Show a progress bar on a child tab until the WebView loads

问题

In an Android app I am using a TabView and one of the tabs shows a WebView. But the page is blank until the web page loads. How would one show a progress bar until the page loads? It cannot be in the title bar because that is hidden by the tab host.

回答1:

I use a ProgressBar for this. With a layout like this:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout [...]>

  <WebView 
        android:id="@+id/WebView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

  <ProgressBar 
       android:id="@+id/ProgressBar"
       android:layout_centerInParent="true"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       style="?android:attr/progressBarStyleLarge"
       android:visibility="gone"/>
</RelativeLayout>

I hide and show the progress indicator using:

 WebView webView = (WebView) findViewById(R.id.WebView);

 final ProgressBar progess = (ProgressBar) findViewById(R.id.ProgressBar);

  webView.setWebViewClient(new WebViewClient() {
  public void onPageStarted(WebView view, String url, Bitmap favicon) {
    progess.setVisibility(View.VISIBLE);
  }

  public void onPageFinished(WebView view, String url) {
    progess.setVisibility(View.GONE);
  }
}

回答2:

There's a really good tutorial on the Android Developers website for that. It shows how to create the 'spinning wheel' progress dialog used throughout Android programs, and even some basics on how to handle loading in a separate thread to prevent your application from freezing while loading.

回答3:

If your question is "how do I find out when the page is loaded?", then:

Create a custom subclass of WebViewClient, overriding onPageFinished()

Attach an instance of your WebViewClient subclass to your WebView via setWebViewClient()

Set up the indefinite progress indicator (bar, dialog, RotateAnimation, etc.)

progressDialog = ProgressDialog.show(this, "", getText(R.string.progressDialogText), true);

before calling loadUrl() on the WebView

Have onPageFinished() get rid of the progress indicator (progressDialog.dismiss())

回答4:

After initializing your view just call this method

startWebView(web_view,"Your Url"); Here web_view is your initialized WebView Object. The startWebView() is given below:

    private void startWebView(WebView webView,String url) {
 webView.setWebViewClient(new WebViewClient() {
            ProgressDialog progressDialog;

            public boolean shouldOverrideUrlLoading(WebView view, String url) {
                view.loadUrl(url);
                return false;
            }

            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                super.onPageStarted(view, url, favicon);
            }

            public void onLoadResource (WebView view, String url) {

                    if (progressDialog == null) {
                        progressDialog = new ProgressDialog(SponceredDetailsActivity.this);
                        progressDialog.setMessage("Loading...");
                        progressDialog.show();
                    }

            }
            public void onPageFinished(WebView view, String url) {
                try{
                    if (progressDialog.isShowing()) {
                        progressDialog.dismiss();
                        progressDialog = null;
                    }

                }catch(Exception exception){
                    exception.printStackTrace();
                }
            }

        });

        webView.getSettings().setJavaScriptEnabled(true);
        webView.loadUrl(url);
    }

Sometimes if URL is dead it will redirected and it will come to onLoadResource() before onPageFinished method. For this reason progress bar will not dismiss. To solve this issue see my this Answer.

Thanks :)

来源：https://stackoverflow.com/questions/2496119/show-a-progress-bar-on-a-child-tab-until-the-webview-loads