1.案例简单介绍

通过读取文件。将中国全部城市写入sqlite数据库中，现通过UIPickView实现中国全部城市的选择，效果图例如以下所看到的

2.城市对象模型

中国全部城市数据请看 ，城市模型对象例如以下

////  CityModel.h//  readData////  Created by 赵超 on 14-8-28.//  Copyright (c) 2014年 赵超. All rights reserved.//#import 
      
       @interface CityModel : NSObject@property (nonatomic,copy) NSString  *pid;      //父级城市ID@property (nonatomic,copy) NSString  *cityName; //城市名@property (nonatomic,copy) NSString  *ids;      //城市ID@end
      

3.城市数据库操作对象

sqlite封操作BseDB类请看 ，然后封装城市对象的数据库操作对象CityDB

CityDB.h文件

////  CityDB.h//  readData////  Created by 赵超 on 14-8-28.//  Copyright (c) 2014年 赵超. All rights reserved.//#import "BaseDB.h"#import "CityModel.h"@interface CityDB : BaseDB/** *CityDB单例 */+(id)ShareDB;/** * 创建数据库 * dbName:数据库名称 */-(void)creatTableWithDataBaseName:(NSString*) dbName;/** * 添加一个城市 * city:城市 * dbName:数据库名称 */-(BOOL)addCity:(CityModel*)city dbName:(NSString*)dbName;/** * 选择全部的城市 * dbName:数据库名称 */-(id)selectAllCity:(NSString*)dbName;/** * 选择全部的省份 * dbName:数据库名称 */-(id)selectAllProvince:(NSString *)dbName;/** * 删除全部城市 * dbName:数据库名称 */-(BOOL)deleteAllCity:(NSString*)dbName;/** * 通过上一级省份选择下级市 * city:上一级城市 * dbName:数据库名称 */-(id)selectCityByProvince:(CityModel*)provice dbName:(NSString*)dbName;@end

CityDB.m文件实现

////  CityDB.m//  readData////  Created by 赵超 on 14-8-28.//  Copyright (c) 2014年 赵超. All rights reserved.//#import "CityDB.h"@implementation CityDBstatic CityDB *citydb;+(id)ShareDB{    if (citydb==nil) {        citydb=[[CityDB alloc] init];    }    return citydb;}-(void)creatTableWithDataBaseName:(NSString *)dbName{     NSString *sql=@"create table china (ids text primary key,cityName text,pid text )";    [self createTable:sql dataBaseName:dbName];}-(BOOL)addCity:(CityModel *)city dbName:(NSString *)dbName{    NSString *sql=@"insert into china values (?

,?,?)"; NSArray *params=@[city.ids,city.cityName,city.pid]; return [self execSql:sql parmas:params dataBaseName:dbName]; } -(id)selectAllCity:(NSString *)dbName{ NSString *sql=@"select ids,cityName,pid from china"; return [self selectCity:sql parmas:nil dbName:dbName]; } -(id)selectCity:(NSString*)sql parmas:(NSArray*)params dbName:(NSString*)dbName{ NSArray *result= [self selectSql:sql parmas:params dataBaseName:dbName]; NSMutableArray *citys=[NSMutableArray array]; for (NSDictionary *dic in result) { CityModel *city=[[CityModel alloc]init]; city.ids=[dic objectForKey:@"ids"]; city.cityName=[dic objectForKey:@"cityName"]; city.pid=[dic objectForKey:@"pid"]; [citys addObject:city]; } return citys; } -(id)selectAllProvince:(NSString *)dbName{ NSString *sql=@"select ids,cityName,pid from china where pid=?"; NSArray *parmas=@[@"0"]; return [self selectCity:sql parmas:parmas dbName:dbName]; } -(id)selectCityByProvince:(CityModel *)provice dbName:(NSString *)dbName{ NSString *sql=@"select * from china where pid=?"; NSArray *params=@[provice.ids]; return [self selectCity:sql parmas:params dbName:dbName]; } -(BOOL)deleteAllCity:(NSString *)dbName{ NSString *sql=@"delete from china"; return [self execSql:sql parmas:nil dataBaseName:dbName]; } @end

4.城市数据处理

中国城市数据放在china.txt中，须要处理后写入数据库中。读取文件装数据写入数据库代码例如以下

//调用CitDB对象向数据库中添加一个城市-(void)addCity:(CityModel* )city{    [[CityDB ShareDB] addCity:city dbName:@"China.sqlite"];}//处理china.txt城市数据。将其写入数据库中-(void)readData{    NSString *path=[[NSBundle mainBundle] pathForResource:@"china" ofType:@"txt"];    NSLog(@"%@",path);    char  pid[30],name[30],ids[30];        FILE *f=fopen([path UTF8String], "r");    int i=0;    while (!feof(f)) {        CityModel *city=[[CityModel alloc] init];        fscanf(f, " %s %s %s ",ids,name,pid);        NSString *pids=[NSString stringWithUTF8String:pid];        NSString *names=[NSString stringWithUTF8String:name];        NSString *idss=[NSString stringWithUTF8String:ids];        city.ids=idss;        city.pid=pids;        city.cityName=names;        //向数据库插入一个城市        [self addCity:city];        NSLog(@"%@ %@ %@ %d",pids,names,idss,++i);            }}

5.UIPickView显示数据

MainViewControoler用户数据的显示。其.h文件内容例如以下

@interface MainViewController : UIViewController
      
       {    CityModel *privceModel;     //选择的省    CityModel *cityModel;       //选择的市    CityModel *subCityModel;    //选择的地级市    CityModel *areaModel;       //选择的区    UILabel *selectCity;        //显示选择的结果}@property (nonatomic,retain) NSArray *privices;    //全部省份@property (nonatomic,retain) NSArray *citys;       //省下相应的市@property (nonatomic,retain) NSArray *subCitys;    //市下相应的地级市@property (nonatomic,retain) NSArray *area;        //区@end
      

在MainViewController的viewDidLoad中加入UIPickView并初始化数据

- (void)viewDidLoad{    [super viewDidLoad];    // Do any additional setup after loading the view.    self.view.backgroundColor=[UIColor grayColor];        UIPickerView *pickView=[[UIPickerView alloc] initWithFrame:CGRectMake(0, 100, 0, 0)];    pickView.dataSource=self;    pickView.delegate=self;    pickView.showsSelectionIndicator=YES;    pickView.backgroundColor=[UIColor whiteColor];        [self.view addSubview:pickView];    //初始化数据    self.privices=[[CityDB ShareDB] selectAllProvince:dataBaseName];    CityModel *city=[self.privices objectAtIndex:0];    self.citys=[[CityDB ShareDB] selectCityByProvince:city dbName:dataBaseName];    city=[self.citys objectAtIndex:0];    self.subCitys=[[CityDB ShareDB] selectCityByProvince:city dbName:dataBaseName];    city=[self.citys objectAtIndex:0];    self.area=[[CityDB ShareDB] selectCityByProvince:city dbName:dataBaseName];        selectCity=[[UILabel alloc] initWithFrame:CGRectMake(0, 40, 320, 30)];}

实现UIPickView的列数和行数代理函数。列数仅仅有4列。第一列的行数是中国全部的省数所以中人返回self.privices.count就能够了。可是第二列必需知道第一列选中哪个省份后，再通过这个省份从数据库库查出以下的市才知道要显示的行数。第3列是基于第2列选中的行数，第4列是基于第3列选中的列数。实现代码例如以下：

//UIPcikView总共4列- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{    return 4;}//为每列载入行数- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{        if (component==0) {        return self.privices.count;    }else    if (component==1) {        //获取第一列选中的省份列表        NSInteger privoceIndex=[pickerView selectedRowInComponent:0];        CityModel *privoice=[self.privices objectAtIndex:privoceIndex];        //从数据库中查询，省份以下的市        self.citys=[[CityDB ShareDB] selectCityByProvince:privoice dbName:dataBaseName];        //返回市的个数        return self.citys.count;     }else    if (component==2) {        NSInteger cityIndex=[pickerView selectedRowInComponent:1];        if (self.citys.count==0) {            return 0;        }        CityModel *subCitys=[self.citys objectAtIndex:cityIndex];        self.subCitys=[[CityDB ShareDB] selectCityByProvince:subCitys dbName:dataBaseName];        return self.subCitys.count;            }else    if (component==3) {        NSInteger subCityIndex=[pickerView selectedRowInComponent:2];        if (self.subCitys.count==0) {            return 0;        }        CityModel *ares=[self.subCitys objectAtIndex:subCityIndex];        self.area=[[CityDB ShareDB] selectCityByProvince:ares dbName:dataBaseName];        return self.area.count;        }else{        return 0;    }    }

为UIPickView载入每行每列的数据，获取数据时要注意有推断是否为空

//获取每列每行的名称-(NSString*)getCityName:(NSInteger)row componet:(NSInteger) component{    if (component==0) {        CityModel *city=[self.privices objectAtIndex:row];        return city.cityName;    }else if (component==1) {        CityModel *city=[self.citys objectAtIndex:row];        return city.cityName;    }else if (component==2) {        if (self.subCitys==nil) {            return @"";        }else{            CityModel *city=[self.subCitys objectAtIndex:row];            return city.cityName;        }    }    else if (component==3) {        if (self.area==nil) {            return @"";        }else{            CityModel *city=[self.area objectAtIndex:row];            return city.cityName;        }            }        return @"";}-(UIView*) pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view{        UILabel *lable=[[UILabel alloc] initWithFrame:CGRectMake(0, 0, 60, 30)];    //获取名称    lable.text=[self getCityName:row componet:component];    lable.font=[UIFont systemFontOfSize:14];        return lable;}

最后实现UIPickView的选择响应事件刷新Pickview。并显示选择的结果

//获取每列每行的名称-(NSString*)getCityName:(NSInteger)row componet:(NSInteger) component{    if (component==0) {        CityModel *city=[self.privices objectAtIndex:row];        return city.cityName;    }else if (component==1) {        CityModel *city=[self.citys objectAtIndex:row];        return city.cityName;    }else if (component==2) {        if (self.subCitys==nil) {            return @"";        }else{            CityModel *city=[self.subCitys objectAtIndex:row];            return city.cityName;        }    }    else if (component==3) {        if (self.area==nil) {            return @"";        }else{            CityModel *city=[self.area objectAtIndex:row];            return city.cityName;        }            }        return @"";}-(UIView*) pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view{        UILabel *lable=[[UILabel alloc] initWithFrame:CGRectMake(0, 0, 60, 30)];    //获取名称    lable.text=[self getCityName:row componet:component];    lable.font=[UIFont systemFontOfSize:14];        return lable;}

项目完整project