Android 应用程序在拉动刷新操作后停止答案

【问题标题】：Android app stops after pull-to-refresh actionAndroid 应用程序在拉动刷新操作后停止
【发布时间】：2020-02-21 10:38:31
【问题描述】：

我遇到了以下问题：我正在使用片段制作一个 android webview 应用程序，并且我想实现一个 SwipeToRefresh 操作。

我尝试这样做，但应用程序在用户的拉动刷新操作后立即停止。以下是不同的代码：

fragment_home.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/holo_red_light">

<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
    android:id="@+id/sr"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <WebView
        android:id="@+id/webviewhome"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></WebView>

</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>

</RelativeLayout>

HomeFragment.java 公共类 HomeFragment 扩展 Fragment {

public HomeFragment(){
    // Required
}

private SwipeRefreshLayout mRefreshLayout;
private WebView mWebView;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    View v = inflater.inflate(R.layout.fragment_home, container, false);
    mRefreshLayout = (SwipeRefreshLayout) v.findViewById(R.id.sr);
    mRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
        @Override
        public void onRefresh() {
            mWebView.reload();
            mRefreshLayout.setRefreshing(false);
        }
    });
    final WebView webView = (WebView) v.findViewById(R.id.webviewhome);
    webView.getSettings().setJavaScriptEnabled(true);
    webView.getSettings().setAppCacheEnabled(true);
    webView.loadUrl("MYURL");
    webView.setWebViewClient(new WebViewClient());
    webView.canGoBack();

    webView.setOnKeyListener(new View.OnKeyListener() {
        public boolean onKey(View v, int keyCode, KeyEvent event) {
            if (keyCode == KeyEvent.KEYCODE_BACK
                    && event.getAction() == MotionEvent.ACTION_UP
                    && webView.canGoBack()) {
                webView.goBack();
                return true;
            }
            return false;
        }
    });

    webView.setWebViewClient(new WebViewClient() {
        public void onReceivedError(WebView webView, int errorCode, String description, String failingUrl) {
            try {
                webView.stopLoading();
            } catch (Exception e) {
            }

            if (webView.canGoBack()) {
                webView.goBack();
            }

            webView.loadUrl("about:blank");
            AlertDialog alertDialog = new AlertDialog.Builder(getContext()).create();
            alertDialog.setTitle("Erreur !");
            alertDialog.setMessage("Veuillez vérifier votre connexion internet et réessayer");
            alertDialog.setButton(DialogInterface.BUTTON_POSITIVE, "Réessayer", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    getActivity().finish();
                    startActivity(getActivity().getIntent());
                }
            });

            alertDialog.show();
            super.onReceivedError(webView, errorCode, description, failingUrl);
        }
    });

    return v;
}

你能帮帮我吗？

【问题讨论】：

您能否在日志中添加您遇到的崩溃错误？
您创建了 mWebView 和 webView-它们是同一个实例吗？
只有在您的 webview 完成加载其内容后，您才需要调用 mRefreshLayout.setRefreshing(false)。您可以在 webview 对象上处理 onPageFinished 回调，然后在那边将刷新设置为 false。
mWebView.reload() 在空对象引用上，初始化 mWebView 并完成！
替换这个 mWebView.reload();通过 webView.reload();您正在初始化 webView 变量并在 mWebView 上调用 reload

标签： android android-fragments webview crash

【解决方案1】：

如果我们没有遗漏您的部分代码，那么您已经为 webview 创建了两个实例，在刷新布局中您正在调用尚未初始化的 mWebView。试试这个：

public HomeFragment(){
    // Required
}

private SwipeRefreshLayout mRefreshLayout;
private WebView WebView;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

View v = inflater.inflate(R.layout.fragment_home, container, false);
mRefreshLayout = (SwipeRefreshLayout) v.findViewById(R.id.sr);
mRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
    @Override
    public void onRefresh() {
        mWebView.reload();
        mRefreshLayout.setRefreshing(false);
    }
});
webView = (WebView) v.findViewById(R.id.webviewhome);
webView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setAppCacheEnabled(true);
webView.loadUrl("MYURL");
webView.setWebViewClient(new WebViewClient());
webView.canGoBack();

webView.setOnKeyListener(new View.OnKeyListener() {
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK
                && event.getAction() == MotionEvent.ACTION_UP
                && webView.canGoBack()) {
            webView.goBack();
            return true;
        }
        return false;
    }
});

webView.setWebViewClient(new WebViewClient() {
    public void onReceivedError(WebView webView, int errorCode, String description, String failingUrl) {
        try {
            webView.stopLoading();
        } catch (Exception e) {
        }

        if (webView.canGoBack()) {
            webView.goBack();
        }

        webView.loadUrl("about:blank");
        AlertDialog alertDialog = new AlertDialog.Builder(getContext()).create();
        alertDialog.setTitle("Erreur !");
        alertDialog.setMessage("Veuillez vérifier votre connexion internet et réessayer");
        alertDialog.setButton(DialogInterface.BUTTON_POSITIVE, "Réessayer", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                getActivity().finish();
                startActivity(getActivity().getIntent());
            }
        });

        alertDialog.show();
        super.onReceivedError(webView, errorCode, description, failingUrl);
    }
});

    return v;
}

【讨论】：

【解决方案2】：

您使用了错误的 webview 参考

public class MyFragment extends Fragment {


    private SwipeRefreshLayout mRefreshLayout;
    private WebView webView;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.fragment_home, container, false);
        mRefreshLayout = (SwipeRefreshLayout) v.findViewById(R.id.sr);
        mRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                webView.reload();
                mRefreshLayout.setRefreshing(false);
            }
        });
        webView = v.findViewById(R.id.webviewhome);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.getSettings().setAppCacheEnabled(true);
        webView.loadUrl("https://stackoverflow.com/questions/tagged/android");
        webView.setWebViewClient(new WebViewClient());
        webView.canGoBack();

        webView.setOnKeyListener(new View.OnKeyListener() {
            public boolean onKey(View v, int keyCode, KeyEvent event) {
                if (keyCode == KeyEvent.KEYCODE_BACK
                        && event.getAction() == MotionEvent.ACTION_UP
                        && webView.canGoBack()) {
                    webView.goBack();
                    return true;
                }
                return false;
            }
        });

        webView.setWebViewClient(new WebViewClient() {
            public void onReceivedError(WebView webView, int errorCode, String description, String failingUrl) {
                try {
                    webView.stopLoading();
                } catch (Exception e) {
                }

                if (webView.canGoBack()) {
                    webView.goBack();
                }

                webView.loadUrl("about:blank");
                AlertDialog alertDialog = new AlertDialog.Builder(getContext()).create();
                alertDialog.setTitle("Erreur !");
                alertDialog.setMessage("Veuillez vérifier votre connexion internet et réessayer");
                alertDialog.setButton(DialogInterface.BUTTON_POSITIVE, "Réessayer", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        getActivity().finish();
                        startActivity(getActivity().getIntent());
                    }
                });

                alertDialog.show();
                super.onReceivedError(webView, errorCode, description, failingUrl);
            }
        });

        return v;
    }
}

【讨论】：