Shulou(Shulou.com)06/01 Report--

Android,java may listen when it is clicked using Button, and there will be a function responsible for callback when it is clicked, so how exactly is it implemented?

What we need to do today is to figure out how to prepare extends EditText and set up listeners on it in order to reduce unnecessary trouble.

[code steps]

1. Define Edit2Text and extends EditText

Public class Edit2Text extends EditText {

OnTextChangedListener changedListener

TextWatcher tWatcher

}

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two。 Define the listener on it: OnTextChangedListener and define the function: onChanged () to perform a specific callback

Public static interface OnTextChangedListener {

Public void onChanged (Edit2Text e2t, String text)

}

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Note the decorating keywords for these lines of code:

1. Static: enable it to exist without Edit2Text

2. Interface: make it automatically populate its internal functions

3. The first parameter e2t in "void onChanged (Edit2Text e2t, String text)" is used to do specific details later.

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3. Set the listener

Public void setOnChangedListener (OnTextChangedListener l) {

ChangedListener = l

}

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4. Define TextWatcher to notify listeners when character content changes

* define TextWatcher'

TWatcher = new TextWatcher () {

@ Override

Public void afterTextChanged (Editable s) {

/ / TODO Auto-generated method stub

06.

}

@ Override

Public void beforeTextChanged (CharSequence s, int start, int count

Int after) {

/ / TODO Auto-generated method stub

}

@ Override

Public void onTextChanged (CharSequence s, int start, int before

Int count) {

/ / TODO Auto-generated method stub

UpdateText (s.toString ())

}

}

This.addTextChangedListener (tWatcher)

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* notify the listener

Private void updateText (String s) {

ChangedListener.onChanged (this, s)

}

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5. How to use

Public class Edit2TextTest extends Activity {

/ * Called when the activity is first created. , /

@ Override

Public void onCreate (Bundle savedInstanceState) {

Super.onCreate (savedInstanceState)

06. SetContentView (R.layout.main)

Edit2Text e2t = new Edit2Text (this)

SetContentView (e2t)

E2t.setOnChangedListener (new Edit2Text.OnTextChangedListener () {

@ Override

Public void onChanged (Edit2Text e2t, String text) {

/ / TODO Auto-generated method stub

Log.d ("TAG", "[String:]" + text)

}

});

}

}

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* Log information:

Java Code Collection Code

01. D/dalvikvm: GC freed 223 objects / 8848 bytes in 108m

02. D/TAG: [String:] I am

03. D/TAG: [String:] I am

04. D/TAG: [String:] i am e

05. D/TAG: [String:] i am ed

06. D/TAG: [String:] i am edi

07. D/TAG: [String:] i am edit

08. D/TAG: [String:] I am edit2

09. D/TAG: [String:] I am edit2t

10. D/TAG: [String:] I am edit2te

11. D/TAG: [String:] I am edit2tex

12. D/TAG: [String:] I am edit2text

13. D/TAG: [String:] I am edit2text

14. D/TAG: [String:] I am edit2text

15. D/TAG: [String:] I am edit2text, h

16. D/TAG: [String:] I am edit2text, he

17. D/TAG: [String:] I am edit2text, hel

18. D/TAG: [String:] I am edit2text, hell

19. D/TAG: [String:] I am edit2text, hello

20. D/TAG: [String:] I am edit2text, hello!

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