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存储数据（上）
这篇文章学到的内容：
1、key-value形式数据的存储方式
2、xml的存储方式
app都要存储数据。androd提供到了四种存储数据的方式：
1、使用shared preferences文件来存储key-value。
2、使用xml存储
3、使用数据库存储。
4、使用文件存储。
这里介绍前两种。
如果你的数据非常的少，比如，就几个key-value值需要存储。如存储玩家玩游戏的进度，存储积分，这些数据都可以用一个key来查询出对应的value，那采用第一种。
如果你的数据有非常多的key-value，建议用xml来存储，而且xml还可以存储较为复杂的数据。
如果你的数据要经常使用快速的增删改查，那就要采用数据库来存储了。
接下来详细的介绍这两种存储方式吧。
key-value形式数据的存储方式
SharedPreferences提供了一个文件来记录key和value值。它也提供了简单的方法来对这些key和value进行读和写。
SharedPreferences提供了两种方法来得到SharedPreferences文件：
1、getSharePrefences()如果你的应用会用到多个SharedPreferences文件，用这个方法。
2、getPreferences()得到这个Activity对应的SharedPreferences文件。
代码如下：
1 package com.babybus.study.savingdata.sharepreferneces;
2
3 import android.app.Activity;
4 import android.content.Context;
5 import android.content.SharedPreferences;
6
7 /**
8 * SharePreferences工具类
9 * @author k-yuyonghao
10 *
11 */
12 public class BBSharePreferencesUtil {
13
14 public static void saveData(Context cxt, String sharePreferencesFileName, String key, String value) {
15
16 SharedPreferences sharedPref = cxt.getSharedPreferences(sharePreferencesFileName, Context.MODE_PRIVATE);
17 SharedPreferences.Editor editor = sharedPref.edit();
18 editor.putString(key, value);
19 editor.commit();
20 }
21
22 public static void saveData(Context cxt, String sharePreferencesFileName, String key, int value) {
23
24 SharedPreferences sharedPref = cxt.getSharedPreferences(sharePreferencesFileName, Context.MODE_PRIVATE);
25 SharedPreferences.Editor editor = sharedPref.edit();
26 editor.putInt(key, value);
27 editor.commit();
28 }
29
30 public static void saveData(Context cxt, String sharePreferencesFileName, String key, boolean value) {
31
32 SharedPreferences sharedPref = cxt.getSharedPreferences(sharePreferencesFileName, Context.MODE_PRIVATE);
33 SharedPreferences.Editor editor = sharedPref.edit();
34 editor.putBoolean(key, value);
35 editor.commit();
36 }
37
38 public static String readStringData(Context cxt, String sharePreferencesFileName, String key) {
39
40 SharedPreferences sharedPref = cxt.getSharedPreferences(sharePreferencesFileName, Context.MODE_PRIVATE);
41 return sharedPref.getString(key, null);
42 }
43
44 public static Integer readIntegerData(Context cxt, String sharePreferencesFileName, String key) {
45
46 SharedPreferences sharedPref = cxt.getSharedPreferences(sharePreferencesFileName, Context.MODE_PRIVATE);
47 return sharedPref.getInt(key, -1);
48 }
49
50 public static Boolean readBooleanData(Context cxt, String sharePreferencesFileName, String key) {
51
52 SharedPreferences sharedPref = cxt.getSharedPreferences(sharePreferencesFileName, Context.MODE_PRIVATE);
53 return sharedPref.getBoolean(key, false);
54 }
55
56
57 public static void saveData(Activity act, String key, String value) {
58
59 SharedPreferences sharedPref = act.getPreferences(Context.MODE_PRIVATE);
60 SharedPreferences.Editor editor = sharedPref.edit();
61 editor.putString(key, value);
62 editor.commit();
63 }
64
65 public static void saveData(Activity act, String key, int value) {
66
67 SharedPreferences sharedPref = act.getPreferences(Context.MODE_PRIVATE);
68 SharedPreferences.Editor editor = sharedPref.edit();
69 editor.putInt(key, value);
70 editor.commit();
71 }
72
73 public static void saveData(Activity act, String key, boolean value) {
74
75 SharedPreferences sharedPref = act.getPreferences(Context.MODE_PRIVATE);
76 SharedPreferences.Editor editor = sharedPref.edit();
77 editor.putBoolean(key, value);
78 editor.commit();
79 }
80
81 public static String readStringData(Activity act, String key) {
82
83 SharedPreferences sharedPref = act.getPreferences(Context.MODE_PRIVATE);
84 return sharedPref.getString(key, null);
85 }
86
87 public static Integer readIntegerData(Activity act, String key) {
88
89 SharedPreferences sharedPref = act.getPreferences(Context.MODE_PRIVATE);
90 return sharedPref.getInt(key, -1);
91 }
92
93 public static Boolean readBooleanData(Activity act, String key) {
94
95 SharedPreferences sharedPref = act.getPreferences(Context.MODE_PRIVATE);
96 return sharedPref.getBoolean(key, false);
97 }
98 }
xml的存储方式
android建议使用pull方式来对xml进行读写。
有的时候，我们需要类似xml那样的结构来存储数据。例如，我需要存储一个班级中的每个学生的信息。学生有姓名，性别，年龄，籍贯等，这些复杂的数据，用sharePreferences来存储显然是不合适的。当然，你可也说，那我可以用数据库，但如果只有几百个学生，没必要用数据库啦，最好的方式，就是把这些信息存放在xml文件里去管理，有轻量又方便。
例如这样的数据：
1 <class> 2 <student> 3 <id>1</id> 4 <name>奇奇</name> 5 <sex>男</sex> 6 <age>3</age> 7 <address>宝宝巴士熊猫镇竹林村123弄</address> 8 </student> 9 <student> 10 <id>2</id> 11 <name>妙妙</name> 12 <sex>女</sex> 13 <age>2</age> 14 <address>宝宝巴士熊猫镇竹林村123弄</address> 15 </student> 16 <student> 17 <id>3</id> 18 <name>兔一一</name> 19 <sex>女</sex> 20 <age>2</age> 21 <address>宝宝巴士兔坡512洞3号</address> 22 </student> 23 <student> 24 <id>4</id> 25 <name>小皮猴</name> 26 <sex>男</sex> 27 <age>5</age> 28 <address>宝宝巴士花果山180街66号</address> 29 </student> 30 </class>
我们一起尝试着写一段代码，在手机的sdcard卡里创建一个xml文件，写入这些学生的信息，然后再把他们读取出来。（掌握了这样的操作，xml的读写就差不多了。）
1、先根据xml格式创建两个类：ClassPo类和StudentPo类。
StudentPo
1 public class StudentPo {
2
3 private int id;
4 private String name;
5 private byte sex;
6 private int age;
7 private String address;
8
9
10
11 public int getId() {
12 return id;
13 }
14 public void setId(int id) {
15 this.id = id;
16 }
17 public String getName() {
18 return name;
19 }
20 public void setName(String name) {
21 this.name = name;
22 }
23 public byte getSex() {
24 return sex;
25 }
26 public void setSex(byte sex) {
27 this.sex = sex;
28 }
29 public int getAge() {
30 return age;
31 }
32 public void setAge(int age) {
33 this.age = age;
34 }
35 public String getAddress() {
36 return address;
37 }
38 public void setAddress(String address) {
39 this.address = address;
40 }
41 }
我们根据xml定义了一个po。
ClassPo类
1 public class ClassPo {
2
3
4 private List<StudentPo> students;
5
6 /**
7 * 获得学生的信息
8 * @return
9 */
10 public List<StudentPo> getStudents() {
11 return students;
12 }
13 /**
14 * 把学生信息写入xml中
15 * @param infos
16 */
17 public void setInfos(List<StudentPo> students) {
18 this.students = students;
19 }
20 }
最重要的，就是使用android提供的XmlSerializer，来进行文件的写和读操作。我在此写了一个管理xml读和写的类：
PullBBStudentService：
1 package com.babybus.study.savingdata.xml;
2
3 import java.io.InputStream;
4 import java.io.OutputStream;
5 import java.util.ArrayList;
6 import java.util.List;
7
8 import org.xmlpull.v1.XmlPullParser;
9 import org.xmlpull.v1.XmlSerializer;
10
11 import android.util.Xml;
12
13 /**
14 * 使用pull方法来存储学生信息
15 * @author k-yuyonghao
16 *
17 */
18 public class PullBBStudentService {
19
20
21 /**
22 * 保存classPo
23 * @param classPo
24 * @param outStream
25 * @param rn 根节点
26 */
27 public static void saveClassInfo(ClassPo classPo, OutputStream outStream) throws Exception{
28
29 XmlSerializer serializer = Xml.newSerializer();
30 serializer.setOutput(outStream, "UTF-8");
31 serializer.startDocument("UTF-8", true);
32 serializer.startTag(null, "class");
33 if (classPo != null) {
34 ArrayList<StudentPo> students = (ArrayList<StudentPo>) classPo.getStudents();
35 if (students != null && students.size() > 0) {
36 for (StudentPo student : students) {
37
38 // 得到信息
39 int id = student.getId();
40 String name = student.getName();
41 byte sex = student.getSex();
42 String address = student.getAddress();
43 int age = student.getAge();
44
45 // 把信息写入
46 serializer.startTag(null, "student");
47 serializer.startTag(null, "id");
48 serializer.text(id + "");
49 serializer.endTag(null, "id");
50
51 serializer.startTag(null, "name");
52 serializer.text(name + "");
53 serializer.endTag(null, "name");
54
55 serializer.startTag(null, "sex");
56 serializer.text(sex + "");
57 serializer.endTag(null, "sex");
58
59 serializer.startTag(null, "age");
60 serializer.text(age + "");
61 serializer.endTag(null, "age");
62
63 serializer.startTag(null, "address");
64 serializer.text(address + "");
65 serializer.endTag(null, "address");
66 serializer.endTag(null, "student");
67 }
68 }
69 serializer.endTag(null, "class");
70 serializer.endDocument();
71 outStream.flush();
72 outStream.close();
73 }
74 }
75
76 /**
77 * 把xml文件中的数据读取出来
78 * @param inStream
79 * @return
80 * @throws Exception
81 * <uti-8>
82 */
83 public static ClassPo getClassInfo(InputStream inStream) throws Exception{
84
85 ClassPo classPo = null;
86 List<StudentPo> students = null;
87 StudentPo student = null;
88
89 XmlPullParser pullParser = Xml.newPullParser();
90 pullParser.setInput(inStream, "UTF-8");
91 int event = pullParser.getEventType();
92 while (event != XmlPullParser.END_DOCUMENT) {
93
94 String eventName = pullParser.getName();
95 switch (event) {
96 case XmlPullParser.START_DOCUMENT:
97 // 开始初始化
98 classPo = new ClassPo();
99 students= new ArrayList<StudentPo>();
100 break;
101 case XmlPullParser.START_TAG:
102 String key = eventName;
103
104 if (key != null && "student".equals(key)) {
105
106 student = new StudentPo();
107
108 }
109 if (key != null && "id".equals(key)) {
110
111 int id = student.getId();
112 if (student != null) {
113 student.setId(id);
114 }
115 }
116 if (key != null && "name".equals(key)) {
117
118 String name = student.getName();
119 if (student != null) {
120 student.setName(name);
121 }
122 }
123 if (key != null && "sex".equals(key)) {
124
125 byte sex = student.getSex();
126 if (student != null) {
127 student.setSex(sex);
128 }
129 }
130 if (key != null && "age".equals(key)) {
131
132 int age = student.getAge();
133 if (student != null) {
134 student.setAge(age);
135 }
136 }
137 if (key != null && "address".equals(key)) {
138
139 String address = student.getAddress();
140 if (student != null) {
141 student.setAddress(address);
142 }
143 }
144
145 break;
146 case XmlPullParser.END_TAG:
147 if (students != null) {
148 if (student != null) {
149 students.add(student);
150 }
151
152 }
153 student = null;
154 break;
155 }
156 event = pullParser.next();
157 }
158 // 把信息写入到classPo类中
159 classPo.setInfos(students);
160 return classPo;
161 }
162 }
使用这两个方法，就可以把学生的信息存储在xml中，也可以从xml文件中，读取每一个学生信息到内存中。
（Note：在这里提一个，pull方式写xml是非常快的，如果你要修改某个学生信息，该怎么做呢？在这里告诉我的工作经验，就是把这些信息全部读出来，然后修改List中对应的学生信息后，你可也使用hasnmap来存储，这样查询速度就非常快。再全部重新写入进去。pull方式写xml是非常快的，在此你不用担心效率问题，这样就解决了修改的问题。）
本站文章为宝宝巴士 SD.Team原创，转载务必在明显处注明：（作者官方网站：宝宝巴士)
转载自【宝宝巴士SuperDo团队】 原文链接: http://www.cnblogs.com/superdo/p/4716495.html