Android SharedPreferences存储的正确写法
SharedPreferences 特点
即便是Android小白都知道的SharedPreferences的用法,这是保存数据最简便的方法,但是不处理好的话后期维护将是一个巨大的坑。那么该如何处理好SharedPreferences才方便维护呢。先从它的特点开始入手吧。
- 通过Context.getSharedPreferences()获取的SharedPreferences是一个单例
- SharedPreferences.edit()每次都会创建一个新的编辑对象,commit()之前一切改动都无效
SharedPreferences的具体实现并不在公开API内,创建方法只有通过Context获取。具体实现我们不去研究,通过Log打印每次获取的对象都是同一个,同样的方法可知道每次edit()都会得到不同的对象。
难以维护的 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保存和读取的方法非常简便,正因此才不易维护,可能因为写错Key而找不出问题所在,当然一般我们都会把Key写成静态常量。但随着项目增大,可能需要多处修改用户信息,每次都要一个个put(), 除了写着厌烦看着难受,当遇到需要增加或减少字段时也非常不便。
SharedPreferences 该这么写
如果能保留原有写法,又能规范方法那是最好不过了,看下SharedPreferences的接口方法并不多,很容易就写个包装类封装下。
import android.content.SharedPreferences; import android.support.annotation.Nullable; import java.util.Map; import java.util.Set; /** * SharedPreferences 包装类 * 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(); } } }
接下来的使用就简单了
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); } // 获取用户信息 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); } // 保存用户信息 public Editor putUserInfo(String id, String name, String head) { mEditor.putString(KEY_ID, id) .putString(KEY_AME, name) .putString(KEY_HEAD, head); return this; } // 清空用户信息 public Editor clearUserInfo() { mEditor.remove(KEY_ID) .remove(KEY_NAME) .remove(KEY_HEAD); return this; } } }
调用即方便扩展,也保留了原有方法。
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);
感谢阅读,希望能帮助到大家,谢谢大家对本站的支持!
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