为什么我不能将此JSON对象传递给另一个活动

时间：2016-04-11 18:13:12

标签： java android json

我正在使用Volley从Json获取新闻。在MainActivity中，我已成功获取并解析了json，因此我对此没有任何问题。 现在每个新闻项目都包含标题和新闻摘录。我想要的是，每次点击新闻摘录时，它都会启动另一个名为 NewsDetails 的活动，  在开始时，＆＃34; ID＆＃34; （json对象）点击了新闻摘录，将被发送到 NewsDetails 。

在 NewsDetails 中，我将连接＆＃34; ID＆＃34;和网站的网址;这也将返回一个json数组。然后我将解析json并显示它;希望这不会给我一个问题。

我遇到困难的地方是尝试发送＆＃34; ID＆＃34;并启动＆＃34; NewsDetails＆＃34;。

到目前为止，这就是我一直在做的事情：

所有MainActivity类 

user.Action().my_dogs()
AttributeError: type object 'User' has no attribute 'user_session '


user.Action.my_dogs()
TypeError: Action() missing 1 required positional argument: 'self'

上面的代码没问题。

整个NewsItems类 

  public class MainActivity extends AppCompatActivity{

    private final String TAG = "MainActivity";

    //Creating a list of newss
    private List<NewsItems> mNewsItemsList;

    //Creating Views
    private RecyclerView recyclerView;
    private RecyclerView.Adapter adapter;
    private ProgressDialog mProgressDialog;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d(TAG, "Device rotated and onCreate called");

        //Initializing Views
        recyclerView = (RecyclerView) findViewById(R.id.news_recycler);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);



        //Initializing the newslist
        mNewsItemsList = new ArrayList<>();
        adapter = new NewsAdapter(mNewsItemsList, this);

        recyclerView.setAdapter(adapter);



        //Caling method to get data
         getData();

    }


    //This method will get data from the web api

    private void getData(){


        Log.d(TAG, "getData called");
        //Showing progress dialog
        mProgressDialog = new ProgressDialog(MainActivity.this);
        mProgressDialog.setCancelable(false);
        mProgressDialog.setMessage(this.getResources().getString(R.string.load_news));
        mProgressDialog.show();


        //Creating a json request
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(ConfigNews.GET_URL,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Log.d(TAG, "onResponse called");
                        //Dismissing the progress dialog
                        if (mProgressDialog != null) {
                            mProgressDialog.hide();
                        }
                        /*progressDialog.dismiss();*/


                        //calling method to parse json array
                        parseData(response);

                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {

                    }
                });

        //Creating request queue
        RequestQueue requestQueue = Volley.newRequestQueue(this);

        //Adding request to the queue
        requestQueue.add(jsonArrayRequest);

    }

    //This method will parse json data
    private void parseData(JSONArray array){
        Log.d(TAG, "Parsing array");

        for(int i = 0; i<array.length(); i++) {
            NewsItems newsItem = new NewsItems();
            JSONObject jsonObject = null;
            try {
                jsonObject = array.getJSONObject(i);
                newsItem.setNews_title(jsonObject.getString(ConfigNews.TAG_NEWS_TITLE));
                newsItem.setNews_excerpt(jsonObject.getString(ConfigNews.TAG_NEWS_EXCERPT));
                newsItem.setNewsId(jsonObject.getInt(ConfigNews.TAG_NEWS_ID));

            } catch (JSONException w) {
                w.printStackTrace();
            }
            mNewsItemsList.add(newsItem);

        }

        adapter.notifyItemRangeChanged(0, adapter.getItemCount());


    }


    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy called");
        if (mProgressDialog != null){
            mProgressDialog.dismiss();
            Log.d(TAG, "mProgress dialog dismissed");

        }
    }

}

以上代码仍然没有问题。

所有NewsAdapter 

public class NewsItems {
      private String news_title;
      private String news_excerpt;
      private String news_id;

      public String getNews_title() {
          return news_title;
      }

      public void setNews_title(String news_title) {
          this.news_title = news_title;
      }

      public String getNews_excerpt() {
          return news_excerpt;
      }

      public void setNews_excerpt(String news_excerpt) {
          this.news_excerpt = news_excerpt;
      }

      public String getNews_id() {
          return news_id;
      }

      public void setNews_id(String news_id) {
          this.news_id = news_id;
      }

  }

这是给我带来问题的部分。

具体行

   public class NewsAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{

    private ImageLoader imageLoader;
    private Context mContext;

    //List of newss
    private List<NewsItems> mNewsItems;

    private final int VIEW_ITEM = 0;
    private final int VIEW_PROG = 1;

    private int lastPosition = -1;

   public NewsAdapter(List<NewsItems> newsItems, Context context) {
       super();

       //Getting all newss
       this.mNewsItems = newsItems;
       this.mContext = context;
   }

    @Override
    public int getItemViewType(int position) {
        if (isPositionItem(position))
            return VIEW_ITEM;
        return VIEW_PROG;
    }

    private boolean isPositionItem(int position) {
       return position != getItemCount()-1;
    }



    @Override
    public RecyclerView.ViewHolder  onCreateViewHolder (ViewGroup parent, int viewType) {
        if (viewType == VIEW_ITEM) {
            View v =  LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.news_summ, parent, false);
            return new TextViewHolder(v);
        } else if (viewType == VIEW_PROG){
            View v = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.recyclerfooter, parent, false);
            return new ProgressViewHolder(v);
        }

        return null;
    }



    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {


        if (holder instanceof TextViewHolder) {
            NewsItems newsList = mNewsItems.get(position);
            ((TextViewHolder) holder).newsTitle.setText(newsList.getNews_title());
            ((TextViewHolder) holder).newsExcerpt.setText(newsList.getNews_excerpt());
            ((TextViewHolder) holder).newsId.setText(String.valueOf(newsList.getNewsId()));

        } else {
            ((ProgressViewHolder) holder).progressBar.setIndeterminate(true);
            ((ProgressViewHolder) holder).loadButton.setText(R.string.reload);
        }


    }


    @Override
    public int getItemCount(){
        //Return the number of items in the data set
        return mNewsItems.size();
    }




    public static class TextViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        public TextView newsTitle,newsExcerpt, newsId;
        public ImageButton imageButton;
        public NewsItems dNewsItems;

        public TextViewHolder (final View newsView) {
            super(newsView);
            newsTitle = (TextView) newsView.findViewById(R.id.news_title);
            newsExcerpt = (TextView) newsView.findViewById(R.id.news_excerpt);
            newsId = (TextView) newsView.findViewById(R.id.news_id);

            newsExcerpt.setOnClickListener(this);


        }



        @Override
        public void onClick(View v) {


            if (v.getId() == newsExcerpt.getId()) {
               if (v.getId() == newsExcerpt.getId()) {
               Intent i = NewsDetails.newIntent(getActivity(), dNewsItems.getNews_id());
               startActivity(i);
               }
            }
        }
    }

    public static class ProgressViewHolder extends RecyclerView.ViewHolder implements  View.OnClickListener{
        Button loadButton;
        ProgressBar progressBar;
        public ProgressViewHolder(View footerView){
            super(footerView);
            loadButton = (Button) footerView.findViewById(R.id.reload_button);
            progressBar = (ProgressBar) footerView.findViewById(R.id.progress_load);

            loadButton.setOnClickListener(this);

            if(NetworkCheck.isAvailableAndConnected(footerView.getContext())) {
                progressBar.setVisibility(View.VISIBLE);


            } else if (!NetworkCheck.isAvailableAndConnected(footerView.getContext())) {
                loadButton.setVisibility(View.VISIBLE);
            }
        }

        @Override
        public void onClick(View v) {
            if (v.getId() == loadButton.getId()) {
                //
            }
        }
    }


}

当我将鼠标悬停在Intent i = NewsDetails.newIntent(getActivity(), dNewsItems.getNews_id()); startActivity(i); 时，它会显示＆＃34;无法解析方法＆＃39; newIntent（？，java.lang.String）＆＃39;＆＃34; 。 然后我将鼠标悬停在newIntent上，表示＆＃34;无法解决方法＆＃39; getActivity（）＆＃39;＆＃34; 。 对于getActivity()，＆＃34;无法解析方法＆＃39; startActivity（android.content.Intent）＆＃39;＆＃34;

所以现在，我的问题是我做错了什么以及我该如何纠正呢？

实施Rohit Arya回答后的NewsAdapter 

startActivity(i);

Stacktrace实施Rohit Arya的回答 

public class NewsAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{

    private ImageLoader imageLoader;
    private Context mContext;

    //List of newss
    private List<NewsItems> mNewsItems;

    private final int VIEW_ITEM = 0;
    private final int VIEW_PROG = 1;

    private int lastPosition = -1;

   public NewsAdapter(List<NewsItems> newsItems, Context context) {
       super();

       //Getting all newss
       this.mNewsItems = newsItems;
       this.mContext = context;
   }

    @Override
    public int getItemViewType(int position) {
        if (isPositionItem(position))
            return VIEW_ITEM;
        return VIEW_PROG;
    }

    private boolean isPositionItem(int position) {
       return position != getItemCount()-1;
    }



    @Override
    public RecyclerView.ViewHolder  onCreateViewHolder (ViewGroup parent, int viewType) {
        if (viewType == VIEW_ITEM) {
            View v =  LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.news_summ, parent, false);
            return new TextViewHolder(v, mContext);
        } else if (viewType == VIEW_PROG){
            View v = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.recyclerfooter, parent, false);
            return new ProgressViewHolder(v);
        }

        return null;
    }



    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {


        if (holder instanceof TextViewHolder) {
            NewsItems newsList = mNewsItems.get(position);
            ((TextViewHolder) holder).newsTitle.setText(newsList.getNews_title());
            ((TextViewHolder) holder).newsExcerpt.setText(newsList.getNews_excerpt());
            ((TextViewHolder) holder).newsId.setText(String.valueOf(newsList.getNewsId()));

        } else {
            ((ProgressViewHolder) holder).progressBar.setIndeterminate(true);
            ((ProgressViewHolder) holder).loadButton.setText(R.string.reload);
        }


    }


    @Override
    public int getItemCount(){
        //Return the number of items in the data set
        return mNewsItems.size();
    }




    public static class TextViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        public TextView newsTitle,newsExcerpt, newsId;
        public ImageButton imageButton;
        public NewsItems dNewsItems;
        private Context context;

        public TextViewHolder (final View newsView, final Context context) {
            super(newsView);
            newsTitle = (TextView) newsView.findViewById(R.id.news_title);
            newsExcerpt = (TextView) newsView.findViewById(R.id.news_excerpt);
            newsId = (TextView) newsView.findViewById(R.id.news_id);

            newsExcerpt.setOnClickListener(this);


        }



        @Override
        public void onClick(View v) {


            if (v.getId() == newsExcerpt.getId()) {
               int newsid = 4536;
               Intent myItent = new Intent(context, NewsDetails.class);
               myItent.putExtra("key", newsid);
               context.startActivity(myItent);
               }
            }
        }
    }

    public static class ProgressViewHolder extends RecyclerView.ViewHolder implements  View.OnClickListener{
        Button loadButton;
        ProgressBar progressBar;
        public ProgressViewHolder(View footerView){
            super(footerView);
            loadButton = (Button) footerView.findViewById(R.id.reload_button);
            progressBar = (ProgressBar) footerView.findViewById(R.id.progress_load);

            loadButton.setOnClickListener(this);

            if(NetworkCheck.isAvailableAndConnected(footerView.getContext())) {
                progressBar.setVisibility(View.VISIBLE);


            } else if (!NetworkCheck.isAvailableAndConnected(footerView.getContext())) {
                loadButton.setVisibility(View.VISIBLE);
            }
        }

        @Override
        public void onClick(View v) {
            if (v.getId() == loadButton.getId()) {
                //
            }
        }
    }


}

从堆栈跟踪第81行开始，压缩到他答案的第04-12 20:15:25.424 8772-8772/com.newsus.app E/AndroidRuntime: FATAL EXCEPTION: main Process: com.newsus.app, PID: 8772 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference at android.content.ComponentName.<init>(ComponentName.java:77) at android.content.Intent.<init>(Intent.java:4336) at com.newsus.app.NewsAdapter$TextViewHolder.onClick(NewsAdapter.java:181) at android.view.View.performClick(View.java:5076) at android.view.View$PerformClick.run(View.java:20279) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5910) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200) 行。

2 个答案:

答案 0 :(得分：2)

将TextViewHolder的构造函数更改为接收context，如下所示：

public static class TextViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
      public TextView newsTitle, newsExcerpt;
      public ImageButton imageButton;
      public NewsItems dNewsItems;
      private Context context;

      public TextViewHolder (final View newsView, final Context context) {
          super(newsView);
          this.context = context;   // EDIT 1: You are missing this
          newsTitle = (TextView) newsView.findViewById(R.id.news_title);
          newsExcerpt = (TextView) newsView.findViewById(R.id.news_excerpt);
          newsExcerpt.setOnClickListener(this);
      }

现在使用此上下文启动这样的活动：

Intent myIntent = new Intent(context, NewsDetails.class);
myIntent.putExtra("key", value); //Optional parameters
context.startActivity(myIntent);

答案 1 :(得分：0)

ViewHolder没有方法getActivity()如果您需要在视图中使用上下文，则必须在构造函数中传递它。

与startActivity()相同的事情你也需要上下文

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