将HttpUrlConnection与针对SDK 21的Android编译时出现错误

Question

I have located the problem, it is not in the code I posted at all. The perils of mulTi-threading and and just recently switching to Android Studio. It is a problem with the Menu in SDK 21 and my not using the guide to switch to using Android 5.0 Themes and ActionBar.

I am having problems with using HttpUrlConnection. I am using it to call an api written in PHP. The app downloads summaries of articles on startup and that works fine. When you click on an article it then download the rest of the information for the article and displays the info in a new activity. At least it is supposed to it has now started crashing anytime you click on a summary. It crashes when it reaches the line conn.connect in the following code

public String downloadUrl(String myurl) throws IOException {
    InputStream is = null;

    HttpURLConnection conn=null;
    String contentAsString=null;
    try {
        URL url = new URL(myurl);
        conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(10000 /* milliseconds */);
        conn.setConnectTimeout(15000 /* milliseconds */);
        conn.setRequestMethod("GET");
        conn.setInstanceFollowRedirects(true);
        conn.setDoInput(true);

        // Starts the query
        conn.connect();
        int response = conn.getResponseCode();
        Log.d("HttpReader", "The response is: " + response);
        is = conn.getInputStream();

        // Convert the InputStream into a string
        contentAsString = readIt(is);



    // Makes sure that the InputStream is closed after the app is
    // finished using it.


    } finally {
        conn.disconnect();
        if (is != null) {
            is.close();
        }
    }
    return contentAsString;
}

I have traced the error to the file Choreographer.java and the following function

  void doCallbacks(int callbackType, long frameTimeNanos) {
    CallbackRecord callbacks;
    synchronized (mLock) {
        // We use "now" to determine when callbacks become due because it's possible
        // for earlier processing phases in a frame to post callbacks that should run
        // in a following phase, such as an input event that causes an animation to start.
        final long now = SystemClock.uptimeMillis();
        callbacks = mCallbackQueues[callbackType].extractDueCallbacksLocked(now);
        if (callbacks == null) {
            return;
        }
        mCallbacksRunning = true;
    }
    try {
        for (CallbackRecord c = callbacks; c != null; c = c.next) {
            if (DEBUG) {
                Log.d(TAG, "RunCallback: type=" + callbackType
                        + ", action=" + c.action + ", token=" + c.token
                        + ", latencyMillis=" + (SystemClock.uptimeMillis() - c.dueTime));
            }
            c.run(frameTimeNanos);
        }
    } finally {
        synchronized (mLock) {
            mCallbacksRunning = false;
            do {
                final CallbackRecord next = callbacks.next;
                recycleCallbackLocked(callbacks);
                callbacks = next;
            } while (callbacks != null);
        }
    }
}

A null pointer exception is thrown in the finally clause callbacks.next gives an NullPtrException.

I have tested the url I am using in Chrome and it retruns the JSON it is supposed to and also tested with curl and again I get the JSON I expect.

I am not sure what is wrong.

Answer 1

我不认为您可以在主线程上运行它-您需要使用AsyncTask对其进行包装。