拦截在webview上加载图像资源

Question

我想拦截HTTP请求并从Web应用程序的资产目录加载给定资源。我认为从assets目录加载资源比通过网络加载资源更好。

我想加载像图像，字体，一些HTML的资源，但我很困惑。我使用AssetManager访问了assets目录中的文件。我尝试了一些代码，我的应用程序崩溃了。

我不确定问题是什么。这是我试过的代码：

public class WebViewClientImpl extends WebViewClient {

    private Activity activity = null;

    public WebViewClientImpl(Activity activity) {
        this.activity = activity;
    }

    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {


        Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
        activity.startActivity(intent);
        return true;
    }


    @Override
    public WebResourceResponse shouldInterceptRequest(WebView view, String url) {

        if(url.startsWith("http://google.com/images/logo.png")){
            return loadFromAssets(url, "images/logo.png", "image/png", "");
        }

        return null;
    }

    private WebResourceResponse loadFromAssets( String url,
        String assetPath, String mimeType, String encoding){

        AssetManager assetManager = this.activity.getAssets();
        InputStream input = null;
        try {
            Log.d(Constants.LOG_TAG, "Loading from assets: " + assetPath);


            input = assetManager.open("/images/logo.png");
            WebResourceResponse response =
                    new WebResourceResponse(mimeType, encoding, input);

            return response;
        } catch (IOException e) {
            Log.e("WEB-APP", "Error loading " + assetPath + " from assets: " +
                e.getMessage(), e);
        }
        return null;
    }
}