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我的应用程序不断崩溃，当我查看我的 logcat 时，我收到两组错误并且我的应用程序崩溃了。如果有人能告诉我出了什么问题以及我能做些什么来防止它，我将非常感激。 

07-27 11:05:53.647: E/AndroidRuntime(913): FATAL EXCEPTION: AsyncTask #2
07-27 10:36:54.139: E/AndroidRuntime(775): java.lang.RuntimeException: An error occured while executing doInBackground()
07-27 10:36:54.139: E/AndroidRuntime(775):  at android.os.AsyncTask$3.done(AsyncTask.java:299)
07-27 10:36:54.139: E/AndroidRuntime(775):  at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
07-27 10:36:54.139: E/AndroidRuntime(775):  at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
07-27 10:36:54.139: E/AndroidRuntime(775):  at java.util.concurrent.FutureTask.run(FutureTask.java:239)
07-27 10:36:54.139: E/AndroidRuntime(775):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
07-27 10:36:54.139: E/AndroidRuntime(775):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
07-27 10:36:54.139: E/AndroidRuntime(775):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
07-27 10:36:54.139: E/AndroidRuntime(775):  at java.lang.Thread.run(Thread.java:856)
07-27 10:36:54.139: E/AndroidRuntime(775): Caused by: java.lang.NullPointerException
07-27 10:36:54.139: E/AndroidRuntime(775):  at com.theproblemsolver.ListView$LoadAllData.doInBackground(ListView.java:92)
07-27 10:36:54.139: E/AndroidRuntime(775):  at com.theproblemsolver.ListView$LoadAllData.doInBackground(ListView.java:1)
07-27 10:36:54.139: E/AndroidRuntime(775):  at android.os.AsyncTask$2.call(AsyncTask.java:287)
07-27 10:36:54.139: E/AndroidRuntime(775):  at java.util.concurrent.FutureTask.run(FutureTask.java:234)
07-27 10:36:54.139: E/AndroidRuntime(775):  ... 4 more

这是我的 logcat 给我的另一个错误......

theproblemsolver.ListView has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{40d0e800 V.E..... R.....ID 0,0-234,72} that was originally added here
07-27 11:05:56.119: E/WindowManager(913): android.view.WindowLeaked: Activity com.theproblemsolver.ListView has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{40d0e800 V.E..... R.....ID 0,0-234,72} that was originally added here
07-27 11:05:56.119: E/WindowManager(913):   at android.view.ViewRootImpl.<init>(ViewRootImpl.java:354)
07-27 11:05:56.119: E/WindowManager(913):   at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:216)
07-27 11:05:56.119: E/WindowManager(913):   at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
07-27 11:05:56.119: E/WindowManager(913):   at android.app.Dialog.show(Dialog.java:281)
07-27 11:05:56.119: E/WindowManager(913):   at com.theproblemsolver.ListView$LoadAllData.onPreExecute(ListView.java:85)
07-27 11:05:56.119: E/WindowManager(913):   at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
07-27 11:05:56.119: E/WindowManager(913):   at android.os.AsyncTask.execute(AsyncTask.java:534)
07-27 11:05:56.119: E/WindowManager(913):   at com.theproblemsolver.ListView.onCreate(ListView.java:52)
07-27 11:05:56.119: E/WindowManager(913):   at android.app.Activity.performCreate(Activity.java:5104)
07-27 11:05:56.119: E/WindowManager(913):   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
27 11:05:56.119: E/WindowManager(913):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-27 11:05:56.119: E/WindowManager(913):   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-27 11:05:56.119: E/WindowManager(913):   at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-27 11:05:56.119: E/WindowManager(913):   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-27 11:05:56.119: E/WindowManager(913):   at android.os.Handler.dispatchMessage(Handler.java:99)
07-27 11:05:56.119: E/WindowManager(913):   at android.os.Looper.loop(Looper.java:137)
07-27 11:05:56.119: E/WindowManager(913):   at android.app.ActivityThread.main(ActivityThread.java:5041)
07-27 11:05:56.119: E/WindowManager(913):   at java.lang.reflect.Method.invokeNative(Native Method)
07-27 11:05:56.119: E/WindowManager(913):   at java.lang.reflect.Method.invoke(Method.java:511)
07-27 11:05:56.119: E/WindowManager(913):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-27 11:05:56.119: E/WindowManager(913):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-27 11:05:56.119: E/WindowManager(913):   at dalvik.system.NativeStart.main(Native Method

主要活动

public class MainActivity extends Activity {

    EditText et;
    Button getanswer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button getanswer = (Button) findViewById(R.id.button1);
        getanswer.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MainActivity.this, ListView.class);
            startActivity(i);
        }


        });
    } 
}

列表视图活动

public class ListView extends ListActivity {

    private ProgressDialog pDialog;

    JSONParsser jParser = new JSONParsser();
    ArrayList<HashMap<String, String>> questionList;

    private static String URI = "http://example.com/json";;

    //JSONObject json = jParser.getJSONFromURI(URI); 

     final String TAG_RESULTS = "ResultsSet";
     final String TAG_SUBJECT = "Subject";
     final String TAG_NUMANSWERS = "NumAnswers";
     final String TAG_QUESTION = "Question";
     final String TAG_QUESTION_CONTENT = "Content";
     final String TAG_QUESTION_CHOSENANSWER = "ChosenAnswer";
     final String TAG_QUESTION_ANSWERS = "Answers";

            JSONArray ResultsSet = null;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState); 
        //setContentView(R.layout.listview);

    questionList = new ArrayList<HashMap<String, String>>();

    android.widget.ListView lv = getListView(); 

    new LoadAllData().execute();

    lv.setOnItemClickListener(new OnItemClickListener() {

    @Override
        public void onItemClick(AdapterView<?> parent, View view,int position, long id) {


        }
    });

}

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (resultCode == 100) {
            Intent intent = getIntent();
            startActivity(intent);
            finish();
        }
    }

    class LoadAllData extends AsyncTask<String, String, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(ListView.this);
            pDialog.setMessage("Loading Data. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(false);
            pDialog.show();
        }

        protected String doInBackground(String... args) {

            try {
                    JSONObject json = jParser.getJSONFromURI(URI);
                    ResultsSet = json.getJSONArray(TAG_RESULTS);

                   for(int i = 0; i < ResultsSet.length(); i++) {
                       JSONObject r = ResultsSet.getJSONObject(i);
                       String Subject = r.getString(TAG_SUBJECT);
                       String NumAnswers = r.getString(TAG_NUMANSWERS);

                       JSONObject Question = r.getJSONObject(TAG_QUESTION);
                       String Content = Question.getString(TAG_QUESTION_CONTENT);
                       String ChosenAnswer = Question.getString(TAG_QUESTION_CHOSENANSWER);
                       String Answers = Question.getString(TAG_QUESTION_ANSWERS);

                       HashMap<String, String> map = new HashMap<String, String>();

                       map.put(TAG_SUBJECT, Subject);
                       map.put(TAG_NUMANSWERS, NumAnswers);

                       questionList.add(map);
                   }



            } catch (JSONException e) {
                e.printStackTrace();
            }
            return null;


        }


        protected void onPostExecute(String file_URI) {

            pDialog.dismiss();
            runOnUiThread(new Runnable() {
            public void run() {
                ListAdapter adapter = new SimpleAdapter(getBaseContext(), questionList,
                        R.layout.row,
                        new String[] { TAG_SUBJECT, TAG_NUMANSWERS }, new int[] {
                        R.id.Subject, R.id.NumAnswers });

                setListAdapter(adapter);



                }
            });

        }
}}

这是包含该JSONObject json = jParser.getJSONFromURI(URI);方法的我的 JSONParsser 类

public class JSONParsser {


    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";
    EditText et;

    public JSONParsser () {
    }

    public JSONObject getJSONFromURI(String URI) {

        try{
        HttpClient client = new DefaultHttpClient();
        try {
            URI website = new URI("http://example.com/json");
            HttpGet request = new HttpGet();
            request.setURI(website);
            try {
                HttpResponse response = client.execute(request);
            HttpEntity httpEntity = response.getEntity();
            is = httpEntity.getContent();

            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } catch (URISyntaxException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        return jObj;

        }finally{}

    }{

    }

}
4

1 回答 1

0

好的，我会写一个答案：

首先将内容分配给 InputStream，然后返回尚未分配的 JSONObject，因此您会得到 NullPointerException。您必须解析输入流的内容。我会做这样的事情：

HttpEntity httpEntity = response.getHttpEntity();
String resultString = EntityUtils.toString(httpEntity);

httpEntity.consumeContent();

return new JSONObject(resultString);

注意：上面的代码没有捕获任何异常，您必须修复它。

然后你有很多不必要的全局变量，不需要你的全局变量。将他们转换为当地人。还请对响应进行 nullcheck，并在返回 JSONObject 之前读取响应的 statusCode，使其为 200。

另外：onPostExecute始终在 UI 线程上运行，仅doInBackground在另一个线程上。

窗口泄漏是因为你没有关闭你Override的. 做这样的事情（当你开始保持对它的引用时）：onDestroy()AsyncTaskAsyncTask

@Override
public void onDestroy() {
    super.onDestroy();

    if (myAsyncTask != null) {
        myAsyncTask.cancel(true);
        myAsyncTask = null;
    }
}
于 2013-07-28T19:37:09.107 回答