Android使用SharedPreferneces存储数据
实现效果：

java代码：

package com.henu.sharedpreferences;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView tvcontent = (TextView) findViewById(R.id.tv_content);
        EditText etcontent = (EditText) findViewById(R.id.et_content);
        if(tvcontent.getText().toString().trim().equals("")){
            SharedPreferences sp = this.getSharedPreferences("data", MODE_PRIVATE);
            tvcontent.setText(sp.getString("content", ""));
            etcontent.setText(sp.getString("content", ""));
        }
    }

    public void save(View v) {
        EditText etcontent = (EditText) findViewById(R.id.et_content);
        SharedPreferences sp = this.getSharedPreferences("data", MODE_PRIVATE);
        SharedPreferences.Editor editor = sp.edit();
        editor.putString("content", etcontent.getText().toString().trim());
        editor.commit();
        Toast.makeText(this, "存入成功", Toast.LENGTH_SHORT).show();
    }

    public void display(View v) {
        TextView tvcontent = (TextView) findViewById(R.id.tv_content);
        SharedPreferences sp = this.getSharedPreferences("data", MODE_PRIVATE);
        tvcontent.setText(sp.getString("content", ""));
        Toast.makeText(this, "取出成功", Toast.LENGTH_SHORT).show();
    }
}

xml代码：

<?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">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">


        <EditText
            android:id="@+id/et_content"
            android:layout_width="match_parent"
            android:layout_height="60dp"
            android:textSize="35dp"
            android:layout_marginTop="40dp"></EditText>

        <Button
            android:layout_marginTop="30dp"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="存入SHAREDPREFERENCES"
            android:layout_gravity="center"
            android:onClick="save"
            android:textSize="35dp"></Button>
        <Button
            android:layout_marginTop="20dp"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="从SHAREDPREFERENCES取出"
            android:layout_gravity="center"
            android:onClick="display"
            android:textSize="33dp"></Button>
        <TextView
            android:textSize="35dp"
            android:layout_marginTop="20dp"
            android:layout_width="match_parent"
            android:layout_height="60dp"
            android:id="@+id/tv_content"></TextView>

    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

**注意：**在写Button的android:onClick="save"点击事件不要忘了在定义函数时 public void save(View v) 加入形参 View v。