<?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="@string/hello"
  />
 <EditText
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:inputType="textPassword"
  android:id="@+id/mima"
 />
 <CheckBox android:text="显示密码"  android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:id="@+id/xianshifou"/>
</LinearLayout>

public class M extends Activity {
  private EditText et;
  private CheckBox cb;
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    et=(EditText)findViewById(R.id.mima);
    cb=(CheckBox)findViewById(R.id.xianshifou);
    cb.setOnCheckedChangeListener(new OnCheckedChangeListener(){
      @Override
      public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
        // TODO Auto-generated method stub
        if(cb.isChecked()){
          //设置EditText的密码为可见的
          et.setTransformationMethod(HideReturnsTransformationMethod.getInstance());
        }else{
          //设置密码为隐藏的
          et.setTransformationMethod(PasswordTransformationMethod.getInstance());
        }
      }
    });
  }
}