android WebView中js的alert()失效

WebView的设置代码

wv = (WebView) findViewById(R.id.webView1);
wv.getSettings().setJavaScriptEnabled(true);//支持js
wv.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);//允许js弹出窗口
wv.loadUrl("http://www.google.com");
wv.setWebViewClient(new WebViewClient()); 

还需要做如下设置，通过这样的转换为android内部的控件的

webView.setWebChromeClient(new WebChromeClient() {
    @Override
    public boolean onJsAlert(WebView view, String url, String message, final JsResult result) {
        AlertDialog.Builder b2 = new AlertDialog.Builder(this)
                .setTitle(R.string.title).setMessage(message)
                .setPositiveButton("ok",
                        new AlertDialog.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog,
                                    int which) {
                                result.confirm();
                                // MyWebView.this.finish();
                            }
                        });

        b2.setCancelable(false);
        b2.create();
        b2.show();
        return true;
    }
}