Android实验——使用SharedPreferences存储简单数据

完成如下程序（主Activity界面如图1所示）：

在图1中点击“参数设置”按钮，启动如图2所示的Activity。在图2中用户输入完用户名后，点击“确定”按钮，将关闭该Activity（此时需要使用SharedPreferences.Editor

保存用户名），主Activity重新回到运行状态，如图3所示（需重写主Activity的生命周期回调方法onStart()或onResume()，完成对SharedPreferences中保存的用户名的读取）。

布局文件

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tv_welcome"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="216dp"
        android:text="欢迎来到我的家园"
        android:textSize="25dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_set"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="28dp"
        android:text="参数设置"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tv_welcome" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

activity_new.xml

 <?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".NewActivity">

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="208dp"
        android:text="请输入用户名:"
        android:textSize="25dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/et_name"
        android:layout_width="198dp"
        android:layout_height="53dp"
        android:layout_marginTop="12dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

    <Button
        android:id="@+id/btn_submit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="48dp"
        android:text="确定"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/et_name" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

package com.example.test9;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends Activity {
    private SharedPreferences preferences;
    private TextView tv_welcome;
    private Button btn_set;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tv_welcome=findViewById(R.id.tv_welcome);
        preferences= this.getSharedPreferences("usersetting",MODE_PRIVATE);
        tv_welcome.setText("欢迎"+preferences.getString("username"," ")+"来到我的家园");

        btn_set=findViewById(R.id.btn_set);
        btn_set.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(MainActivity.this,NewActivity.class);
                //启动指定Activity并等待返回的结果，其中0是请求码，用于标识该请求。
                startActivity(intent);
                MainActivity.this.finish();
            }
        });

    }
}

NewActivity.java

package com.example.test9;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class NewActivity extends Activity {

    private SharedPreferences preferences;
    private SharedPreferences.Editor editor;
    private Button btn_submit;
    private EditText et_name;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_new);

        et_name=findViewById(R.id.et_name);
        btn_submit=findViewById(R.id.btn_submit);

        btn_submit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                preferences=getSharedPreferences("usersetting",MODE_PRIVATE);
                editor=preferences.edit();
                //将输入的数据写入SharedPreference
                editor.putString("username",et_name.getText().toString());
                editor.commit();


                Intent intent=new Intent(NewActivity.this,MainActivity.class);
                startActivity(intent);
                NewActivity.this.finish();
            }
        });

    }
}