iOS Foundation-uikit Frame-Advanced View-uipickerview-Instance 1: Order (no relationship between columns and columns)

A. Order
0. Create a plist file with the root array, which contains 3 arrays, each with a heap of food names
Load this plist file
1> declaring Array properties
@property (Nonatomic,strong) Nsarray *foods;
2> lazy Loading (at the end of the implementation file)
#pragma mark-Lazy loading
-(Nsarray *) foods
{
if (_foods = = nil) {
NSString *fullpath = [[NSBundle mainbundle] pathforresource:@ "foods.plist" oftype:nil];
_foods = [Nsarray Arraywithcontentsoffile:fullpath];
}
return _foods;
}

1. Drag a Picker view control, right-click to set the data source to the controller

2. Follow the data source protocol and implement a data source approach
#pragma mark-Data source methods
Return Pickerview How many columns there are altogether
-(Nsinteger) Numberofcomponentsinpickerview: (Uipickerview *) Pickerview
{
return self.foods.count;
}

Returns how many rows are in column Pickerview component
-(Nsinteger) Pickerview: (Uipickerview *) Pickerview numberofrowsincomponents: (Nsinteger) component
{
return self.foods[components].count;
}

3. Right-click on the Picker view control to set the proxy as the controller

4. Follow the proxy protocol and implement the Proxy method
#pragma mark-Proxy method
//Return to the row row of column component what is displayed
-(NSString *) Pickerview: (Uipickerview * ) Pickerview Titleforrow: (nsinteger) Row forcomponents: (Nsinteger) component
{
Return self.foods[components][ Row];
}

Second, show à la carte results
1. Drag a view, drag 6 tabs on the view, and connect the label with the scrolling change
2. Implementing a Proxy method (listening on a selected row)
#pragma mark-Proxy method
// When a row of Pickerview is selected, the
//will pass in the selected column and line numbers as parameters
//The
-(void) Pikerview is called only when a row is selected by the finger: (Uipickerview * ) Pickerview Didselectrow: (nsinteger) Row incomponent: (Nsinteger) component
{
//1. Get data for corresponding column rows
NSString * name = Self.foods[component][row];
//2. Determine which column is selected, set the corresponding data according to the column number
if (0 = = component) {
//fruit
Self.fruitLabel.text = name;
} else if (1 = = component)
{
//main course
Self.stapleLabel.text = name;
}else
{
//Beverage
Self.drinkLabel.text = name;
   }

3. Set the default value displayed in Viewdidload (simulate Manual Check)
for (int component = 0; component<self.foods.count;component++)
{
    [self pcikerview:nil didselectrow:0 Incomponent:component];
}

Iii. Random selection of vegetables
1. Drag a view (height 64, including status bar 20), drag 1 buttons and a label on top
Middle and small skill: Y is 64, (same as height), height is 44.
2. Monitor button click (Connect and implement method)
.//here to get Pickerview, call its method, so first connect the Pickerview (Outlet).
#pragma mark-Tap the Monitor button
-(Ibaction) Randomfood: (UIButton *) sender{
Let Pickerview actively select a row
Let Pickerview select Row row for incomponent column
Generate random values based on the number of elements in each column
for (int component = 0;component <self.foods.count;component++)
{
Gets the total number of data for the corresponding column
int total = [self.foods[component] count];
Generates a random number based on the total number of each column (the currently generated random number)
int randomnumber = arc4random ()% Total;

Gets the currently selected row (the row that was last randomly moved to)
int oldrow = [Self.pickerview selectedrowincomponent:0];
Compares the last line number and the currently generated random number, if the same, regenerates
while (Oldrow = = Randomnumber) {
Randomnumber = arc4random ()% Total;
}

Let Pickervier scroll to a line
[Self.pickerview selectrow:randomnumber incomponent:component Animated:yes];

Select a row by code
[Self Pcikerview:nil didselectrow:randomnumber incomponent:component];
}
% 12 is always [0,11], the other is the same, that is, there are several numbers on the%

Q: Why not use [self.foods[2] count] without self.foods[0].count?
Answer: because self.foods[0] = = [Self.foods objectatindex:0];
and Objectatindex: The return value of the method is Id,id is a dynamic type, only when run to know what type, the dynamic type does not have the Count method, so it cannot be called. But to take the old-fashioned way [self.foods[2] count]

iOS Foundation-uikit Frame-Advanced View-uipickerview-Instance 1: Order (no relationship between columns and columns)