怎么在Android应用中利用ListView实现一个选择模式

 if (mChoiceMode != CHOICE_MODE_NONE && mCheckStates != null) {
      if (child instanceof Checkable) {
        ((Checkable) child).setChecked(mCheckStates.get(position));
      } else if (getContext().getApplicationInfo().targetSdkVersion
          >= android.os.Build.VERSION_CODES.HONEYCOMB) {
        child.setActivated(mCheckStates.get(position));
      }
    }

public class Countries {
 public static final String[] COUNTRIES = new String[] {
   "Afghanistan", "Albania", "Algeria", "American Samoa", "Andorra",
   "Angola", "Anguilla", "Antarctica", "Antigua and Barbuda",
   "Argentina", "Armenia", "Aruba", "Australia", "Austria",
   "Azerbaijan", "Bahrain", "Bangladesh", "Barbados", "Belarus",
   "Belgium", "Belize", "Benin", "Bermuda", "Bhutan", "Bolivia",
   "Bosnia and Herzegovina", "Botswana", "Bouvet Island", "Brazil",
   "British Indian Ocean Territory", "British Virgin Islands",
   "Brunei", "Bulgaria", "Burkina Faso", "Burundi", "Cote d'Ivoire",
   "Cambodia", "Cameroon", "Canada", "Cape Verde", "Cayman Islands",
   "Central African Republic", "Chad", "Chile", "China",
   "Christmas Island", "Cocos (Keeling) Islands", "Colombia",
   "Comoros", "Congo", "Cook Islands", "Costa Rica", "Croatia",
   "Cuba", "Cyprus", "Czech Republic",
   "Democratic Republic of the Congo", "Denmark", "Djibouti",
   "Dominica", "Dominican Republic", "East Timor", "Ecuador",
   "Egypt", "El Salvador", "Equatorial Guinea", "Eritrea",
   "Estonia", "Ethiopia", "Faeroe Islands", "Falkland Islands",
   "Fiji", "Finland", "Former Yugoslav Republic of Macedonia",
   "France", "French Guiana", "French Polynesia",
   "French Southern Territories", "Gabon", "Georgia", "Germany",
   "Ghana", "Gibraltar", "Greece", "Greenland", "Grenada",
   "Guadeloupe", "Guam", "Guatemala", "Guinea", "Guinea-Bissau",
   "Guyana", "Haiti", "Heard Island and McDonald Islands",
   "Honduras", "Hong Kong", "Hungary", "Iceland", "India",
   "Indonesia", "Iran", "Iraq", "Ireland", "Israel", "Italy",
   "Jamaica", "Japan", "Jordan", "Kazakhstan", "Kenya", "Kiribati",
   "Kuwait", "Kyrgyzstan", "Laos", "Latvia", "Lebanon", "Lesotho",
   "Liberia", "Libya", "Liechtenstein", "Lithuania", "Luxembourg",
   "Macau", "Madagascar", "Malawi", "Malaysia", "Maldives", "Mali",
   "Malta", "Marshall Islands", "Martinique", "Mauritania",
   "Mauritius", "Mayotte", "Mexico", "Micronesia", "Moldova",
   "Monaco", "Mongolia", "Montserrat", "Morocco", "Mozambique",
   "Myanmar", "Namibia", "Nauru", "Nepal", "Netherlands",
   "Netherlands Antilles", "New Caledonia", "New Zealand",
   "Nicaragua", "Niger", "Nigeria", "Niue", "Norfolk Island",
   "North Korea", "Northern Marianas", "Norway", "Oman", "Pakistan",
   "Palau", "Panama", "Papua New Guinea", "Paraguay", "Peru",
   "Philippines", "Pitcairn Islands", "Poland", "Portugal",
   "Puerto Rico", "Qatar", "Reunion", "Romania", "Russia", "Rwanda",
   "Sqo Tome and Principe", "Saint Helena", "Saint Kitts and Nevis",
   "Saint Lucia", "Saint Pierre and Miquelon",
   "Saint Vincent and the Grenadines", "Samoa", "San Marino",
   "Saudi Arabia", "Senegal", "Seychelles", "Sierra Leone",
   "Singapore", "Slovakia", "Slovenia", "Solomon Islands",
   "Somalia", "South Africa",
   "South Georgia and the South Sandwich Islands", "South Korea",
   "Spain", "Sri Lanka", "Sudan", "Suriname",
   "Svalbard and Jan Mayen", "Swaziland", "Sweden", "Switzerland",
   "Syria", "Taiwan", "Tajikistan", "Tanzania", "Thailand",
   "The Bahamas", "The Gambia", "Togo", "Tokelau", "Tonga",
   "Trinidad and Tobago", "Tunisia", "Turkey", "Turkmenistan",
   "Turks and Caicos Islands", "Tuvalu", "Virgin Islands", "Uganda",
   "Ukraine", "United Arab Emirates", "United Kingdom",
   "United States", "United States Minor Outlying Islands",
   "Uruguay", "Uzbekistan", "Vanuatu", "Vatican City", "Venezuela",
   "Vietnam", "Wallis and Futuna", "Western Sahara", "Yemen",
   "Yugoslavia", "Zambia", "Zimbabwe" };
}

public class CountryView extends LinearLayout implements Checkable {

 private TextView mTitle;
 private CheckBox mCheckBox;

 public CountryView(Context context) {
  this(context, null);
 }

 public CountryView(Context context, AttributeSet attrs) {
  super(context, attrs);
  LayoutInflater inflater = LayoutInflater.from(context);
  View v = inflater.inflate(R.layout.country_view, this, true);
  mTitle = (TextView) v.findViewById(R.id.country_view_title);
  mCheckBox = (CheckBox) v.findViewById(R.id.country_view_checkbox);
 }

 public void setTitle(String title) {
  mTitle.setText(title);
 }

 @Override
 public boolean isChecked() {
  return mCheckBox.isChecked();
 }

 @Override
 public void setChecked(boolean checked) {
  mCheckBox.setChecked(checked);
 }

 @Override
 public void toggle() {
  mCheckBox.toggle();
 }

}

public class CountryAdapter extends ArrayAdapter<Country> {

 public CountryAdapter(Context context, int textViewResourceId,
   List<Country> objects) {
  super(context, textViewResourceId, objects);
 }

 @Override
 public View getView(int position, View convertView, ViewGroup parent) {
  if ( convertView == null ) {
   convertView = new CountryView(getContext());
  }

  Country country = getItem(position);

  CountryView countryView = (CountryView) convertView;
  countryView.setTitle(country.getName());

  return convertView;
 }
}

public class Country {
 private String name;

 public Country() {

 }

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

}

public class Hack30Activity extends Activity {
  private ListView mListView;
  private CountryAdapter mAdapter;
  private List<Country> mCountries;
  private String mToastFmt;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_hack30);
    createCountriesList();
    mToastFmt = getString(R.string.activity_main_toast_fmt);
    mAdapter = new CountryAdapter(this, -1, mCountries);
    mListView = (ListView) findViewById(R.id.activity_main_list);
    mListView.setAdapter(mAdapter);
  }

  public void onPickCountryClick(View v) {
    int pos = mListView.getCheckedItemPosition();

    if (ListView.INVALID_POSITION != pos) {
      String msg = String.format(mToastFmt, mCountries.get(pos)
          .getName());
      Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
    }
  }

  private void createCountriesList() {
    mCountries = new ArrayList<Country>(Countries.COUNTRIES.length);
    for (int i = 0; i < Countries.COUNTRIES.length; i++) {
      Country country = new Country();
      country.setName(Countries.COUNTRIES[i]);
      mCountries.add(country);
    }
  }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal" >

  <TextView
    android:id="@+id/country_view_title"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_weight="0.9"
    android:padding="10dp" />

  <CheckBox
    android:id="@+id/country_view_checkbox"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_weight="0.1"
    android:clickable="false"
    android:focusable="false"
    android:focusableInTouchMode="false"
    android:gravity="center_vertical"
    android:padding="10dp" />

</LinearLayout>

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical" >

  <Button
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:onClick="onPickCountryClick"
    android:text="@string/activity_main_add_selection" />

  <ListView
    android:id="@+id/activity_main_list"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:choiceMode="singleChoice" />

</LinearLayout>

<string name="activity_main_toast_fmt">Chosen country: %s</string>
  <string name="activity_main_add_selection">Pick Country</string>