3Activity">
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:id="@+id/button_send_activity1"
            android:layout_weight="1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="设置一个页面1的跳转"/>
        <Button
            android:id="@+id/button_send_activity2"
            android:layout_width="wrap_content"
            android:layout_weight="1"
            android:layout_height="wrap_content"
            android:text="设置一个页面2的跳转"/>

    </LinearLayout>
    <EditText
        android:id="@+id/edit_input"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <Button
        android:id="@+id/button_takeout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="取出全局变量值"/>
    <TextView
        android:id="@+id/text_response"
        android:layout_width="wrap_content"
        android:layout_marginTop="100dp"
        android:textStyle="bold"
        android:textColor="#F00"
        android:layout_height="wrap_content"
        />

</LinearLayout>
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修改MainActivity.java

package com.example.globalvariableuse;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private Button button1,button2,button3;
    private TextView textView;
    private EditText editText;
    //新建变量
    String variable;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button1 = (Button) findViewById(R.id.button_send_activity2);
        button2 = (Button) findViewById(R.id.button_send_activity3);
        button3 = (Button) findViewById(R.id.button_takeout);
        textView = (TextView) findViewById(R.id.text_response);
        editText = (EditText) findViewById(R.id.edit_input);
    }

    @Override
    protected void onStart() {
        super.onStart();
        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
        button3.setOnClickListener(this);
        System.out.println("是否传入值");
        System.out.println(variable);

    }
    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.button_send_activity2:
                Intent Twointent = new Intent(MainActivity.this,Main2Activity.class);
                startActivity(Twointent);
                break;
            case R.id.button_send_activity3:
                Intent Threeintent = new Intent(MainActivity.this,Main3Activity.class);
                startActivity(Threeintent);
                break;
            case R.id.button_takeout:
                //赋variable值为我们取出来的editText的输入值
                variable = editText.getText().toString();
                //进行是否为空判断，虽然初始值为空，写这个if条件判断，
                // 是为了活动1和活动3，可以根据输入值是否为空，
                // 来进行判断，进行简单修改全局变量的值
                if (!"".equals(variable)){
                    //将输入的值赋给全局变量variable
                    MyApplication.setGlobalvariable(variable);
                }
                //通过textView显示我们赋的值
                textView.setText("将全局变量取出:"+MyApplication.getGlobalvariable());
                System.out.println("是否获取到输入值"+MyApplication.getGlobalvariable());
                break;
                default:
        }
    }
}

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修改Main2Activity.java

package com.example.globalvariableuse;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class Main2Activity extends AppCompatActivity implements View.OnClickListener {
    private Button button1,button2,button3;
    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        button1 = (Button) findViewById(R.id.button_send_activity1);
        button2 = (Button) findViewById(R.id.button_send_activity3);
        button3 = (Button) findViewById(R.id.button_takeout);
        textView = (TextView) findViewById(R.id.text_response);
    }

    @Override
    protected void onStart() {
        super.onStart();
        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
        button3.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.button_send_activity1:
                Intent Twointent = new Intent(this,MainActivity.class);
                startActivity(Twointent);
                break;
            case R.id.button_send_activity3:
                Intent Threeintent = new Intent(this,Main3Activity.class);
                startActivity(Threeintent);
                break;
            case R.id.button_takeout:
                textView.setText("将全局变量取出:"+MyApplication.getGlobalvariable());
                break;
            default:
        }
    }
}

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修改Main3Activity.java布局文件

package com.example.globalvariableuse;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class Main3Activity extends AppCompatActivity implements View.OnClickListener {
    private Button button1,button2,button3;
    private TextView textView;
    private EditText editText;
    //新建变量
    String variable;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);
        button1 = (Button) findViewById(R.id.button_send_activity1);
        button2 = (Button) findViewById(R.id.button_send_activity2);
        button3 = (Button) findViewById(R.id.button_takeout);
        textView = (TextView) findViewById(R.id.text_response);
        editText = (EditText) findViewById(R.id.edit_input);
    }

    @Override
    protected void onStart() {
        super.onStart();
        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
        button3.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.button_send_activity1:
                Intent Twointent = new Intent(this,MainActivity.class);
                startActivity(Twointent);
                break;
            case R.id.button_send_activity2:
                Intent Threeintent = new Intent(this,Main2Activity.class);
                startActivity(Threeintent);
                break;
            case R.id.button_takeout:
                variable = editText.getText().toString();
                if (!"".equals(variable)) {
                //将输入的值赋给全局变量variable
                MyApplication.setGlobalvariable(variable);
                }
                textView.setText("将全局变量取出:"+MyApplication.getGlobalvariable());
                break;
            default:
        }
    }
}
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到此本篇功能已经实现，欢迎讨论。

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