Webview 应用程序检查网络并在没有网络时显示“无互联网连接”，并在网络可用时重新加载

Question

I created a simple webview app that displays an error.html from assets when there is no network, but users cannot continue with webview once network is available. users are simply stuck in the error.html page. what i have been trying to do now is to make the webview app to check for network and display "no internet connection" if there is none and also reload when network is available.

Manifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.mary">


    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />


    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.Holo.Light">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Splash"
            android:label="@string/app_name"
            android:theme="@style/AppTheme">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

MainActivity.java

private WebView mWebView;

SwipeRefreshLayout swipe;



private void setFullScreen() {
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(
            WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN
    );
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);



   swipe = (SwipeRefreshLayout) findViewById(R.id.swipe);
   swipe.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
       @Override
       public void onRefresh() {

           LoadWeb(mWebView.getUrl());
       }
   });

    LoadWeb("http://m.mary.org");


}

public void  LoadWeb(String url){

    mWebView = (WebView) findViewById(R.id.activity_main_webview);
    WebSettings webSettings = mWebView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    mWebView.loadUrl(url);
    swipe.setRefreshing(true);


    mWebView.setDownloadListener(new DownloadListener() {
        @Override
        public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype, long contentLength) {

            DownloadManager.Request myRequest = new DownloadManager.Request(Uri.parse(url));
            myRequest.allowScanningByMediaScanner();
            myRequest.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);

            DownloadManager myManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
            myManager.enqueue(myRequest);

            Toast.makeText(MainActivity.this, "Your File is downloading....", Toast.LENGTH_SHORT).show();
        }});

    mWebView.setWebViewClient(new com.example.mary.MyAppWebViewClient(){

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

            mWebView.loadUrl("file:///android_asset/error.html");
        }

        public void onPageFinished(WebView view, String url) {
            //hide loading image

            swipe.setRefreshing(false);
            //show webview
            findViewById(R.id.activity_main_webview).setVisibility(View.VISIBLE);
        }});

}

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

MyAppWebViewClient.java

@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
    if(Uri.parse(url).getHost().endsWith("m.mary.org")) {
        return false;
    }

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

Answer 1

create a broadcast receiver:

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;

import java.util.HashSet;
import java.util.Set;

public class NetworkStateReceiver extends BroadcastReceiver {

protected Set<NetworkStateReceiverListener> listeners;
protected Boolean connected;

public NetworkStateReceiver() {
    listeners = new HashSet<NetworkStateReceiverListener>();
    connected = null;
}

public void onReceive(Context context, Intent intent) {
    if(intent == null || intent.getExtras() == null)
        return;

    ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo ni = manager.getActiveNetworkInfo();

    if(ni != null && ni.getState() == NetworkInfo.State.CONNECTED) {
        connected = true;
    } else if(intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY,Boolean.FALSE)) {
        connected = false;
    }

    notifyStateToAll();
}

private void notifyStateToAll() {
    for(NetworkStateReceiverListener listener : listeners)
        notifyState(listener);
}

private void notifyState(NetworkStateReceiverListener listener) {
    if(connected == null || listener == null)
        return;

    if(connected == true)
        listener.networkAvailable();
    else
        listener.networkUnavailable();
}

public void addListener(NetworkStateReceiverListener l) {
    listeners.add(l);
    notifyState(l);
}

public void removeListener(NetworkStateReceiverListener l) {
    listeners.remove(l);
}

public interface NetworkStateReceiverListener {
    public void networkAvailable();
    public void networkUnavailable();
}
}

in your activity use it like this:

private NetworkStateReceiver.NetworkStateReceiverListener networkStateReceiverListener = new NetworkStateReceiver.NetworkStateReceiverListener() {
    @Override
    public void networkAvailable() {
        //todo: refresh webview
    }

@Override
public void networkUnavailable() {
  //todo: show error
}
};

permission in manifest:

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />