Multi-window sharing data

Android provides a simple data storage method SharedPreferences [Shared Preferences], which is a lightweight data storage method used to store some simple configuration information, which is stored in an XML file in the form of key-value pairs.

2. Use shared parameters to read and write files

Use the getPreferences(name, mode) method of the Activity to get the SharedPreferences object
Use the edit() of the SharedPreferences object to get the Editor object
Use the putXxx() method of the Editor object to write data; use the getXxx() of the SharedPreferences object to read data
for writing Operation, use the commit() method of the Editor object to submit data to the specified file

Case presentation:

`Empty Activity`Create an Android application based on a template`ShareData`

Copy the background image to `drawable`the directory

`MainActivity`Rename `FirstActivity`the corresponding layout file `actiivty_main.xml`to`activity_first.xml`

`Empty Activity`Create a second interface class based on a template

Change the string resource file`strings.xml`

Specific code:

<resources> 
    <string name="app_name">Shared parameter demonstration - read and write data</string> 
    <string name="write_data">Write data</string> 
    <string name="read_data">Read data< /string> 
    <string name="jump_to_second">Jump to the second window</string> 
</resources>

Open the layout resource file`activity_first.xml写入代码：`

Specific code:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:background="@drawable/background1"
    android:orientation="vertical"
    android:gravity="center"
    tools:context=".FirstActivity">

    <Button
        android:id="@+id/btn_write_data"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:onClick="doWriteData"
        android:text="@string/write_data"
        android:textSize="20sp" />

    <Button
        android:id="@+id/btn_jump_to_second"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:onClick="doJumpToSecond"
        android:text="@string/jump_to_second"
        android:enabled="false"
        android:textSize="20sp" />
</LinearLayout>

Open the layout resource file`activity_second.xml输入代码：`

Specific code:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:background="@drawable/background2"
    android:gravity="center"
    android:orientation="vertical"
    tools:context=".SecondActivity">
    <Button
        android:id="@+id/btn_read_date"
        android:layout_width="220dp"
        android:layout_height="wrap_content"
        android:text="@string/read_data"
        android:onClick="doReadData"
        android:textSize="20sp"/>
    <TextView
        android:id="@+id/tv_person_info"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:textSize="20sp"/>

</LinearLayout>

open interface class`FirstActivity输入：`

Specific code:

package net.zyt.share_date; 

import androidx.appcompat.app.AppCompatActivity; 

import android.content.Context; 
import android.content.Intent; 
import android.content.SharedPreferences; 
import android.os.Bundle 
; ; 
import android.widget.Toast; 

public class FirstActivity extends AppCompatActivity { 
    private static final String NAME="person_info";//Configuration file interface 
    private static final int MODE= Context.MODE_PRIVATE;//File access mode 
    private SharedPreferences sp;// Shared parameter object 
    private SharedPreferences.Editor editor;//Editor object 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        //Use the layout resource file to set the user interface 
        setContentView(R.layout.activity_first); 
        //Get the shared parameter object 
        sp=getSharedPreferences(NAME,MODE); 
        //Get the editor object 
        editor= sp.edit(); 
    } 
    // Write data, button data click processing method 
    public void doWriteData(View view){ 

        editor.putString("name","Xiaohong"); 
        editor.putString("gender","female"); 
        editor.putInt(" age",50); 
        editor.putString("hobby","reading, drawing, playing games"); 
        // Submit data and write to the specified file 
        if (editor.commit()) { 
            Toast.makeText(this , "Congratulations, the data is successfully written to the file!", Toast.LENGTH_SHORT).show(); 
            findViewById(R.id.btn_jump_to_second).setEnabled(true);//Make [jump to the second window] button available
        } else { 
        ", Toast.LENGTH_SHORT).show(); }

    } 

    //【Jump to the second window】Click event processing method 

    public void doJumpToSecond (View view) { 
//Create the intent to jump to the second window 
        Intent intent = new Intent( this,SecondActivity. class); 
        //Start the second window by intent 
        startActivity(intent); 
    } 

}

open interface class`SecondActivity输入：`

Specific code:

package net.zyt.share_date; 

import androidx.appcompat.app.AppCompatActivity; 

import android.content.Context; 
import android.content.SharedPreferences; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.TextView ; 
import android.widget.Toast; 

public class SecondActivity extends AppCompatActivity { 
    private static final String NAME="person_info";//Configuration file interface 
    private static final int MODE= Context.MODE_PRIVATE;//File access mode 
    private SharedPreferences sp;// Shared parameter object 
    private TextView tvPersonInfo;//Personal information label 

    @Override 
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);
        //Use the layout resource file to set the user interface
        setContentView(R.layout.activity_second); 
        //Get the control instance through the control resource identifier 
        tvPersonInfo=findViewById(R.id.tv_person_info); 
        //Get the shared parameter object 
        sp=getSharedPreferences(NAME,MODE); 
    } 
    //Read Data]Click event processing method 
    public void doReadData(View view){ 
        //Get file data through shared parameter object 
        String name=sp.getString("name",""); 
        String gender=sp.getString("gender", ""); 
        int age=sp.getInt("age",0); 
        String hobby=sp.getString("hobby",""); 
        // Create personal information string builder 
        StringBuilder builder=new StringBuilder();  
        builder.append("Name: "+name+"\n")
                .append("Gender"+gender+"\n") 
                .append("age"+age+"\n") 
                .append("hobby"+hobby+"\n"); 
        // Get the personal information string 
        String personInfo=builder.toString(); 
        // Display the person by toast Information 
        Toast.makeText(this,personInfo,Toast.LENGTH_SHORT).show(); 
        // Display personal information in the label 
        tvPersonInfo.setText(personInfo); 
    } 
}