출처: http://ememomo.tistory.com/36
/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.text;
/**
* When an object of a type is attached to an Editable, its methods will
* be called when the text is changed.
*/
public interface TextWatcher extends NoCopySpan {
/**
* This method is called to notify you that, within <code>s</code>,
* the <code>count</code> characters beginning at <code>start</code>
* are about to be replaced by new text with length <code>after</code>.
* It is an error to attempt to make changes to <code>s</code> from
* this callback.
*/
public void beforeTextChanged(CharSequence s, int start,
int count, int after);
/**
* This method is called to notify you that, within <code>s</code>,
* the <code>count</code> characters beginning at <code>start</code>
* have just replaced old text that had length <code>before</code>.
* It is an error to attempt to make changes to <code>s</code> from
* this callback.
*/
public void onTextChanged(CharSequence s, int start, int before, int count);
/**
* This method is called to notify you that, somewhere within
* <code>s</code>, the text has been changed.
* It is legitimate to make further changes to <code>s</code> 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 {@link Spannable#setSpan} in {@link #onTextChanged}
* to mark your place and then look up from here where the span
* ended up.
*/
public void afterTextChanged(Editable s);
}
TextWatcher 인터페이스를 보면 beforeTextChanged / onTextChanged / afterTextChanged 함수를 오버라이딩 하여야 한다.
각각의 함수는 이름을 보면 대충 언제 구동되는지 알 수 있을 것이다.
이 인터페이스를 이용해서 입력값에 대한 실시간 변화를 감지해 낼 수 잇다. 예를 들어 가격을 입력하는 창이라던지, 글자를
입력하는 창에서 조건을 걸어 검사를 할때 유용하게 사용 할 수 있다.
이번예제는 TextWatcher 인터페이스를 이용해서 글자수를 제한 해 보는 예제이다.
하나의 입력창이 있고 , 그 입력창을 글자수를 실시간으로 반영 하며, 50자 이상일때 입력을 제한하는 Toast 메시지를 띄우는
예제이다.
화면을 살펴 보면
이런식의 예제이다. 이를 응용하면 가격표에 자동으로 , 표시를 추가하는등의 함수도 작성 할 수 있다.
쓰는 법은 간단하니 코드를 살펴 보자.
main.xml
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:background="#ffffff"
android:gravity="center"
>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="9dip"
android:layout_marginTop="10dip" />
<TextView
android:id="@+id/review_length"
android:layout_marginTop="15dip"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingRight="5dip"
android:layout_marginLeft="240dip"
android:text="0/50자" />
</LinearLayout>
<EditText
android:id="@+id/estimate_review_content"
android:layout_marginLeft="8dip"
android:layout_marginTop="1dip"
android:maxLength="50"
android:padding="7dip"
android:layout_width="200dip"
android:layout_height="75dip" />
</LinearLayout>
Strudy_0522.java
package com.tistory.ememomo;
import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class Strudy_0522 extends Activity implements TextWatcher{
private EditText review_content;
private TextView review_length;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
review_content = (EditText) findViewById(R.id.estimate_review_content);
review_length = (TextView) findViewById(R.id.review_length);
review_content.addTextChangedListener(this);
}
@Override
public void afterTextChanged(Editable s) {
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
if(s.length() >= 50)
{
Toast.makeText(Strudy_0522.this, "글은 50자 까지 입력 가능합니다.", Toast.LENGTH_SHORT).show();
}
review_length.setText( s.length() + "/50자");
}
}
EditText 입력창에 addTextChangedListener 리스너를 달아 주고 그 리스너를 이용하는건 TextView에다 넘겨주었다.
내가 처리한곳은 onTextChanged 함수 내에서 처리 했지만, 입력받기 전 중 후로 처리를 할 수 있으니 잘 살펴 보길 바란다.
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