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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。
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
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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);
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