如果我的android webview中没有可用的internet，如何显示消息

您好，我正在使用android webview应用程序。我在我的应用程序中成功地使用了我的url，并且它仅在internet连接可用时才起作用。但我想在没有internet连接时显示一些消息。我如何才能做到这一点？？？请帮助我，因为我是android开发新手，谢谢：）

在打开应用程序之前调用此方法

webView

如果此方法

返回true

则意味着internet连接是可访问的，您可以处理到webView，否则会显示一些

Toast

，或者如果此方法

返回false

则可以显示

对话框

编辑

在
主要活动中使用此代码，如下所示

if(isNetworkStatusAvialable (getApplicationContext())) {
    Toast.makeText(getApplicationContext(), "internet avialable", Toast.LENGTH_SHORT).show();
} else {
    Toast.makeText(getApplicationContext(), "internet is not avialable", Toast.LENGTH_SHORT).show();

}

方法

public static boolean isNetworkStatusAvialable (Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    if (connectivityManager != null) 
    {
        NetworkInfo netInfos = connectivityManager.getActiveNetworkInfo();
        if(netInfos != null)
        if(netInfos.isConnected()) 
            return true;
    }
    return false;
}

创建一个新类并签入任何其他活动，如

MainActivity.java
java
使用以下代码：

boolean internetCheck;
/*
     * 
     * Method to check Internet connection is available
     */

    public static boolean isInternetAvailable(Context context) {
        boolean haveConnectedWifi = false;
        boolean haveConnectedMobile = false;
        boolean connectionavailable = false;
        ConnectivityManager cm = (ConnectivityManager) context
                .getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo[] netInfo = cm.getAllNetworkInfo();
        NetworkInfo informationabtnet = cm.getActiveNetworkInfo();
        for (NetworkInfo ni : netInfo) {
            try {

                if (ni.getTypeName().equalsIgnoreCase("WIFI"))
                    if (ni.isConnected())
                        haveConnectedWifi = true;
                if (ni.getTypeName().equalsIgnoreCase("MOBILE"))
                    if (ni.isConnected())
                        haveConnectedMobile = true;
                if (informationabtnet.isAvailable()
                        && informationabtnet.isConnected())
                    connectionavailable = true;

            } catch (Exception e) {
                // TODO: handle exception
                System.out.println("Inside utils catch clause , exception is"
                        + e.toString());
                e.printStackTrace();
                /*
                 * haveConnectedWifi = false; haveConnectedMobile = false;
                 * connectionavailable = false;
                 */
            }
        }
        return haveConnectedWifi || haveConnectedMobile;
    }

如果网络可用，则返回true，否则返回false
在mantifest中添加以下权限

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


我是这样做的：

创建两个java文件，如下所示：

NetworkConnectivity.java

package com.connectivity;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Handler;

public class NetworkConnectivity {

    private static NetworkConnectivity sharedNetworkConnectivity = null;

    private Activity activity = null;

    private final Handler handler = new Handler();
    private Runnable runnable = null;

    private boolean stopRequested = false;
    private boolean monitorStarted = false;

    private static final int NETWORK_CONNECTION_YES = 1;
    private static final int NETWORK_CONNECTION_NO = -1;
    private static final int NETWORK_CONNECTION_UKNOWN = 0;

    private int connected = NETWORK_CONNECTION_UKNOWN;

    public static final int MONITOR_RATE_WHEN_CONNECTED_MS = 5000;
    public static final int MONITOR_RATE_WHEN_DISCONNECTED_MS = 1000;

    private final List<NetworkMonitorListener> networkMonitorListeners = new ArrayList<NetworkMonitorListener>();

    private NetworkConnectivity() {
    }

    public synchronized static NetworkConnectivity sharedNetworkConnectivity() {
        if (sharedNetworkConnectivity == null) {
            sharedNetworkConnectivity = new NetworkConnectivity();
        }

        return sharedNetworkConnectivity;
    }

    public void configure(Activity activity) {
        this.activity = activity;
    }

    public synchronized boolean startNetworkMonitor() {
        if (this.activity == null) {
            return false;
        }

        if (monitorStarted) {
            return true;
        }

        stopRequested = false;
        monitorStarted = true;

        (new Thread(new Runnable() {
            @Override
            public void run() {
                doCheckConnection();
            }
        })).start();

        return true;
    }

    public synchronized void stopNetworkMonitor() {
        stopRequested = true;
        monitorStarted = false;
    }

    public void addNetworkMonitorListener(NetworkMonitorListener l) {
        this.networkMonitorListeners.add(l);
        this.notifyNetworkMonitorListener(l);
    }

    public boolean removeNetworkMonitorListener(NetworkMonitorListener l) {
        return this.networkMonitorListeners.remove(l);
    }

    private void doCheckConnection() {

        if (stopRequested) {
            runnable = null;
            return;
        }

        final boolean connectedBool = this.isConnected();
        final int _connected = (connectedBool ? NETWORK_CONNECTION_YES
                : NETWORK_CONNECTION_NO);

        if (this.connected != _connected) {

            this.connected = _connected;

            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    notifyNetworkMonitorListeners();
                }
            });
        }

        runnable = new Runnable() {
            @Override
            public void run() {
                doCheckConnection();
            }
        };

        handler.postDelayed(runnable,
                (connectedBool ? MONITOR_RATE_WHEN_CONNECTED_MS
                        : MONITOR_RATE_WHEN_DISCONNECTED_MS));
    }

    public boolean isConnected() {
        try {
            ConnectivityManager cm = (ConnectivityManager) activity
                    .getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo netInfo = cm.getActiveNetworkInfo();

            if (netInfo != null && netInfo.isConnected()) {
                return true;
            } else {
                return false;
            }
        } catch (Exception e) {
            return false;
        }
    }

    private void notifyNetworkMonitorListener(NetworkMonitorListener l) {
        try {
            if (this.connected == NETWORK_CONNECTION_YES) {
                l.connectionEstablished();
            } else if (this.connected == NETWORK_CONNECTION_NO) {
                l.connectionLost();
            } else {
                l.connectionCheckInProgress();
            }
        } catch (Exception e) {
        }
    }

    private void notifyNetworkMonitorListeners() {
        for (NetworkMonitorListener l : this.networkMonitorListeners) {
            this.notifyNetworkMonitorListener(l);
        }
    }

}

package com.connectivity;

public interface NetworkMonitorListener {

    public void connectionEstablished();
    public void connectionLost();
    public void connectionCheckInProgress();
}

最后是用法：

NetworkConnectivity.sharedNetworkConnectivity().configure(this);
        NetworkConnectivity.sharedNetworkConnectivity().startNetworkMonitor();
        NetworkConnectivity.sharedNetworkConnectivity()
                .addNetworkMonitorListener(new NetworkMonitorListener() {
                    @Override
                    public void connectionCheckInProgress() {
                        // Okay to make UI updates (check-in-progress is rare)
                    }

                    @Override
                    public void connectionEstablished() {
                        // Okay to make UI updates -- do something now that
                        // connection is avaialble

                        Toast.makeText(getBaseContext(), "Connection established", Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void connectionLost() {
                        // Okay to make UI updates -- bummer, no connection

                        Toast.makeText(getBaseContext(), "Connection lost.", Toast.LENGTH_LONG).show();
                    }
                });

使用上述用法，您将能够在运行时检查internet连接。互联网连接一断，
Toast
就会出现（按照上面的代码）。
正如Brain所说的

要确定设备何时具有网络连接，请请求权限
，然后您可以使用以下代码进行检查。首先将这些变量定义为类变量

private Context c;
private boolean isConnected = true;

在
onCreate（）方法中初始化
c=this

然后检查连通性

ConnectivityManager connectivityManager = (ConnectivityManager)
    c.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivityManager != null) {
    NetworkInfo ni = connectivityManager.getActiveNetworkInfo();
    if (ni.getState() != NetworkInfo.State.CONNECTED) {
        // record the fact that there is not connection
        isConnected = false;
    }
}

然后，要截取
WebView
请求，可以执行以下操作。如果使用此方法，您可能希望自定义错误消息，以包括
onReceivedError
方法中可用的一些信息

final String offlineMessageHtml = "DEFINE THIS";
final String timeoutMessageHtml = "DEFINE THIS";

WebView browser = (WebView) findViewById(R.id.webview);
browser.setNetworkAvailable(isConnected);
browser.setWebViewClient(new WebViewClient() {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        if (isConnected) {
            // return false to let the WebView handle the URL
            return false;
        } else {
            // show the proper "not connected" message
            view.loadData(offlineMessageHtml, "text/html", "utf-8");
            // return true if the host application wants to leave the current 
            // WebView and handle the url itself
            return true;
        }
    }
    @Override
    public void onReceivedError (WebView view, int errorCode, 
        String description, String failingUrl) {
        if (errorCode == ERROR_TIMEOUT) {
            view.stopLoading();  // may not be needed
            view.loadData(timeoutMessageHtml, "text/html", "utf-8");
        }
    }
});

如果您正在使用internet连接检查internet可能不可用，即使已连接移动或wi-fi网络，但您的internet连接检查程序返回“真正使用”类似的信息
您是否已获得许可<代码>
好的，我已经编辑了答案，你现在检查了吗？？logcat的输出是什么？你能建议一下如何使它的UI更有用吗？.nw它的jst带有启动屏幕的webview。你想要什么
UI
？您的要求是什么？我只是想让webview更具吸引力。这意味着我希望在加载web内容时对页面的顶部和底部进行一些设计。
ConnectivityManager connectivityManager = (ConnectivityManager)
    c.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivityManager != null) {
    NetworkInfo ni = connectivityManager.getActiveNetworkInfo();
    if (ni.getState() != NetworkInfo.State.CONNECTED) {
        // record the fact that there is not connection
        isConnected = false;
    }
}

final String offlineMessageHtml = "DEFINE THIS";
final String timeoutMessageHtml = "DEFINE THIS";

WebView browser = (WebView) findViewById(R.id.webview);
browser.setNetworkAvailable(isConnected);
browser.setWebViewClient(new WebViewClient() {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        if (isConnected) {
            // return false to let the WebView handle the URL
            return false;
        } else {
            // show the proper "not connected" message
            view.loadData(offlineMessageHtml, "text/html", "utf-8");
            // return true if the host application wants to leave the current 
            // WebView and handle the url itself
            return true;
        }
    }
    @Override
    public void onReceivedError (WebView view, int errorCode, 
        String description, String failingUrl) {
        if (errorCode == ERROR_TIMEOUT) {
            view.stopLoading();  // may not be needed
            view.loadData(timeoutMessageHtml, "text/html", "utf-8");
        }
    }
});