<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:id="@+id/LinearLayout1"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

    <TextView

        android:id="@+id/msg"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:text="@string/msg" />

    <EditText

        android:id="@+id/pwd"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:inputType="textPassword"

        android:text="" />

    <CheckBox

        android:id="@+id/showpwd"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:checked="false"

        android:text="@string/cktext" />

</LinearLayout>

public class MainActivity extends Activity {

    private EditText myPassword=null;

    private CheckBox myCheckBox=null;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        this.myPassword=(EditText)findViewById(R.id.pwd);

        this.myCheckBox=(CheckBox)findViewById(R.id.showpwd);

        this.myCheckBox.setOnClickListener(new OnClickListenerImpl());

    }

    private class OnClickListenerImpl implements OnClickListener{

        @Override

        public void onClick(View v) {

            // TODO Auto-generated method stub

            if(MainActivity.this.myCheckBox.isChecked()){

                MainActivity.this.myPassword.setTransformationMethod(HideReturnsTransformationMethod.getInstance());

            }else {

                MainActivity.this.myPassword.setTransformationMethod(PasswordTransformationMethod.getInstance());

            }

        }

    }