专高一第二周作业（SD卡,Fragment,TabLayout）

最新推荐文章于 2024-11-07 11:04:42 发布

原创最新推荐文章于 2024-11-07 11:04:42 发布 · 251 阅读

CC 4.0 BY-SA版权

这篇博客详细介绍了在Android中进行SD卡的四种操作，包括写入和读取JSON文件、从网络下载并保存图片到SD卡以及异步读取图片。同时，还涵盖了登录保存密码的实现，以及使用Fragment进行页面跳转，结合ListView展示数据的完整流程，包括网络请求、适配器和主页面的设计。

技能练习

SD卡的四种操作

准备工作

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    //声明四个按钮
    private Button writejson;
    private Button readjson;
    private Button urlpic;
    private Button readpic;
    private TextView showjson;
    private ImageView showpic;
    private String json = "http://www.qubaobei.com/ios/cf/dish_list.php?stage_id=1&limit=10&page=1";
    private String picurl="http://www.qubaobei.com/ios/cf/uploadfile/132/9/8289.jpg";

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

        //判断SD卡是否挂载
        final String externalStorageState = Environment.getExternalStorageState();
        //获取SD看的根目录
        final File externalStorageDirectory = Environment.getExternalStorageDirectory();
        //获取SD卡公开目录pictures文件
        File externalStoragePublicDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);

        //初始化
        writejson = (Button) findViewById(R.id.writejson);
        readjson = (Button) findViewById(R.id.readjson);
        urlpic = (Button) findViewById(R.id.urlpic);
        readpic = (Button) findViewById(R.id.readpic);
        showjson = (TextView) findViewById(R.id.showjson);
        showpic = (ImageView) findViewById(R.id.showpic);


        //设置动态请求SD卡的权限
        requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE,Manifest.permission.WRITE_EXTERNAL_STORAGE},100);

布局

<?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"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <Button
         android:id="@+id/writejson"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="写入json串"/>

    <Button
        android:id="@+id/readjson"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="读取json串"/>

    <Button
        android:id="@+id/readpic"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="从SD卡中读取一张图片"/>

    <Button
        android:id="@+id/urlpic"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="从网上下载一张图片"/>

    <TextView
        android:id="@+id/showjson"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:text="这里是显示读取的json字符串的"
        android:textColor="#000"
        android:layout_marginTop="20dp"/>

    <ImageView
        android:id="@+id/showpic"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@mipmap/ic_launcher"
        android:layout_marginTop="10dp"/>
</LinearLayout>

写入json

		writejson.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //判断SD卡是否挂载
                if (externalStorageState.equals(Environment.MEDIA_MOUNTED)){
                    //获取sd卡的根路径
//                    File externalStorageDirectory = Environment.getExternalStorageDirectory();
                    FileOutputStream fos = null;

                    try {
                        //File(要写到的位置.写成的文件名字和格式);
                        fos = new FileOutputStream(new File(externalStorageDirectory,"json.txt"));
                        fos.write(json.getBytes());
                    } catch (Exception e) {
                        e.printStackTrace();
                    }finally {
                        if (fos!=null){
                            try {
                                fos.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }

                        }
                    }
                    Log.i(TAG, "onClick: 写入成功");
                }
            }
        });

读取json

readjson.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                //获取SD卡的根路径
//                File externalStorageDirectory1 = Environment.getExternalStorageDirectory();
                //查看SD卡是否挂载
//                String externalStorageState1 = Environment.getExternalStorageState();


                //判断SD卡是否挂载了
                if (externalStorageState.equals(Environment.MEDIA_MOUNTED)){
                    FileInputStream is = null;
                    StringBuffer sb = new StringBuffer();
                    try {
                        is = new FileInputStream(new File(externalStorageDirectory,"json.txt"));
                        byte[] bytes = new byte[1024];
                        int len = 0;
                        while ((len = is.read(bytes))!=-1){
                            sb.append(new String(bytes,0,len));
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }finally {
                        if (is != null){
                            try {
                                is.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                    Log.i(TAG, "onClick: 读取成功");
                    showjson.setText(sb.toString());
                }

            }
        });

从网上下载一张图片到SD卡中

 urlpic.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //进行网络下载，要用到异步
                new MyTask().execute(picurl);
            }
        });

异步

package com.example.weekhomework1013;

import android.net.Uri;
import android.os.AsyncTask;
import android.os.Environment;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

class MyTask extends AsyncTask<String,String,String> {
    @Override
    protected String doInBackground(String... strings) {
        FileOutputStream fos = null;
        InputStream is = null;//网络连接的输入流
        HttpURLConnection connection = null;//想SD卡写的输出流
        try {
            //进行下载
            URL url = new URL(strings[0]);
            connection= (HttpURLConnection) url.openConnection();
            connection.setConnectTimeout(5*1000);
            connection.setReadTimeout(5*1000);
            if (connection.getResponseCode() == 200){
                is = connection.getInputStream();
                //判断SD卡是否挂载
                if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
                        //获取SD卡的路径
                    File externalStorageDirectory = Environment.getExternalStorageDirectory();
                    fos = new FileOutputStream(new File(externalStorageDirectory,"wangbolup.jpg"));
                    byte[] bytes = new byte[1024];
                    int len = 0;
                    while ((len = is.read(bytes))!=-1){
                        fos.write(bytes,0,len);
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {//关流
            if (fos!=null){
                try {
                    fos.close();
                } catch (IOException e) {

                }
            }
            if (is!=null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (connection!=null){
                connection.disconnect();
            }
        }
        return null;
    }
}

从SD卡中读取图片

 readpic.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Bitmap bitmap = null;
                //判断SD卡是否挂载
                if (externalStorageState.equals(Environment.MEDIA_MOUNTED)){
                    File file = new File(externalStorageDirectory, "wangbolup.jpg");
                    //BitmapFactory可以直接根据SD卡图片路径转成一个bitmap对象
                    bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
                }
                showpic.setImageBitmap(bitmap);
            }
        });

登录保存密码

布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".Main2Activity">
               <TextView
                   android:id="@+id/heand"
                   android:layout_width="wrap_content"
                   android:layout_height="wrap_content"
                   android:text="登录界面"
                   android:textSize="30sp"
                   android:textColor="#000"
                   android:layout_centerHorizontal="true"
                   android:layout_marginTop="40dp"/>
                <EditText
                    android:id="@+id/username"
                    android:layout_width="300dp"
                    android:layout_height="wrap_content"
                    android:layout_centerHorizontal="true"
                    android:layout_marginTop="200dp"
                    android:hint="请输入用户名"/>
                <EditText
                    android:id="@+id/pwd"
                    android:layout_width="300dp"
                    android:layout_below="@+id/username"
                    android:layout_height="wrap_content"
                    android:layout_centerHorizontal="true"
                    android:layout_marginTop="20dp"
                    android:hint="请输入密码"/>
                <CheckBox
                    android:id="@+id/remember"
                    android:layout_below="@+id/pwd"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="记住密码"
                    android:layout_marginLeft="56dp"
                    android:layout_marginTop="10dp"/>
                <Button
                    android:id="@+id/login"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="登录"
                    android:layout_toRightOf="@+id/remember"
                    android:layout_below="@+id/pwd"
                    android:layout_marginLeft="125dp"/>
</RelativeLayout>

代码

package com.example.app2;

import android.content.SharedPreferences;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.TextView;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;

public class Main2Activity extends AppCompatActivity {

    //声明
    private TextView heand;
    private EditText username;
    private EditText pwd;
    private CheckBox remember;
    private Button login;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        //初始化
        heand = (TextView) findViewById(R.id.heand);
        username = (EditText) findViewById(R.id.username);
        pwd = (EditText) findViewById(R.id.pwd);
        remember = (CheckBox) findViewById(R.id.remember);
        login = (Button) findViewById(R.id.login);

        //SD卡挂载
        final String externalStorageState = Environment.getExternalStorageState();
        //SD卡的路径
        final File externalStorageDirectory = Environment.getExternalStorageDirectory();


        //开始就读取SD卡，查看有没有记住的信息  有就直接赋值上去
        SharedPreferences user = getSharedPreferences("user", MODE_PRIVATE);
        String username_read = user.getString("username", "");
        String password_read = user.getString("password", "");
        boolean remember_read = user.getBoolean("remember", false);
        username.setText(username_read);
        pwd.setText(password_read);
        remember.setChecked(remember_read);

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //判断SD卡是否挂载了
                if (externalStorageState.equals(Environment.MEDIA_MOUNTED)){
                    try {
                        if (Main2Activity.this.remember.isChecked()){
                            Editable name = Main2Activity.this.username.getText();
                            Editable password = pwd.getText();
                            //设置写入的文件名称和读取方式
                            SharedPreferences user = getSharedPreferences("user", MODE_PRIVATE);

                            //通过sp的edit方法，来写入数据
                            SharedPreferences.Editor edit = user.edit();
                            edit.putString("username",name.toString());
                            edit.putString("password",password.toString());
                            edit.putBoolean("remember",true);

                            //提交
                            edit.commit();
                        }else{
                            SharedPreferences user1 = getSharedPreferences("user", MODE_PRIVATE);
                            SharedPreferences.Editor edit = user1.edit();
                            edit.clear();
                            edit.commit();

                        }

                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }


            }
        });

    }
}

页面跳转读写SD卡 ListView展示数据

布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".fragment.DageFragment">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="主界面"
            android:layout_centerHorizontal="true"
            android:textSize="30sp"
            android:layout_marginTop="20dp"/>

    <Button
        android:id="@+id/writeSD"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="150dp"
        android:text="存入SD卡"/>

    <Button
        android:id="@+id/readSD"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="250dp"
        android:text="读取SD卡"/>

    <Button
        android:id="@+id/rli"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="350dp"
        android:text="日历"/>

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".Main2Activity">
                <android.support.design.widget.TabLayout
                    android:id="@+id/tl"
                    android:layout_width="match_parent"
                    android:layout_height="50dp">

                </android.support.design.widget.TabLayout>

                <LinearLayout
                    android:id="@+id/ll"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:layout_below="@+id/tl"
                    android:layout_above="@+id/footer"
                    android:orientation="vertical">
                </LinearLayout>
                               
                <RadioGroup
                    android:id="@+id/footer"
                    android:layout_width="match_parent"
                    android:layout_height="50dp"
                    android:layout_alignParentBottom="true"
                    android:orientation="horizontal">
                            <RadioButton
                                android:id="@+id/dage"
                                android:layout_width="0dp"
                                android:layout_weight="1"
                                android:layout_height="match_parent"
                                android:button="@null"
                                android:text="大哥吃肉"
                                android:gravity="center"/>
                            <RadioButton
                                android:id="@+id/erdi"
                                android:layout_width="0dp"
                                android:layout_weight="1"
                                android:layout_height="match_parent"
                                android:button="@null"
                                android:text="二弟吃面"
                                android:gravity="center"/>
                            <RadioButton
                                android:id="@+id/sandi"
                                android:layout_width="0dp"
                                android:layout_weight="1"
                                android:layout_height="match_parent"
                                android:button="@null"
                                android:text="三弟喝汤"
                                android:gravity="center"/>
                            <RadioButton
                                android:id="@+id/sidi"
                                android:layout_width="0dp"
                                android:layout_weight="1"
                                android:layout_height="match_parent"
                                android:button="@null"
                                android:text="四弟刷碗"
                                android:gravity="center"/>
                </RadioGroup>
    
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
    tools:context=".fragment.ErdiFragment">

    <ListView
        android:id="@+id/lviewid"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></ListView>

</FrameLayout>

网络请求

package com.example.app3;

import android.util.Log;

import com.bumptech.glide.load.resource.bytes.ByteBufferRewinder;
import com.google.gson.Gson;

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

public class Httputils {
    private static final String TAG = "Httputils";
    public static String geturl(String s){
        InputStream is = null;
        ByteArrayOutputStream baos = null;
        try {
            URL url = new URL(s);
            Log.i(TAG, "geturl: "+s);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            connection.setRequestMethod("GET");
            connection.connect();
            if (connection.getResponseCode() == 200){
                is = connection.getInputStream();
                baos = new ByteArrayOutputStream();
                int len = 0;
                byte[] bytes = new byte[1024];
                while ((len = is.read(bytes))!=-1){
                    baos.write(bytes,0,len);
                }
                Log.i(TAG, "geturl: "+baos.toString());
                String s1 = baos.toString();
                return s1;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}

Fragment跳转

package com.example.app3;

import android.support.design.widget.TabLayout;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.RadioButton;

import com.example.app3.fragment.DageFragment;
import com.example.app3.fragment.ErdiFragment;
import com.example.app3.fragment.SandiFragment;
import com.example.app3.fragment.SidiFragment;

public class Main2Activity extends AppCompatActivity {

    private TabLayout tl;
    private LinearLayout ll;
    private RadioButton dage;
    private RadioButton erdi;
    private RadioButton sandi;
    private RadioButton sidi;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        //初始化
        tl = (TabLayout) findViewById(R.id.tl);
        ll = (LinearLayout) findViewById(R.id.ll);
        dage = (RadioButton) findViewById(R.id.dage);
        erdi = (RadioButton) findViewById(R.id.erdi);
        sandi = (RadioButton) findViewById(R.id.sandi);
        sidi = (RadioButton) findViewById(R.id.sidi);


        //添加fragment
        final FragmentManager supportFragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = supportFragmentManager.beginTransaction();

        //初始化
        final DageFragment dageFragment = new DageFragment();
        final ErdiFragment erdiFragment = new ErdiFragment();
        final SandiFragment sandiFragment = new SandiFragment();
        final SidiFragment sidiFragment = new SidiFragment();

        //添加
        fragmentTransaction.add(R.id.ll,dageFragment);
        fragmentTransaction.add(R.id.ll,erdiFragment);
        fragmentTransaction.add(R.id.ll,sandiFragment);
        fragmentTransaction.add(R.id.ll,sidiFragment);

        fragmentTransaction.show(dageFragment);
        fragmentTransaction.hide(erdiFragment);
        fragmentTransaction.hide(sandiFragment);
        fragmentTransaction.hide(sidiFragment);
        //提交
        fragmentTransaction.commit();

        dage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FragmentManager supportFragmentManager1 = getSupportFragmentManager();
                FragmentTransaction fragmentTransaction1 = supportFragmentManager1.beginTransaction();
                fragmentTransaction1.show(dageFragment);
                fragmentTransaction1.hide(erdiFragment);
                fragmentTransaction1.hide(sandiFragment);
                fragmentTransaction1.hide(sidiFragment);
                fragmentTransaction1.commit();
            }
        });

        erdi.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FragmentManager supportFragmentManager1 = getSupportFragmentManager();
                FragmentTransaction fragmentTransaction1 = supportFragmentManager1.beginTransaction();
                fragmentTransaction1.show(erdiFragment);
                fragmentTransaction1.hide(dageFragment);
                fragmentTransaction1.hide(sandiFragment);
                fragmentTransaction1.hide(sidiFragment);
                fragmentTransaction1.commit();
            }
        });

        sandi.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FragmentManager supportFragmentManager1 = getSupportFragmentManager();
                FragmentTransaction fragmentTransaction1 = supportFragmentManager1.beginTransaction();
                fragmentTransaction1.show(sandiFragment);
                fragmentTransaction1.hide(dageFragment);
                fragmentTransaction1.hide(erdiFragment);
                fragmentTransaction1.hide(sidiFragment);
                fragmentTransaction1.commit();
            }
        });

        sidi.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FragmentManager supportFragmentManager1 = getSupportFragmentManager();
                FragmentTransaction fragmentTransaction1 = supportFragmentManager1.beginTransaction();
                fragmentTransaction1.show(sidiFragment);
                fragmentTransaction1.hide(dageFragment);
                fragmentTransaction1.hide(erdiFragment);
                fragmentTransaction1.hide(sandiFragment);
                fragmentTransaction1.commit();
            }
        });

    }
}

创建一个公共的List

package com.example.app3;

import java.util.ArrayList;
import java.util.List;

public class Together  {
    public static List<JavaBean> totallist = new ArrayList<>();
}

主页

package com.example.app3.fragment;


import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Environment;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;

import com.alibaba.fastjson.JSON;
import com.example.app3.Httputils;
import com.example.app3.JavaBean;
import com.example.app3.R;
import com.example.app3.Together;
import com.google.gson.Gson;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;

/**
 * A simple {@link Fragment} subclass.
 */
public class DageFragment extends Fragment {

    private static final String TAG = "DageFragment";

    private Button writeSD;
    private Button readSD;
    private Button rli;
    private String url="http://api.yunzhancn.cn/api/app.interface.php?siteid=78703&act=column&ctype=4";
    private String s;



    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View inflate = inflater.inflate(R.layout.fragment_dage, container, false);
        
        writeSD = (Button) inflate.findViewById(R.id.writeSD);
        readSD = (Button) inflate.findViewById(R.id.readSD);
        rli = (Button) inflate.findViewById(R.id.rli);

        //SD卡是否挂载
        final String externalStorageState = Environment.getExternalStorageState();
        //SD卡的根目录
        final File externalStorageDirectory = Environment.getExternalStorageDirectory();

        //动态询问SD卡权限
        requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.READ_EXTERNAL_STORAGE},100);

        //子线程进行网络请求
        new Thread(new Runnable() {
            @Override
            public void run() {
                String geturl = Httputils.geturl(url);
                List<JavaBean> javaBeans = JSON.parseArray(geturl, JavaBean.class);
                Together.totallist.addAll(javaBeans);
                s = javaBeans.toString();
                Log.i(TAG, "run: "+s);
            }
        }).start();

        //写入的按钮
        writeSD.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (externalStorageState.equals(Environment.MEDIA_MOUNTED)){
                        FileOutputStream  fos = null;
                        try {
                            fos = new FileOutputStream(new File(externalStorageDirectory,"json2.txt"));
                            fos.write(s.getBytes());
                        } catch (Exception e) {
                            e.printStackTrace();
                        }finally {
                            if (fos != null){
                                try {
                                    fos.close();
                                } catch (IOException e) {
                                    e.printStackTrace();
                                }
                            }
                        }
                        Log.i(TAG, "onClick: 写入成功");
                    }
            }
        });

        //读的按钮
        readSD.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //判断SD卡是否挂载
                if (externalStorageState.equals(Environment.MEDIA_MOUNTED)){
                    FileInputStream is = null;
                    StringBuffer sb = null;
                    try {
                        is = new FileInputStream(new File(externalStorageDirectory,"json2.txt"));
                        sb = new StringBuffer();
                        int len = 0;
                        byte[] bytes = new byte[1024];
                        while((len = is.read(bytes))!=-1){
                            sb.append(new String(bytes,0,len));
                        }
                        Toast.makeText(getActivity(), sb.toString(), Toast.LENGTH_SHORT).show();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        });

        return inflate;
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == 100 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
        }else{
            getActivity().finish();
            Toast.makeText(getActivity(), "未获取授权", Toast.LENGTH_SHORT).show();
        }
    }
}

适配器

package com.example.app3;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.bumptech.glide.Glide;

import java.util.List;

public class MyAdapter extends BaseAdapter {
    private Context context;
    private LayoutInflater layoutInflater;

    public MyAdapter(Context context) {
        this.context = context;
        layoutInflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return Together.totallist.size();
    }

    @Override
    public Object getItem(int position) {
        return Together.totallist.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        if (convertView == null){
            holder = new ViewHolder();
            convertView = layoutInflater.inflate(R.layout.layout_item,null);
            holder.pic = convertView.findViewById(R.id.pic);
            holder.msg = convertView.findViewById(R.id.msg);
            convertView.setTag(holder);
        }else{
            holder = (ViewHolder) convertView.getTag();
        }
        holder.msg.setText(Together.totallist.get(position).getName());
        Glide.with(context).load(Together.totallist.get(position).getThumb()).into(holder.pic);
        return convertView;
    }
    static  class ViewHolder{
            private ImageView pic;
            private TextView msg;
    }
}

ListView展示页面

package com.example.app3.fragment;


import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;

import com.example.app3.MyAdapter;
import com.example.app3.R;

/**
 * A simple {@link Fragment} subclass.
 */
public class ErdiFragment extends Fragment {

    private ListView lviewid;

    public ErdiFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View inflate = inflater.inflate(R.layout.fragment_erdi, container, false);
        lviewid = (ListView) inflate.findViewById(R.id.lviewid);

        MyAdapter myAdapter = new MyAdapter(getActivity());
        lviewid.setAdapter(myAdapter);

        return inflate;
    }

}