Android开发中SharePreferences的基本用法（用户偏好设置）

SharePreferences主要用于记录用户的一些偏好设置，比如：用户账号，密码之类的，数据量非常小的数据。

效果如下：

MainActivity.java的代码如下：

package com.deepreality.sharedpreferencesdemo;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import java.util.Map;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText etUserName, etPassword;
    private Button btnLogin;
    private String strUserName;
    private String strPassword;
    private Context mContext;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = this;
        bindViews();
    }

    private void bindViews() {
        etUserName = findViewById(R.id.main_etUserName);
        etPassword = findViewById(R.id.main_etPassword);
        btnLogin = findViewById(R.id.main_btnLogin);
        btnLogin.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.main_btnLogin:{
                strUserName = etUserName.getText().toString();
                strPassword = etPassword.getText().toString();
                //保存用户偏好设置到my_sp.xml文件中
                SPUtils.put(mContext, "username", strUserName);
                SPUtils.put(mContext, "password", strPassword);
                break;
            }
            default:break;
        }
    }


    /**
     * 当前Activity启动时的操作，在onCreate方法之后
     */
    @Override
    protected void onStart() {
        super.onStart();
        //读取本地的用户偏好设置
        etUserName.setText(SPUtils.get(mContext, "username", "").toString());
        etPassword.setText(SPUtils.get(mContext, "username", "").toString());

    }
}

下面提供两个工具类：MD5Utils（MD5加密工具类），SPUtils（用户偏好设置工具类）。

MD5Utils.java

package com.deepreality.sharedpreferencesdemo;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Utils {
    public static String getMD5(String content) {
        try {
            MessageDigest digest = MessageDigest.getInstance("MD5");
            digest.update(content.getBytes());
            return getHashString(digest);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return null;
    }

    private static String getHashString(MessageDigest digest) {
        StringBuilder builder = new StringBuilder();
        for (byte b : digest.digest()) {
            builder.append(Integer.toHexString((b >> 4) & 0xf));
            builder.append(Integer.toHexString(b & 0xf));
        }
        return builder.toString();
    }
}

SPUtils.java

package com.deepreality.sharedpreferencesdemo;

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

import java.util.Map;

public class SPUtils {
    /**
     * 保存在手机里的SP文件名
     */
    public static final String FILE_NAME = "my_sp";

    /**
     * 保存数据
     */
    public static void put(Context context, String key, Object obj) {
        SharedPreferences sp = context.getSharedPreferences(FILE_NAME, context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sp.edit();
        if (obj instanceof Boolean) {
            editor.putBoolean(key, (Boolean) obj);
        } else if (obj instanceof Float) {
            editor.putFloat(key, (Float) obj);
        } else if (obj instanceof Integer) {
            editor.putInt(key, (Integer) obj);
        } else if (obj instanceof Long) {
            editor.putLong(key, (Long) obj);
        } else {
            editor.putString(key, (String) obj);
        }
        editor.commit();
    }


    /**
     * 获取指定数据
     */
    public static Object get(Context context, String key, Object defaultObj) {
        SharedPreferences sp = context.getSharedPreferences(FILE_NAME, context.MODE_PRIVATE);
        if (defaultObj instanceof Boolean) {
            return sp.getBoolean(key, (Boolean) defaultObj);
        } else if (defaultObj instanceof Float) {
            return sp.getFloat(key, (Float) defaultObj);
        } else if (defaultObj instanceof Integer) {
            return sp.getInt(key, (Integer) defaultObj);
        } else if (defaultObj instanceof Long) {
            return sp.getLong(key, (Long) defaultObj);
        } else if (defaultObj instanceof String) {
            return sp.getString(key, (String) defaultObj);
        }
        return null;
    }

    /**
     * 删除指定数据
     */
    public static void remove(Context context, String key) {
        SharedPreferences sp = context.getSharedPreferences(FILE_NAME, context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sp.edit();
        editor.remove(key);
        editor.commit();
    }


    /**
     * 返回所有键值对
     */
    public static Map<String, ?> getAll(Context context) {
        SharedPreferences sp = context.getSharedPreferences(FILE_NAME, context.MODE_PRIVATE);
        Map<String, ?> map = sp.getAll();
        return map;
    }

    /**
     * 删除所有数据
     */
    public static void clear(Context context) {
        SharedPreferences sp = context.getSharedPreferences(FILE_NAME, context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sp.edit();
        editor.clear();
        editor.commit();
    }

    /**
     * 检查key对应的数据是否存在
     */
    public static boolean contains(Context context, String key) {
        SharedPreferences sp = context.getSharedPreferences(FILE_NAME, context.MODE_PRIVATE);
        return sp.contains(key);
    }
}