Android数据的几种存储方式和方法

sharedPreference入门

 

1.保存信息

SharedPreferences sp = context.getSharedPreferences("config", Context.MODE_PRIVATE);

Editor editor = sp.edit();

editor.putString("username", username);

editor.putString("password", password);

editor.commit();

2.获取信息

SharedPreferences sp = this.getSharedPreferences("config", Context.MODE_PRIVATE);

sp.getString("username", "");

sp.getString("password", "");

?

 

xml文件的序列化

 

?

public void save(View view) {

 XmlSerializer xmlSerializer = Xml.newSerializer();

File file = new File(Environment.getExternalStorageDirectory(),

"config.xml");

try {

FileOutputStream fos = new FileOutputStream(file);

xmlSerializer. setOutput(fos, "utf-8");

xmlSerializer. startDocument("utf-8", true);

 

xmlSerializer. startTag(null, "smss");

 

for (SmsInfo info : infos) {

xmlSerializer.startTag(null, "sms");

xmlSerializer. attribute(null, "id", info.getId() + "");

 

xmlSerializer.startTag(null, "date");

xmlSerializer. text(info.getDate() + "");

xmlSerializer.endTag(null, "date");

 

xmlSerializer.startTag(null, "address");

xmlSerializer.text(info.getAddress());

xmlSerializer.endTag(null, "address");

 

xmlSerializer.startTag(null, "body");

xmlSerializer.text(info.getBody());

xmlSerializer.endTag(null, "body");

 

xmlSerializer.endTag(null, "sms");

}

xmlSerializer.endTag(null, "smss");

 

xmlSerializer.endDocument();

fos.close();

Toast.makeText(this, "保存成功", 0).show();

 

} catch (Exception e) {

e.printStackTrace();

Toast.makeText(this, "保存失败", 0).show();

}

 

}

采用pull解析xml文件

1.准备一个xml文件，将其拷贝到工程的src目录下

<?xml version="1.0" encoding="utf-8"?>

<infos>

<city id="1">

<temp>20'C/30'C</temp>

<weather>多云</weather>

<wind>南风3级</wind>

<name>上海</name>

<pm>200</pm>

</city>

 

<city id="2">

<temp>20'C/35'C</temp>

<weather>暴雨</weather>

<wind>南风10级</wind>

<name>北京</name>

<pm>800</pm>

</city>

 

<city id="3">

<temp>0'C/10'C</temp>

<weather>暴雪</weather>

<wind>北风32级</wind>

<name>广州</name>

<pm>200</pm>

</city>

 

</infos>

2.核心代码

public static ArrayList<WeatherInfo> getWeatherInfo(InputStream is)

throws Exception {

ArrayList<WeatherInfo> infos = null;

WeatherInfo info = null;

 

 // XmlPullParser parser = Xml.newPullParser();

 

XmlPullParserFactory fac = XmlPullParserFactory.newInstance();

XmlPullParser parser = fac.newPullParser();

 

parser.setInput(is, "utf-8");

int type = parser.getEventType();

while (type != XmlPullParser.END_DOCUMENT) {

switch (type) {

case XmlPullParser.START_TAG:

if ("infos".equals(parser.getName())) {

infos = new ArrayList<WeatherInfo>();

} else if ("city".equals(parser.getName())) {

info = new WeatherInfo();

info.setId(Integer.parseInt(parser.getAttributeValue(0)));

} else if ("temp".equals(parser.getName())) {

info.setTemp(parser.nextText());

} else if ("weather".equals(parser.getName())) {

info.setWeather(parser.nextText());

} else if ("wind".equals(parser.getName())) {

info.setWind(parser.nextText());

} else if ("name".equals(parser.getName())) {

info.setName(parser.nextText());

} else if ("pm".equals(parser.getName())) {

info.setPm(parser.nextText());

}

break;

 

case XmlPullParser.END_TAG:

if ("city".equals(parser.getName())) {

infos.add(info);

info = null;

}

break;

}

type = parser.next();

}

return infos;

 

}

3.调用

 

public class WeatherActivity extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

TextView tv_info = (TextView) this.findViewById(R.id.vt_info);

 

try {

ArrayList<WeatherInfo> infos = WeaterService

.getWeatherInfo(WeatherActivity.class.getClassLoader()

.getResourceAsStream("weather.xml"));

StringBuffer sb = new StringBuffer();

for (WeatherInfo info : infos) {

sb.append(info);

sb.append("\n");

}

tv_info.setText(sb.toString());

} catch (Exception e) {

e.printStackTrace();

Toast.makeText(this, "xml解析失败", 0).show();

}

 

}

}

 

android下创建一个sqlite数据库

public class PersonSQLiteOpenHelper extends SQLiteOpenHelper {

private static final String DBFILENAME = "person.db";

private static int db_version = 2;

 

public PersonSQLiteOpenHelper(Context context) {

super(context, DBFILENAME, null, db_version);

}

 

/**

 * 当数据库第一次创建时调用

 */

@Override

public void onCreate(SQLiteDatabase db) {

String sql = "create table person(id integer primary key autoincrement,name varchar(20),number varchar(20))";

db.execSQL(sql);

}

 

/**

 * 当数据库的版本号发生增加的时候调用

 */

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

System.out.println("数据库更改！");

String sql = "alter table person add account varchar(20)";

db.execSQL(sql);

}

 

}

 

sql语句实现数据库的增删改查

1.添加条目

public void add(String name, String number) {

SQLiteDatabase db = this.helper.getWritableDatabase();

db.execSQL("insert into person(name,number) values(?,?)", new Object[] {

name, number });

db.close();

}

2.查找条目是否存在

public boolean find(String name) {

SQLiteDatabase db = this.helper.getReadableDatabase();

Cursor cursor = db.rawQuery("select * from person where name=?",

new String[] { name });

boolean result = cursor.moveToNext();

cursor.close();

db.close();

return result;

}

3.更新条目

public void update(String name, String newNumber) {

SQLiteDatabase db = this.helper.getWritableDatabase();

db.execSQL("update person set number=? where name=?", new Object[] {

newNumber, name });

db.close();

}

4.删除条目

public void delete(String name) {

SQLiteDatabase db = this.helper.getWritableDatabase();

db.execSQL("delete from person where name=?", new Object[] { name });

db.close();

}

5.查找所有条目

public ArrayList<Person> findAll() {

SQLiteDatabase db = this.helper.getReadableDatabase();

ArrayList<Person> persons = new ArrayList<Person>();

Cursor cursor = db.rawQuery("select * from person", null);

while (cursor.moveToNext()) {

int id = cursor.getInt(cursor.getColumnIndex("id"));

String name = cursor.getString(cursor.getColumnIndex("name"));

String number = cursor.getString(cursor.getColumnIndex("number"));

Person p = new Person(id, name, number);

persons.add(p);

}

cursor.close();

db.close();

return persons;

 

}

 

系统api实现数据库的增删改查&sqlite3工具的使用

1.添加条目

public long add(String name, String number) {

SQLiteDatabase db = this.helper.getWritableDatabase();

ContentValues values = new ContentValues();

values.put("name", name);

values.put("number", number);

long id = db.insert("person", null, values);

db.close();

return id;

}

 

2.查找条目是否存在

public boolean find(String name) {

SQLiteDatabase db = this.helper.getReadableDatabase();

Cursor cursor = db.query("person", null, "name=?",

new String[] { name }, null, null, null);

boolean result = cursor.moveToNext();

cursor.close();

db.close();

return result;

}

 

3.更新条目

public int update(String name, String newNumber) {

SQLiteDatabase db = this.helper.getWritableDatabase();

ContentValues values = new ContentValues();

values.put("number", newNumber);

int number = db.update("person", values, "name=?",

new String[] { name });

db.close();

return number;

}

 

4.删除条目

public int delete(String name) {

SQLiteDatabase db = this.helper.getWritableDatabase();

// db.execSQL("delete from person where name=?", new Object[] { name });

int number = db.delete("person", "name=?", new String[] { name });

db.close();

return number;

}

 

5.查找所有条目

public ArrayList<Person> findAll() {

SQLiteDatabase db = this.helper.getReadableDatabase();

ArrayList<Person> persons = new ArrayList<Person>();

Cursor cursor = db.query("person", null, null, null, null, null, null);

while (cursor.moveToNext()) {

int id = cursor.getInt(cursor.getColumnIndex("id"));

String name = cursor.getString(cursor.getColumnIndex("name"));

String number = cursor.getString(cursor.getColumnIndex("number"));

Person p = new Person(id, name, number);

persons.add(p);

}

cursor.close();

db.close();

return persons;

 

}

 

 

 

数据库的事务

public void testTransaction() {

PersonSQLiteOpenHelper helper = new PersonSQLiteOpenHelper(getContext());

SQLiteDatabase db = helper.getWritableDatabase();

 db.beginTransaction();

try {

db.execSQL(

"update person set account = account + 1000 where name=?",

new Object[] { "tom" });

int i = 1 / 0;

db.execSQL(

"update person set account = account - 1000 where name=?",

new Object[] { "jerry" });

 db.setTransactionSuccessful();

} catch (Exception e) {

e.printStackTrace();

} finally {

 db.endTransaction();

                        db.close(); 

                }

}