在 WebView 中检查互联网连接

各位程序员大家好！

我的 WebView 应用程序出现问题...

我想在启动时添加一个“连接检查”，当没有可用的 Internet 连接或 WebView 超时时，该检查会弹出错误。我无法自己完成它，因为我是 Android 编程新手。

我还想添加一个选项菜单，我可以在其中重新加载实际页面。

希望可以有人帮帮我...

实际代码：

package net.schwarzis.htl_cloud;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;




@SuppressLint("JavascriptInterface") public class MainActivity extends Activity {
    /** Called when the activity is first created. */

    private WebView browser = null;



        public boolean shouldOverrideUrlLoading(WebView view, String url) {

            browser.loadUrl(url);
            return true;
        }

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        // connect to our browser so we can manipulate it
        browser = (WebView) findViewById(R.id.mybrowser);

        // get settings so we can config our WebView instance
        WebSettings settings = browser.getSettings();

        // JavaScript?  Of course!
        settings.setJavaScriptEnabled(true);
        // clear cache
        browser.clearCache(true);

        final ProgressDialog pd=new ProgressDialog(this);
        pd.setMessage("Lade...");
        browser.setWebViewClient(new WebViewClient() {
            public void onPageFinished(WebView view, String url) {
                 pd.dismiss();
            }
       @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {

        pd.show();
        browser.loadUrl(url);
        return true;
    }
        });
                // this is necessary for "alert()" to work
                browser.setWebChromeClient(new WebChromeClient());

                // add our custom functionality to the javascript environment
                browser.addJavascriptInterface(new MyCoolJSHandler(), "Cloud");

                // load a page to get things started
     pd.show();
                browser.loadUrl("http://cloud.schwarzis.net");



        }


        @Override
        public boolean onKeyDown(int keyCode, KeyEvent event) {
             final ProgressDialog pd=new ProgressDialog(this);
             pd.setMessage("Lade...");
            if(event.getAction() == KeyEvent.ACTION_DOWN){
                switch(keyCode)
                {
                case KeyEvent.KEYCODE_BACK:
                    if(browser.canGoBack() == true){
                        pd.show();
                        browser.goBack();
                    }else{
                          pd.show();
                        finish();
                    }
                    pd.dismiss();
                    return true;
                }

            }
            return super.onKeyDown(keyCode, event);
        }



    final class MyCoolJSHandler
    {
        // write to LogCat (Info)
        public void Info(String str) {
            Log.i("GoingNative",str);
        }

        // write to LogCat (Error)
        public void Error(String str) {
            Log.e("GoingNative",str);
        }

        // Kill the app
        public void EndApp() {
            finish(); 
        }
    }

}

用户可以使用以下方法来检查互联网连接是否可用。

public boolean isNetworkAvailable() {
    // Get Connectivity Manager class object from Systems Service
    ConnectivityManager cm = (ConnectivityManager)  getSystemService(Context.CONNECTIVITY_SERVICE);

    // Get Network Info from connectivity Manager
    NetworkInfo networkInfo = cm.getActiveNetworkInfo();

    // if no network is available networkInfo will be null
    // otherwise check if we are connected
    if (networkInfo != null && networkInfo.isConnected()) {
        return true;
    }
    return false;
}

您需要在 AndroidManifest.xml 文件中提供以下权限

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