尝试调用虚方法
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【中文标题】尝试调用虚方法【英文标题】：Attempt to invoke virtual method 【发布时间】：2014-03-26 13:24:14 【问题描述】：我试图在我的onCreateView 中获取一些LinearLayouts，但我的应用程序崩溃并显示以下消息：
23430-23430/? W/System.err﹕ java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
代码如下：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
new Body().execute();
card01 = (LinearLayout) getView().findViewById(R.id.card01);
card02 = (LinearLayout) getView().findViewById(R.id.card02);
card03 = (LinearLayout) getView().findViewById(R.id.card03);
card04 = (LinearLayout) getView().findViewById(R.id.card04);
card05 = (LinearLayout) getView().findViewById(R.id.card05);
card06 = (LinearLayout) getView().findViewById(R.id.card06);
card01.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
Toast.makeText(getActivity(), "Card Clicked", Toast.LENGTH_SHORT).show();
);
return rootView;
这是一个纯粹的Fragment 类。调用此Fragment 的Activity 不包含此Fragment。我做错了吗？ Fragmentalways 是否应该在 Activity 内？
按要求整AsyncTask：
// AsyncTask
private class Body extends AsyncTask<Void, Void, Void>
@Override
protected void onPreExecute()
super.onPreExecute();
mProgressDialog = new ProgressDialog(getActivity());
mProgressDialog.setTitle("Fetching your info");
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
mProgressDialog.show();
@Override
protected Void doInBackground(Void... params)
Document doc;
try
// Connect to the web site
doc = Jsoup.connect(url).get();
// Using Elements to get the Meta data
//Date of Event
Elements dateElement = doc.select("span[class=date-display-single]");
//Headline of Event
Elements titleElement = doc.select("h2[property=schema:name]");
//Description of Event
Elements bodyElement = doc.select("div[class=field field-name-body field-type-text-with-summary field-label-hidden]");
// get the dates
date1 = dateElement.eq(0).text();
date2 = dateElement.eq(1).text();
date3 = dateElement.eq(2).text();
date4 = dateElement.eq(3).text();
date5 = dateElement.eq(4).text();
date6 = dateElement.eq(5).text();
// get headlines
head1 = titleElement.eq(0).text();
head2 = titleElement.eq(1).text();
head3 = titleElement.eq(2).text();
head4 = titleElement.eq(3).text();
head5 = titleElement.eq(4).text();
head6 = titleElement.eq(5).text();
// get description
body1 = bodyElement.eq(0).toString();
body1 = Jsoup.parse(body1.replaceAll("<br />", "br2n")).toString();
body1 = Jsoup.parse(body1.replaceAll("</p>", "p2n")).text();
body1 = body1.replaceAll("br2n", "\n");
body1 = body1.replaceAll("p2n", "\n\n");
body2 = bodyElement.eq(1).toString();
body2 = Jsoup.parse(body2.replaceAll("<br />", "br2n")).toString();
body2 = Jsoup.parse(body2.replaceAll("</p>", "p2n")).text();
body2 = body2.replaceAll("br2n", "\n");
body2 = body2.replaceAll("p2n", "\n\n");
body3 = bodyElement.eq(2).toString();
body3 = Jsoup.parse(body3.replaceAll("<br />", "br2n")).toString();
body3 = Jsoup.parse(body3.replaceAll("</p>", "p2n")).text();
body3 = body3.replaceAll("br2n", "\n");
body3 = body3.replaceAll("p2n", "\n\n");
body4 = bodyElement.eq(3).toString();
body4 = Jsoup.parse(body4.replaceAll("<br />", "br2n")).toString();
body4 = Jsoup.parse(body4.replaceAll("</p>", "p2n")).text();
body4 = body4.replaceAll("br2n", "\n");
body4 = body4.replaceAll("p2n", "\n\n");
body5 = bodyElement.eq(4).toString();
body5 = Jsoup.parse(body5.replaceAll("<br />", "br2n")).toString();
body5 = Jsoup.parse(body5.replaceAll("</p>", "p2n")).text();
body5 = body5.replaceAll("br2n", "\n");
body5 = body5.replaceAll("p2n", "\n\n");
body6 = bodyElement.eq(5).toString();
body6 = Jsoup.parse(body6.replaceAll("<br />", "br2n")).toString();
body6 = Jsoup.parse(body6.replaceAll("</p>", "p2n")).text();
body6 = body6.replaceAll("br2n", "\n");
body6 = body6.replaceAll("p2n", "\n\n");
//cut out the date in the headlines (13 characters) if the String has something to cut
//Let's hope the website stays like this
if (head1.length() > 0)
head1 = head1.substring(13);
if (head2.length() > 0)
head2 = head2.substring(13);
if (head3.length() > 0)
head3 = head3.substring(13);
if (head4.length() > 0)
head4 = head4.substring(13);
if (head5.length() > 0)
head5 = head5.substring(13);
if (head6.length() > 0)
head6 = head6.substring(13);
//Get Event Labels
AssetManager am = getActivity().getAssets();
bwe = BitmapFactory.decodeStream(am.open("label/bwe.jpg"));
commaklar = BitmapFactory.decodeStream(am.open("label/commaklar.jpg"));
// musica = BitmapFactory.decodeStream(am.open("label/musica.jpg"));
doualatag = BitmapFactory.decodeStream(am.open("label/doualatag.jpg"));
synestesia = BitmapFactory.decodeStream(am.open("label/synestesia.jpg"));
douala = BitmapFactory.decodeStream(am.open("label/douala.jpg"));
// tanzen = BitmapFactory.decodeStream(am.open("label/tanzen.jpg"));
// nacht = BitmapFactory.decodeStream(am.open("label/nacht.jpg"));
catch (Exception e)
e.printStackTrace();
return null;
@Override
protected void onPostExecute(Void result)
mProgressDialog.dismiss();
try
RobotoTextView date_widget1 = (RobotoTextView) getActivity().findViewById(R.id.date01);
date_widget1.setText(date1);
RobotoTextView head_widget1 = (RobotoTextView) getActivity().findViewById(R.id.head01);
head_widget1.setText(head1);
RobotoTextView body_widget1 = (RobotoTextView) getActivity().findViewById(R.id.body1);
Whitelist.simpleText().addTags("br", "p");
body_widget1.setText(body1);
ImageView label1 = (ImageView) getView().findViewById(R.id.label1);
if (head1.contains("BLACKWHITE"))
label1.setImageBitmap(bwe);
if (date1.contains("Do"))
;
label1.setImageBitmap(doualatag);
if (head1.contains("COMMAKLAR"))
label1.setImageBitmap(commaklar);
if (head1.toLowerCase().contains("synestesia") | head1.contains("SYNESTESIA"))
label1.setImageBitmap(synestesia);
if (label1.getDrawable() == null)
label1.setImageBitmap(douala);
RobotoTextView date_widget2 = (RobotoTextView) getActivity().findViewById(R.id.date02);
date_widget2.setText(date2);
RobotoTextView head_widget2 = (RobotoTextView) getActivity().findViewById(R.id.head02);
head_widget2.setText(head2);
RobotoTextView body_widget2 = (RobotoTextView) getActivity().findViewById(R.id.body2);
body_widget2.setText(body2);
ImageView label2 = (ImageView) getView().findViewById(R.id.label2);
if (head2.contains("BLACKWHITE"))
label2.setImageBitmap(bwe);
if (date2.contains("Do"))
label2.setImageBitmap(doualatag);
if (head2.contains("COMMAKLAR"))
label2.setImageBitmap(commaklar);
if (head2.toLowerCase().contains("synestesia"))
label2.setImageBitmap(synestesia);
if (label2.getDrawable() == null)
label2.setImageBitmap(douala);
RobotoTextView date_widget3 = (RobotoTextView) getActivity().findViewById(R.id.date03);
date_widget3.setText(date3);
RobotoTextView head_widget3 = (RobotoTextView) getActivity().findViewById(R.id.head03);
head_widget3.setText(head3);
RobotoTextView body_widget3 = (RobotoTextView) getActivity().findViewById(R.id.body3);
body_widget3.setText(body3);
ImageView label3 = (ImageView) getView().findViewById(R.id.label3);
if (head3.contains("BLACKWHITE"))
label3.setImageBitmap(bwe);
if (date3.contains("Do"))
label3.setImageBitmap(doualatag);
if (head3.contains("COMMAKLAR"))
label3.setImageBitmap(commaklar);
if (head3.toLowerCase().contains("synestesia"))
label3.setImageBitmap(synestesia);
if (label3.getDrawable() == null)
label3.setImageBitmap(douala);
RobotoTextView date_widget4 = (RobotoTextView) getActivity().findViewById(R.id.date04);
date_widget4.setText(date4);
RobotoTextView head_widget4 = (RobotoTextView) getActivity().findViewById(R.id.head04);
head_widget4.setText(head4);
RobotoTextView body_widget4 = (RobotoTextView) getActivity().findViewById(R.id.body4);
body_widget4.setText(body4);
ImageView label4 = (ImageView) getView().findViewById(R.id.label4);
if (head4.contains("BLACKWHITE"))
label4.setImageBitmap(bwe);
if (date4.contains("Do"))
label4.setImageBitmap(doualatag);
if (head4.contains("COMMAKLAR"))
label4.setImageBitmap(commaklar);
if (head4.toLowerCase().contains("synestesia"))
label4.setImageBitmap(synestesia);
if (label4.getDrawable() == null)
label4.setImageBitmap(douala);
if (!head5.equals(""))
RobotoTextView date_widget5 = (RobotoTextView) getActivity().findViewById(R.id.date05);
date_widget5.setText(date5);
RobotoTextView head_widget5 = (RobotoTextView) getActivity().findViewById(R.id.head05);
head_widget5.setText(head5);
RobotoTextView body_widget5 = (RobotoTextView) getActivity().findViewById(R.id.body5);
body_widget5.setText(body5);
ImageView label5 = (ImageView) getView().findViewById(R.id.label5);
if (head5.contains("BLACKWHITE"))
label5.setImageBitmap(bwe);
if (date5.contains("Do"))
label5.setImageBitmap(doualatag);
if (head5.contains("COMMAKLAR"))
label5.setImageBitmap(commaklar);
if (head5.toLowerCase().contains("synestesia"))
label5.setImageBitmap(synestesia);
if (label5.getDrawable() == null)
label5.setImageBitmap(douala);
if (!head6.equals(""))
RobotoTextView date_widget6 = (RobotoTextView) getActivity().findViewById(R.id.date06);
date_widget6.setText(date6);
RobotoTextView head_widget6 = (RobotoTextView) getActivity().findViewById(R.id.head06);
head_widget6.setText(head6);
RobotoTextView body_widget6 = (RobotoTextView) getActivity().findViewById(R.id.body6);
body_widget6.setText(body6);
ImageView label6 = (ImageView) getView().findViewById(R.id.label6);
if (head6.contains("BLACKWHITE"))
label6.setImageBitmap(bwe);
if (date6.contains("Do"))
label6.setImageBitmap(doualatag);
if (head6.contains("COMMAKLAR"))
label6.setImageBitmap(commaklar);
if (head6.toLowerCase().contains("synestesia"))
label6.setImageBitmap(synestesia);
if (label6.getDrawable() == null)
label6.setImageBitmap(douala);
catch (NullPointerException e)
e.printStackTrace();
【问题讨论】：
【参考方案1】：在我尝试使组件扩展视图时导致相同的NullPointerException，可能是由于使用了LayoutInflater
View view = LayoutInflater.from(context).inflate(R.layout.layout_index_bar, null);
container = (LinearLayout) view.findViewById(R.id.indexContainer);
【讨论】：
【参考方案2】：改成
card01 = (LinearLayout) rootView.findViewById(R.id.card01);
card02 = (LinearLayout) rootView.findViewById(R.id.card02);
card03 = (LinearLayout) rootView.findViewById(R.id.card03);
card04 = (LinearLayout) rootView.findViewById(R.id.card04);
card05 = (LinearLayout) rootView.findViewById(R.id.card05);
card06 = (LinearLayout) rootView.findViewById(R.id.card06);
你膨胀了一个布局。视图属于膨胀布局。所以使用视图对象来初始化onCreateView中的视图
Fragment 由 Acitvity 托管
您可以在onActivityCreated 中使用getView 并初始化视图
在onCreateView 中初始化你的TextView。由于 Asynctask 是一个内部类，你可以在那里更新 ui
声明
RobotoTextView date_widget2;
作为实例变量
然后在onCreateView中
date_widget2= (RobotoTextView) rootView.findViewById(R.id.date02);
【讨论】：
好的，谢谢。如您所见，在那之前我有一个 AsyncTask 。我在onPostExecute 中遇到了同样的异常，但不能使用 rootview。我应该把new Body().execute() 放在onActivityCreated 中吗？
@mike.b93 你在异步任务中做什么。取决于那个
我解析一个网站并在onPostExecute 上将文本设置为TextViews
让我们continue this discussion in chat【参考方案3】：
您太早调用getView() - 它只会返回您自己从onCreateView() 返回的视图。
在onCreateView() 内部使用最近膨胀的rootView 而不是getView()。
【讨论】：
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