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Android——共享参数SharedPreferences_android sharedpreferences
作者：代码吟游诗人 | 2024-02-05 12:29:20
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android 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>
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基于XML格式的特点，SharedPreferences主要适用于如下场合：
- 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。
- 文本形式的数据。若是二进制数据，则要保存在文件中。
- 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);
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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
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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
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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>
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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(); } }
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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>
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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); } }
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