代碼解析
MainActivity
該接口的設計目的主要是建立一個自定義View-屏幕左邊的檢索條。代碼的解析如下：
// Activity that display customized list view and search box
public class MainActivity extends Activity {
// an array of countries to display in the list
static final String[] ITEMS = new String[] { "East Timor", "Ecuador", "Egypt", "El Salvador", "Equatorial Guinea",
"Eritrea", "Estonia", "Ethiopia", "Faeroe Islands", "Falkland Islands", "Fiji", "Finland", "Afghanistan",
"Albania", "Algeria", "American Samoa", "Andorra", "Angola", "Anguilla", "Antarctica",
"Antigua and Barbuda", "Argentina", "Armenia", "Aruba", "Australia", "Austria", "Azerbaijan", "Bahrain",
"Bangladesh", "Barbados", "Belarus", "Belgium", "Monaco", "Mongolia", "Montserrat", "Morocco",
"Mozambique", "Myanmar", "Namibia", "Nauru", "Nepal", "Netherlands", "Netherlands Antilles",
"New Caledonia", "New Zealand", "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", "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", "French Southern Territories", "Gabon", "Georgia", "Germany", "Ghana",
"Gibraltar", "Greece", "Greenland", "Grenada", "Guadeloupe", "Guam", "Guatemala", "Guinea",
"Guinea-Bissau", "Martinique", "Mauritania", "Mauritius", "Mayotte", "Mexico", "Micronesia", "Moldova",
"Bosnia and Herzegovina", "Botswana", "Bouvet Island", "Brazil", "British Indian Ocean Territory",
"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", "Uganda", "Ukraine",
"United Arab Emirates", "United Kingdom", "United States", "United States Minor Outlying Islands",
"Uruguay", "Uzbekistan", "Vanuatu", "Vatican City", "Venezuela", "Vietnam", "Virgin Islands",
"Wallis and Futuna", "Western Sahara", "British Virgin Islands", "Brunei", "Bulgaria", "Burkina Faso",
"Burundi", "Cote d'Ivoire", "Cambodia", "Cameroon", "Canada", "Cape Verde", "Cayman Islands",
"Central African Republic", "Chad", "Chile", "China", "Reunion", "Romania", "Russia", "Rwanda",
"Sqo Tome and Principe", "Saint Helena", "Saint Kitts and Nevis", "Saint Lucia",
"Saint Pierre and Miquelon", "Belize", "Benin", "Bermuda", "Bhutan", "Bolivia", "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", "Former Yugoslav Republic of Macedonia", "France", "French Guiana",
"French Polynesia", "Macau", "Madagascar", "Malawi", "Malaysia", "Maldives", "Mali", "Malta",
"Marshall Islands", "Yemen", "Yugoslavia", "Zambia", "Zimbabwe" };
// unsorted list items
ArrayList<String> mItems;
// array list to store section positions
ArrayList<Integer> mListSectionPos;
// array list to store listView data
ArrayList<String> mListItems;
// custom list view with pinned header
PinnedHeaderListView mListView;
// custom adapter
PinnedHeaderAdapter mAdaptor;
// search box
EditText mSearchView;
// loading view
ProgressBar mLoadingView;
// empty view
TextView mEmptyView;
@SuppressWarnings("unchecked")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// UI elements
setupViews();
// Array to ArrayList
mItems = new ArrayList<String>(Arrays.asList(ITEMS));
mListSectionPos = new ArrayList<Integer>();
mListItems = new ArrayList<String>();
// for handling configuration change
if (savedInstanceState != null) {
mListItems = savedInstanceState.getStringArrayList("mListItems");
mListSectionPos = savedInstanceState.getIntegerArrayList("mListSectionPos");
if (mListItems != null && mListItems.size() > 0 && mListSectionPos != null && mListSectionPos.size() > 0) {
setListAdaptor();
}
String constraint = savedInstanceState.getString("constraint");
if (constraint != null && constraint.length() > 0) {
mSearchView.setText(constraint);
setIndexBarViewVisibility(constraint);
}
} else {
new Poplulate().execute(mItems);
}
}
private void setupViews() {
setContentView(R.layout.main_act);
mSearchView = (EditText) findViewById(R.id.search_view);
mLoadingView = (ProgressBar) findViewById(R.id.loading_view);
mListView = (PinnedHeaderListView) findViewById(R.id.list_view);
mEmptyView = (TextView) findViewById(R.id.empty_view);
}
// I encountered an interesting problem with a TextWatcher listening for
// changes in an EditText.
// The afterTextChanged method was called, each time, the device orientation
// changed.
// An answer on Stackoverflow let me understand what was happening: Android
// recreates the activity, and
// the automatic restoration of the state of the input fields, is happening
// after onCreate had finished,
// where the TextWatcher was added as a TextChangedListener.The solution to
// the problem consisted in adding
// the TextWatcher in onPostCreate, which is called after restoration has
// taken place
//
// http://stackoverflow.com/questions/6028218/android-retain-callback-state-after-configuration-change/6029070#6029070
// http://stackoverflow.com/questions/5151095/textwatcher-called-even-if-text-is-set-before-adding-the-watcher
@Override
protected void onPostCreate(Bundle savedInstanceState) {
mSearchView.addTextChangedListener(filterTextWatcher);
super.onPostCreate(savedInstanceState);
}
private void setListAdaptor() {
// create instance of PinnedHeaderAdapter and set adapter to list view
mAdaptor = new PinnedHeaderAdapter(this, mListItems, mListSectionPos);
mListView.setAdapter(mAdaptor);
LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
// set header view
View pinnedHeaderView = inflater.inflate(R.layout.section_row_view, mListView, false);
mListView.setPinnedHeaderView(pinnedHeaderView);
// set index bar view
IndexBarView indexBarView = (IndexBarView) inflater.inflate(R.layout.index_bar_view, mListView, false);
indexBarView.setData(mListView, mListItems, mListSectionPos);
mListView.setIndexBarView(indexBarView);
// set preview text view
View previewTextView = inflater.inflate(R.layout.preview_view, mListView, false);
mListView.setPreviewView(previewTextView);
// for configure pinned header view on scroll change
mListView.setOnScrollListener(mAdaptor);
}
private TextWatcher filterTextWatcher = new TextWatcher() {
public void afterTextChanged(Editable s) {
String str = s.toString();
if (mAdaptor != null && str != null)
mAdaptor.getFilter().filter(str);
}
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
public void onTextChanged(CharSequence s, int start, int before, int count) {
}
};
public class ListFilter extends Filter {
@Override
protected FilterResults performFiltering(CharSequence constraint) {
// NOTE: this function is *always* called from a background thread,
// and
// not the UI thread.
String constraintStr = constraint.toString().toLowerCase(Locale.getDefault());
FilterResults result = new FilterResults();
if (constraint != null && constraint.toString().length() > 0) {
ArrayList<String> filterItems = new ArrayList<String>();
synchronized (this) {
for (String item : mItems) {
if (item.toLowerCase(Locale.getDefault()).startsWith(constraintStr)) {
filterItems.add(item);
}
}
result.count = filterItems.size();
result.values = filterItems;
}
} else {
synchronized (this) {
result.count = mItems.size();
result.values = mItems;
}
}
return result;
}
@SuppressWarnings("unchecked")
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
ArrayList<String> filtered = (ArrayList<String>) results.values;
setIndexBarViewVisibility(constraint.toString());
// sort array and extract sections in background Thread
new Poplulate().execute(filtered);
}
}
private void setIndexBarViewVisibility(String constraint) {
// hide index bar for search results
if (constraint != null && constraint.length() > 0) {
mListView.setIndexBarVisibility(false);
} else {
mListView.setIndexBarVisibility(true);
}
}
// sort array and extract sections in background Thread here we use
// AsyncTask
private class Poplulate extends AsyncTask<ArrayList<String>, Void, Void> {
private void showLoading(View contentView, View loadingView, View emptyView) {
contentView.setVisibility(View.GONE);
loadingView.setVisibility(View.VISIBLE);
emptyView.setVisibility(View.GONE);
}
private void showContent(View contentView, View loadingView, View emptyView) {
contentView.setVisibility(View.VISIBLE);
loadingView.setVisibility(View.GONE);
emptyView.setVisibility(View.GONE);
}
private void showEmptyText(View contentView, View loadingView, View emptyView) {
contentView.setVisibility(View.GONE);
loadingView.setVisibility(View.GONE);
emptyView.setVisibility(View.VISIBLE);
}
@Override
protected void onPreExecute() {
// show loading indicator
showLoading(mListView, mLoadingView, mEmptyView);
super.onPreExecute();
}
@Override
protected Void doInBackground(ArrayList<String>... params) {
mListItems.clear();
mListSectionPos.clear();
ArrayList<String> items = params[0];
if (mItems.size() > 0) {
// NOT forget to sort array
Collections.sort(items, new SortIgnoreCase());
String prev_section = "";
for (String current_item : items) {
String current_section = current_item.substring(0, 1).toUpperCase(Locale.getDefault());
if (!prev_section.equals(current_section)) {
mListItems.add(current_section);
mListItems.add(current_item);
// array list of section positions
mListSectionPos.add(mListItems.indexOf(current_section));
prev_section = current_section;
} else {
mListItems.add(current_item);
}
}
}
return null;
}
@Override
protected void onPostExecute(Void result) {
if (!isCancelled()) {
if (mListItems.size() <= 0) {
showEmptyText(mListView, mLoadingView, mEmptyView);
} else {
setListAdaptor();
showContent(mListView, mLoadingView, mEmptyView);
}
}
super.onPostExecute(result);
}
}
public class SortIgnoreCase implements Comparator<String> {
public int compare(String s1, String s2) {
return s1.compareToIgnoreCase(s2);
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
if (mListItems != null && mListItems.size() > 0) {
outState.putStringArrayList("mListItems", mListItems);
}
if (mListSectionPos != null && mListSectionPos.size() > 0) {
outState.putIntegerArrayList("mListSectionPos", mListSectionPos);
}
String searchText = mSearchView.getText().toString();
if (searchText != null && searchText.length() > 0) {
outState.putString("constraint", searchText);
}
super.onSaveInstanceState(outState);
}
}
