轉(zhuǎn)載自SharedPreferences該怎樣寫
SharedPreferences 特點(diǎn)
即便是 Android 小白都知道的 SharedPreferences 的用法流纹，這是保存數(shù)據(jù)最簡(jiǎn)便的方法，但是不處理好的話后期維護(hù)將是一個(gè)巨大的坑违诗。那么該如何處理 SharedPreferences 才方便維護(hù)呢。先從它的特點(diǎn)開始入手吧疮蹦。
● 通過(guò) Context.getSharedPreferences() 獲取的 SharedPreferences 是一個(gè)單例 SharedPreferences.edit() 每次都會(huì)創(chuàng)建一個(gè)新的編輯對(duì)象诸迟， commit() 之前一切改動(dòng)都無(wú)效
● SharedPreferences 的具體實(shí)現(xiàn)并不在公開 API 內(nèi)，創(chuàng)建方法只有通 Context 獲取。具體實(shí)現(xiàn)我們不去研究阵苇，通過(guò) Log 打印每次獲取的對(duì)象都是同一個(gè)壁公，同樣的方法可知道每次 edit() 都會(huì)得到不同的對(duì)象。
難以維護(hù)的 SharedPreferences
SharedPreference userPreferences = context.getSharedPreferences("UserInfo", Context.MODE_PRIVATE);
userPreferences.edit()
.putString("id", "myId")
.putString("name", "myName")
.putString("head", "myHead")
.commit();
Log.e("id", userPreferences.getString("id",""));
Log.e("name", userPreferences.getString("name",""));
Log.e("head", userPreferences.getString("head",""));
如上一段 SharedPreferences 保存和讀取的方法非常簡(jiǎn)便绅项，正因此才不易維護(hù)紊册，可能因?yàn)閷戝e(cuò) Key 而找不出問(wèn)題所在，當(dāng)然一般我們都會(huì)把 Key 寫成靜態(tài)常量快耿。但隨著項(xiàng)目增大囊陡，可能需要多處修改用戶信息，每次都要一個(gè)個(gè)put() , 除了寫著厭煩看著難受掀亥，當(dāng)遇到需要增加或減少字段時(shí)也非常不便撞反。
SharedPreferences 該這么寫
如果能保留原有寫法，又能規(guī)范方法那是最好不過(guò)了搪花，看下SharedPreferences 的接口方法并不多遏片，很容易就寫個(gè)包裝類封裝下。** PreferencesWrapper 是裝飾模式撮竿，這里作用是替代繼承吮便，因?yàn)闆]法直接繼承SharedPreferences 的實(shí)現(xiàn)類**
import android.content.SharedPreferences;
import android.support.annotation.Nullable;
import java.util.Map;
import java.util.Set;
/**
* SharedPreferences 包裝類
* Created by wittytutu on 17-3-29.
*/
public class PreferencesWrapper implements SharedPreferences {
protected SharedPreferences mPreferences;
public PreferencesWrapper(SharedPreferences preferences) {
mPreferences = preferences;
}
@Override
public Map getAll() {
return mPreferences.getAll();
}
@Nullable
@Override
public String getString(String key, @Nullable String defValue) {
return mPreferences.getString(key, defValue);
}
@Nullable
@Override
public Set getStringSet(String key, @Nullable Set defValues) {
return mPreferences.getStringSet(key, defValues);
}
@Override
public int getInt(String key, int defValue) {
return mPreferences.getInt(key, defValue);
}
@Override
public long getLong(String key, long defValue) {
return mPreferences.getLong(key, defValue);
}
@Override
public float getFloat(String key, float defValue) {
return mPreferences.getFloat(key, defValue);
}
@Override
public boolean getBoolean(String key, boolean defValue) {
return mPreferences.getBoolean(key, defValue);
}
@Override
public boolean contains(String key) {
return mPreferences.contains(key);
}
@Override
public EditorWrapper edit() {
return new EditorWrapper(mPreferences.edit());
}
@Override
public void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
mPreferences.registerOnSharedPreferenceChangeListener(listener);
}
@Override
public void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
mPreferences.unregisterOnSharedPreferenceChangeListener(listener);
}
public static class EditorWrapper implements Editor {
protected Editor mEditor;
public EditorWrapper(Editor editor) {
mEditor = editor;
}
@Override
public EditorWrapper putString(String key, @Nullable String value) {
mEditor.putString(key, value);
return this;
}
@Override
public EditorWrapper putStringSet(String key, @Nullable Set values) {
mEditor.putStringSet(key, values);
return this;
}
@Override
public EditorWrapper putInt(String key, int value) {
mEditor.putInt(key, value);
return this;
}
@Override
public EditorWrapper putLong(String key, long value) {
mEditor.putLong(key, value);
return this;
}
@Override
public EditorWrapper putFloat(String key, float value) {
mEditor.putFloat(key, value);
return this;
}
@Override
public EditorWrapper putBoolean(String key, boolean value) {
mEditor.putBoolean(key, value);
return this;
}
@Override
public EditorWrapper remove(String key) {
mEditor.remove(key);
return this;
}
@Override
public EditorWrapper clear() {
mEditor.clear();
return this;
}
@Override
public boolean commit() {
return mEditor.commit();
}
@Override
public void apply() {
mEditor.apply();
}
}
}
接下來(lái)的使用就簡(jiǎn)單了
public class UserInfoPreferences extends PreferencesWrapper {
private static final String NAME = "UserInfo";
public static final KEY_ID = "id"
public static final KEY_NAME = "name";
public static final KEY_HEAD = "head";
public static final KEY_SEX = "sex";
private static volatile UserInfoPreferences mPreferences;
public static UserInfoPreferences getInstance(Context context){
if(mPreferences == null) {
synchronized (UserInfoPreferences.class){
if(mPreferences == null) {
SharedPreferences preferences = context.getApplicationCtontext().getShaedPreferences(NAME, Context.MODE_PRIVATE);
mPreferences = new UserInfoPreferences(preferences);
}
}
}
return mPreferences;
}
public UserInfoPreferences(SharedPreferences preferences) {
super(preferences);
}
// 獲取用戶信息
public UserInfo getUserInfo(){
String id = mPreferences.getString(KEY_ID, "");
String name = mPreferences.getString(KEY_NAME, "");
String head = mPreferences.getString(KEY_HEAD, "");
return new UserInfo(id, name, head);
}
@Override
public Editor edit(){
return new Editor(mPreferences.edit());
}
public static class Editor extends EditorWrapper {
public Editor(SharedPreferences.Editor editor) {
super(editor);
}
// 保存用戶信息
public Editor putUserInfo(String id, String name, String head) {
mEditor.putString(KEY_ID, id)
.putString(KEY_AME, name)
.putString(KEY_HEAD, head);
return this;
}
// 清空用戶信息
public Editor clearUserInfo() {
mEditor.remove(KEY_ID)
.remove(KEY_NAME)
.remove(KEY_HEAD);
return this;
}
}
}
調(diào)用即方便擴(kuò)展，也保留了原有方法幢踏。
UserInfoPreferences preferences = UserInfoPreferences.getInstance(context);
preferences.edit()
.clearUserInfo()
.putUserInfo("myId", "myName", "myHead")
.putInt(KEY_SEX, 0)
.commit();
UserInfo userInfo = preferences.getUserInfo();
int sex = preferences.getInt(KEY_SEX, 0);