iOS Programming (bilingual edition)-View-frame/bounds/center

1. Frame

Each view has a frame property, which is a cgrect structure that describes the position of the rectangle where the view resides in its parent view .

(The default origin of the screen coordinate system is in the upper-left corner, the x-axis stretches to the right, and the y-axis stretches down).

Sets the frame normally through the specified initializer of the view initWithFrame

Let's take a look at an example that initializes 3 rectangular regions that overlap each other.

(OBJECTIVE-C code)

uiview* V1 = [[UIView alloc] Initwithframe:cgrectmake (113,111, the,194)];v1.backgroundcolor= [Uicolor colorwithred:1Green:.4Blue1Alpha1]; UIView* v2 = [[UIView alloc] Initwithframe:cgrectmake ( A, About, the,194)];v2.backgroundcolor= [Uicolor colorwithred:.5Green1Blue0Alpha1]; UIView* V3 = [[UIView alloc] Initwithframe:cgrectmake ( +,197, the, the)];v3.backgroundcolor= [Uicolor colorwithred:1Green0Blue0Alpha1]; [Mainview ADDSUBVIEW:V1]; [V1 addsubview:v2]; [Mainview Addsubview:v3];

(Swift code IOS9)

Let V1 = UIView (Frame:cgrectmake (113,111, the,194)) V1.backgroundcolor= Uicolor (red:1, Green:0.4, Blue:1, Alpha:1) Let v2= UIView (Frame:cgrectmake ( A, About, the,194)) V2.backgroundcolor= Uicolor (red:0.5, Green:1, Blue:0, Alpha:1) Let V3= UIView (Frame:cgrectmake ( +,197, the, the)) V3.backgroundcolor= Uicolor (red:1, Green:0, Blue:0, Alpha:1) Mainview.addsubview (v1) V1.addsubview (v2) Mainview.addsubview (v3)

Operation Result:

2. Bounds

Bounds is also a cgrect structure, unlike frame, which describes the rectangular area of the view itself, relative to its own coordinate system .

The following example creates a rectangular view of 2 overlays with a sub-view of the smaller green

(OBJECTIVE-C code)

uiview* V1 = [[UIView alloc] Initwithframe:cgrectmake (113,111, the,194)];v1.backgroundcolor= [Uicolor colorwithred:1Green:.4Blue1Alpha1];//when drawing inside a view, it is often necessary to use the view's boundsuiview* v2 = [[UIView alloc] Initwithframe:cgrectinset (V1.bounds,Ten,Ten)];v2.backgroundcolor= [Uicolor colorwithred:.5Green1Blue0Alpha1]; [Mainview ADDSUBVIEW:V1]; [V1 addsubview:v2];

(Swift code IOS9)

Let V1 = UIView (Frame:cgrectmake (113,111, the,194)) V1.backgroundcolor= Uicolor (red:1, Green:0.4, Blue:1, Alpha:1)//when drawing inside a view, it is often necessary to use the view's boundsLet V2 = UIView (frame:v1.bounds.insetBy (DX:TenDy:Ten)) V2.backgroundcolor= Uicolor (red:0.5, Green:1, Blue:0, Alpha:1) Mainview.addsubview (v1) V1.addsubview (v2)

Operation Result:

The following example completely overrides the parent view by changing the bounds of the green sub-view

(OBJECTIVE-C code)

uiview* V1 = [[UIView alloc] Initwithframe:cgrectmake (113,111, the,194)];v1.backgroundcolor= [Uicolor colorwithred:1Green:.4Blue1Alpha1]; UIView* v2 = [[UIView alloc] Initwithframe:cgrectinset (V1.bounds,Ten,Ten)];v2.backgroundcolor= [Uicolor colorwithred:.5Green1Blue0Alpha1]; [Mainview ADDSUBVIEW:V1]; [V1 addsubview:v2];//Redefine the bounds of a child viewCGRect r =V2.bounds;r.size.height+= -; R.size.width+= -; V2.bounds= R;

(Swift code IOS9)

Let V1 = UIView (Frame:cgrectmake (113,111, the,194)) V1.backgroundcolor= Uicolor (red:1, Green:0.4, Blue:1, Alpha:1) Let v2= UIView (frame:v1.bounds.insetBy (DX:TenDy:Ten)) V2.backgroundcolor= Uicolor (red:0.5, Green:1, Blue:0, Alpha:1) Mainview.addsubview (v1) V1.addsubview (v2) v2.bounds.size.height+= -V2.bounds.size.width+= -

Operation Result:

In the following example, the origin of the purple parent view is slightly offset.

(OBJECTIVE-C code)

uiview* V1 = [[UIView alloc] Initwithframe:cgrectmake (113,111, the,194)];v1.backgroundcolor= [Uicolor colorwithred:1Green:.4Blue1Alpha1]; UIView* v2 = [[UIView alloc] Initwithframe:cgrectinset (V1.bounds,Ten,Ten)];v2.backgroundcolor= [Uicolor colorwithred:.5Green1Blue0Alpha1]; [Mainview ADDSUBVIEW:V1]; [V1 addsubview:v2];//change the parent view's origin coordinatesCGRect r =v1.bounds;r.origin.x+=Ten; R.ORIGIN.Y+=Ten; V1.bounds= R;

(Swift code IOS9)

Let V1 = UIView (Frame:cgrectmake (113,111, the,194)) V1.backgroundcolor= Uicolor (red:1, Green:0.4, Blue:1, Alpha:1) Let v2= UIView (frame:v1.bounds.insetBy (DX:TenDy:Ten)) V2.backgroundcolor= Uicolor (red:0.5, Green:1, Blue:0, Alpha:1) Mainview.addsubview (v1) V1.addsubview (v2)//change the parent view's origin coordinatesV1.bounds.origin.x + =TenV1.BOUNDS.ORIGIN.Y+=Ten

Operation Result:

3. Center

Center point Location coordinates of the view

4. About the main window and the device screen

The device screen (Uiscreen.mainscreen ()) does not have a frame, but it has bounds.

The main window does not have a parent view, but its frame can be set to the bounds of the screen.

Let w = UIWindow (Frame:UIScreen.mainScreen (). Bounds)

5. About the difference between frame and bounds

Word is the former relative to the parent view, whereas the latter is relative to itself.

Let's take a look at the picture, it's more intuitive.

In the case where the view is not rotated, they are similar, with slightly different coordinates, such as:

The coordinates of the transform are very different after the views have been rotated like this, see:

iOS Programming (bilingual edition)-View-frame/bounds/center