Android 4.4 Browser set most visited at home page 實現

     本文只分析當主頁爲Most Visited時的實現。

Tab.java中實現了WebViewClient的shouldInterceptRequest接口，該函數爲回調函數，最終由native代碼調用。調用過程爲

shouldInterceptRequest() CallbackProxy.java <- shouldInterceptRequest() BrowserFrame.java <- shouldInterceptRequest() WebCoreFrameBridge.cpp

Tab.java

public WebResourceResponse shouldInterceptRequest(WebView view,
        String url) {
    WebResourceResponse res = HomeProvider.shouldInterceptRequest(
            mContext, url);
    return res;
}

HomeProvider

       home page中的數據是從數據庫中讀取的，HomeProvider提供了數據。

HomeProvider.java

public static final String MOST_VISITED = "content://" + "com.android.browser.home" + "/index";  //android4.3

public static final String MOST_VISITED = "content://" + "com.android.browser.home" + "/";   //android 4.4

重要區別。

public static WebResourceResponse shouldInterceptRequest(Context context,
        String url) {
    try {
        boolean useMostVisited = BrowserSettings.getInstance().useMostVisitedHomepage();
        if (useMostVisited && url.startsWith("content://")) {
            Uri uri = Uri.parse(url);
            if (AUTHORITY.equals(uri.getAuthority())) {
                InputStream ins = context.getContentResolver()
                        .openInputStream(uri);
                return new WebResourceResponse("text/html", "utf-8", ins);
            }
        }
    } catch (Exception e) {}
    return null;
}

 

@Override

public ParcelFileDescriptor openFile(Uri uri, String mode) {
    try {
        ParcelFileDescriptor[] pipes = ParcelFileDescriptor.createPipe();
        final ParcelFileDescriptor write = pipes[1];
        AssetFileDescriptor afd = new AssetFileDescriptor(write, 0, -1);
        new RequestHandler(getContext(), uri, afd.createOutputStream()).start();
        return pipes[0];
    } catch (IOException e) {
        Log.e(TAG, "Failed to handle request: " + uri, e);
        return null;
    }
}

        pipes[0]即爲shouldInterceptRequest中的ins。

WebResourceResponse

       先來看WebResourceResponse。

        WebResourceResponse位於framework中，它繼承了StreamLoader ，具體就不在分析了，在這裏它的作用就是把文件作爲一個流讀出來模擬HTTP協議。

RequestHandler

       數據是由RequestHandler寫入HomeProvider讀出的。

public class RequestHandler extends Thread {

    private static final String TAG = "RequestHandler";
    private static final int INDEX = 1;
    private static final int RESOURCE = 2;
    private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

    Uri mUri;
    Context mContext;
    OutputStream mOutput;

    static {
        sUriMatcher.addURI(HomeProvider.AUTHORITY, "/", INDEX);  //android 4.4
        
 sUriMatcher.addURI(HomeProvider.AUTHORITY, "index", INDEX);  //android 4.3
      //就是這個匹配字符串引起在android 4.4 中設置最長訪問 的是主頁。報出的ERR_ACCESS_DENIED 錯誤 同時還需要在BrowserSettings裏面設置可以讀取content的權限。android 4.4 默認把它給關閉了
        sUriMatcher.addURI(HomeProvider.AUTHORITY, "res/*/*", RESOURCE);
    }

    public RequestHandler(Context context, Uri uri, OutputStream out) {
        mUri = uri;
        mContext = context.getApplicationContext();
        mOutput = out;
    }

    @Override
    public void run() {
        super.run();
        try {
            doHandleRequest();
        } catch (Exception e) {
            Log.e(TAG, "Failed to handle request: " + mUri, e);
        } finally {
            cleanup();
        }
    }

    void doHandleRequest() throws IOException {
        int match = sUriMatcher.match(mUri);
        switch (match) {
        case INDEX:
            writeTemplatedIndex();
            break;
        case RESOURCE:
            writeResource(getUriResourcePath());
            break;
        }
    }

        訪問主頁時執行writeTemplatedIndex()

void writeTemplatedIndex() throws IOException {
    Template t = Template.getCachedTemplate(mContext, R.raw.most_visited);
    Cursor cursor = mContext.getContentResolver().query(Browser.BOOKMARKS_URI,
            new String[] { "DISTINCT url", "title", "thumbnail" },
            "(visits > 0 OR bookmark = 1) AND url NOT LIKE 'content:%' AND thumbnail IS NOT NULL", null, "visits DESC LIMIT 12");

    t.assignLoop("most_visited", new Template.CursorListEntityWrapper(cursor) {
        @Override
        public void writeValue(OutputStream stream, String key) throws IOException {
            Cursor cursor = getCursor();
            if (key.equals("url")) {
                stream.write(htmlEncode(cursor.getString(0)));
            } else if (key.equals("title")) {
                stream.write(htmlEncode(cursor.getString(1)));
            } else if (key.equals("thumbnail")) {
                stream.write("data:image/png;base64,".getBytes());
                byte[] thumb = cursor.getBlob(2);
                stream.write(Base64.encode(thumb, Base64.DEFAULT));
            }
        }
    });
    t.write(mOutput);
}

        writeTemplatedIndex()中首先從database中讀取數據，

Template t = Template.getCachedTemplate(mContext, R.raw.most_visited);

        是從文件中讀出HTML文件並進行解析writeValue則將從數據庫中讀出的數據加入解析後的數據中。

最後t.write(mOutput)則將數據寫入pipes[1]中。

在BrowserSettings裏面的syncStaticSettings 設置 settings.setAllowContentAccess(true);避免出現ERR_ACCESS_DENIED