数据存储——四种存储方式——共享参数SharedPreferences——保存路径是：/data/data/应用包名/shared_prefs/文件名.xml...

亦凉 2023-09-28 14:30 9阅读 0赞

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共享参数的用法

SharedPreferences是Android的一个轻量级存储工具，采用的存储结构是Key-Value的键值对方式。

共享参数的存储介质是符合XML规范的配置文件。保存路径是：/data/data/应用包名/shared\_prefs/文件名.xml

下面是一个共享参数的XML文件示例：

<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
    <map>
        <string name="name">Mr Lee</string>
        <int name="age" value="30" />
        <boolean name="married" value="true" />
        <float name="weight" value="100.0" />
    </map>

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// 从share.xml中获取共享参数对象
        SharedPreferences shared = getSharedPreferences("share", MODE_PRIVATE);
    
        // 下面是写入共享参数的代码例子
        SharedPreferences.Editor editor = shared.edit();  // 获得编辑器的对象
        editor.putString("name", "Mr Lee");  // 添加一个名叫name的字符串参数
        editor.putInt("age", 30);  // 添加一个名叫age的整型参数
        editor.putBoolean("married", true);  // 添加一个名叫married的布尔型参数
        editor.putFloat("weight", 100f);  // 添加一个名叫weight的浮点数参数
        editor.commit();  // 提交编辑器中的修改
    
        // 下面是读取共享参数的代码例子
        String name = shared.getString("name", "");  // 从共享参数中获得名叫name的字符串
        int age = shared.getInt("age", 0);  // 从共享参数中获得名叫age的整型数
        boolean married = shared.getBoolean("married", false);  // 从共享参数中获得名叫married的布尔数
        float weight = shared.getFloat("weight", 0);  // 从共享参数中获得名叫weight的浮点数

==========================================================================================

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<?xml version="1.0" encoding="utf-8"?>
    <selector xmlns:android="http://schemas.android.com/apk/res/android">
        <item android:state_focused="true" android:drawable="@drawable/shape_edit_focus"/>
        <item android:drawable="@drawable/shape_edit_normal"/>
    </selector>

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<?xml version="1.0" encoding="utf-8"?>
    <shape xmlns:android="http://schemas.android.com/apk/res/android" >
    
        
        <solid android:color="#ffffff" />
    
        
        <stroke
            android:width="1dp"
            android:color="#aaaaaa" />
    
        
        <corners android:radius="5dp" />
    
        
        <padding
            android:bottom="2dp"
            android:left="2dp"
            android:right="2dp"
            android:top="2dp" />
    
    </shape>

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<?xml version="1.0" encoding="utf-8"?>
    <shape xmlns:android="http://schemas.android.com/apk/res/android" >
    
        
        <solid android:color="#ffffff" />
    
        
        <stroke
            android:width="1dp"
            android:color="#0000ff" />
    
        
        <corners android:radius="5dp" />
    
        
        <padding
            android:bottom="2dp"
            android:left="2dp"
            android:right="2dp"
            android:top="2dp" />
    
    </shape>

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package com.example.myapplication;
    
    import android.content.SharedPreferences;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.text.TextUtils;
    import android.view.View;
    import android.widget.CheckBox;
    import android.widget.CompoundButton;
    import android.widget.EditText;
    
    public class MainActivity extends AppCompatActivity implements View.OnClickListener, CompoundButton.OnCheckedChangeListener
    {
        private SharedPreferences mShared; // 声明一个共享参数对象
        private EditText et_name;
        private EditText et_age;
        private EditText et_height;
        private EditText et_weight;
        private boolean isMarried = false;
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            et_name = findViewById(R.id.et_name);
            et_age = findViewById(R.id.et_age);
            et_height = findViewById(R.id.et_height);
            et_weight = findViewById(R.id.et_weight);
    
            CheckBox ck_married = findViewById(R.id.ck_married);
    
            ck_married.setOnCheckedChangeListener(this);
    
            findViewById(R.id.btn_save).setOnClickListener(this);
    
            // 从share.xml中获取共享参数对象
            mShared = getSharedPreferences("share", MODE_PRIVATE);
        }
    
        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            isMarried = isChecked;
        }
    
        @Override
        public void onClick(View v)
        {
            if (v.getId() == R.id.btn_save)
            {
                String name = et_name.getText().toString();
                String age = et_age.getText().toString();
                String height = et_height.getText().toString();
                String weight = et_weight.getText().toString();
    
                if (TextUtils.isEmpty(name))
                {
                    ToastUtil.show(this, "请先填写姓名");
                    return;
                } else if (TextUtils.isEmpty(age))
                {
                    ToastUtil.show(this, "请先填写年龄");
                    return;
                } else if (TextUtils.isEmpty(height))
                {
                    ToastUtil.show(this, "请先填写身高");
                    return;
                } else if (TextUtils.isEmpty(weight))
                {
                    ToastUtil.show(this, "请先填写体重");
                    return;
                }
    
                SharedPreferences.Editor editor = mShared.edit(); // 获得编辑器的对象
    
                editor.putString("name", name); // 添加一个名叫name的字符串参数
                editor.putInt("age", Integer.parseInt(age)); // 添加一个名叫age的整型参数
                editor.putLong("height", Long.parseLong(height)); // 添加一个名叫height的长整型参数
                editor.putFloat("weight", Float.parseFloat(weight)); // 添加一个名叫weight的浮点数参数
                editor.putBoolean("married", isMarried); // 添加一个名叫married的布尔型参数
                editor.putString("update_time", DateUtil.getNowDateTime("yyyy-MM-dd HH:mm:ss"));
    
                editor.commit(); // 提交编辑器中的修改
    
                ToastUtil.show(this, "数据已写入共享参数");
            }
        }
    
    }

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package com.example.myapplication;
    
    import android.content.Context;
    import android.widget.Toast;
    
    public class ToastUtil {
    
        public static void show(Context ctx, String desc) {
            Toast.makeText(ctx, desc, Toast.LENGTH_SHORT).show();
        }
    }

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=========================================================================================

之前保持的数据：

<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
    <map>
        <string name="update_time">20220710152200</string>
        <string name="name">王12正国</string>
        <float name="weight" value="21.86" />
        <boolean name="married" value="true" />
        <int name="age" value="32" />
        <long name="height" value="178" />
    </map>

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package com.example.myapplication;
    
    import android.content.SharedPreferences;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.widget.TextView;
    
    import java.util.Map;
    
    public class MainActivity extends AppCompatActivity
    {
        private TextView tv_share;
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            tv_share = findViewById(R.id.tv_share);
    
            readSharedPreferences(); // 从共享参数中读取信息
        }
    
        // 从共享参数中读取信息
        private void readSharedPreferences()
        {
            // 从share.xml中获取共享参数对象
            SharedPreferences shared = getSharedPreferences("share", MODE_PRIVATE);
            String desc = "共享参数中保存的信息如下：";
    
            // 获取共享参数保存的所有映射配对信息
            Map<String, Object> mapParam = (Map<String, Object>) shared.getAll();
    
            // 遍历该映射对象，并将配对信息形成描述文字
            for (Map.Entry<String, Object> item_map : mapParam.entrySet())
            {
                String key = item_map.getKey(); // 获取该配对的键信息
                Object value = item_map.getValue(); // 获取该配对的值信息
    
                if (value instanceof String) { // 如果配对值的类型为字符串
                    desc = String.format("%s\n　%s的取值为%s", desc, key, shared.getString(key, ""));
                } else if (value instanceof Integer) { // 如果配对值的类型为整型数
                    desc = String.format("%s\n　%s的取值为%d", desc, key, shared.getInt(key, 0));
                } else if (value instanceof Float) { // 如果配对值的类型为浮点数
                    desc = String.format("%s\n　%s的取值为%f", desc, key, shared.getFloat(key, 0.0f));
                } else if (value instanceof Boolean) { // 如果配对值的类型为布尔数
                    desc = String.format("%s\n　%s的取值为%b", desc, key, shared.getBoolean(key, false));
                } else if (value instanceof Long) { // 如果配对值的类型为长整型
                    desc = String.format("%s\n　%s的取值为%d", desc, key, shared.getLong(key, 0L));
                } else { // 如果配对值的类型为未知类型
                    desc = String.format("%s\n参数%s的取值为未知类型", desc, key);
                }
            }
            if (mapParam.size() <= 0) {
                desc = "共享参数中保存的信息为空";
            }
    
            tv_share.setText(desc);
        }
    
    }

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==============================================================================================

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