监听EditText的变化

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http://liangruijun.blog.51cto.com/3061169/729505

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.javapackage 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("你输出的整型数字有误，请改正");          builder.setPositiveButton("确定", 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="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

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