17.picker view的基本使用

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//在picker view的练习国旗的选择中-(UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view{    NSLog(@"%p",view);    ContryView *view1=(ContryView *)view;    //该view的重用在iOS7有bug    if (!view1) {        view1=[ContryView getCountryView];    }    view1.country=self.contrys[row];    return view1;}可以自定义一个view类利用xib生产view ，设置一个model数据源后返回一个view给picker view即可.//该方法可以设置picker view的每列的每行的高度-(CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component{    return 44;}

在省份选择的练习中，第二行的城市是根据第一行的状态选择的，先确定第一行的选择是什么，然后加载第二行的数据-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{    Shengfen *shenfen=self.shengfen[component];    if (component==0) {        return self.shengfen.count;    }else{        NSInteger select=[pickerView selectedRowInComponent:0];        Shengfen *shenfen1=self.shengfen[select];    return shenfen1.cities.count;    }}-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{    if (component==0) {        Shengfen *shenfen=self.shengfen[row];        return shenfen.name;    }else{        NSInteger select=[pickerView selectedRowInComponent:0];        Shengfen *shenfen=self.shengfen[select];      return shenfen.cities[row];    }}- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{    if (component==0) {        [pickerView reloadComponent:1];        //第一列选择之后，立刻跳到第二列的第一行        [pickerView selectRow:0 inComponent:1 animated:YES];    }    NSInteger select=[pickerView selectedRowInComponent:0];    Shengfen *shenfen=self.shengfen[select];    NSString *str=nil;    if (component==1) {       str= shenfen.cities[row];    }    NSString *str1=[NSString stringWithFormat:@"%@  %@",shenfen.name,str];    self.label.text=str1;}

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