10. Android Theme和Styles内部定义解析
昨天我们讲到的有关在AndroidManifest.xml中定义Activity的theme方法来实现无标题的方法，在使用xml让你的Activity无标题方法 一文中讲到的，很多网友不明白为什么这样做，其实在Android123以前的文章中多次提到了styles样式定义方法，今天Android开发网再次 把一些网友回顾了解下android样式的内部定义。在一个工程的res/values/theme.xml中我们可以方便的定义自己的风格主题，比如下
面的cwjTheme中我们使用了基于android内部的白色调的背景Theme.Light，设置windowsNoTitle为true代表没有标 题，背景颜色我们使用了android内部定义的透明，同时设置listView控件的样式为cwjListView，xml样式代码如下:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="cwjTheme" parent="android:Theme.Light">
<itemname="android:windowNoTitle">true</item>
<itemname="android:windowBackground">@android:color/transparent</item>
<item name="android:listViewStyle">@style/cwjListView</item>
</style>
有关ListView控件我们自定义的风格就是修改下系统listview这个控件的每行分隔符样式，这里我们在工程下res/drawable文件夹下放一个图片名为list_selector图片，这样我们的cwjListView的代码可以这样写
<style name="cwjListView"parent="@android:style/Widget.ListView">
<item name="android:listSelector">@drawable/list_selector</item>
</style>
</resources>
通过定义style可以设置更多，比如让cwjListView的字体颜色就加入textAppearance属性，比如 <itemname="textAppearance">@android:style/TextAppearance</item> 等等。
11.Android JSON解析示例代码
来 自Google官方的有关Android平台的JSON解析示例，如果远程服务器使用了json而不是xml的数据提供，在Android平台上已经内置 的org.json包可以很方便的实现手机客户端的解析处理。下面Android123一起分析下这个例子，帮助Android开发者需要有关 HTTP通讯、正则表达式、JSON解析、appWidget开发的一些知识。
public class WordWidget extends AppWidgetProvider { //appWidget
@Override
public void onUpdate(Context context, AppWidgetManagerappWidgetManager,
int[]appWidgetIds) {
context.startService(newIntent(context, UpdateService.class)); //避免ANR，所以Widget中开了个服务
}
public static class UpdateServiceextends Service {
@Override
public void onStart(Intent intent,int startId) {
// Build thewidget update for today
RemoteViewsupdateViews = buildUpdate(this);
ComponentName thisWidget = new ComponentName(this, WordWidget.class);
AppWidgetManagermanager = AppWidgetManager.getInstance(this);
manager.updateAppWidget(thisWidget, updateViews);
}
publicRemoteViews buildUpdate(Context context) {
// Pick outmonth names from resources
Resourcesres = context.getResources();
String[]monthNames = res.getStringArray(R.array.month_names);
Time today = new Time();
today.setToNow();
String pageName = res.getString(R.string.template_wotd_title,
monthNames[today.month], today.monthDay);
RemoteViewsupdateViews = null;
StringpageContent = "";
try {
SimpleWikiHelper.prepareUserAgent(context);
pageContent = SimpleWikiHelper.getPageContent(pageName, false);
} catch(ApiException e) {
Log.e("WordWidget", "Couldn't contact API", e);
} catch(ParseException e) {
Log.e("WordWidget", "Couldn't parse API response", e);
}
Pattern pattern = Pattern.compile(SimpleWikiHelper.WORD_OF_DAY_REGEX); //正则表达式处理，有关定义见下面的SimpleWikiHelper类
Matchermatcher = pattern.matcher(pageContent);
if(matcher.find()) {
updateViews = new RemoteViews(context.getPackageName(), R.layout.widget_word);
String wordTitle = matcher.group(1);
updateViews.setTextViewText(R.id.word_title, wordTitle);
updateViews.setTextViewText(R.id.word_type, matcher.group(2));
updateViews.setTextViewText(R.id.definition, matcher.group(3).trim());
String definePage = res.getString(R.string.template_define_url,
Uri.encode(wordTitle));
Intent defineIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(definePage)); //这里是打开相应的网页，所以Uri是http的url，action是view即打开web浏览器
PendingIntent pendingIntent = PendingIntent.getActivity(context,
0 /* no requestCode */, defineIntent, 0 /* no flags */);
updateViews.setOnClickPendingIntent(R.id.widget, pendingIntent); //单击Widget打开Activity
} else {
updateViews = new RemoteViews(context.getPackageName(),R.layout.widget_message);
CharSequence errorMessage = context.getText(R.string.widget_error);
updateViews.setTextViewText(R.id.message, errorMessage);
}
returnupdateViews;
}
@Override
public IBinder onBind(Intent intent){
// We don'tneed to bind to this service
return null;
}
}
}
有关网络通讯的实体类，以及一些常量定义如下:
public class SimpleWikiHelper {
private static final String TAG ="SimpleWikiHelper";
public static final StringWORD_OF_DAY_REGEX =
"(?s)\\{\\{wotd\\|(.+?)\\|(.+?)\\|([^#\\|]+).*?\\}\\}";
private static final StringWIKTIONARY_PAGE =
"http://en.wiktionary.org/w/api.php?action=query&prop=revisions&titles=%s&" +
"rvprop=content&format=json%s";
private static final StringWIKTIONARY_EXPAND_TEMPLATES =
"&rvexpandtemplates=true";
private static final int HTTP_STATUS_OK= 200;
private static byte[] sBuffer = newbyte[512];
private static String sUserAgent = null;
public static class ApiExceptionextends Exception {
public ApiException(StringdetailMessage, Throwable throwable) {
super(detailMessage,throwable);
}
publicApiException(String detailMessage) {
super(detailMessage);
}
}
public static class ParseExceptionextends Exception {
public ParseException(StringdetailMessage, Throwable throwable) {
super(detailMessage, throwable);
}
}
public static voidprepareUserAgent(Context context) {
try {
// Readpackage name and version number from manifest
PackageManager manager = context.getPackageManager();
PackageInfoinfo = manager.getPackageInfo(context.getPackageName(), 0);
sUserAgent =String.format(context.getString(R.string.template_user_agent),
info.packageName, info.versionName);
}catch(NameNotFoundException e) {
Log.e(TAG,"Couldn't find package information in PackageManager", e);
}
}
public static StringgetPageContent(String title, boolean expandTemplates)
throwsApiException, ParseException {
String encodedTitle =Uri.encode(title);
String expandClause =expandTemplates ? WIKTIONARY_EXPAND_TEMPLATES : "";
String content =getUrlContent(String.format(WIKTIONARY_PAGE, encodedTitle, expandClause));
try {
JSONObjectresponse = new JSONObject(content);
JSONObjectquery = response.getJSONObject("query");
JSONObjectpages = query.getJSONObject("pages");
JSONObjectpage = pages.getJSONObject((String) pages.keys().next());
JSONArrayrevisions = page.getJSONArray("revisions");
JSONObjectrevision = revisions.getJSONObject(0);
returnrevision.getString("*");
} catch (JSONException e) {
throw new ParseException("Problemparsing API response", e);
}
}
protected static synchronized StringgetUrlContent(String url) throws ApiException {
if (sUserAgent == null) {
throw newApiException("User-Agent string must be prepared");
}
HttpClientclient = new DefaultHttpClient();
HttpGet request = new HttpGet(url);
request.setHeader("User-Agent", sUserAgent); //设置客户端标识
try {
HttpResponseresponse = client.execute(request);
StatusLine status = response.getStatusLine();
if(status.getStatusCode() != HTTP_STATUS_OK) {
throw new ApiException("Invalid response from server: " +
status.toString());
}
HttpEntity entity = response.getEntity();
InputStreaminputStream = entity.getContent(); //获取HTTP返回的数据流
ByteArrayOutputStream content = new ByteArrayOutputStream();
int readBytes = 0;
while((readBytes = inputStream.read(sBuffer)) != -1) {
content.write(sBuffer, 0, readBytes); //转化为字节数组流
}
return new String(content.toByteArray()); //从字节数组构建String
} catch (IOException e) {
throw newApiException("Problem communicating with API", e);
}
}
}
有关整个每日维基的widget例子比较简单，主要是帮助大家积累常用代码，了解Android平台 JSON的处理方式，毕竟很多Server还是Java的。