Android WebView，从缓存加载并尝试刷新

Question

我正在尝试创建一个加载网页并将其存储在缓存中的小型应用程序。滑动刷新时它必须尝试更新，但如果没有互联网访问它应该保持当前版本。

目前，我有 "swipe to force refresh" 和 "load from the cache" 工作，但似乎无法弄清楚如何 "attempt to refresh if possible"。

swipeRefreshLayout = findViewById(R.id.swipe);
swipeRefreshLayout.setOnRefreshListener(
        new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                myWebView.clearCache(true);
                myWebView.reload();
            }
        }
);

WebSettings webSettings = myWebView.getSettings();
webSettings.setJavaScriptEnabled(true);
webSettings.setAppCacheEnabled(true);
webSettings.setAppCachePath(getBaseContext().getCacheDir().getPath());
webSettings.setCacheMode(WebSettings.LOAD_CACHE_ELSE_NETWORK);

myWebView.loadUrl(config.getString("website_root"));
myWebView.setWebViewClient(new WebViewClient() {
    @Override
    public void onPageStarted(WebView view, String url, Bitmap favicon) {
        if (!swipeRefreshLayout.isRefreshing()) {
            swipeRefreshLayout.setRefreshing(true);
        }
    }

    @Override
    public void onPageFinished(WebView view, String url) {
        swipeRefreshLayout.setRefreshing(false);
    }
});

Answer 1

基于 documentation 的 WebSettings.LOAD_CACHE_ELSE_NETWORK:

Use cached resources when they are available, even if they have expired. Otherwise load resources from the network

因此，您的视图总是从缓存中加载。

您可以使用以下方法： 1. 检查连通性：

private boolean isNetworkConnected() {
    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

    return cm.getActiveNetworkInfo() != null;
}

之前而不是设置：

WebSettings webSettings = myWebView.getSettings();
webSettings.setJavaScriptEnabled(true);
webSettings.setAppCacheEnabled(true);
webSettings.setAppCachePath(getBaseContext().getCacheDir().getPath());

webSettings.setCacheMode(isNetworkConnected()?WebSettings.LOAD_NO_CACHE: WebSettings.LOAD_CACHE_ONLY);

滑动刷新，你也可以这样做：

swipeRefreshLayout.setOnRefreshListener(
        new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                if(isNetworkConnected()){
                    ...
                    myWebView.reload();
                } else {
                      //Do something for non-connectivity
                }
        }
    });

Android WebView，从缓存加载并尝试刷新

Android WebView, load from cache and attempt to refresh

java

android

android-webview

swiperefreshlayout