Checkbox(打勾显示输入的密码)
要想判断Checkbox是不是被选中，必须注册OnCheckedChangedListener。没什么难点，直接看代码。

package com.kevin.checkbox;import android.app.Activity;import android.os.Bundle;import android.text.method.HideReturnsTransformationMethod;import android.text.method.PasswordTransformationMethod;import android.widget.CheckBox;import android.widget.CompoundButton;import android.widget.CompoundButton.OnCheckedChangeListener;import android.widget.EditText;public class Main extends Activity {private CheckBox chk_show;private EditText et_password;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        et_password = (EditText) findViewById(R.id.et_password);        chk_show = (CheckBox) findViewById(R.id.chk_show);        chk_show.setOnCheckedChangeListener(new CheckChangedListener());    }        class CheckChangedListener implements OnCheckedChangeListener{@Overridepublic void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {if(isChecked){// 设置EditText的内容为显示et_password.setTransformationMethod(HideReturnsTransformationMethod.getInstance());}else{// 设置EditText的内容为隐藏et_password.setTransformationMethod(PasswordTransformationMethod.getInstance());}}        }}