Android——共享参数SharedPreferences

4数据存储

共享参数SharedPreferences、数据库SQLite、SD卡文件、App的全局内存

4.1共享参数SharedPreferences

SharedPreferences是一个轻量级存储工具，采用的存储结构时Key-Value的键值对方式

SharedPreferences的存储介质是符合XML规范的配置文件。

保存SharedPreferences键值对信息的文件路径时/data/data/应用包名/shared_prefs/文件名.xml

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

​ 基于XML格式的特点，SharedPreferences主要适用于如下场合：

1. 简单且孤立的数据。若是复杂且相互间有关的数据，则要保存在数据库中。
2. 文本形式的数据。若是二进制数据，则要保存在文件中。
3. 需要持久化存储的数据。在App退出后再次启动时，之前保存的数据仍然有效。

实际开发中，共享参数经常存储的数据有App的个性化配置信息、用户使用App的行为信息、临时需要保存的片段信息等

SharedPreferences对数据的存储和读取操作类似于Map，也有put函数用于存储数据、get函数用于读取数据。在使用共享参数之前，要先调用getSharedPreferences函数声明文件名与操作模式：

SharedPreferences mShared = getSharedPreferences("share", MODE_PRIVATE);

getSharedPreferences方法的第一个参数是文件名，上面的share表示当前使用的共享参数文件名是share.xml；第二个参数是操作模式，一般都填MODE_PRIVATE，表示私有模式。

共享参数存储数据要借助于Editor类：

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",23);// 添加一个名叫age的整形参数
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

共享参数读取数据相对简单，直接使用对象即可完成数据读取方法的调用，注意get方法的第二个参数表示默认值：

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的整形数
boolean married = getBoolean("married",false);// 从共享参数中获得名叫married的布尔数
float weight = getFloat("weight",0);// 从共享参数中获得名叫weight的浮点数

Write:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:focusable="true"
    android:focusableInTouchMode="true"
    android:orientation="vertical"
    android:padding="10dp" >

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="50dp" >

        <TextView
            android:id="@+id/tv_name"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_alignParentLeft="true"
            android:gravity="center"
            android:text="姓名："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <EditText
            android:id="@+id/et_name"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="5dp"
            android:layout_toRightOf="@+id/tv_name"
            android:background="@drawable/editext_selector"
            android:gravity="left|center"
            android:hint="请输入姓名"
            android:inputType="text"
            android:maxLength="12"
            android:textColor="@color/black"
            android:textColorHint="@color/grey"
            android:textCursorDrawable="@drawable/text_cursor"
            android:textSize="17sp" />
    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="50dp" >

        <TextView
            android:id="@+id/tv_age"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_alignParentLeft="true"
            android:gravity="center"
            android:text="年龄："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <EditText
            android:id="@+id/et_age"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="5dp"
            android:layout_toRightOf="@+id/tv_age"
            android:background="@drawable/editext_selector"
            android:gravity="left|center"
            android:hint="请输入年龄"
            android:inputType="number"
            android:maxLength="2"
            android:textColor="@color/black"
            android:textColorHint="@color/grey"
            android:textCursorDrawable="@drawable/text_cursor"
            android:textSize="17sp" />
    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="50dp" >

        <TextView
            android:id="@+id/tv_height"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_alignParentLeft="true"
            android:gravity="center"
            android:text="身高："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <EditText
            android:id="@+id/et_height"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="5dp"
            android:layout_toRightOf="@+id/tv_height"
            android:background="@drawable/editext_selector"
            android:gravity="left|center"
            android:hint="请输入身高"
            android:inputType="number"
            android:maxLength="3"
            android:textColor="@color/black"
            android:textColorHint="@color/grey"
            android:textCursorDrawable="@drawable/text_cursor"
            android:textSize="17sp" />
    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="50dp" >

        <TextView
            android:id="@+id/tv_weight"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_alignParentLeft="true"
            android:gravity="center"
            android:text="体重："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <EditText
            android:id="@+id/et_weight"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="5dp"
            android:layout_toRightOf="@+id/tv_weight"
            android:background="@drawable/editext_selector"
            android:gravity="left|center"
            android:hint="请输入体重"
            android:inputType="numberDecimal"
            android:maxLength="5"
            android:textColor="@color/black"
            android:textColorHint="@color/grey"
            android:textCursorDrawable="@drawable/text_cursor"
            android:textSize="17sp" />
    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="50dp" >

        <TextView
            android:id="@+id/tv_married"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_alignParentLeft="true"
            android:gravity="center"
            android:text="婚否："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <Spinner
            android:id="@+id/sp_married"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_toRightOf="@+id/tv_married"
            android:gravity="left|center"
            android:spinnerMode="dialog" />
    </RelativeLayout>

    <Button
        android:id="@+id/btn_save"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="保存到共享参数"
        android:textColor="@color/black"
        android:textSize="20sp" />

</LinearLayout>

public class ShareWriteActivity extends AppCompatActivity implements View.OnClickListener {

    private SharedPreferences mShared;
    private EditText et_name;
    private EditText et_age;
    private EditText et_height;
    private EditText et_weight;
    private boolean bMarried = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_share_write);
        et_name = (EditText) findViewById(R.id.et_name);
        et_age = (EditText) findViewById(R.id.et_age);
        et_height = (EditText) findViewById(R.id.et_height);
        et_weight = (EditText) findViewById(R.id.et_weight);
        findViewById(R.id.btn_save).setOnClickListener(this);

        ArrayAdapter<String> typeAdapter = new ArrayAdapter<String>(this,
                R.layout.item_select, typeArray);
        typeAdapter.setDropDownViewResource(R.layout.item_dropdown);
        Spinner sp_married = (Spinner) findViewById(R.id.sp_married);
        sp_married.setPrompt("请选择婚姻状况");
        sp_married.setAdapter(typeAdapter);
        sp_married.setSelection(0);
        sp_married.setOnItemSelectedListener(new TypeSelectedListener());

        mShared = getSharedPreferences("share", MODE_PRIVATE);
    }

    private String[] typeArray = {"未婚", "已婚"};
    class TypeSelectedListener implements AdapterView.OnItemSelectedListener {
        public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
            bMarried = (arg2==0)?false:true;
        }

        public void onNothingSelected(AdapterView<?> arg0) {
        }
    }

    @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 (name==null || name.length()<=0) {
                showToast("请先填写姓名");
                return;
            }
            if (age==null || age.length()<=0) {
                showToast("请先填写年龄");
                return;
            }
            if (height==null || height.length()<=0) {
                showToast("请先填写身高");
                return;
            }
            if (weight==null || weight.length()<=0) {
                showToast("请先填写体重");
                return;
            }

            SharedPreferences.Editor editor = mShared.edit();
            editor.putString("name", name);
            editor.putInt("age", Integer.parseInt(age));
            editor.putLong("height", Long.parseLong(height));
            editor.putFloat("weight", Float.parseFloat(weight));
            editor.putBoolean("married", bMarried);
            editor.putString("update_time", DateUtil.getNowDateTime("yyyy-MM-dd HH:mm:ss"));
            editor.commit();
            showToast("数据已写入共享参数");
        }
    }

    private void showToast(String desc) {
        Toast.makeText(this, desc, Toast.LENGTH_SHORT).show();
    }

}

Read:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:focusable="true"
    android:focusableInTouchMode="true"
    android:orientation="vertical"
    android:padding="10dp" >

    <TextView
        android:id="@+id/tv_share"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textColor="@color/black"
        android:textSize="17sp" />

</LinearLayout>

public class ShareReadActivity extends AppCompatActivity {

    private SharedPreferences mShared;
    private TextView tv_share;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_share_read);
        tv_share = (TextView) findViewById(R.id.tv_share);
        readSharedPreferences();
    }

    private void readSharedPreferences() {
        SharedPreferences mShared = getSharedPreferences("share", MODE_PRIVATE);
        String desc = "共享参数中保存的信息如下：";
        Map<String, Object> mapParam = (Map<String, Object>) mShared.getAll();
        for (Map.Entry<String, Object> item_map : mapParam.entrySet()) {
            String key = item_map.getKey();
            Object value = item_map.getValue();
            if (value instanceof String) {
                desc = String.format("%s\n　%s的取值为%s", desc, key,
                        mShared.getString(key, ""));
            } else if (value instanceof Integer) {
                desc = String.format("%s\n　%s的取值为%d", desc, key,
                        mShared.getInt(key, 0));
            } else if (value instanceof Float) {
                desc = String.format("%s\n　%s的取值为%f", desc, key,
                        mShared.getFloat(key, 0.0f));
            } else if (value instanceof Boolean) {
                desc = String.format("%s\n　%s的取值为%b", desc, key,
                        mShared.getBoolean(key, false));
            } else if (value instanceof Long) {
                desc = String.format("%s\n　%s的取值为%d", desc, key,
                        mShared.getLong(key, 0l));
            } else {
                desc = String.format("%s\n参数%s的取值为未知类型", desc, key);
            }
        }
        if (mapParam==null || mapParam.size()<=0) {
            desc = "共享参数中保存的信息为空";
        }
        tv_share.setText(desc);
    }

}