java - 应用程序在 setImageResource() 处崩溃

Question

我在

得到一个 NullPointerException

image.setImageResource(R.drawable.cover);

这是我的代码:

NewsFeed.this.runOnUiThread(new Runnable(){
    @Override 
    public void run() { 
        //Your code to run in GUI thread here 
        image.setImageResource(R.drawable.cover);
    }
});

此代码在 doInBackground() 方法中运行。这是我的 XML 格式的 ImageView:

<ImageView
    android:id="@+id/imageView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:adjustViewBounds="true" />

NewsFeed.java

public class NewsFeed extends ListActivity {
    MainActivity mainAct = new MainActivity();
    private ProgressDialog pDialog;
    // json url

    // json tags
    // JSON Node names
    private static final String TAG_DATA = "data";
    private static final String TAG_ID = "id";
    private static String TAG_MESSAGE = "message";
    private static final String TAG_CREATETIME = "created_time";
    protected static final String JSONObject = null;

    // contacts JSONArray
    JSONArray contacts = null;
    TimerTask timerTask;
    Handler handler;
    Timer ourtimer;
    String url, gotToken, static_token, imgUrl, nextUrl = "none",
            prevUrl = "none", paging;
    ImageView image;
    Bitmap myBitmap;

    // Hashmap for ListView
    ArrayList<HashMap<String, String>> contactList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        // Bundle gotBasket = getIntent().getExtras();
        // gotToken = gotBasket.getString("Access_Token");
        static_token = "xxxxxxxxxxxxxxxx";
        url = "https://graph.facebook.com/v2.2/awaaziitkgp/feed?access_token="
                + static_token;


        setContentView(R.layout.news_feed);
        image = (ImageView) findViewById(R.id.imageView1);
        final TextView button1 = (TextView) findViewById(R.id.button1);
        final TextView newPosts = (TextView) findViewById(R.id.nextPosts);
        final TextView prevPosts = (TextView) findViewById(R.id.previousPosts);

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

        ListView lv = getListView();
        // Calling async task to get json
        new GetContacts().execute();
        }


private class GetContacts extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // Showing progress dialog
    }

        @Override
        protected Void doInBackground(Void... arg0) {
            // Creating service handler class instance
            ServiceHandler sh = new ServiceHandler();

            // Making a request to url and getting response
            String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);

            Log.d("Response: ", "> " + jsonStr);

            if (jsonStr != null) {
                try {
                    JSONObject jsonObj = new JSONObject(jsonStr);
                    // Getting JSON Array node
                    contacts = jsonObj.getJSONArray(TAG_DATA);
                    JSONObject pagingObj = jsonObj.getJSONObject("paging");
                    // String nextObj = pagingObj.getString("next");
                    nextUrl = pagingObj.getString("next");
                    // JSONObject prevObj= pagingObj.getJSONObject("previous");
                    prevUrl = pagingObj.getString("previous");
                    Log.d("contact.length", String.valueOf(contacts.length()));

                    // looping through All Contacts
                    for (int i = 0; i < 25; i++) {
                        JSONObject c = contacts.getJSONObject(i);
                        // tmp hashmap for single contact
                        HashMap<String, String> data = new HashMap<String, String>();
                        String message = null;
                        String id = c.getString(TAG_ID);
                        data.put(TAG_ID, id);
                        if (c.has("description") == true) {
                            message = c.getString("description");
                            Log.d("Getting Description", message);
                        }
                        if (c.has("picture") == true) {
                            try {
                                Log.d("IT HAS PICTURE! TADA!!", "Image Found");

                                imgUrl = c.getString("picture");
                                Thread thread = new Thread(){
                                    public void run(){
                                      System.out.println("Thread Running");
                                      NewsFeed.this.runOnUiThread(new Runnable(){
                                            @Override 
                                            public void run() { 
                                               //Your code to run in GUI thread here 

                                                URL newUrl = null;
                                                try {
                                                    newUrl = new URL(imgUrl);
                                                } catch (MalformedURLException e) {
                                                    // TODO Auto-generated catch block
                                                    e.printStackTrace();
                                                }
                                                myBitmap = getBitmapFromUrl(newUrl);
                                                image.setImageBitmap(myBitmap);

                                            }
                                        });
                                    }
                                  };

                                  thread.start();



                            } catch (Exception e) {
                                Log.d("ERROR LOADING IMAGE",
                                        "Why you do this, InputStream? Why?");
                            }
                        }else{
                            NewsFeed.this.runOnUiThread(new Runnable(){
                                @Override 
                                public void run() { 
                                   //Your code to run in GUI thread here 
                            ((ImageView) findViewById(R.id.imageView1)).setImageResource(R.drawable.cover);
                                }
                            });
                        }

                                        }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            } else {
                Log.e("ServiceHandler", "Couldn't get any data from the url");
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);


        }

Answer 1

在这里您可以获得解决方案。

 ((ImageView)findViewById(R.id.image_view1)).setImageResource(R.drawable.cover);

XML fragment :

<ImageView
    android:id="@+id/image_view1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />