以下是我的MainActivity类代码
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setContentView(R.layout.activity_main);
WebView webView = new WebView(this);
//add the JavaScriptInterface so that JavaScript is able to use LocalStorageJavaScriptInterface's methods when calling "LocalStorage"
webView.addJavascriptInterface(new LocalStorageJavaScriptInterface(this), "LocalStorage");
WebSettings settings = webView.getSettings();
// TO enable JS
settings.setJavaScriptEnabled(true);
// To enable Localstorage
settings.setDomStorageEnabled(true);
//those two lines seem necessary to keep data that were stored even if the app was killed.
settings.setDatabaseEnabled(true);
/*
webView.setWebChromeClient(new WebChromeClient() {
public void onExceededDatabaseQuota(String url, String databaseIdentifier, long currentQuota, long estimatedSize, long totalUsedQuota, WebStorage.QuotaUpdater quotaUpdater) {
quotaUpdater.updateQuota(5 * 1024 * 1024);
}
});*/
//load HTML File in webview
webView.loadUrl("file:///android_asset/main.html");
setContentView(webView);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
// getMenuInflater().inflate(R.menu.main, menu);
return true;
}
/**
* This class is used as a substitution of the local storage in Android webviews
*
* @author Diane
*/
public class LocalStorageJavaScriptInterface {
private Context mContext;
private LocalStorage localStorageDBHelper;
private SQLiteDatabase database;
LocalStorageJavaScriptInterface(Context c) {
mContext = c;
localStorageDBHelper = LocalStorage.getInstance(mContext);
}
/**
* This method allows to get an item for the given key
* @param key : the key to look for in the local storage
* @return the item having the given key
*/
@JavascriptInterface
public String getItem(String key)
{
String value = null;
if(key != null)
{
database = localStorageDBHelper.getReadableDatabase();
Cursor cursor = database.query(LocalStorage.LOCALSTORAGE_TABLE_NAME,
null,
LocalStorage.LOCALSTORAGE_ID + " = ?",
new String [] {key},null, null, null);
if(cursor.moveToFirst())
{
value = cursor.getString(1);
}
cursor.close();
database.close();
}
return value;
}
/**
* set the value for the given key, or create the set of datas if the key does not exist already.
* @param key
* @param value
*/
@JavascriptInterface
public void setItem(String key,String value)
{
if(key != null && value != null)
{
String oldValue = getItem(key);
database = localStorageDBHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(LocalStorage.LOCALSTORAGE_ID, key);
values.put(LocalStorage.LOCALSTORAGE_VALUE, value);
if(oldValue != null)
{
database.update(LocalStorage.LOCALSTORAGE_TABLE_NAME, values, LocalStorage.LOCALSTORAGE_ID + " = " + key, null);
}
else
{
database.insert(LocalStorage.LOCALSTORAGE_TABLE_NAME, null, values);
}
database.close();
}
}
/**
* removes the item corresponding to the given key
* @param key
*/
@JavascriptInterface
public void removeItem(String key)
{
if(key != null)
{
database = localStorageDBHelper.getWritableDatabase();
database.delete(LocalStorage.LOCALSTORAGE_TABLE_NAME, LocalStorage.LOCALSTORAGE_ID + " = " + key, null);
database.close();
}
}
/**
* clears all the local storage.
*/
@JavascriptInterface
public void clear()
{
database = localStorageDBHelper.getWritableDatabase();
database.delete(LocalStorage.LOCALSTORAGE_TABLE_NAME, null, null);
database.close();
}
}
}
基本上我使用的是AndroidLocalstorage插件https://github.com/didimoo/AndroidLocalStorage，它基本上用作localStorage的后备选项。
以下是我的AndroidMainifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android_playlist"
android:versionCode="1"
android:versionName="1.0" >
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.android_playlist.MainActivity"
android:label="@string/app_name"
android:screenOrientation="portrait"
>
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
基本上问题是javascriptInterface对我不起作用。
我在我的js文件中添加了以下代码行，用于加载
try{
//we replace default localStorage with our Android Database one
window.localStorage=LocalStorage;
}catch(e){
//LocalStorage class was not found. be sure to add it to the webview
console.log("error", e);
console.log("LocalStorage ERROR : can't find android class LocalStorage. switching to raw localStorage")
}
但是当我检查浏览器控制台时，我总是得到console.log，它位于catch。
有人可以说明我的代码有什么问题以及为什么Javascript界面对我不起作用。
以下是我在控制台中收到的错误
{stack: (...), message: "LocalStorage is not defined"}
我忘了提到的一件事是我在笔记本电脑浏览器上测试这个，只需使用file：protocol加载HTML文件即可。 这有关系吗？
答案 0 :(得分：0)
window.localStorage=LocalStorage;
上面的代码表示window对象具有名为localStorage的属性，并且您尝试将其值设置为LocalStorage。由android创建的LocalStorage对象，可以保证但最终localStorage属性为窗口对象没有保证。因此引发异常。希望这个ans会帮助你。
答案 1 :(得分：0)
我终于在我的代码中发现了这个问题，在AndroidMainifest XML中，我的targetSDK版本是18。 它应该是19，因为我没有在MainActivity中设置数据库路径和数据库大小。
原始代码
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="18" />
更改了代码
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="19" />