Question

在我的活动中，我正在调用一个函数：

JSONObject jObj = SupportFunctions.returnJSONObject(url);

该功能如下所示：

public static JSONObject returnJSONObject(String url) {

    JSONObject jObj = null;
    InputStream iS = null;
    String result = null;

    // HTTP
    try {

        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(url);
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        iS = entity.getContent();

    }
    catch (Exception e) {
        Log.e("QUIZ", e.getMessage());
        return null;
    }

    return jObj;
}

通话结果为：

Pick [Android Application] <terminated>Pick [Android Application]   
<disconnected>DalvikVM [localhost:8600] 
    Pick [Android Application]  
DalvikVM [localhost:8600] (may be out of synch) 
    Thread [<1> main] (Suspended (exception RuntimeException))  
        <VM does not provide monitor information>   
        ActivityThread.performLaunchActivity(ActivityThread$ActivityClientRecord, Intent) line: 2295    
        ActivityThread.handleLaunchActivity(ActivityThread$ActivityClientRecord, Intent) line: 2349 
        ActivityThread.access$700(ActivityThread, ActivityThread$ActivityClientRecord, Intent) line: 159    
        ActivityThread$H.handleMessage(Message) line: 1316  
        ActivityThread$H(Handler).dispatchMessage(Message) line: 99 
        Looper.loop() line: 137 
        ActivityThread.main(String[]) line: 5419    
        Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]  
        Method.invoke(Object, Object...) line: 525  
        ZygoteInit$MethodAndArgsCaller.run() line: 1187 
        ZygoteInit.main(String[]) line: 1003    
        NativeStart.main(String[]) line: not available [native method]  
    Thread [<11> Binder_3] (Running) (may be out of synch)  
    Thread [<10> Binder_2] (Running) (may be out of synch)  
    Thread [<9> Binder_1] (Running) (may be out of synch)

为什么呼叫会产生此错误？ HttpResponse response = httpclient.execute(httppost);似乎失败了！

Answer 1

从你的问题，我可以看到主线程被暂停。假设您在主线程中执行HTTP请求，这可能是您的问题。通常它会产生一个NetworkOnMainThreadException，我相信当你继续使用调试器时会发生这种情况。

由于您不能在主线程中执行HTTP请求，因此解决方案可以是：

JSONArray mJsonArray;

// Inner class to do http request out from main thread
class HttpRequestTask extends AsyncTask<String, Void, Void> {
    @Override
    protected Void doInBackground(String... url) {
        InputStream iS = null;

        // HTTP
        try {

            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost(url[0]);
            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            iS = entity.getContent();
        }
        catch (Exception e) {
            Log.e("QUIZ", e.getMessage());
            return null;
        }

        if (iS != null) {
            mJsonArray = new JSONArray(urlInputStream.toString());
        }

        return null;
    }

    protected void onPostExecute(Long result) {
        // A toast to inform that the http requeset just finished.
        // The json object will be available in mJsonArray class field.
        Toast.makeText(YourActivity.this, "HTTP request finished", Toast.LENGTH_SHORT).show();
    }
}

最后，要创建异步任务并运行它：

new HttpRequestTask().execute(url);

Answer 2

这可能不是问题，但我们永远不会知道：你是否在清单中要求获得互联网许可？

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

函数调用导致Dalvik错误

2 个答案: