Android监听EditText内容变化

1、给EditText追加ChangedListener

EditText editText = (EditText) findViewById(R.id.edittext);

editText.addTextChangedListener(watcher); 

2、描述监听

private TextWatcher watcher = new TextWatcher() {

@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// TODO Auto-generated method stub

}

@Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
// TODO Auto-generated method stub

}

@Override
public void afterTextChanged(Editable s) {
// TODO Auto-generated method stub

}
};

监听EditText的变化

使用EditText的addTextChangedListener(TextWatcher watcher)方法对EditText实现监听，TextWatcher是一个接口类，所以必须实现TextWatcher里的抽象方法：

当EditText里面的内容有变化的时候，触发TextChangedListener事件，就会调用TextWatcher里面的抽象方法。

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; 

publicclass MainActivity extends Activity { 
private EditText text; 
String str; 
@Override
publicvoid 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
publicvoid afterTextChanged(Editable s) { 
// TODO Auto-generated method stub 
Log.d("TAG","afterTextChanged--------------->"); 
} 

@Override
publicvoid beforeTextChanged(CharSequence s, int start, int count, 
int after) { 
// TODO Auto-generated method stub 
Log.d("TAG","beforeTextChanged--------------->"); 
} 

@Override
publicvoid 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(); 
} 

} 
}; 
privatevoid showDialog(){ 
AlertDialog dialog; 
AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this); 
builder.setTitle("消息").setIcon(android.R.drawable.stat_notify_error); 
builder.setMessage("你输出的整型数字有误，请改正"); 

builder.setPositiveButton("确定",new DialogInterface.OnClickListener(){ 
@Override
publicvoid onClick(DialogInterface dialog, int which) { 
// TODO Auto-generated method stub 

} 
}); 
dialog = builder.create(); 
dialog.show(); 
} 
} 

main.xml

<?xmlversion="1.0"encoding="utf-8"?>
<LinearLayoutxmlns: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="请输入整型数字"
/>
<EditText
android:id="@+id/text"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>
</LinearLayout>

效果图：

当我们在输入框输入不是整型数字的时候，会立刻弹出输入框，提示你改正