我在类moviemodel中有getter和setter
我收到了这个错误
FATAL EXCEPTION: main Process: com.example.shailendra.fulljson, PID: 7251
java.lang.NullPointerException
at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330)
at android.widget.ListView.setAdapter(ListView.java:480)
at .MainActivity$JsonClass.onPostExecute(MainActivity)
MainActivity。的java
class MainActivity extends AppCompatActivity {
Button clickMe;
ListView listView;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView=(ListView)findViewById(R.id.listView);
clickMe= (Button)findViewById(R.id.clickMe);
clickMe.setOnClickListener( new View.OnClickListener() {
@Override
public void onClick(View v) {
new JsonClass().execute("http://jsonparsing.parseapp.com/jsonData/moviesData.txt");
}
});
}
class JsonClass extends AsyncTask<String,Void,List<MovieModel>> {
ListView listView=(ListView)findViewById(R.id.listView);
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected List<MovieModel> doInBackground(String... params) {
HttpURLConnection connection=null;
BufferedReader reader=null;
MovieModel movieModel = new MovieModel();
MovieModel.Cast cast= new MovieModel.Cast();
try {
URL url= new URL(params[0]);
connection=(HttpURLConnection)url.openConnection();
connection.connect();
InputStream stream=connection.getInputStream();
InputStreamReader isr= new InputStreamReader(stream);
reader =new BufferedReader(isr);
StringBuffer buffer=new StringBuffer();
String line="";
while((line=reader.readLine())!=null) {
buffer.append(line);
}
String finalJson=buffer.toString();
JSONObject parentObject= new JSONObject(finalJson);
JSONArray parentArray= parentObject.getJSONArray("movies");
List<MovieModel> movieModelList= new ArrayList<>();
for(int i=0;i<parentArray.length();i++) {
JSONObject answerObject = parentArray.getJSONObject(i);
movieModel.setMovie(answerObject.getString("movie"));
movieModel.setYear(answerObject.getInt("year"));
movieModel.setRating((float) answerObject.getDouble("rating"));
movieModel.setDirector(answerObject.getString("director"));
movieModel.setDuration(answerObject.getInt("duration"));
movieModel.settagLine(answerObject.getString("tagline"));
movieModel.setImage(answerObject.getString("image"));
movieModel.setStory(answerObject.getString("story"));
List<MovieModel.Cast> castList= new ArrayList<>();
for(int j=0;j<answerObject.getJSONArray("cast").length();j++) {
JSONObject castObject= answerObject.getJSONArray("cast").getJSONObject(j);
cast.setName(castObject.getString("name"));
castList.add(cast);
}
movieModel.setCastList(castList);
movieModelList.add(movieModel);
}
return movieModelList;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} finally {
if(connection!=null) {
connection.disconnect();
}
try {
if(reader!=null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
@Override
protected void onPostExecute(List<MovieModel> s) {
super.onPostExecute(s);
MovieAdapter adapter = new MovieAdapter(getApplicationContext(),R.layout.row,s);
listView.setAdapter(adapter);
}
}
public class MovieAdapter extends ArrayAdapter {
public List<MovieModel> movieModelList;
private int resource;
private LayoutInflater inflater;
public MovieAdapter(Context context, int resource, List<MovieModel> objects) {
super(context, resource, objects);
movieModelList=objects;
this.resource=resource;
inflater=(LayoutInflater)getSystemService(LAYOUT_INFLATER_SERVICE);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView==null) {
convertView=inflater.inflate(resource,null);
}
ImageView ivMovieIcon;
TextView tvMovie;
TextView tvTagLine;
TextView tvYear;
TextView tvDuration;
TextView tvDirector;
TextView tvCast;
TextView tvStory;
RatingBar rbMovieRating;
ivMovieIcon =(ImageView)convertView.findViewById(R.id.ivicon);
tvTagLine=(TextView)convertView.findViewById(R.id.tvTagLine);
tvYear=(TextView)convertView.findViewById(R.id.tvYear);
tvDuration=(TextView)convertView.findViewById(R.id.tvDuration);
tvDirector=(TextView)convertView.findViewById(R.id.tvDirector);
tvStory=(TextView)convertView.findViewById(R.id.tvStory);
tvCast=(TextView)convertView.findViewById(R.id.tvCast);
rbMovieRating=(RatingBar) convertView.findViewById(R.id.rbMovie);
tvMovie=(TextView)convertView.findViewById(R.id.tvMovie);
tvCast.setText(movieModelList.get(position).getDuration());
tvDirector.setText(movieModelList.get(position).getDirector());
tvYear.setText("Year: " + movieModelList.get(position).getYear());
tvStory.setText(movieModelList.get(position).getStory());
tvDuration.setText(movieModelList.get(position).getDuration());
tvTagLine.setText(movieModelList.get(position).getTagLine());
tvMovie.setText(movieModelList.get(position).getMovie());
StringBuffer stringBuffer= new StringBuffer();
for(MovieModel.Cast cast: movieModelList.get(position).getCastList()) {
stringBuffer.append(cast.getName()+ ", ");
}
tvCast.setText(stringBuffer);
rbMovieRating.setRating(movieModelList.get(position).getRating()/2);
return convertView;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
// new JsonClass().execute("http://jsonparsing.parseapp.com/jsonData/moviesData.txt");
//
// return true;
}
return super.onOptionsItemSelected(item);
}
}
答案 0 :(得分：0)
好吧，这可能会发生，因为你在doInBackground结束时返回null。
要么
return movieModelList;
或者像这样初始化适配器。
MovieAdapter adapter = new MovieAdapter(getApplicationContext(),R.layout.row,movieModelList);
我的建议是你在Adapter类中为ArrayList使用不同的变量名，这样你就不会被混淆。
快乐编码。
答案 1 :(得分：0)
此行可能正在创建例外。
convertView=inflater.inflate(resource,null);
您可以像这样替换此行。
convertView=inflater.inflate(resource,parent,false);
在“onPostExecute Method”
中检查“s”是否为空@Override
protected void onPostExecute(List<MovieModel> s) {
if(s!=null && s.size()>0) {
MovieAdapter adapter = new MovieAdapter(getApplicationContext(),R.layout.row,s);
listView.setAdapter(adapter);
}
super.onPostExecute(s);
}
答案 2 :(得分：0)
您在该列表视图中得到答案意味着s返回null，或者您的数据未从Web正确解析。从json好奇概念网站查看你的json，看看s是否返回null。
答案 3 :(得分：-1)
在Post方法中更改此内容：
MovieAdapter adapter = new MovieAdapter(getApplicationContext(),R.layout.row,movieModelList);
listView.setAdapter(adapter);
让我知道它的作用与否？