Question

我有一个列表视图，其中包含图像和图像名称，我正在从JSON Web服务加载数据并将其显示在列表视图中。

public class AndroidJSONParsingActivity extends ListActivity {

    // url to make request
    private static String url = "my url";

    // JSON Node names
     String Doctors = "Doctors";
     String DoctorName = "DoctorName";
     String ImageName = "ImageName";

     // contacts JSONArray
    JSONArray Doctor = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        ImageView image = (ImageView)findViewById(R.id.ImageView);
        // Hashmap for ListView
        ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();

        // Creating JSON Parser instance
        JSONParser jParser = new JSONParser();

        // getting JSON string from URL
        JSONObject json = jParser.getJSONFromUrl(url);

        try {
            // Getting Array of Contacts
            Doctor = json.getJSONArray(Doctors);

            // looping through All Contacts
            for(int i = 0; i < Doctor.length(); i++){
                JSONObject c = Doctor.getJSONObject(i);
                Log.d("TAG", "JSON IS: " + Doctor.toString());

                String imageBaseDirectory = "http://92.253.101.239:81/sudandoctors/UploadedFiles/";
                String imageName = c.getString(ImageName);//get image name from json parsing;
                System.err.println("imageBaseDirectory = "+imageBaseDirectory);
                System.err.println("imageName = "+imageName);
                System.err.println("two = "+imageBaseDirectory+imageName);
                image.setImageURI(Uri.parse(imageBaseDirectory+imageName));

                String n = imageBaseDirectory+imageName;
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                // adding each child node to HashMap key => value
                map.put("DoctorName", c.getString("DoctorName"));
                map.put("ImageName", n);

                // adding HashList to ArrayList
                contactList.add(map);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }


        /**
         * Updating parsed JSON data into ListView
         * */
        ListAdapter adapter = new SimpleAdapter(this, contactList,
                R.layout.list_item,
                new String[] { DoctorName, ImageName }, new int[] {
                        R.id.name, R.id.ImageView });

        setListAdapter(adapter);


    }

}

我收到了这个错误

12-13 14:06:07.793: E/AndroidRuntime(1148): FATAL EXCEPTION: main
12-13 14:06:07.793: E/AndroidRuntime(1148): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.androidhive.jsonparsing/com.androidhive.jsonparsing.AndroidJSONParsingActivity}: java.lang.NullPointerException
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.os.Looper.loop(Looper.java:123)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.app.ActivityThread.main(ActivityThread.java:3683)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at java.lang.reflect.Method.invokeNative(Native Method)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at java.lang.reflect.Method.invoke(Method.java:507)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at dalvik.system.NativeStart.main(Native Method)
12-13 14:06:07.793: E/AndroidRuntime(1148): Caused by: java.lang.NullPointerException
12-13 14:06:07.793: E/AndroidRuntime(1148):     at com.androidhive.jsonparsing.AndroidJSONParsingActivity.onCreate(AndroidJSONParsingActivity.java:61)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-13 14:06:07.793: E/AndroidRuntime(1148):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
12-13 14:06:07.793: E/AndroidRuntime(1148):     ... 11 more

当我在浏览器中使用链接时，它实际上给了我图片，那么问题是什么

Answer 1

Try this.. does exactly what you want

stackoverflow问题的另一个例子。

To display images in a listview, you need to create a list adapter class that extends from BaseAdapter and create each view there.

以上代码工作正常。根据您的要求进行更改。

或go to this awesome example LazyList. shows how to load images in listview. It make you to understand nicely

将图像JSON加载到列表视图

1 个答案: