在 WebView 中检查 Internet 连接

Question

各位程序员好！

我的 WebView-App 有问题...

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 超时时弹出错误。我无法自己完成，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。

希望有人可以帮助我...

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(); 
        }
    }

}

Answer 1

首先在清单中你应该有这些

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

关于你的 onCreate

AlertDialog.Builder alertDialogBuilder = null;

把它放在 onCreate 中

            alertDialogBuilder = new AlertDialog.Builder(
                this.context);

            // set title
            alertDialogBuilder.setTitle("No connection");

            // set dialog message
            alertDialogBuilder
                .setMessage("No connection, Retry")
                .setCancelable(true);

                // create alert dialog
                AlertDialog alertDialog = alertDialogBuilder.create();

那就用这个方法吧。

private boolean isNetworkConnected() {
  ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
  NetworkInfo ni = cm.getActiveNetworkInfo();
  if (ni == null) {
   // There are no active networks.
            alertDialog.show();
   return false;
  } else
  browser.getSettings().setJavaScriptEnabled(true);
  browser.loadUrl( "javascript:window.location.reload( true )" );
   return true;
 }

并刷新您的 webview 使用

browser.getSettings().setJavaScriptEnabled(true);
browser.loadUrl( "javascript:window.location.reload( true )" );

这里有一个很棒的代码教程，This。

Answer 2

以下方法的用户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 AndroidMenifest.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>

Answer 3

要检查连接是否可用，您可以使用：

private boolean isNetAvailable() {
        ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetworkInfo = connectivityManager
                .getActiveNetworkInfo();
        return activeNetworkInfo != null && activeNetworkInfo.isConnected();
    }

至于菜单中的刷新，在res -> menu -> yourMenu.xml中添加刷新<item>，给它一个id，并在你的Activity中添加一个onItemSelected()（覆盖它）方法。