Question

我有这个应用程序，当它处于离线模式时使用webview呈现缓存的内容，并在连接到互联网时显示来自服务器的网页...

代码段如下所示。它在我运行应用程序时崩溃。

我无法弄清楚出了什么问题。我还在清单文件中设置了uses-permission android：name =“android.permission.INTERNET”。

package com.html5webappcache.android;

import android.app.Activity;
import android.net.ConnectivityManager;
import android.os.Bundle;
import android.view.Window;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebStorage.QuotaUpdater;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;
import android.widget.TextView;

public class HTML5WebAppCacheTestActivity extends Activity {
    final Activity activity = this;
    private ConnectivityManager cm;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Adds Progrss bar Support
        this.getWindow().requestFeature(Window.FEATURE_PROGRESS);
        setContentView(R.layout.main );

        getWindow().setFeatureInt( Window.FEATURE_PROGRESS, Window.PROGRESS_VISIBILITY_ON); 

        WebView engine=(WebView)findViewById(R.id.web_engine);
        engine.getSettings().setJavaScriptEnabled(true);
        engine.getSettings().setBuiltInZoomControls(true);
        engine.getSettings().setLoadsImagesAutomatically(true);
        engine.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
        engine.setInitialScale(1);

        engine.setWebChromeClient(new WebChromeClient() {
              @Override
                 public void onReachedMaxAppCacheSize(long spaceNeeded, long totalUsedQuota,QuotaUpdater quotaUpdater)
                 {
                       quotaUpdater.updateQuota(spaceNeeded * 2);
                 }
              public void onProgressChanged(WebView view, int progress)
              {
                  activity.setTitle("Loading...");
                  activity.setProgress(progress * 100);



                  if(progress == 100)
                  { activity.setTitle(R.string.app_name);

                  }
              }
           });
        engine.getSettings().setDomStorageEnabled(true);
       // Set cache size to 8 mb by default. should be more than enough
        engine.getSettings().setAppCacheMaxSize(1024*1024*8);
        engine.getSettings().setAppCachePath("/data/data/com.html5webappcache.android/cache");
        engine.getSettings().setAllowFileAccess(true);
        engine.getSettings().setAppCacheEnabled(true);
        engine.getSettings().setCacheMode(WebSettings.LOAD_DEFAULT);

         cm = (ConnectivityManager) this.getSystemService(Activity.CONNECTIVITY_SERVICE);
         if(cm.getActiveNetworkInfo().isConnected())
         {
         engine.getSettings().setCacheMode(WebSettings.LOAD_DEFAULT);
         engine.loadUrl("http://www.bifter.co.uk/");
         }
             else{
                engine.getSettings().setCacheMode(WebSettings.LOAD_CACHE_ELSE_NETWORK);
                 engine.loadUrl("http://www.bifter.co.uk/");
             }











    }
}

Answer 1

也许NetworkInfo对象为null，并且您获得NullPointerException。查找代码行的最佳方法是使用logcat并查看堆栈跟踪。

顺便说一句，我使用类似的方式在WebViews中使用缓存，但是使用我的设备（Desire + CM7）它不起作用，因为从不使用缓存..

亲切的问候， jayearn

Answer 2

webview1 = (WebView) findViewById(R.id.webView1);

    WebSettings webSettings = webview1.getSettings();
    webSettings.setJavaScriptEnabled(true);
    webSettings.setCacheMode(WebSettings.LOAD_NORMAL); <--- CHANGE THIS
    webSettings.setAppCacheMaxSize(1024*1024*8);
    webview1.addJavascriptInterface(new JavaScriptInterface(this),
            "Android");
    webview1.setWebViewClient(new MyWebViewClient());
    webview1.setBackgroundColor(Color.BLACK);


    try {
        current_url = "http://........link";
        webview1.loadUrl(current_url);
    } catch (Exception e) {
        Log.v("Loading Webview Failed", "Loading the webview Failed");
    }

    current_fact = 0;

Answer 3

添加 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 在AndroidManifest.xml中。它将像魔术一样工作。 LogCat帮助。

Answer 4

您还需要检查networkInfo是否为null 所以基本上你的if语句应该是

if(cm.getActiveNetworkInfo() == null || !cm.getActiveNetworkInfo().isConnected()){
//load cache
}else{
//load default
}

不要忘记添加这些权限

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

至于AppCachePath，如果你正在为Android 2.2+构建，那么请改用

engine.getSettings().setAppCachePath(getApplication().getCacheDir().toString());

这将保证在卸载应用程序时删除缓存

未连接到互联网时在Android Webview中加载缓存在连接到互联网时显示来自服务器的内容

4 个答案: