这次主要是对SD卡外部存储和SharedPreferences存储的补充说明
还是以qq案例来说

首先外部存储

存储的位置为/storage/emulated/0目录下具体为你定义的地方这里也有个小坑
还有就是不需要使用内部存储的openFileOutput方法和openFileInput方法

首先要在清单文件里申请SD卡写读文件的权限
两种方式静态和动态申请
自然在清单文件里配置静态申请简单了
    </application>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

然后看工具类的编写

也就是对内部存储的更改

package com.example.store;

import android.content.Context;
import android.os.Environment;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

//工具类 实现QQ的账号密码存储和读取
public class SDTool_qqAcitivity {
    public static boolean saveUser(Context context, String user, String pwd) {
        String state = Environment.getExternalStorageState();
        if (state.equals(Environment.MEDIA_MOUNTED)) {
//            File path = Environment.getExternalStorageDirectory();
            File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
//            File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS);
            File file = new File(path, "haha.txt");
            FileOutputStream fos = null;
            try {
//                fos = context.openFileOutput("haha.txt", Context.MODE_PRIVATE);
                fos= new FileOutputStream(file);
                //将数据转换为字节码的形式写入haha.txt中
                fos.write((user + ":" + pwd).getBytes());
            } catch (Exception e) {
                e.printStackTrace();
                return false;
            } finally {
                if (fos != null) {
                    try {
                        fos.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                        return false;
                    }
                }
            }
            return true;
        } else {
            return false;
        }

    }

    public static Map<String, String> getUser(Context context) {
        String state = Environment.getExternalStorageState();
        if (state.equals(Environment.MEDIA_MOUNTED)) {
//            File path = Environment.getExternalStorageDirectory();
           File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);


            File file = new File(path, "haha.txt");
            String str = "";
            FileInputStream fis = null;
            try {
//                fis = context.openFileInput("haha.txt");
                fis=new FileInputStream(file);
                byte[] buffer = new byte[fis.available()];
                fis.read(buffer);
                str = new String(buffer);
                HashMap<String, String> map = new HashMap<String, String>();
                String[] split = str.split(":");
                map.put("user", split[0]);
                map.put("pwd", split[1]);
                return map;
            } catch (Exception e) {
                e.printStackTrace();
                return null;
            } finally {
                if (fis != null) {
                    try {
                        fis.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return null;
    }


}

坑坑坑如果你获取路径写的是如下的活会实现不了保存密码也不会在文件里找到
// File path = Environment.getExternalStorageDirectory();
你必须给他一个确定的地方
例如：
Filepath=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
这样文件就保存到DOWNLOADS目录下了

还有个重要的坑

就是我一直想实现不了密码保存
原因是
// Map<String, String> user =SDTool_qqAcitivity.getUser(this);
boolean b = SPTool_qqAcitivity.saveUser(QQ_Activity.this, user, pwd);
你要确定你调用的是哪个工具

然后就是SharedPreferences存储

它主要是一个轻量级的存储介绍方法吗都在33里面介绍了就不赘婿了
然后就是文件存储在：

对的存储的格式为xml

然后咱们看工具类的编写

主要就是调用编辑器方法
package com.example.store;

import android.content.Context;
import android.content.SharedPreferences;

//工具类 实现QQ的账号密码存储和读取
public class SPTool_qqAcitivity {
    public static boolean saveUser(Context context, String user, String pwd) {
        SharedPreferences sharedPreferences = context.getSharedPreferences("haha", Context.MODE_PRIVATE);
        SharedPreferences.Editor edit = sharedPreferences.edit();
        edit.putString("user", user);
        edit.putString("pwd", pwd);
        edit.commit();
        return true;
    }

    public static String getUser(Context context, String key) {
        SharedPreferences sharedPreferences = context.getSharedPreferences("haha", Context.MODE_PRIVATE);
        String string = sharedPreferences.getString(key, "没找到");
        return string;
    }
}

注意注意要在主文件中修改你调用的工具同上一样：
略微修改
因为改成了String方法

//        Map<String, String> user =SDTool_qqAcitivity.getUser(this);
//        user = Tool_qqAcitivity.getUser(this);
//        if (user != null) {
//            et_account.setText(user.get("user"));
//            et_password.setText(user.get("pwd"));
//        }
        String user = SPTool_qqAcitivity.getUser(this, "user");
        String pwd = SPTool_qqAcitivity.getUser(this, "pwd");
        et_account.setText(user);
        et_password.setText(pwd);

再来个小补充把就是我33并没有trycatch处理异常

这样是不对的所以在这里小小补充下代码

package com.example.store;

import android.content.SharedPreferences;
import android.os.Bundle;
import android.os.Environment;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import java.io.IOException;
import java.util.Map;

public class QQ_Activity extends AppCompatActivity {
    //初始化
    private EditText et_account;
    private EditText et_password;
    private Button btn_login;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_qq);
        et_account = findViewById(R.id.et_account);
        et_password = findViewById(R.id.et_password);
        btn_login = findViewById(R.id.btn_login);
//        Map<String, String> user =SDTool_qqAcitivity.getUser(this);
//        user = Tool_qqAcitivity.getUser(this);
//        if (user != null) {
//            et_account.setText(user.get("user"));
//            et_password.setText(user.get("pwd"));
//        }
        String user = SPTool_qqAcitivity.getUser(this, "user");
        String pwd = SPTool_qqAcitivity.getUser(this, "pwd");
        et_account.setText(user);
        et_password.setText(pwd);


        btn_login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String user = et_account.getText().toString().trim();
                String pwd = et_password.getText().toString();
                //检查是否为空
                if (TextUtils.isEmpty(user)) {
                    Toast.makeText(QQ_Activity.this, "请输入账号", Toast.LENGTH_SHORT).show();
                }
                if (TextUtils.isEmpty(pwd)) {
                    Toast.makeText(QQ_Activity.this, "请输入密码", Toast.LENGTH_SHORT).show();
                }
                Toast.makeText(QQ_Activity.this, "登录成功", Toast.LENGTH_SHORT).show();
                //保存用户信息 调用工具
                boolean b = SPTool_qqAcitivity.saveUser(QQ_Activity.this, user, pwd);
                if (b) {
                    Toast.makeText(QQ_Activity.this, "保存成功", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(QQ_Activity.this, "保存失败", Toast.LENGTH_SHORT).show();
                }

            }
        });
    }

}

欧克了那个SQLite数据库存储33中已经很清楚的介绍
那三个存储方法算over了剩下的就是内容提供者和网络存储了

posted on 2024-04-27 09:51 不爱美女爱辣条阅读(4) 评论(0) 编辑收藏举报

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