使用WebView.load(data,"text/html", "utf-8")加载显示乱码问题分析

来源：互联网发布：js中的radio length 编辑：程序博客网时间：2024/06/06 01:36

本文引用的源码为android 4.4.4版本

请尊重博主劳动成果，转载请标明原文链接。

使用WebView的load(data,”text/html”, “utf-8”)加载含有中文的网页时，页面上的中文字符显示为乱码。网页没有问题，使用PC浏览器查看显示正常。
load方法源码

    public void loadData(String data, String mimeType, String encoding) {        checkThread();        if (DebugFlags.TRACE_API) Log.d(LOGTAG, "loadData");        mProvider.loadData(data, mimeType, encoding);    }

真正执行加载网页操作的是mProvider，而它是什么类型的对象呢?

    private WebViewProvider mProvider;    ...    private void ensureProviderCreated() {        checkThread();        if (mProvider == null) {            // As this can get called during the base class constructor chain, pass the minimum            // number of dependencies here; the rest are deferred to init().            //调用方法getFactory获取WebViewFactoryProvider对象，然后使用该对象的createWebView方法创建。            mProvider = getFactory().createWebView(this, new PrivateAccess());        }    }    //生成WebViewFactoryProvider方法    private static synchronized WebViewFactoryProvider getFactory() {        return WebViewFactory.getProvider();    }

WebViewFactoryProvider是一个接口，那么就查看WebViewFactory类。WebViewFactory的getProvider方法调用getFactoryClass()获取到字节码，然后通过反射创建了WebViewChromiumFactoryProvider对象。

public final class WebViewFactory {    //类路径    private static final String CHROMIUM_WEBVIEW_FACTORY =            "com.android.webview.chromium.WebViewChromiumFactoryProvider";    ...    private static class Preloader {        static WebViewFactoryProvider sPreloadedProvider;        //静态代码块，字节码加载进来便创建了WebViewFactoryProvider对象        static {            try {                //通过反射创建对象                sPreloadedProvider = getFactoryClass().newInstance();            } catch (Exception e) {                Log.w(LOGTAG, "error preloading provider", e);            }        }    }    …    static WebViewFactoryProvider getProvider() {        synchronized (sProviderLock) {            //存在对象，则返回            if (sProviderInstance != null) return sProviderInstance;            Class<WebViewFactoryProvider> providerClass;            try {                //获取字节码对象                providerClass = getFactoryClass();            } catch (ClassNotFoundException e) {                Log.e(LOGTAG, "error loading provider", e);                throw new AndroidRuntimeException(e);            }            //对象存在且字节码相同            if (Preloader.sPreloadedProvider != null &&                Preloader.sPreloadedProvider.getClass() == providerClass) {                //赋值                sProviderInstance = Preloader.sPreloadedProvider;                return sProviderInstance;            }            StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();            try {                //通过字节码创建对象                sProviderInstance = providerClass.newInstance();                if (DEBUG) Log.v(LOGTAG, "Loaded provider: " + sProviderInstance);                return sProviderInstance;            } catch (Exception e) {                Log.e(LOGTAG, "error instantiating provider", e);                throw new AndroidRuntimeException(e);            } finally {                StrictMode.setThreadPolicy(oldPolicy);            }        }    }    //获取字节码的方法    private static Class<WebViewFactoryProvider> getFactoryClass() throws ClassNotFoundException {        return (Class<WebViewFactoryProvider>) Class.forName(CHROMIUM_WEBVIEW_FACTORY);    }}

WebViewFactory被加载进来，便创建WebViewChromiumFactoryProvider对象。源码在frameworks/webview/chromium/java/com/android/webview/chromium/WebViewChromiumFactoryProvider.java。
那就看看WebViewChromiumFactoryProvider.loadData方法代码：

public WebViewProvider createWebView(WebView webView, WebView.PrivateAccess privateAccess) {        WebViewChromium wvc = new WebViewChromium(this, webView, privateAccess);        synchronized (mLock) {            if (mWebViewsToStart != null) {                mWebViewsToStart.add(new WeakReference<WebViewChromium>(wvc));            }        }        ResourceProvider.registerResources(webView.getContext());        return wvc;    }

该方法创建了WebViewChromium对象，并返回了该对象。在ensureProviderCreated方法中创建了该对象，并将其赋值给WebView中的mProvider属性。也就是说，在WebView中网页相关的操作都是WebViewChromium真正在执行。

WebViewChromium的源码在：frameworks/webview/chromium/java/com/android/webview/chromium/WebViewChromium.java。
看看WebViewChromium的loadData方法：

public void loadData(String data, String mimeType, String encoding) {        loadUrlOnUiThread(LoadUrlParams.createLoadDataParams(                fixupData(data), fixupMimeType(mimeType), isBase64Encoded(encoding)));    }

使用LoadUrlParams类的静态方法createLoadDataParams对传入的参数做了封装。
继续查看LoadUrlParams，源码在：external/chromium_org/content/public/android/java/src/org/chromium/content/browser/LoadUrlParams.java。

    public static LoadUrlParams createLoadDataParams(        String data, String mimeType, boolean isBase64Encoded) {        return createLoadDataParams(data, mimeType, isBase64Encoded, null);    }    public static LoadUrlParams createLoadDataParams(            String data, String mimeType, boolean isBase64Encoded, String charset) {        StringBuilder dataUrl = new StringBuilder("data:");        //类型        dataUrl.append(mimeType);        //编码类型        if (charset != null && !charset.isEmpty()) {            dataUrl.append(";charset=" + charset);        }        //是否为base64编码        if (isBase64Encoded) {            dataUrl.append(";base64");        }        //分割符        dataUrl.append(",");        //网页        dataUrl.append(data);        LoadUrlParams params = new LoadUrlParams(dataUrl.toString());        params.setLoadType(LoadUrlParams.LOAD_TYPE_DATA);        params.setTransitionType(PageTransitionTypes.PAGE_TRANSITION_TYPED);        return params;    }

由以上源码可知：WebView的loadData方法传入的参数encoding并没有被封装到LoadUrlParams中，所以导致中文显示乱码。
调用createLoadDataParams(
String data, String mimeType, boolean isBase64Encoded, String charset)方法肯定是能够将编码类型封装到LoadUrlParams。往回看看，哪里调用了该方法。WebViewChromium中的方法loadDataWithBaseURL(String baseUrl, String data, String mimeType, String encoding, String historyUrl)有调用到。

    public void loadDataWithBaseURL(String baseUrl, String data, String mimeType, String encoding,            String historyUrl) {        data = fixupData(data);        mimeType = fixupMimeType(mimeType);        LoadUrlParams loadUrlParams;        baseUrl = fixupBase(baseUrl);        historyUrl = fixupHistory(historyUrl);        if (baseUrl.startsWith("data:")) {            // For backwards compatibility with WebViewClassic, we use the value of |encoding|            // as the charset, as long as it's not "base64".            boolean isBase64 = isBase64Encoded(encoding);            //如果是base64编码：传入的编码类型为null；不是则传入设置的编码类型            loadUrlParams = LoadUrlParams.createLoadDataParamsWithBaseUrl(                    data, mimeType, isBase64, baseUrl, historyUrl, isBase64 ? null : encoding);        } else {            // When loading data with a non-data: base URL, the classic WebView would effectively            // "dump" that string of data into the WebView without going through regular URL            // loading steps such as decoding URL-encoded entities. We achieve this same behavior by            // base64 encoding the data that is passed here and then loading that as a data: URL.            try {                //设置为utf-8编码                loadUrlParams = LoadUrlParams.createLoadDataParamsWithBaseUrl(                        Base64.encodeToString(data.getBytes("utf-8"), Base64.DEFAULT), mimeType,                        true, baseUrl, historyUrl, "utf-8");            } catch (java.io.UnsupportedEncodingException e) {                Log.wtf(TAG, "Unable to load data string " + data, e);                return;            }        }        loadUrlOnUiThread(loadUrlParams);    }

WebView中的loadDataWithBaseURL(String baseUrl, String data, String mimeType, String encoding, String historyUrl) 方法调用了该方法，所以使用该方法能够解决乱码问题。
使用这种方式便可以解决中文乱码。

loadDataWithBaseURL(null, "html", "text/html", "UTF-8", null);

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