安卓开发学习------6.练习SharedPreferences用法和文件IO

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SharedPreferences是安卓里的一种存储方式，利用键值对来存储，比较小巧。
更多的使用的还是文件的IO方式来进行存储数据。
代码如下，submit按键测试SharedPreferences功能，存储的是程序启动的次数，write按键是写入文本文件，read按键是将文本内容写入标题栏。
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=".ListActivity22">

    <TextView
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="                      欢迎使用"
        android:textSize="30dp"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/xin"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="文本："
        android:textSize="30dp"
        app:layout_constraintTop_toBottomOf="@id/tv" />

    <EditText
        android:id="@+id/ming"
        android:layout_width="300dp"
        android:layout_height="50dp"
        app:layout_constraintLeft_toRightOf="@id/xin"
        app:layout_constraintTop_toBottomOf="@id/tv" />

    <TextView
        android:id="@+id/xue"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="学号："
        android:textSize="30dp"
        app:layout_constraintTop_toBottomOf="@id/xin" />

    <EditText
        android:id="@+id/hao"
        android:layout_width="300dp"
        android:layout_height="50dp"
        app:layout_constraintLeft_toRightOf="@id/xue"
        app:layout_constraintTop_toBottomOf="@id/ming" />

    <TextView
        android:id="@+id/xinbie"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="性别："
        android:textSize="30dp"
        app:layout_constraintTop_toBottomOf="@id/xue" />

    <RadioGroup
        android:id="@+id/rg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintLeft_toRightOf="@id/xinbie"
        app:layout_constraintTop_toBottomOf="@+id/hao">

        <RadioButton
            android:id="@+id/rb1"
            android:layout_width="150dp"
            android:layout_height="50dp"
            android:text="Female"
            app:layout_constraintLeft_toRightOf="@id/xinbie"
            app:layout_constraintTop_toBottomOf="@+id/hao" />

        <RadioButton
            android:id="@+id/rb2"
            android:layout_width="150dp"
            android:layout_height="50dp"
            android:text="Male"
            app:layout_constraintLeft_toRightOf="@id/rb2"
            app:layout_constraintTop_toBottomOf="@+id/hao" />
    </RadioGroup>

    <TextView
        android:id="@+id/mudi"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="使用目的："
        android:textSize="30dp"
        app:layout_constraintTop_toBottomOf="@id/xinbie" />

    <CheckBox
        android:id="@+id/xuexi"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="学习"
        app:layout_constraintTop_toBottomOf="@id/mudi" />

    <CheckBox
        android:id="@+id/xiazai"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="下载资源"
        app:layout_constraintLeft_toRightOf="@id/xuexi"
        app:layout_constraintTop_toBottomOf="@id/mudi"

        />

    <CheckBox
        android:id="@+id/weiguan"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="上传资源"
        app:layout_constraintLeft_toRightOf="@id/xiazai"
        app:layout_constraintTop_toBottomOf="@id/mudi"

        />

    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="看广告"
        app:layout_constraintLeft_toRightOf="@id/weiguan"
        app:layout_constraintTop_toBottomOf="@id/mudi" />

    <TextView
        android:id="@+id/nianji"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:text="年级："
        android:textSize="30dp"
        app:layout_constraintTop_toBottomOf="@id/xuexi" />

    <Spinner
        android:id="@+id/sp"
        android:layout_width="300dp"
        android:layout_height="50dp"
        android:entries="@array/mysp_arry"
        app:layout_constraintLeft_toRightOf="@id/nianji"
        app:layout_constraintTop_toBottomOf="@id/xuexi" />



    <TextView
        android:id="@+id/guanggao"
        android:layout_width="wrap_content"
        android:layout_height="20dp"
        android:text="广告投放"
        android:textSize="10dp"
        app:layout_constraintTop_toBottomOf="@id/nianji" />

    <ListView
        android:id="@+id/lv3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toBottomOf="@id/guanggao" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toBottomOf="@id/lv3"
        android:id="@+id/btn"
        android:text="Submit"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toRightOf="@id/btn"
        app:layout_constraintTop_toBottomOf="@id/lv3"
        android:id="@+id/btn1"
        android:text="Write"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toRightOf="@id/btn1"
        app:layout_constraintTop_toBottomOf="@id/lv3"
        android:id="@+id/btn2"
        android:text="Read"/>



</androidx.constraintlayout.widget.ConstraintLayout>

Activity.java代码：

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;

public class ListActivity22 extends AppCompatActivity {
    public String[] sp_array = {"广告位长期招租"};

    public ListView lv3;
    public RadioGroup rg;
    public Button btn;
    public String str;
    public TextView tv;
    public Button  btn1;
    public Button  btn2;
     public EditText ming;//获取xml里的editortext的内容，前面那个editortext就是叫ming

    public final String file_name = "ttt.txt";
    public SharedPreferences sp;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list22);


        lv3 = findViewById(R.id.lv3);
        lv3.setAdapter(new MyAdapter(ListActivity22.this));

        rg = findViewById(R.id.rg);//这一操作是将控件连接起来的操作。
        rg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {
                switch(checkedId){
                    case R.id.rb1:str = "Female";break;
                    case R.id.rb2: str = "Male";break;
                    default: str = "nothing";break;
                }
            }
        });

        //shareedpreferce example
        sp = getSharedPreferences("config",MODE_PRIVATE);
        int c_count = sp.getInt("count",0);
        SharedPreferences.Editor editor = sp.edit();
        editor.putInt("count",++c_count);
        editor.commit();//记得提交


        tv = findViewById(R.id.tv);
        btn = findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                tv.setText(str);
                Toast.makeText(ListActivity22.this,String.valueOf(sp.getInt("count",0)),Toast.LENGTH_LONG).show();//toast弹出消息

            }
        });
        ming = findViewById(R.id.ming);
        btn1 = findViewById(R.id.btn1);
        btn2 = findViewById(R.id.btn2);
        //下面写这些按钮的响应事件
        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
              //这里面就是写响应事件
                //write text from edittext to file
                try {
                    FileOutputStream fos = openFileOutput(file_name,MODE_PRIVATE);
                    PrintStream ps = new PrintStream(fos);
                    ps.println(ming.getText());
                    ps.close();
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // read text from file to textview
                try {
                    FileInputStream fis = openFileInput(file_name);
                    byte[] buff = new byte[1024];
                    int hasRead = 0;
                    StringBuilder sb = new StringBuilder("");
                    while((hasRead=fis.read(buff))>0){
                        sb.append(new String(buff,0,hasRead));
                    }
                    fis.close();
                    tv.setText(sb.toString());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });





    }

    private class MyAdapter extends BaseAdapter {
        Context context;

        public MyAdapter(Context context) {
            super();
            this.context = context;
        }

        public MyAdapter() {
            super();
            this.context = context;
        }

        @Override
        public int getCount() {
        return sp_array.length;

        }

        @Override
        public Object getItem(int position) {
            return position;
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View v, ViewGroup parent) {
            if(position%2==0){
                v = LayoutInflater .from(context).inflate(R.layout.activity_calculator,null);
            }else {
                v = v = LayoutInflater.from(context).inflate(R.layout.activity_yueshu, null);
            }
            TextView tvv1 = v.findViewById(R.id.tvv1);
            TextView tvv2 = v.findViewById(R.id.tvv2);
            tvv1.setText(sp_array[position]);
            tvv2.setText("张三");
            return  v;
        }
    }
}

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