1.案例簡介

通過讀取文件，將中國所有城市寫入sqlite數據庫中，現通過UIPickView實現中國所有城市的選擇，效果圖如下所示

2.城市對象模型

//
//  CityModel.h
//  readData
//
//  Created by 趙超 on 14-8-28.
//  Copyright (c) 2014年 趙超. All rights reserved.
//

#import 

@interface CityModel : NSObject

@property (nonatomic,copy) NSString  *pid;      //父級城市ID
@property (nonatomic,copy) NSString  *cityName; //城市名
@property (nonatomic,copy) NSString  *ids;      //城市ID

@end

3.城市數據庫操作對象

sqlite封操作BseDB類請看，然後封裝城市對象的數據庫操作對象CityDB CityDB.h文件

//
//  CityDB.h
//  readData
//
//  Created by 趙超 on 14-8-28.
//  Copyright (c) 2014年 趙超. All rights reserved.
//

#import BaseDB.h
#import CityModel.h

@interface CityDB : BaseDB
/**
 *CityDB單例
 */
+(id)ShareDB;

/**
 * 創建數據庫
 * dbName:數據庫名稱
 */
-(void)creatTableWithDataBaseName:(NSString*) dbName;

/**
 * 增加一個城市
 * city:城市
 * dbName:數據庫名稱
 */
-(BOOL)addCity:(CityModel*)city dbName:(NSString*)dbName;
/**
 * 選擇所有的城市
 * dbName:數據庫名稱
 */
-(id)selectAllCity:(NSString*)dbName;
/**
 * 選擇所有的省份
 * dbName:數據庫名稱
 */
-(id)selectAllProvince:(NSString *)dbName;
/**
 * 刪除所有城市
 * dbName:數據庫名稱
 */
-(BOOL)deleteAllCity:(NSString*)dbName;
/**
 * 通過上一級省份選擇下級市
 * city:上一級城市
 * dbName:數據庫名稱
 */
-(id)selectCityByProvince:(CityModel*)provice dbName:(NSString*)dbName;


@end

CityDB.m文件實現

//
//  CityDB.m
//  readData
//
//  Created by 趙超 on 14-8-28.
//  Copyright (c) 2014年 趙超. All rights reserved.
//

#import CityDB.h

@implementation CityDB

static 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.城市數據處理

中國城市數據放在china.txt中，需要處理後寫入數據庫中，讀取文件裝數據寫入數據庫代碼如下

//調用CitDB對象向數據庫中增加一個城市
-(void)addCity:(CityModel* )city{
    [[CityDB ShareDB] addCity:city dbName:@China.sqlite];
}
//處理china.txt城市數據，將其寫入數據庫中
-(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;
        //向數據庫插入一個城市
        [self addCity:city];
        NSLog(@%@ %@ %@ %d,pids,names,idss,++i);
        
    }
}

5.UIPickView顯示數據

MainViewControoler用戶數據的顯示，其.h文件內容如下

@interface MainViewController : UIViewController{
    CityModel *privceModel;     //選擇的省
    CityModel *cityModel;       //選擇的市
    CityModel *subCityModel;    //選擇的地級市
    CityModel *areaModel;       //選擇的區
    UILabel *selectCity;        //顯示選擇的結果
}


@property (nonatomic,retain) NSArray *privices;    //所有省份

@property (nonatomic,retain) NSArray *citys;       //省下對應的市

@property (nonatomic,retain) NSArray *subCitys;    //市下對應的地級市

@property (nonatomic,retain) NSArray *area;        //區


@end

在MainViewController的viewDidLoad中添加UIPickView並初始化數據

- (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];
    //初始化數據
    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)];
}

實現UIPickView的列數和行數代理函數，列數只有4列，第一列的行數是中國所有的省數所以中人返回self.privices.count就可以了，但是第二列必需知道第一列選中哪個省份後，再通過這個省份從數據庫庫查出下面的市才知道要顯示的行數，第3列是基於第2列選中的行數，第4列是基於第3列選中的列數，實現代碼如下：

//UIPcikView總共4列
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
    return 4;
}

//為每列加載行數
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{
    
    if (component==0) {
        return self.privices.count;
    }else
    if (component==1) {
        //獲取第一列選中的省份列表
        NSInteger privoceIndex=[pickerView selectedRowInComponent:0];
        CityModel *privoice=[self.privices objectAtIndex:privoceIndex];
        //從數據庫中查詢，省份下面的市
        self.citys=[[CityDB ShareDB] selectCityByProvince:privoice dbName:dataBaseName];
        //返回市的個數
        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;
    }
    
}

為UIPickView加載每行每列的數據，獲取數據時要注意有判斷是否為空

//獲取每列每行的名稱
-(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)];
    //獲取名稱
    lable.text=[self getCityName:row componet:component];
    lable.font=[UIFont systemFontOfSize:14];
    
    return lable;
}

最後實現UIPickView的選擇響應事件刷新Pickview，並顯示選擇的結果

//獲取每列每行的名稱
-(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)];
    //獲取名稱
    lable.text=[self getCityName:row componet:component];
    lable.font=[UIFont systemFontOfSize:14];
    
    return lable;
}