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Android: On EditText Changed Listener

2017年12月12日 ⁄ 综合 ⁄ 共 2870字 ⁄ 字号小中大 ⁄ 评论关闭

Android:
On EditText Changed Listener

In my project I have a EditText.
I want to show how many characters are there in the EditText and
show it in the TextView.
I have written following code and it works fine. However, my problem is when I click Backspace it counts up. I need to decrement the number. What should I do? How can I take Backspace Key?

    tv = (TextView)findViewById(R.id.charCounts);
    textMessage = (EditText)findViewById(R.id.textMessage);
    textMessage.addTextChangedListener(new TextWatcher(){
        public void afterTextChanged(Editable s) {
            i++;
            tv.setText(String.valueOf(i) + " / " + String.valueOf(charCounts));
        }
        public void beforeTextChanged(CharSequence s, int start, int count, int after){}
        public void onTextChanged(CharSequence s, int start, int before, int count){}
    });

public interface

TextWatcher

implements NoCopySpan

android.text.TextWatcher

Known
Indirect Subclasses

AbsListView, ExpandableListView, GridView, ListView, PasswordTransformationMethod, PhoneNumberFormattingTextWatcher

Class Overview

When an object of a type is attached to an Editable, its methods will be called when the text is changed.

Summary

Public Methods
abstract void	afterTextChanged(Editable s) This method is called to notify you that, somewhere within `s`, the text has been changed.
abstract void	beforeTextChanged(CharSequence s, int start, int count, int after) This method is called to notify you that, within `s`, the `count` characters beginning at `start` are about to be replaced by new text with length `after`.
abstract void	onTextChanged(CharSequence s, int start, int before, int count) This method is called to notify you that, within `s`, the `count` characters beginning at `start` have just replaced old text that had length `before`.

Public Methods

public abstract void afterTextChanged (Editable s)

Added in API level 1

This method is called to notify you that, somewhere within s, the text has been changed. It is legitimate to make further
changes to s from this callback, but be careful not to get yourself into an infinite loop, because any changes you make will cause this method to be called again recursively. (You are
not told where the change took place because other afterTextChanged() methods may already have made other changes and invalidated the offsets. But if you need to know here, you can use setSpan(Object, int, int, int) in onTextChanged(CharSequence, int, int, int) to mark your place and then look up from here where the span ended up.

public abstract void beforeTextChanged (CharSequence s,
int start, int count, int after)

Added in API level 1

This method is called to notify you that, within s, the count characters
beginning at start are about to be replaced by new text with length after. It is an error to attempt to make
changes to s from this callback.

public abstract void onTextChanged (CharSequence s,
int start, int before, int count)

Added in API level 1

This method is called to notify you that, within s, the count characters
beginning at start have just replaced old text that had length before. It is an error to attempt to make changes
to s from this callback.

【上篇】设置控件的随机显示位置 setlayoutparams 设置控件的随机显示位置 setlayoutparams
【下篇】水平居中和垂直居中

作者: busiest

该日志由 busiest 于6年前发表在综合分类下，最后更新于 2017年12月12日.
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