How to hide native.newTextField after clicking submit?

问题

I'm trying trying to have users name fade in one letter at a time vertically. Example: Adam "A" would appear after 1 second , "d" would appear after 3 seconds under the displayed A, "a" would appear after 5 seconds under the displayed d, "m" would appear after 7 seconds under the displayed a. The visuals would have a sort of domino effect.When they appear they would stay displayed on screen.

When if I comment out userNameField:removeSelf () then the code works fine. I get the effect I want, but the problem is that I still have the userNamefield showing.

Please let me know if you need to see more code.

local greeting = display.newText( "Greetings, enter your name",0,0,native.systemFont, 20 )
greeting.x = display.contentWidth/2
greeting.y = 100

local submitButton = display.newImage( "submit.png"  ,display.contentWidth/2, display.contentHeight - 50 )

local userNameField = native.newTextField( display.contentWidth * 0.5 , 150, 250, 45)
userNameField.inputtype = "defualt"


local incrementor = 0
function showNameLetters()

userNameField:removeSelf( )
if incrementor <= string.len ("userNameField.text") then
    incrementor = incrementor + 1
    personLetters = string.sub (userNameField.text, incrementor,incrementor)
    display_personLetters = display.newText (personLetters, 290,30*incrementor, native.systemFont, 30)
        display_personLetters.alpha = 0
    transition.to(display_personLetters,{time = 3000, alpha = 1, onComplete = showNameLetters})
end
end

Update:

I've found a solution to my problem, by adding userNameField.isVisible = false in my function.

I've also found something very weird, and wish to have someone explain why this happens. If I add greeting:removeSelf() and submitButton:removeSelf() (I've commented them out in my code below to show you where I put them for testing). I get weird result of only the first letter fading in. If i set greeting.isVisible = false and submitButton.isVisible = false. The code works fine.

I'm so confused why object:removeSelf() wouldn't work. Can someone please clear this up for me.

That is, if I replace the following line:

userNameField:removeSelf( )

with:

userNameField.isVisible = false

then the app works fine. Please suggest me why/ any solution for the question. THanks in advance...

回答1:

It seems like you're calling the showNameLetters multiple times, this means that you're removing the native text field more than once. Nil it and check for nil before removing it like this:

if userNameField ~= nil then
 userNameField:removeSelf()
 userNameField = nil
end

回答2:

It shows that you are using data from userNameField after removing it (in the line below):

personLetters = string.sub (userNameField.text, incrementor,incrementor)

As well as you are calling object:removeSelf() again and again without checking its existance (as mentioned by hades2510). So before removing userNameField, check for it's existance:

if userNameField ~= nil then
 userNameField:removeSelf()
 userNameField = nil
end

And you won't get userNameField.text while userNameField is nil. So use a temporary variable to hold the previous userNameField.text and get the saved data from that variable when needed.

Extra note: Are you sure, you have to check the length of the text "userNameField.text" in the following line, or the variable userNameField.text? If you have to use the data from the text field, then this will also matter.

if incrementor <= string.len ("userNameField.text") then
  ........
end

Keep coding....................... :)

来源：https://stackoverflow.com/questions/22726814/how-to-hide-native-newtextfield-after-clicking-submit

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