防止 WebView 显示“网页不可用”

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Check out the discussion at Android WebView onReceivedError(). It's quite long, but the consensus seems to be that a) you can't stop the "web page not available" page appearing, but b) you could always load an empty page after you get an onReceivedError

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I suppose that if you insist on doing this, you could just check if the resource is there before calling the loadURL function. Just simply override the functions and do the check before calling the super()

REMARK (maybe off-topic): In http, there is a method called HEAD which is described as follow:

The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response

This method might be handy. Anyway how ever you implement it ... check this code:

import java.util.Map;


import android.content.Context;
import android.webkit.WebView;


public class WebViewPreLoad extends WebView{


public WebViewPreLoad(Context context) {
super(context);
}
public void loadUrl(String str){
if(//Check if exists)
super.loadUrl(str);
else
//handle error
}
public void loadUrl(String url, Map<String,String> extraHeaders){
if(//Check if exists)
super.loadUrl(url, extraHeaders);
else
//handle error
}
}

You could try this check using

if(url.openConnection().getContentLength() > 0)

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You could use a GET request to get the page content and then display that data using the Webview , this way you are not using multiple server calls. Alternative you can use Javascript to check the DOM object for validity.

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try this shouldOverrideUrlLoading , before redirect to another url check for internet conncetion based on that page should be loaded or not.

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Perhaps I misunderstand the question, but it sounds like you're saying you get the error received callback, and you just are asking what is the best way to not show the error? Why don't you just either remove the web view from the screen and/or show another view on top of it?

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I would just change the webpage to whatever you are using for error handling:

getWindow().requestFeature(Window.FEATURE_PROGRESS);
webview.getSettings().setJavaScriptEnabled(true);
final Activity activity = this;
webview.setWebChromeClient(new WebChromeClient() {
public void onProgressChanged(WebView view, int progress) {
// Activities and WebViews measure progress with different scales.
// The progress meter will automatically disappear when we reach 100%
activity.setProgress(progress * 1000);
}
});
webview.setWebViewClient(new WebViewClient() {
public void onReceivedError(WebView view, int errorCode, String description, String
failingUrl) {
Toast.makeText(activity, "Oh no! " + description, Toast.LENGTH_SHORT).show();
}
});
webview.loadUrl("http://slashdot.org/");

this can all be found on http://developer.android.com/reference/android/webkit/WebView.html

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最佳答案

First create your own error page in HTML and put it in your assets folder, Let's call it myerrorpage.html Then with onReceivedError:

mWebView.setWebViewClient(new WebViewClient() {
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
mWebView.loadUrl("file:///android_asset/myerrorpage.html");


}
});

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I've been working on this problem of ditching those irritable Google error pages today. It is possible with the Android example code seen above and in plenty of other forums (ask how I know):

wv.setWebViewClient(new WebViewClient() {
public void onReceivedError(WebView view, int errorCode,
String description, String failingUrl) {
if (view.canGoBack()) {
view.goBack();
}
Toast.makeText(getBaseContext(), description, Toast.LENGTH_LONG).show();
}
}
});

IF you put it in shouldOverrideUrlLoading() as one more webclient. At least, this is working for me on my 2.3.6 device. We'll see where else it works later. That would only depress me now, I'm sure. The goBack bit is mine. You may not want it.

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When webview is embedded in some custom view such that user almost believes that he is seeing a native view and not a webview, in such scenario showing the "page could not be loaded" error is preposterous. What I usually do in such situation is I load blank page and show a toast message as below

webView.setWebViewClient(new WebViewClient() {


@Override
public void onReceivedError(WebView view, int errorCode,
String description, String failingUrl) {
Log.e(TAG," Error occured while loading the web page at Url"+ failingUrl+"." +description);
view.loadUrl("about:blank");
Toast.makeText(App.getContext(), "Error occured, please check newtwork connectivity", Toast.LENGTH_SHORT).show();
super.onReceivedError(view, errorCode, description, failingUrl);
}
});

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Finally, I solved this. (It works till now..)

My solution is like this...

Prepare the layout to show when an error occurred instead of Web Page (a dirty 'page not found message') The layout has one button, "RELOAD" with some guide messages.
If an error occurred, Remember using boolean and show the layout we prepare.
If user click "RELOAD" button, set mbErrorOccured to false. And Set mbReloadPressed to true.
if mbErrorOccured is false and mbReloadPressed is true, it means webview loaded page successfully. 'Cause if error occurred again, mbErrorOccured will be set true on onReceivedError(...)

Here is my full source. Check this out.

public class MyWebViewActivity extends ActionBarActivity implements OnClickListener {


private final String TAG = MyWebViewActivity.class.getSimpleName();
private WebView mWebView = null;
private final String URL = "http://www.google.com";
private LinearLayout mlLayoutRequestError = null;
private Handler mhErrorLayoutHide = null;


private boolean mbErrorOccured = false;
private boolean mbReloadPressed = false;


@SuppressLint("SetJavaScriptEnabled")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_webview);


((Button) findViewById(R.id.btnRetry)).setOnClickListener(this);
mlLayoutRequestError = (LinearLayout) findViewById(R.id.lLayoutRequestError);
mhErrorLayoutHide = getErrorLayoutHideHandler();


mWebView = (WebView) findViewById(R.id.webviewMain);
mWebView.setWebViewClient(new MyWebViewClient());
WebSettings settings = mWebView.getSettings();
settings.setJavaScriptEnabled(true);
mWebView.setWebChromeClient(getChromeClient());
mWebView.loadUrl(URL);
}


@Override
public boolean onSupportNavigateUp() {
return super.onSupportNavigateUp();
}


@Override
public void onClick(View v) {
int id = v.getId();


if (id == R.id.btnRetry) {
if (!mbErrorOccured) {
return;
}


mbReloadPressed = true;
mWebView.reload();
mbErrorOccured = false;
}
}


@Override
public void onBackPressed() {
if (mWebView.canGoBack()) {
mWebView.goBack();
return;
}
else {
finish();
}


super.onBackPressed();
}


class MyWebViewClient extends WebViewClient {
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
return super.shouldOverrideUrlLoading(view, url);
}


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


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


@Override
public void onPageFinished(WebView view, String url) {
if (mbErrorOccured == false && mbReloadPressed) {
hideErrorLayout();
mbReloadPressed = false;
}


super.onPageFinished(view, url);
}


@Override
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
mbErrorOccured = true;
showErrorLayout();
super.onReceivedError(view, errorCode, description, failingUrl);
}
}


private WebChromeClient getChromeClient() {
final ProgressDialog progressDialog = new ProgressDialog(MyWebViewActivity.this);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setCancelable(false);


return new WebChromeClient() {
@Override
public void onProgressChanged(WebView view, int newProgress) {
super.onProgressChanged(view, newProgress);
}
};
}


private void showErrorLayout() {
mlLayoutRequestError.setVisibility(View.VISIBLE);
}


private void hideErrorLayout() {
mhErrorLayoutHide.sendEmptyMessageDelayed(10000, 200);
}


private Handler getErrorLayoutHideHandler() {
return new Handler() {
@Override
public void handleMessage(Message msg) {
mlLayoutRequestError.setVisibility(View.GONE);
super.handleMessage(msg);
}
};
}
}

Addition:Here is layout....

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/rLayoutWithWebView"
android:layout_width="match_parent"
android:layout_height="match_parent" >


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


<LinearLayout
android:id="@+id/lLayoutRequestError"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_centerInParent="true"
android:background="@color/white"
android:gravity="center"
android:orientation="vertical"
android:visibility="gone" >


<Button
android:id="@+id/btnRetry"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:minWidth="120dp"
android:text="RELOAD"
android:textSize="20dp"
android:textStyle="bold" />
</LinearLayout>

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override your WebViewClient method

@Override
public void onReceivedError(WebView view, int errorCode,
String description, String failingUrl) {
view.clearView();
}

view.loadUrl('about:blank') has side-effects, as it cancels the original URL loading.

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The best solution I have found is to load an empty page in the OnReceivedError event like this:

@Override
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
super.onReceivedError(view, errorCode, description, failingUrl);


view.loadUrl("about:blank");
}

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Try this

 @SuppressWarnings("deprecation")
@Override
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
// Your handling
}


@Override
public void onReceivedError(WebView view, WebResourceRequest req, WebResourceError rerr) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
onReceivedError(view, rerr.getErrorCode(), rerr.getDescription().toString(), req.getUrl().toString());
}
}

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We can set the visibility of webView to 0(view.INVISIBLE) and show some message. This code works for my app running on lolipop.

@SuppressWarnings("deprecation")
@Override
public void onReceivedError(WebView webView, int errorCode, String description, String failingUrl) {
// hide webView content and show custom msg
webView.setVisibility(View.INVISIBLE);
Toast.makeText(NrumWebViewActivity.this,getString(R.string.server_not_responding), Toast.LENGTH_SHORT).show();
}


@TargetApi(android.os.Build.VERSION_CODES.M)
@Override
public void onReceivedError(WebView view, WebResourceRequest req, WebResourceError rerr) {
// Redirect to deprecated method, so you can use it in all SDK versions
onReceivedError(view, rerr.getErrorCode(), rerr.getDescription().toString(), req.getUrl().toString());
}

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Here I found the easiest solution. check out this..

   @Override
public void onReceivedError(WebView view, int errorCode,
String description, String failingUrl) {
//                view.loadUrl("about:blank");
mWebView.stopLoading();
if (!mUtils.isInterentConnection()) {
Toast.makeText(ReportingActivity.this, "Please Check Internet Connection!", Toast.LENGTH_SHORT).show();
}
super.onReceivedError(view, errorCode, description, failingUrl);
}

And here is isInterentConnection() method...

public boolean isInterentConnection() {
ConnectivityManager manager = (ConnectivityManager) mContext
.getSystemService(Context.CONNECTIVITY_SERVICE);
if (manager != null) {
NetworkInfo info[] = manager.getAllNetworkInfo();
if (info != null) {
for (int i = 0; i < info.length; i++) {
if (info[i].getState() == NetworkInfo.State.CONNECTED) {
return true;
}
}
}
}
return false;
}

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I've had to face this issue and also tried to solve it from different perspectives. Finally I found a solution by using a single flag to check if an error happened.

... extends WebViewClient {


boolean error;


@Override
public void onPageStarted(WebView view, String url, Bitmap favicon) {


showLoading(true);
super.onPageStarted(view, url, favicon);


error  = false; // IMPORTANT
}


@Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);


if(!error) {
Observable.timer(100, TimeUnit.MICROSECONDS, AndroidSchedulers.mainThread())
.subscribe((data) -> view.setVisibility(View.VISIBLE) );
}


showLoading(false);
}




@Override
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {


view.stopLoading();


view.setVisibility(View.INVISIBLE)
error  = true;


// Handle the error
}




@Override
@TargetApi(android.os.Build.VERSION_CODES.M)
public void onReceivedError(WebView view,
WebResourceRequest request,
WebResourceError error) {


this.onReceivedError(view, error.getErrorCode(),
error.getDescription().toString(),
request.getUrl().toString());
}
}

This way I hide the page every time there's an error and show it when the page has loaded again properly.

Also added a small delay in case.

I avoided the solution of loading an empty page as it does not allow you to do webview.reload() later on due to it adds that new page in the navigation history.