Android開發教程：監聽EditText的變化

之前的有關EditText的文章，只是介紹EditText的一些最基本的用法，這次來深入學習一下EditText。

監聽EditText的變化

使用EditText的addTextChangedListener(TextWatcher watcher)方法對EditText實現監聽，TextWatcher是一個接口類，所以必須實現TextWatcher裡的抽象方法：

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當EditText裡面的內容有變化的時候，觸發TextChangedListener事件，就會調用TextWatcher裡面的抽象方法。

MainActivity.java

package com.lingdududu.watcher;  
 
import Android.app.Activity;  
import android.app.AlertDialog;  
import android.content.DialogInterface;  
import android.os.Bundle;  
import android.text.Editable;  
import android.text.TextWatcher;  
import android.util.Log;  
import android.widget.EditText;  
 
public class MainActivity extends Activity {  
    private EditText text;  
    String str;  
    @Override 
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
          
        text = (EditText)findViewById(R.id.text);  
        text.addTextChangedListener(textWatcher);  
    }  
      
    private TextWatcher textWatcher = new TextWatcher() {  
          
        @Override    
        public void afterTextChanged(Editable s) {     
            // TODO Auto-generated method stub     
            Log.d("TAG","afterTextChanged--------------->");   
        }   
          
        @Override 
        public void beforeTextChanged(CharSequence s, int start, int count,  
                int after) {  
            // TODO Auto-generated method stub  
            Log.d("TAG","beforeTextChanged--------------->");  
        }  
 
         @Override    
        public void onTextChanged(CharSequence s, int start, int before,     
                int count) {     
            Log.d("TAG","onTextChanged--------------->");    
            str = text.getText().toString();  
            try {  
                //if ((heighText.getText().toString())!=null)   
                Integer.parseInt(str);  
                  
            } catch (Exception e) {  
                // TODO: handle exception  
                showDialog();  
            }  
                              
        }                    
    };  
 
    private void showDialog(){  
        AlertDialog dialog;  
        AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);  
        builder.setTitle("消息").setIcon(android.R.drawable.stat_notify_error);  
        builder.setMessage("你輸出的整型數字有誤，請改正");  
        builder.setPositiveButton("確定", new DialogInterface.OnClickListener(){  
            @Override 
            public void onClick(DialogInterface dialog, int which) {  
                // TODO Auto-generated method stub  
                  
            }                     
        });  
        dialog = builder.create();  
        dialog.show();  
    }  
} 

main.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    > 
<TextView    
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:text="請輸入整型數字" 
    /> 
<EditText   
    android:id="@+id/text" 
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    /> 
</LinearLayout> 

效果圖：

當我們在輸入框輸入不是整型數字的時候，會立刻彈出輸入框，提示你改正

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