在Android中使用HTML5本地存储，地理位置，离线应用

● 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storage
 localStorage.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 initialized
         var 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 results
     for (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*5B
     document.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.png
 images/background.png
 clock.html
 clock.css
 clock.js

 NETWORK:
 test.cgi

 CACHE:
 style/default.css

 FALLBACK:
 /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);
 }

 

原文链接： http://johncookie.iteye.com/blog/1182459