java - 从android中的url加载图像

Question

我有我的 MainActivity，它以 json 格式从我的数据库获取数据。我正在尝试使用 LazyAdapter.class 在列表的每一行中加载图像。这是我的 MainActivity.class 和 LazyAdapter.class

public class MainActivity extends SherlockListActivity implements iRibbonMenuCallback {

        ActionBar mActionBar;
        private RibbonMenuView rbmView;
        // Creating JSON Parser object
        JSONParser jParser = new JSONParser();
         // Progress Dialog
        private ProgressDialog pDialog;
        public static ArrayList<String> spinnerArray = new ArrayList<String>(); ;
        public static ArrayList<HashMap<String, String>> productsList;


        // url to get all products list
        private static String url_all_products = "http://********************/app/get_all_products.php";

        // JSON Node names
        private static final String TAG_SUCCESS = "success";
        private static final String TAG_PRODUCTS = "movies";
        private static final String TAG_PID = "id";
        public static final String TAG_FIRSTNAME = "movie_name";
        public static final String TAG_MOVIE_URL = "movie_url";
        public static final String TAG_MOVIE_IMAGE = "movie_image";
        String url;
        // products JSONArray
        JSONArray products = null;
        ListView lv;
        ListAdapter adapter;

        LazyAdapter lazy;


        // flag for Internet connection status
        Boolean isInternetPresent = false;

        // Connection detector class
        ConnectionDetector cd;


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

    //ribbonmenu

    rbmView = (RibbonMenuView) findViewById(R.id.ribbonMenuView1);
    rbmView.setMenuClickCallback(this);
    rbmView.setMenuItems(R.menu.ribbon_menu);

    /** Getting a reference to action bar of this activity */
    mActionBar = getSupportActionBar();
    //test
    mActionBar.setDisplayHomeAsUpEnabled(true);

    // creating connection detector class instance
    cd = new ConnectionDetector(getApplicationContext());
    // get Internet status
    isInternetPresent = cd.isConnectingToInternet();

    if (isInternetPresent) 
    {

             productsList = new ArrayList<HashMap<String, String>>();
             Log.d("URL get log: ", url_all_products);
             new LoadAllProducts().execute();
    }else{


        // Internet connection is not present
        // Ask user to connect to Internet
        showAlertDialog(this, "No Internet Connection",
                "You don't have internet connection.", false);
    }


 // Get listview
   ListView lv = getListView();


    // on seleting single product
    // launching Edit Product Screen
    lv.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {
            // getting values from selected ListItem
            String movie_url = ((TextView) view.findViewById(R.id.movie_url)).getText()
                    .toString();
            // Starting new intent
            Intent in = new Intent(getApplicationContext(),
                    TestActivity.class);
            // sending pid to next activity
            in.putExtra(url, movie_url);


            // starting new activity and expecting some response back
            startActivityForResult(in, 100);
        }


    });



}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    // if result code 100
    if (resultCode == 100) {
        // if result code 100 is received 
        // means user edited/deleted product
        // reload this screen again
        Intent intent = getIntent();
        finish();
        startActivity(intent);
    }

}


/**
 * Function to display simple Alert Dialog
 * @param androidFragment - application context
 * @param title - alert dialog title
 * @param message - alert message
 * @param status - success/failure (used to set icon)
 * */
public void showAlertDialog(Context androidFragment, String title, String message, Boolean status) {
    AlertDialog alertDialog = new AlertDialog.Builder(androidFragment).create();

    // Setting Dialog Title
    alertDialog.setTitle(title);

    // Setting Dialog Message
    alertDialog.setMessage(message);

    // Showing Alert Message
    alertDialog.show();
}

 @Override
    public boolean onOptionsItemSelected(MenuItem item){
        super.onOptionsItemSelected(item);
        switch(item.getItemId()){
        case android.R.id.home:
            rbmView.toggleMenu();
        break;

        }
        return true;
    }


@Override
public void RibbonMenuItemClick(int itemId) {
    // TODO Auto-generated method stub

}

// Response from Edit Product Activity



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

    /**
     * Before starting background thread Show Progress Dialog
     * */

    @Override
    protected void onPreExecute() {
        super.onPreExecute();


        pDialog = new ProgressDialog(MainActivity.this);
        pDialog.setMessage("Loading movies...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();

    }

    /**
     * getting All products from url
     * */
    protected String doInBackground(String... args) {
        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        // getting JSON string from URL
        Log.d("URL get log: ", url_all_products);
        JSONObject json = jParser.getJSONFromUrl(url_all_products, "POST", params);

        // Check your log cat for JSON reponse
        Log.d("All Products: ", json.toString());

        try {
            // Checking for SUCCESS TAG
            int success = json.getInt(TAG_SUCCESS);

            if (success == 1) {
                // products found
                // Getting Array of Products
                products = json.getJSONArray(TAG_PRODUCTS);

                // looping through All Products
                for (int i = 0; i < products.length(); i++) {
                    JSONObject c = products.getJSONObject(i);

                    // Storing each json item in variable
                    String id = c.getString(TAG_PID);
                    String name = c.getString(TAG_FIRSTNAME);
                    String movie_url = c.getString(TAG_MOVIE_URL);
                    String movie_image = c.getString(TAG_MOVIE_IMAGE);

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

                    // adding each child node to HashMap key => value
                    map.put(TAG_PID, id);
                    map.put(TAG_FIRSTNAME, name);
                    map.put(TAG_MOVIE_URL, movie_url);
                    map.put(TAG_MOVIE_IMAGE, movie_image);

                    // adding HashList to ArrayList
                    productsList.add(map);
                    //spinnerArray.add(name);
                }
            } 


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

        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog after getting all products
                    pDialog.dismiss();
                    /*
                    if(pDialog.isShowing())
                    {
                      try
                      {
                        pDialog.dismiss();
                      }
                      catch(Exception e) {// nothing }


                    }

                    }

                    */

        runOnUiThread(new Runnable() {
            public void run() {
                /**
                 * Updating parsed JSON data into ListView
                 * */

                /*
                ListAdapter adapter = new SimpleAdapter(MainActivity.this, productsList,R.layout.inbox_list_item, new String[] { TAG_PID,TAG_FIRSTNAME,TAG_MOVIE_URL},new int[] { R.id.pid, R.id.name, R.id.movie_url });
                // updating listview
                setListAdapter(adapter);
                */

                // Getting adapter by passing xml data ArrayList
                lazy=new LazyAdapter(MainActivity.this, productsList);        
                lv.setAdapter(lazy);
            }
        }
    );
}

 }  

}

还有我的 LazyAdapter

public class LazyAdapter extends BaseAdapter {

private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader; 

public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
    activity = a;
    data=d;
    inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    imageLoader=new ImageLoader(activity.getApplicationContext());
}

public int getCount() {
    return data.size();
}

public Object getItem(int position) {
    return position;
}

public long getItemId(int position) {
    return position;
}

public View getView(int position, View convertView, ViewGroup parent) {
    View vi=convertView;
    if(convertView==null)
        vi = inflater.inflate(R.layout.inbox_list_item, null);

    TextView name = (TextView)vi.findViewById(R.id.name); // title
    //TextView artist = (TextView)vi.findViewById(R.id.artist); // artist name
    //TextView duration = (TextView)vi.findViewById(R.id.duration); // duration
    ImageView thumb_image=(ImageView)vi.findViewById(R.id.list_image); // thumb image

    HashMap<String, String> song = new HashMap<String, String>();
    song = data.get(position);

    // Setting all values in listview
    name.setText(song.get(MainActivity.TAG_FIRSTNAME));
    //artist.setText(song.get(MainActivity.TAG_MOVIE_URL));
    //duration.setText(song.get(MainActivity.KEY_DURATION));
    imageLoader.DisplayImage(song.get(MainActivity.TAG_MOVIE_IMAGE), thumb_image);
    return vi;
}
}

我收到此错误

11-23 19:04:48.049: E/AndroidRuntime(28672): FATAL EXCEPTION: main
11-23 19:04:48.049: E/AndroidRuntime(28672): java.lang.NullPointerException
11-23 19:04:48.049: E/AndroidRuntime(28672):    at com.example.goldmovies.MainActivity$LoadAllProducts$1.run(MainActivity.java:311)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at android.app.Activity.runOnUiThread(Activity.java:4175)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at com.example.goldmovies.MainActivity$LoadAllProducts.onPostExecute(MainActivity.java:297)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at com.example.goldmovies.MainActivity$LoadAllProducts.onPostExecute(MainActivity.java:1)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at android.os.AsyncTask.finish(AsyncTask.java:602)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at android.os.AsyncTask.access$600(AsyncTask.java:156)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at android.os.Looper.loop(Looper.java:137)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at android.app.ActivityThread.main(ActivityThread.java:4517)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at java.lang.reflect.Method.invokeNative(Native Method)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at java.lang.reflect.Method.invoke(Method.java:511)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
11-23 19:04:48.049: E/AndroidRuntime(28672):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

您正在类里面使用 ListView lv;在 oncreate 内

两者是不同的。lv 为空