数据本地化

约定不等于承诺〃 2024-02-17 22:25 12阅读 0赞

## 1 SQLite数据库 ##

### 1.1 SQLite ###

SQLite是一款轻量级的数据库，它的设计目标是嵌入式的，而且目前已经在很多嵌入式产品中使用了它，它占用资源非常的低，在嵌入式设备中，可能只需要几百K的内存就够了。它能够支持Windows/Linux/Unix等主流的操作系统，同时，能够跟很多程序语言相结合，比如Tcl、C\#、PHP、Java等，还有ODBC接口，同样，比起Mysql、PostgreSQL这两款开源世界著名的数据库管理系统来讲，它的处理速度较快。SQLite第一个Alpha版本诞生于2000年5月。

### 1.2 SQLite数据类型 ###

一般数据库采用的固定的静态数据类型，而SQLite采用的是**动态数据类型**，会根据存入值自动判断。

**SQLite具有以下五种数据类型：**

①NULL：空值。

②INTEGER：有符号整型，具体取决于存入数字的范围大小。

③REAL：浮点数字，存储8-byte IEEE浮点数

④TEXT：字符串文本

⑤BLOB：二进制对象。

实际上，**sqlite3也接受如下数据类型**：

samllint 16位元的整数

integer 32位元的整数

decimal(p, s) p：精确值和s大小的十进制位整数，精确值p是指全部有几个数（digits）大小值，s是指小数点后有几位数。如果没有特别指定，则系统会设为p=5， s=0.

float 32位元的实数

double 64位元的实数

char(n) n长度的字串，n不能超过254

varchar(n)长度不固定且最长为n的子串，n不能超过4000

graphic(n) 和 char(n) 一样，不过其单位是两个字元double-bytes，n不能超过127，这个形态是为了支援两个字元长度的字体，例如中文字。

vargraphic(n)可变长度且最大长度为n的双字元字串，n不能超过2000

date 包含了年份、月份、日期

time包含了小时、分钟、秒

timestamp包含了年、月、日、时、分、秒、千分之一秒

datetime包含日期时间格式，必须写成2018-05-20，不能写为2018-5-20，否则在读取时产生错误

![Center][]

### 1.3 sqlite3数据库使用 ###

**一款sqlite的GUI工具：**

![Center 1][]

与MySQL类似，具体参考MySQL。

![Center 2][]

使用【sqlite3 数据库名】，可以进入一个数据库；如果数据库不存在，则直接创建一个数据库

![Center 3][]

### 1.4 示例 ###

创建数据库data.db，创建表t\_student，并编写student类的增删改查

**本程序采用单元测试的方式，执行程序，并不运行在虚拟机或真机上**

可对单元测试中的方法进行单个测试：

**![Center 4][]**

**activity.java：**

public class MainActivity extends Activity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
        }
    
        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.main, menu);
            return true;
        }
    }

**Student.java：**

public class Student {
    	private int sid;
    	private String name;
    	private short age;
    	public Student() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    	public Student(int sid, String name, short age) {
    		super();
    		this.sid = sid;
    		this.name = name;
    		this.age = age;
    	}
    	public int getSid() {
    		return sid;
    	}
    	public void setSid(int sid) {
    		this.sid = sid;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public short getAge() {
    		return age;
    	}
    	public void setAge(short age) {
    		this.age = age;
    	}
    	@Override
    	public String toString() {
    		return "sid=" +sid+ "; name=" +name+ "; age=" +age;
    	}
    }

**SQLiteOpenHelper：**

public class DBOpenHelper extends SQLiteOpenHelper {
    	private static final int VERSION = 1;
    	private static final String DBNAME = "data.db";
    	
    	public DBOpenHelper(Context context) {
    		super(context, DBNAME, null, VERSION);
    	}
    	public DBOpenHelper(Context context, String name, CursorFactory factory,
    			int version) {
    		super(context, name, factory, version);
    	}
    
    	@Override
    	public void onCreate(SQLiteDatabase db) {
    		db.execSQL("create table t_student(sid integer primary key, name varchar(20), age integer)");
    	}
    
    	@Override
    	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    		// TODO Auto-generated method stub
    
    	}
    }

**StudentDAO.java**

public class StudentDAO {
    	private DBOpenHelper dbopenHelper;
    	private SQLiteDatabase sqliteDB;
    	
    	public StudentDAO(Context context) {
    		dbopenHelper = new DBOpenHelper(context);
    	}
    	
    	public void add(Student stu) {
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		sqliteDB.execSQL("insert into t_student(sid, name, age) values(?, ?, ?)", 
    				new Object[]{stu.getSid(), stu.getName(), stu.getAge()});
    	}
    	
    	public void update(Student stu) {
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		sqliteDB.execSQL("update t_student set name=?, age=? where sid=?", 
    				new Object[]{stu.getName(), stu.getAge(), stu.getSid()});
    	}
    	
    	public Student find(int sid) {
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		Cursor cursor = sqliteDB.rawQuery("select sid,name,age from t_student where sid=?",
    				new String[]{String.valueOf(sid)});
    		if(cursor.moveToNext()) {
    			return new Student(cursor.getInt(cursor.getColumnIndex("sid"))
    					, cursor.getString(cursor.getColumnIndex("name"))
    					, cursor.getShort(cursor.getColumnIndex("age")) );
    		}
    		return null;
    	}
    	
    	public void delete(Integer...sids) {
    		if(sids.length > 0) {
    			StringBuffer sb = new StringBuffer();
    			for(int i=0; i<sids.length; i++) {
    				sb.append('?').append(',');
    			}
    			sb.deleteCharAt(sb.length()-1);
    			sqliteDB = dbopenHelper.getWritableDatabase();
    			sqliteDB.execSQL("delete from t_student where sid in (" +sb+ ")", 
    					(Object[])sids);
    		}
    	}
    	
    	public List<Student> getScrollData(int start, int count) {
    		List<Student> students = new ArrayList<Student>();
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		Cursor cursor = sqliteDB.rawQuery("select * from t_student limit ?, ?", 
    				new String[]{String.valueOf(start), String.valueOf(count)});
    		while(cursor.moveToNext()) {
    			students.add(new Student(
    					cursor.getInt(cursor.getColumnIndex("sid")), 
    					cursor.getString(cursor.getColumnIndex("name")), 
    					cursor.getShort(cursor.getColumnIndex("age")) ));
    		}
    		return students;
    	}
    	
    	public long getCount() {
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		Cursor cursor = sqliteDB.rawQuery("select count(sid) from t_student", null);
    		if(cursor.moveToNext()) {
    			return cursor.getLong(0);
    		}
    		return 0;
    	}
    }

**AndroidManifest.xml：**

<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.sqlitedemo"
        android:versionCode="1"
        android:versionName="1.0" >
    
        <uses-sdk
            android:minSdkVersion="8"
            android:targetSdkVersion="18" />
    
        <application
            android:allowBackup="true"
            android:icon="@drawable/ic_launcher"
            android:label="@string/app_name"
            android:theme="@style/AppTheme" >
            <activity
                android:name="com.example.sqlitedemo.MainActivity"
                android:label="@string/app_name" >
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
    
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
            <uses-library android:name="android.test.runner"/>  
        </application>
    
        <instrumentation android:name="android.test.InstrumentationTestRunner"
            				android:targetPackage="com.example.sqlitedemo"
            				android:label="Test My App" />  
        
    </manifest>

**针对StudentDAO编写一个单元测试类StudentDAOTest：**

public class StudentDAOTest extends AndroidTestCase {
    	private final static String TAG = "StudentDAOTest";
    	
    	
    	public void testAdd() {
    		StudentDAO studentDAO = new StudentDAO(this.getContext());
    		Student stu = new Student(1, "jiaozl", (short) 12);
    		studentDAO.add(stu);
    		Log.i(TAG, "add succeeded");
    	}
    	
    	public void testUpdate() {
    		StudentDAO studentDAO = new StudentDAO(this.getContext());
    		Student stu = studentDAO.find(1);
    		stu.setName("kuka");
    		studentDAO.update(stu);
    		Log.i(TAG, "update succeeded");
    	}
    	
    	public void testFind() {
    		StudentDAO studentDAO = new StudentDAO(this.getContext());
    		Student stu = studentDAO.find(1);
    		if(null == stu) {
    			Log.i(TAG, "not find");
    		} else {
    			Log.i(TAG, stu.toString());
    		}
    	}
    	public void testGetScrollData() {
    		StudentDAO studentDAO = new StudentDAO(this.getContext());
    		List<Student> stus = studentDAO.getScrollData(0, 1);
    		for(Student stu:stus) {
    			Log.i(TAG, stu.toString());
    		}
    	}
    	
    	public void testGetCount() {
    		StudentDAO studentDAO = new StudentDAO(this.getContext());
    		long count = studentDAO.getCount();
    		Log.i(TAG, count+"");
    	}
    	
    }

### 1.5 对1.4中StudentDAO中的方法进行改造 ###

使用SQLiteDB库提供给我们的另一种方法

public void add(Student stu) {
    		sqliteDB = dbopenHelper.getWritableDatabase();
    //		sqliteDB.execSQL("insert into t_student(sid, name, age) values(?, ?, ?)", 
    //				new Object[]{stu.getSid(), stu.getName(), stu.getAge()});
    		
    		ContentValues contentValues = new ContentValues();
    		contentValues.put("sid", stu.getSid());
    		contentValues.put("name", stu.getName());
    		contentValues.put("age", stu.getAge());
    		// nullColumnHack：当values参数为空或者里面没有内容的时候，我们的inert会失败（底层数据库不允许插入空值）
    		// 为了防止这种情况，我们指定了一个列名，当发现要插入的行为空时，就会将你指定的这个列的值设为null，
    		// 然后再向数据库中插入
    		sqliteDB.insert("t_student", "sid", contentValues);
    	}
    public void update(Student stu) {
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		ContentValues values = new ContentValues();
    		values.put("name", stu.getName());
    		values.put("age", stu.getAge());
    		sqliteDB.update("t_student", values, "sid=?", 
    				new String[]{String.valueOf(stu.getSid())});
    	}
    	
    	public Student find(int sid) {
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		Cursor cursor = sqliteDB.query("t_student", new String[]{"sid", "name", "age", "sex"},
    				"sid=?", new String[]{String.valueOf(sid)}, null, null, null);
    		if(cursor.moveToNext()) {
    			return new Student(cursor.getInt(cursor.getColumnIndex("sid"))
    					, cursor.getString(cursor.getColumnIndex("name"))
    					, cursor.getShort(cursor.getColumnIndex("age")) );
    		}
    		return null;
    	}
    	
    	public void delete(Integer...sids) {
    		if(sids.length > 0) {
    			StringBuffer sb = new StringBuffer();
    			String[] strPid = new String[sids.length];
    			for(int i=0; i<sids.length; i++) {
    				sb.append('?').append(',');
    				strPid[i]=String.valueOf(sids[i]);
    			}
    			sb.deleteCharAt(sb.length()-1);
    			sqliteDB = dbopenHelper.getWritableDatabase();
    			sqliteDB.delete("t_student", "sid in("+sb+")", strPid);
    		}
    	}
    	
    	public List<Student> getScrollData(int start, int count) {
    		List<Student> students = new ArrayList<Student>();
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		Cursor cursor = sqliteDB.query("t_student", new String[]{"sid", "name", "age"}, null, null, null, null, "sid desc", start+","+count);
    		while(cursor.moveToNext()) {
    			students.add(new Student(
    					cursor.getInt(cursor.getColumnIndex("sid")), 
    					cursor.getString(cursor.getColumnIndex("name")), 
    					cursor.getShort(cursor.getColumnIndex("age")) ));
    		}
    		return students;
    	}
    	
    	public long getCount() {
    		sqliteDB = dbopenHelper.getWritableDatabase();
    		Cursor cursor = sqliteDB.query("t_student", new String[]{"count(*)"}, null, null, null, null, null);
    		if(cursor.moveToNext()) {
    			return cursor.getLong(0);
    		}
    		return 0;
    	}

### 1.6 数据库更新 ###

public class DBOpenHelper extends SQLiteOpenHelper {
    	private static final int VERSION = 1;
    	private static final String DBNAME = "data.db";
    	private static final String STUDENT = "t_student";
    	private static final String TAG = "DBOpenHelper";
    	
    	public DBOpenHelper(Context context) {
    		super(context, DBNAME, null, VERSION);
    	}
    	public DBOpenHelper(Context context, String name, CursorFactory factory,
    			int version) {
    		super(context, name, factory, version);
    	}
    
    	@Override
    	public void onCreate(SQLiteDatabase db) {
    		db.execSQL("create table "+STUDENT+"(sid integer primary key, name varchar(20), age integer)");
    	}
    
    	@Override
    	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    		Log.i(TAG, "update");
    		/*
    		 数据库更新完毕后，建议注释下列语句 
    		 */
    		String tempTable = "temp_student";
    		db.execSQL("alter table " + STUDENT + " rename to "+ tempTable);
    		db.execSQL("create table "+STUDENT+"(sid integer primary key, name varchar(20), age integer, sex varchar(2))");
    		String sql = "insert into "+STUDENT+" (name, age, sex) select name,age,'男' from " + tempTable;
    		db.execSQL(sql);
    	}
    }

## 2 文件 ##

### 2.1 两个重要的方法 ###

①openFileOutput(String name, int mode)

name: 文件名称，不能包含分隔符“/”，如果文件不存在，Android会自动创建。创建的文件目录为：【/data/data/<package\_name>/files】。

mode: 操作模式------->

*  MODE\_APPEND：如果文件中已经存在内容，则在内容末尾追加
 *  MODE\_PRIVATE：文件仅能被该程序访问
 *  MODE\_WORLD\_READABLE：文件允许被其他应用程序读
 *  MODE\_WORLD\_WRITEABLE：文件允许被其他应用程序写
 *  MODE\_WORLD\_READABLE + MODE\_WORLD\_WRITEABLE

②openFileInput(String name)

### 2.2 示例 ###

**FileService.java**

public class FileService {
    	/**
    	 * 文件保存
    	 * @param outStream
    	 * @param content
    	 * @throws Exception
    	 */
    	public void save(OutputStream outStream, String content) throws Exception {
    		outStream.write(content.getBytes());
    		outStream.close();
    	}
    	/**
    	 * 读取文件信息
    	 */
    	public String read(InputStream inStream) throws Exception {
    		ByteArrayOutputStream outStream = new ByteArrayOutputStream();
    		byte[] buffer = new byte[1024];
    		int len;
    		while((len=inStream.read(buffer))!=-1) {
    			outStream.write(buffer, 0, len);
    		}
    		byte[] data = outStream.toByteArray();
    		outStream.close();
    		inStream.close();
    		return new String(data);
    	}
    }

**FileServiceTest.java**

public class FileServiceTest extends AndroidTestCase {
    	private static final String TAG = "FileServiceTest";
    	public void testSave() throws Exception {
    		OutputStream outStream = this.getContext().openFileOutput(
    				"jiaozl.txt", Context.MODE_APPEND);
    		FileService service = new FileService();
    		service.save(outStream, "hello world!");
    	}
    	
    	public void testRead() throws Exception {
    		InputStream inStream = this.getContext().openFileInput("jiaozl.txt");
    		FileService service = new FileService();
    		String content = service.read(inStream);
    		Log.i(TAG, content);
    	}
    }

**AndroidManifest.xml**

<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.filedemo"
        android:versionCode="1"
        android:versionName="1.0" >
    
        <uses-sdk
            android:minSdkVersion="8"
            android:targetSdkVersion="18" />
    
        <application
            android:allowBackup="true"
            android:icon="@drawable/ic_launcher"
            android:label="@string/app_name"
            android:theme="@style/AppTheme" >
            <activity
                android:name="com.example.filedemo.MainActivity"
                android:label="@string/app_name" >
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
    
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
            <uses-library android:name="android.test.runner"/> 
        </application>
    	<instrumentation android:name="android.test.InstrumentationTestRunner"
    	    android:targetPackage="com.example.filedemo"
    	    android:label="test file service"></instrumentation> 
    </manifest>

## 3 SharedPreferences ##

示例：

![Center 5][] ![Center 6][] ![Center 7][]

public class MainActivity extends Activity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            ((Button)findViewById(R.id.save)).setOnClickListener(listener);
            ((Button)findViewById(R.id.show)).setOnClickListener(listener);
        }
    
        private OnClickListener listener = new OnClickListener() {
    		@Override
    		public void onClick(View v) {
    			SharedPreferences pres = MainActivity.this.getSharedPreferences(
    					"jiaozl", Context.MODE_APPEND);
    			switch (v.getId()) {
    			case R.id.save:
    				Editor editor = pres.edit();
    				editor.putString("name", "jiaozl");
    				editor.putInt("age", Integer.valueOf(23));
    				editor.commit();
    				Toast.makeText(MainActivity.this, "保存成功", Toast.LENGTH_LONG).show();
    				break;
    			case R.id.show:
    				String name = pres.getString("name", "NO");
    				int age = pres.getInt("age", 0);
    				String bir = pres.getString("bir", "NO");
    				Toast.makeText(MainActivity.this, "Name: "+name+";age: " +age+"; bir: " + bir, Toast.LENGTH_LONG).show();
    				break;
    			default:
    				break;
    			}
    		}
    	};
    }

## 4 内容提供者---ContentProvider ##

## 5 网络 ##

[Center]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/035c6592d9004b2e84a10e8bbd9edf70.png
[Center 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/7a4ecb10b61e4fb5a598665d100d4582.png
[Center 2]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/6307cc72f1ff4ef1bdb6844465abce66.png
[Center 3]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/c91e3b7c4c3f40f8be5d290449d1592a.png
[Center 4]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/f8f34e9f0a1f4e7ab55b3d65fbd757a1.png
[Center 5]: https://img-blog.csdn.net/20170531153607435?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvdTAxMzk0MzQyMA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
[Center 6]: https://img-blog.csdn.net/20170531153632748?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvdTAxMzk0MzQyMA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
[Center 7]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/e444d07b102f4744a09c388b99b1a877.png