Question

我创建了这个方法，如果URL有效，则首先检查，然后检查它是否链接到图像或是否是YouTube视频。我的程序到达

时失败

String contentType = connection.getHeaderField("Content-Type");

方法的一部分。为什么会这样？

此外，使用URLUtil.isValidUrl（）检查其是否为有效URL以及创建连接并尝试打开该连接是无关紧要的。

private boolean checkContent() {
    //check if valid image
    boolean img = false;
    boolean youtube = false;
    if(URLUtil.isValidUrl(imageAddress)) {
        URLConnection connection = null;
        try {
            connection = new URL(imageAddress).openConnection();
        } catch (IOException e) {
            e.printStackTrace();
        }
        String contentType = connection.getHeaderField("Content-Type");
        img = contentType.startsWith("image/");

        if(!img) {
            // Check host of url if youtube exists
            Uri uri = Uri.parse(imageAddress);
            if ("www.youtube.com".equals(uri.getHost()))
                youtube = true;
        }
    }
    return img || youtube;
}

我的Manifest中有互联网权限!!!

Process: com.example.robert.demo, PID: 11504
java.lang.IllegalStateException: Could not execute method of the activity
        at android.view.View$1.onClick(View.java:4020)
        at android.view.View.performClick(View.java:4780)
        at android.view.View$PerformClick.run(View.java:19866)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5257)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

java.lang.reflect.InvocationTargetException
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at android.view.View$1.onClick(View.java:4015)
            at android.view.View.performClick(View.java:4780)
            at android.view.View$PerformClick.run(View.java:19866)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: android.os.NetworkOnMainThreadException
            at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1147)
            at java.net.InetAddress.lookupHostByName(InetAddress.java:418)
            at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252)
            at java.net.InetAddress.getAllByName(InetAddress.java:215)
            at com.android.okhttp.HostResolver$1.getAllByName(HostResolver.java:29)
            at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:232)
            at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:124)
            at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:272)
            at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:211)
            at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:382)
            at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:332)
            at com.android.okhttp.internal.http.HttpURLConnectionImpl.getHeaderField(HttpURLConnectionImpl.java:161)
            at com.example.robert.demo.Demo.checkContent(Demo.java:110)
            at com.example.robert.demo.Demo.submitFile(Demo.java:89)
            at com.example.robert.demo.Demo.submitClick(Demo.java:65)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at android.view.View$1.onClick(View.java:4015)
            at android.view.View.performClick(View.java:4780)
            at android.view.View$PerformClick.run(View.java:19866)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Answer 1

使用Map<String, List<String>>获取标题文件。试试这个：

 private boolean checkContent() {
        //check if valid image
        boolean img = false;
        boolean youtube = false;
        if(URLUtil.isValidUrl(imageAddress)) {
            URLConnection connection = null;
            try {
                connection = new URL(imageAddress).openConnection();
            } catch (IOException e) {
                e.printStackTrace();
            }

Map<String, List<String>> map = conn.getHeaderFields();
    //This area shows keys and values for headerfields in logcat.
    for (Map.Entry<String, List<String>> entry : map.entrySet()) {
        Log.d("Keysss", "Key : " + entry.getKey() + 
                 " ,Value : " + entry.getValue());
    }

    //get header by 'key'
    String contentType= connection.getHeaderField("Content-Type");

            img = contentType.startsWith("image/");

            if(!img) {
                // Check host of url if youtube exists
                Uri uri = Uri.parse(imageAddress);
                if ("www.youtube.com".equals(uri.getHost()))
                    youtube = true;
            }
        }
        return img || youtube;
    }

Answer 2

1）引起：android.os.NetworkOnMainThreadException at android.os.StrictMode $ AndroidBlockGuardPolicy.onNetwork（StrictMode.java:1147）在java.net.InetAddress.lookupHostByName（InetAddress.java:418）at java.net.InetAddress.getAllByNameImpl（InetAddress.java:252）

尝试在单独的线程上运行Web方法代码，如下所示：

if(URLUtil.isValidUrl(imageAddress)) {
    Thread thread = new Thread() {
        @Override
        public void run() {
            URLConnection connection = null;
            try {
                connection = new URL(imageAddress).openConnection();
            } catch (IOException e) {
                e.printStackTrace();
            }
            String contentType = connection.getHeaderField("Content-Type");
            img = contentType.startsWith("image/");

            if(!img) {
                // Check host of url if youtube exists
                Uri uri = Uri.parse(imageAddress);
                if ("www.youtube.com".equals(uri.getHost()))
                    youtube = true;
                }
            }
    };
    thread.start();
}

如何检查URL是图像还是Youtube视频

2 个答案: