Java WebView检查连接

大家好，外面的程序员们

我是android编程的初学者，我的应用程序不会显示没有可用的连接：

显示：404 HTML屏幕| 应显示：消息“无网络连接”

谢谢你的帮助

package net.schwarzis.htl_cloud;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
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 isOnline() {
        ConnectivityManager cm =
            (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnectedOrConnecting()) {
            // 1. Instantiate an AlertDialog.Builder with its constructor
            AlertDialog.Builder builder = new AlertDialog.Builder(this);

            // 2. Chain together various setter methods to set the dialog characteristics
            builder.setMessage("Please connect to the internet...")
                   .setTitle("No network connection!");

            // 3. Get the AlertDialog from create()
            AlertDialog dialog = builder.create();
            builder.show();
            return true;
        }
        return false;
    }

        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(); 
        }
    }

}

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确保已在清单文件中添加“Internet”权限

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

除此之外，我觉得你的代码很好

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希望能有帮助。

你的问题还不清楚。你能再解释一下吗？谢谢