Android 7.1 WebView 实现方式选择

Chrome方法已废弃

后续测试, Chrome已经无法使用此方法, 也找不到当初对应测试的版本
Google Chrome app is no longer the WebView provider in Android 10

后续采用Google WebView, 改法参照下文

<webviewproviders>
    
    <webviewprovider description="Android WebView" packageName="com.android.webview" availableByDefault="true">
    webviewprovider>
    <webviewprovider description="Google WebView" packageName="com.google.android.webview" availableByDefault="false">
    webviewprovider>
webviewproviders>

平台

RK3288 + Android 7.1

说明

选项位置: 设置 > 开发者选项 > WebView实现

1.在Pixel上, 可以显示两个选项: Android System WebView 和 Chrome
尝试把Chorme 禁用后, 选项中, 仅剩下Android System WebView.

2.尝试在RK3288主板上安装Chrome, 并增加相应配置

	<webviewprovider description="Chrome WebView X" packageName="com.android.chrome" availableByDefault="true">
    webviewprovider>

编译烧录后, 可以看到, 新增了Chrome WebView X, 测试选择不同的实现方法, 均可正常使用.

为确认装入Chrome后可以生效, 已删除源码自带/system/app/webview

相关源码

|-- packages/apps/Settings/src/com/android/settings/DevelopmentSettings.java

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        mWindowManager = IWindowManager.Stub.asInterface(ServiceManager.getService("window"));
        mBackupManager = IBackupManager.Stub.asInterface(
                ServiceManager.getService(Context.BACKUP_SERVICE));
//获取 IWebViewUpdateService
        mWebViewUpdateService  =
            IWebViewUpdateService.Stub.asInterface(ServiceManager.getService("webviewupdate"));
			...
	}

	
    private void updateWebViewProviderOptions() {
        try {
// 从IWebViewUpdateService中获取可用的WebView 包名, 并填充列表.
            WebViewProviderInfo[] providers = mWebViewUpdateService.getValidWebViewPackages();
            if (providers == null) {
                Log.e(TAG, "No WebView providers available");
                return;
            }
            ArrayList<String> options = new ArrayList<String>();
            ArrayList<String> values = new ArrayList<String>();
            for(int n = 0; n < providers.length; n++) {
                if (Utils.isPackageEnabled(getActivity(), providers[n].packageName)) {
                    options.add(providers[n].description);
                    values.add(providers[n].packageName);
                }
            }
            mWebViewProvider.setEntries(options.toArray(new String[options.size()]));
            mWebViewProvider.setEntryValues(values.toArray(new String[values.size()]));

            String value = mWebViewUpdateService.getCurrentWebViewPackageName();
            if (value == null) {
                value = "";
            }

            for (int i = 0; i < values.size(); i++) {
                if (value.contentEquals(values.get(i))) {
                    mWebViewProvider.setValueIndex(i);
                    return;
                }
            }
        } catch(RemoteException e) {
        }
    }

|-- frameworks/base/services/core/java/com/android/server/webkit/WebViewUpdateServiceImpl.java

	public WebViewUpdateServiceImpl(Context context, SystemInterface systemInterface) {
        mContext = context;
        mSystemInterface = systemInterface;
        mWebViewUpdater = new WebViewUpdater(mContext, mSystemInterface);
    }

    WebViewProviderInfo[] getValidWebViewPackages() {
        return mWebViewUpdater.getValidAndInstalledWebViewPackages();
    }
    private static class WebViewUpdater {
        private ProviderAndPackageInfo[] getValidWebViewPackagesAndInfos(boolean onlyInstalled) {
            WebViewProviderInfo[] allProviders = mSystemInterface.getWebViewPackages();
            List<ProviderAndPackageInfo> providers = new ArrayList<>();
            for(int n = 0; n < allProviders.length; n++) {
                try {
                    PackageInfo packageInfo =
                        mSystemInterface.getPackageInfoForProvider(allProviders[n]);
                    if ((!onlyInstalled || isInstalledPackage(packageInfo))
                            && isValidProvider(allProviders[n], packageInfo)) {
                        providers.add(new ProviderAndPackageInfo(allProviders[n], packageInfo));
                    }
                } catch (NameNotFoundException e) {
                    // Don't add non-existent packages
                }
            }
            return providers.toArray(new ProviderAndPackageInfo[providers.size()]);
        }
	}

|-- frameworks/base/services/core/java/com/android/server/webkit/WebViewUpdateService.java

    public WebViewUpdateService(Context context) {
        super(context);
        mImpl = new WebViewUpdateServiceImpl(context, SystemImpl.getInstance());
    }

|-- frameworks/base/services/core/java/com/android/server/webkit/SystemInterface.java

public class SystemImpl implements SystemInterface {
	...
    private final WebViewProviderInfo[] mWebViewProviderPackages;

    // Initialization-on-demand holder idiom for getting the WebView provider packages once and
    // for all in a thread-safe manner.
    private static class LazyHolder {
        private static final SystemImpl INSTANCE = new SystemImpl();
    }

    public static SystemImpl getInstance() {
        return LazyHolder.INSTANCE;
    }

    private SystemImpl() {
        int numFallbackPackages = 0;
        int numAvailableByDefaultPackages = 0;
        int numAvByDefaultAndNotFallback = 0;
        XmlResourceParser parser = null;
        List<WebViewProviderInfo> webViewProviders = new ArrayList<WebViewProviderInfo>();
        try {
//读取系统配置文件config_webview_packages.xml中的值:
            parser = AppGlobals.getInitialApplication().getResources().getXml(
                    com.android.internal.R.xml.config_webview_packages);
            XmlUtils.beginDocument(parser, TAG_START);
            while(true) {
                XmlUtils.nextElement(parser);
                String element = parser.getName();
                if (element == null) {
                    break;
                }
                if (element.equals(TAG_WEBVIEW_PROVIDER)) {
                    String packageName = parser.getAttributeValue(null, TAG_PACKAGE_NAME);
                    if (packageName == null) {
                        throw new AndroidRuntimeException(
                                "WebView provider in framework resources missing package name");
                    }
                    String description = parser.getAttributeValue(null, TAG_DESCRIPTION);
                    if (description == null) {
                        throw new AndroidRuntimeException(
                                "WebView provider in framework resources missing description");
                    }
                    boolean availableByDefault = "true".equals(
                            parser.getAttributeValue(null, TAG_AVAILABILITY));
                    boolean isFallback = "true".equals(
                            parser.getAttributeValue(null, TAG_FALLBACK));
                    WebViewProviderInfo currentProvider = new WebViewProviderInfo(
                            packageName, description, availableByDefault, isFallback,
                            readSignatures(parser));
                    if (currentProvider.isFallback) {
                        numFallbackPackages++;
                        if (!currentProvider.availableByDefault) {
                            throw new AndroidRuntimeException(
                                    "Each WebView fallback package must be available by default.");
                        }
                        if (numFallbackPackages > 1) {
                            throw new AndroidRuntimeException(
                                    "There can be at most one WebView fallback package.");
                        }
                    }
                    if (currentProvider.availableByDefault) {
                        numAvailableByDefaultPackages++;
                        if (!currentProvider.isFallback) {
                            numAvByDefaultAndNotFallback++;
                        }
                    }
                    webViewProviders.add(currentProvider);
                }
                else {
                    Log.e(TAG, "Found an element that is not a WebView provider");
                }
            }
        } catch (XmlPullParserException | IOException e) {
            throw new AndroidRuntimeException("Error when parsing WebView config " + e);
        } finally {
            if (parser != null) parser.close();
        }
        if (numAvailableByDefaultPackages == 0) {
            throw new AndroidRuntimeException("There must be at least one WebView package "
                    + "that is available by default");
        }
        if (numAvByDefaultAndNotFallback == 0) {
            throw new AndroidRuntimeException("There must be at least one WebView package "
                    + "that is available by default and not a fallback");
        }
        mWebViewProviderPackages =
                webViewProviders.toArray(new WebViewProviderInfo[webViewProviders.size()]);
    }

|-- frameworks/base/core/res/res/xml/config_webview_packages.xml

<webviewproviders>
    
    <webviewprovider description="Android WebView" packageName="com.android.webview" availableByDefault="true">
    webviewprovider>
webviewproviders>

扩展

|-- frameworks/base/core/java/android/webkit/WebView.java

    private WebViewProvider mProvider;
    protected WebView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes,
            Map<String, Object> javaScriptInterfaces, boolean privateBrowsing) {
        super(context, attrs, defStyleAttr, defStyleRes);
        if (context == null) {
            throw new IllegalArgumentException("Invalid context argument");
        }
        sEnforceThreadChecking = context.getApplicationInfo().targetSdkVersion >=
                Build.VERSION_CODES.JELLY_BEAN_MR2;
        checkThread();

        ensureProviderCreated();
        mProvider.init(javaScriptInterfaces, privateBrowsing);
        // Post condition of creating a webview is the CookieSyncManager.getInstance() is allowed.
        CookieSyncManager.setGetInstanceIsAllowed();
    }

    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().
            mProvider = getFactory().createWebView(this, new PrivateAccess());
        }
    }

	private static synchronized WebViewFactoryProvider getFactory() {
        return WebViewFactory.getProvider();
    }
//加载网址
    public void loadUrl(String url, Map<String, String> additionalHttpHeaders) {
        checkThread();
        mProvider.loadUrl(url, additionalHttpHeaders);
    }

|-- frameworks/base/core/java/android/webkit/WebViewFactory.java

    static WebViewFactoryProvider getProvider() {
        synchronized (sProviderLock) {
			...
            try {
                Class<WebViewFactoryProvider> providerClass = getProviderClass();
                try {
                    sProviderInstance = providerClass.getConstructor(WebViewDelegate.class)
                            .newInstance(new WebViewDelegate());
                    if (DEBUG) Log.v(LOGTAG, "Loaded provider: " + sProviderInstance);
                    return sProviderInstance;
                } catch (Exception e) {
					...
                }
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);
                StrictMode.setThreadPolicy(oldPolicy);
            }
        }
    }

	private static Class<WebViewFactoryProvider> getProviderClass() {
        Context webViewContext = null;
        Application initialApplication = AppGlobals.getInitialApplication();

        try {
            
            try {
                webViewContext = getWebViewContextAndSetProvider();
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);
            }
            Log.i(LOGTAG, "Loading " + sPackageInfo.packageName + " version " +
                    sPackageInfo.versionName + " (code " + sPackageInfo.versionCode + ")");

            Trace.traceBegin(Trace.TRACE_TAG_WEBVIEW, "WebViewFactory.getChromiumProviderClass()");
            try {
                initialApplication.getAssets().addAssetPathAsSharedLibrary(
                        webViewContext.getApplicationInfo().sourceDir);
                ClassLoader clazzLoader = webViewContext.getClassLoader();

                Trace.traceBegin(Trace.TRACE_TAG_WEBVIEW, "WebViewFactory.loadNativeLibrary()");
                loadNativeLibrary(clazzLoader);
                Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);

                Trace.traceBegin(Trace.TRACE_TAG_WEBVIEW, "Class.forName()");
                try {
                    return (Class<WebViewFactoryProvider>) Class.forName(CHROMIUM_WEBVIEW_FACTORY,
                            true, clazzLoader);
                } finally {
                    Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);
                }
            } catch (ClassNotFoundException e) {
                Log.e(LOGTAG, "error loading provider", e);
                throw new AndroidRuntimeException(e);
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);
            }
        } catch (MissingWebViewPackageException e) {
            // If the package doesn't exist, then try loading the null WebView instead.
            // If that succeeds, then this is a device without WebView support; if it fails then
            // swallow the failure, complain that the real WebView is missing and rethrow the
            // original exception.
            try {
                return (Class<WebViewFactoryProvider>) Class.forName(NULL_WEBVIEW_FACTORY);
            } catch (ClassNotFoundException e2) {
                // Ignore.
            }
            Log.e(LOGTAG, "Chromium WebView package does not exist", e);
            throw new AndroidRuntimeException(e);
        }
    }

    private static Context getWebViewContextAndSetProvider() {
        Application initialApplication = AppGlobals.getInitialApplication();
        try {
            WebViewProviderResponse response = null;
            try {
//IWebViewUpdateService 
                response = getUpdateService().waitForAndGetProvider();
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);
            }
			...
            try {
                ActivityManagerNative.getDefault().addPackageDependency(
                        response.packageInfo.packageName);
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);
            }
            // Fetch package info and verify it against the chosen package
            PackageInfo newPackageInfo = null;
            try {
                newPackageInfo = initialApplication.getPackageManager().getPackageInfo(
                    response.packageInfo.packageName,
                    PackageManager.GET_SHARED_LIBRARY_FILES
                    | PackageManager.MATCH_DEBUG_TRIAGED_MISSING
                    // Make sure that we fetch the current provider even if its not
                    // installed for the current user
                    | PackageManager.MATCH_UNINSTALLED_PACKAGES
                    // Fetch signatures for verification
                    | PackageManager.GET_SIGNATURES
                    // Get meta-data for meta data flag verification
                    | PackageManager.GET_META_DATA);
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);
            }

            // Validate the newly fetched package info, throws MissingWebViewPackageException on
            // failure
            verifyPackageInfo(response.packageInfo, newPackageInfo);

            Trace.traceBegin(Trace.TRACE_TAG_WEBVIEW,
                    "initialApplication.createApplicationContext");
            try {
                // Construct an app context to load the Java code into the current app.
                Context webViewContext = initialApplication.createApplicationContext(
                        newPackageInfo.applicationInfo,
                        Context.CONTEXT_INCLUDE_CODE | Context.CONTEXT_IGNORE_SECURITY);
                sPackageInfo = newPackageInfo;
                return webViewContext;
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_WEBVIEW);
            }
        } catch (RemoteException | PackageManager.NameNotFoundException e) {
            throw new MissingWebViewPackageException("Failed to load WebView provider: " + e);
        }
    }


    /** @hide */
    public static IWebViewUpdateService getUpdateService() {
        return IWebViewUpdateService.Stub.asInterface(
                ServiceManager.getService(WEBVIEW_UPDATE_SERVICE_NAME));
    }