Android的4中数据存储方式

//每个程序都有自己的数据库，默认情况下是各自互相不干扰
//创建一个数据库，并且打开
/* 第一个参数：数据库名字
 * 第二个参数：数据库访问权限
 * 第三个参数：游标实例化工厂类，可以不需要
 */
SQLiteDatabase db = openOrCreateDatabase("user.db", MODE_PRIVATE, null);
db.execSQL("create table if not exists usertb (_id integer primary key autoincrement,name text not null,age integer not null,sex text not null)");
db.execSQL("insert into usertb(name,sex,age)values(‘张三‘,‘女‘,18)");
db.execSQL("insert into usertb(name,sex,age)values(‘李四‘,‘女‘,20)");
db.execSQL("insert into usertb(name,sex,age)values(‘王五‘,‘男‘,33)");
		
Cursor c = db.rawQuery("select * from usertb", null);
if(c!=null){
	while(c.moveToNext()){
		Log.i("info","_id"+c.getInt(c.getColumnIndex("_id")));
		Log.i("info","name"+c.getString(c.getColumnIndex("name")));
		Log.i("info","age"+c.getInt(c.getColumnIndex("age")));
		Log.i("info","sex"+c.getString(c.getColumnIndex("sex")));
		Log.i("info","!!!!!!!!!!!!!!!!!!!!!!!!!!!1");
	}
	c.close();
}
db.close();

SQLiteDatabase db = openOrCreateDatabase("stu.db", MODE_PRIVATE, null);
db.execSQL("create table if not exists usertb (_id integer primary key autoincrement,name text not null,age integer not null,sex text not null)");
ContentValues values = new ContentValues();
values.put("name","张三");
values.put("age",44);
values.put("sex","男");
db.insert("str.db",null,values);
values.clear();
values.put("name","李四");
values.put("age",22);
values.put("sex","男");
db.insert("str.db",null,values);
values.clear();
values.put("name","王五");
values.put("age",22);
values.put("sex","男");
db.insert("str.db",null,values);
values.clear();
//更新
values.put("sex","女")
db.update("stutb",values,"_id>?",new String[]{"2"});//将id>2的性别更改为女
db.delete("stutb","name like ?",new String[]{"%五%"});//删除名字中所有带有五的记录
Cursor c = db.query("stutb",null,"_id>?",new String[]{"0"},null,null,"name");//查询所有按名字排序
if(c!=null){
	String[]columns =c.getColumnNames();
	while(c.moveToNext()){
		for(String columnName : columns){
			Log.i("info",c.getString(c.getColumnIndex(columnname)));
		}
	}
	c.close();
}
db.close();

public DBOpenHelper(Context context, String name) {
super(context, name, null, 1);
		
}
@Override//首次创建数据库的时候调用，一般写建库建表的操作
public void onCreate(SQLiteDatabase db) {
	db.execSQL("create table if not exists stutb(_id integer primary key autoincrement,name text not null,age integer not null,sex text not null)");
	db.execSQL("insert into stutb(name,sex,age)values(‘张三‘,‘女‘,17)");
}

@Override//数据库版本更新时自行调用
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
	// TODO Auto-generated method stub
		
}
//然后再MainActivity里修改onCreate函数
DBOpenHelper  helper=  new DBOpenHelper(MainActivity.this, "stu.db");
//helper.getReadableDatabase();//获取一个只读数据库,只能查询，不能写入，不能更新
SQLiteDatabase db = helper.getWritableDatabase();
//db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);
Cursor c = db.rawQuery("select * from stutb",null);
if(c!=null){
	String[]columns =c.getColumnNames();
	while(c.moveToNext()){
		for(String columnName : columns){
			Log.i("info",c.getString(c.getColumnIndex(columnName)));
		}
	}
	c.close();
}
db.close();

private void writeTextFile(String filename,string text) whrows IOException{
	FileOutputStream fos = null;
	BufferedOutputStream bos = null;

	try{
		fos = openFileOutput(filename,MODE_PRIVATE);
		bos = new BufferedOutputStream(fos);
		bos.write(text.getBytes("UTF-8"))
	}finally{
		try{
			if(bos!=null)bos.close();
		}catch(IOException e){}

		try{
			if(fos!=null)fos.close();
		}catch(IOException e){}
	}
}
//文件输入流读取数据示例代码：
private String readTextFile(String filename)throws IOException{
	FileInputStream fis = null;
	BufferedInputStream bis = null;

	try{
		fis = openFileInput(filename);
		bis = new BufferredInputStream(fis);

		String realPath=this.getFilesDir().getPath().toString()+"/";
		File file = new File(realPath+ filename);
		byte[] buf = new byte[(int)file.length()];
		bis.read(buf);
	}finally{
	
	}
}