<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/txt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="请输入：" />

    <EditText
        android:id="@+id/txt1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:password="true"
        android:textSize="30px" />

    <CheckBox
        android:id="@+id/checkbox1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="显示密码" />

</LinearLayout>

package org.lxh.demo;

import android.app.Activity;
import android.os.Bundle;
import android.text.method.HideReturnsTransformationMethod;
import android.text.method.PasswordTransformationMethod;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.TextView;

public class Hello extends Activity {
  private EditText password = null;
  private CheckBox show = null;

  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState); // 生命周期方法
    super.setContentView(R.layout.main); // 设置要使用的布局管理器
    this.password = (EditText) super.findViewById(R.id.txt1);
    this.show = (CheckBox) super.findViewById(R.id.checkbox1);
    this.show.setOnClickListener(new OnClickListenerImpl());

  }

  private class OnClickListenerImpl implements OnClickListener {

    public void onClick(View arg0) {
      if (show.isChecked()) {
        Hello.this.password
            .setTransformationMethod(HideReturnsTransformationMethod
                .getInstance());
      } else {
        Hello.this.password
            .setTransformationMethod(PasswordTransformationMethod
                .getInstance());
      }

    }

  }
}