利用HTML5开发Android笔记（下篇）

资源来自于www.mhtml5.com 杨丰盛老师成都场的PPT分享一个很简明的demo 可以作为入门基础

学习的过程中做了点笔记整理如下虽然内容比较简单但是数量还是比较多的所以分了3篇

（上）包括Android设备多分辨率的问题，Android中构建HTML5应用程序基础

（中）包括Android与JS之间的互动，Android处理JS的警告对话框等，Android中的调试

（下）包括本地储存在Android中的应用，地理位置的应用，离线应用的构建

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进入正题

● HTML5本地存储在Android中的应用

HTML5提供了2种客户端存储数据新方法：

localStorage 没有时间限制

sessionStorage 针对一个Session的数据存储

<script type="text/javascript"> localStorage.lastname="Smith"; document.write(localStorage.lastname); </script> <script type="text/javascript"> sessionStorage.lastname="Smith"; document.write(sessionStorage.lastname);</script>

WebStorage的API:

//清空storagelocalStorage.clear();//设置一个键值localStorage.setItem(“yarin”,“yangfegnsheng”);//获取一个键值localStorage.getItem(“yarin”); //获取指定下标的键的名称（如同Array）localStorage.key(0); //return “fresh” //删除一个键值localStorage.removeItem(“yarin”);注意一定要在设置中开启哦setDomStorageEnabled（true）

在Android中进行操作

//启用数据库webSettings.setDatabaseEnabled(true);  String dir = this.getApplicationContext().getDir("database", Context.MODE_PRIVATE).getPath();//设置数据库路径webSettings.setDatabasePath(dir);//使用localStorage则必须打开webSettings.setDomStorageEnabled(true);//扩充数据库的容量（在WebChromeClinet中实现）public void onExceededDatabaseQuota(String url, String databaseIdentifier, long currentQuota, long estimatedSize, long totalUsedQuota, WebStorage.QuotaUpdater quotaUpdater) {quotaUpdater.updateQuota(estimatedSize * 2);}

在JS中按常规进行数据库操作

function initDatabase() {try {    if (!window.openDatabase) {        alert('Databases are not supported by your browser');    } else {        var shortName = 'YARINDB';        var version = '1.0';        var displayName = 'yarin db';        var maxSize = 100000; // in bytes        YARINDB = openDatabase(shortName, version, displayName, maxSize);createTables();selectAll();    }} catch(e) {    if (e == 2) {        // Version mismatch.        console.log("Invalid database version.");    } else {        console.log("Unknown error "+ e +".");    }    return;} }function createTables(){YARINDB.transaction(function (transaction) {transaction.executeSql('CREATE TABLE IF NOT EXISTS yarin(id INTEGER NOT NULL PRIMARY KEY, name TEXT NOT NULL,desc TEXT NOT NULL);', [], nullDataHandler, errorHandler);});insertData();}function insertData(){YARINDB.transaction(function (transaction) {//Starter data when page is initializedvar data = ['1','yarin yang','I am yarin'];  transaction.executeSql("INSERT INTO yarin(id, name, desc) VALUES (?, ?, ?)", [data[0], data[1], data[2]]);});}function errorHandler(transaction, error){if (error.code==1){// DB Table already exists} else {// Error is a human-readable string.console.log('Oops.  Error was '+error.message+' (Code '+error.code+')');}return false;}function nullDataHandler(){console.log("SQL Query Succeeded");}function selectAll(){ YARINDB.transaction(function (transaction) {transaction.executeSql("SELECT * FROM yarin;", [], dataSelectHandler, errorHandler);});}function dataSelectHandler(transaction, results){// Handle the resultsfor (var i=0; i<results.rows.length; i++) {var row = results.rows.item(i);var newFeature = new Object();newFeature.name   = row['name'];newFeature.decs = row['desc'];document.getElementById("name").innerHTML="name:"+newFeature.name;document.getElementById("desc").innerHTML="desc:"+newFeature.decs;}}function updateData(){YARINDB.transaction(function (transaction) {var data = ['fengsheng yang','I am fengsheng']; transaction.executeSql("UPDATE yarin SET name=?, desc=? WHERE id = 1", [data[0], data[1]]);});selectAll();}function ddeleteTables(){YARINDB.transaction(function (transaction) {transaction.executeSql("DROP TABLE yarin;", [], nullDataHandler, errorHandler);});console.log("Table 'page_settings' has been dropped.");}注意onLoad中的初始化工作function initLocalStorage(){if (window.localStorage) {textarea.addEventListener("keyup", function() {window.localStorage["value"] = this.value;window.localStorage["time"] = new Date().getTime();}, false);} else {alert("LocalStorage are not supported in this browser.");}}window.onload = function() {initDatabase();initLocalStorage();}

● HTML5地理位置服务在Android中的应用

Android中

//启用地理定位webSettings.setGeolocationEnabled(true);//设置定位的数据库路径webSettings.setGeolocationDatabasePath(dir);//配置权限（同样在WebChromeClient中实现）public void onGeolocationPermissionsShowPrompt(String origin,    GeolocationPermissions.Callback callback) {callback.invoke(origin, true, false);super.onGeolocationPermissionsShowPrompt(origin, callback);}

在Manifest中添加权限

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /><uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

HTML5中 通过navigator.geolocation对象获取地理位置信息

常用的navigator.geolocation对象有以下三种方法：

//获取当前地理位置navigator.geolocation.getCurrentPosition(success_callback_function, error_callback_function, position_options)//持续获取地理位置navigator.geolocation.watchPosition(success_callback_function, error_callback_function, position_options)//清除持续获取地理位置事件navigator.geolocation.clearWatch(watch_position_id)

其中success_callback_function为成功之后处理的函数，error_callback_function为失败之后返回的处理函数，参数position_options是配置项

在JS中的代码

//定位function get_location() {if (navigator.geolocation) {navigator.geolocation.getCurrentPosition(show_map,handle_error,{enableHighAccuracy:false,maximumAge:1000,timeout:15000});} else {alert("Your browser does not support HTML5 geoLocation");}}function show_map(position) {var latitude = position.coords.latitude;var longitude = position.coords.longitude;var city = position.coords.city;//telnet localhost 5554//geo fix -82.411629 28.054553//geo fix -121.45356 46.51119 4392//geo nmea $GPGGA,001431.092,0118.2653,N,10351.1359,E,0,00,,-19.6,M,4.1,M,,0000*5Bdocument.getElementById("Latitude").innerHTML="latitude:"+latitude;document.getElementById("Longitude").innerHTML="longitude:"+longitude;document.getElementById("City").innerHTML="city:"+city;}function handle_error(err) {switch (err.code) {case 1:alert("permission denied");break;case 2:alert("the network is down or the position satellites can't be contacted");break;case 3:alert("time out");break;default:alert("unknown error");break;}}

其中position对象包含很多数据 error代码及选项可以查看文档

● 构建HTML5离线应用

需要提供一个cache manifest文件，理出所有需要在离线状态下使用的资源

例如

CACHE MANIFEST #这是注释images/sound-icon.pngimages/background.pngclock.html clock.css clock.js  NETWORK: test.cgiCACHE: style/default.cssFALLBACK: /files/projects /projects

在html标签中声明 <html manifest="clock.manifest">

HTML5离线应用更新缓存机制

分为手动更新和自动更新2种

自动更新：

在cache manifest文件本身发生变化时更新缓存资源文件发生变化不会触发更新

手动更新：

使用window.applicationCache

if (window.applicationCache.status == window.applicationCache.UPDATEREADY) ｛window.applicationCache.update();｝

在线状态检测

HTML5 提供了两种检测是否在线的方式：navigator.online（true/false） 和 online/offline事件。

在Android中构建离线应用

//开启应用程序缓存webSettingssetAppCacheEnabled(true);String dir = this.getApplicationContext().getDir("cache", Context.MODE_PRIVATE).getPath();//设置应用缓存的路径webSettings.setAppCachePath(dir);//设置缓存的模式webSettings.setCacheMode(WebSettings.LOAD_DEFAULT);//设置应用缓存的最大尺寸webSettings.setAppCacheMaxSize(1024*1024*8);//扩充缓存的容量public void onReachedMaxAppCacheSize(long spaceNeeded,long totalUsedQuota, WebStorage.QuotaUpdater quotaUpdater) {quotaUpdater.updateQuota(spaceNeeded * 2);}

（完）还有一个尾巴关于canvas绘图的不如之前记录的来的详细就不做介绍了

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