IOS Advanced Nineth Day (0408)

0408makekeyAndVisible explanation

A program can have multiple windows, but only one window can be the main window. As shown in, the Window2 is the main window. The main window is of great use. Starting from iOS7, you can interact with the main window or the secondary window, such as text boxes. But in IOS6 and its previous versions, Non-Keywindow (non-main window) cannot be interacted with, that is, you cannot enter text into a text box

If you find that a text box cannot enter text, it is necessary to think that the window in which the text box is located is not the main window

The performance of the iOS main window and the non-main window:

Gets the main window of the current program

Some summary:

The keyboard is also in a window windows, if you want to change things on the keyboard, you get the keyboard in the window, you can get the keyboard, you can get the keyboard of the child control, you can change the keyboard button

Uinavigationcontroller push-in Stack controller method

Uinavigationcontroller out the Stack method, the default is only the current Topviewcontroller, you can directly pop to the specified Viewcontroller, you can also direct pop to Rootviewcontroller

The life cycle of the controller

As shown in the following examples:

Handling of memory warnings

1, first appdelegate received a warning

2. Then start looking for the root controller to see which sub-controller of the root controller is experiencing a memory warning

3. Find the sub-controller that received the memory warning, do some processing (perhaps the sdwebimage cache, may be some member variable =nil empty, may also be releasing some non-highest priority controller resources. What is a controller that is not the highest priority, is not the controller that is being displayed on the current interface. If you return to the previously released controller, the system will automatically create the controller's view again, revive the controller, invoke the Viewdidload method, and execute the controller's full life cycle.

The following diagram illustrates the process of memory warning

IOS Advanced Nineth Day (0408)