Question

我有一个扩展listactivity的类。我正在解析json文件中的数据并将数据放入列表中。我还创建了一个复选框，以检查学生是否在检查。为此我创建了一个数组来从列表中获取位置。我正在获取学生姓名，但复选框正在给我空值。请帮忙！！！这是我的代码，

public class Student_data extends ListActivity {
private ProgressDialog pDialog;
private Button button;
ListView lv;

// URL to get contacts JSON
private static String url = "http://10.0.2.2/studentdata.json";

private static int[] present, absent;
private static int i = 0, j = 0, x;

// JSON Node names
private static final String TAG_DEP_ID = "dep_id";
private static final String TAG_HEAD = "stdata";
private static final String TAG_NAME = "name";
private static final String TAG_ENROLL = "enrollment";

// contacts JSONArray
JSONArray data = null;

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

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

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

    button = (Button) findViewById(R.id.saveData);
    button.setOnClickListener(new ButtonClick());

    lv = getListView();

    new GetContacts().execute();
    lv.setOnItemClickListener(new CheckBoxClick());
}

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

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // Showing progress dialog
        pDialog = new ProgressDialog(Student_data.this);
        pDialog.setMessage("Please wait...");
        pDialog.setCancelable(false);
        pDialog.show();
    }

    @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
                data = jsonObj.getJSONArray(TAG_HEAD);

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

                    String id = c.getString(TAG_DEP_ID);
                    String name = c.getString(TAG_NAME);
                    String enrll = c.getString(TAG_ENROLL);

                    // tmp hashmap for single contact
                    HashMap<String, String> contact = new HashMap<String, String>();

                    // adding each child node to HashMap key => value
                    contact.put(TAG_DEP_ID, id);
                    contact.put(TAG_NAME, name);
                    contact.put(TAG_ENROLL, enrll);

                    // adding contact to contact list
                    studentList.add(contact);
                }
            } 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);
        // Dismiss the progress dialog
        if (pDialog.isShowing())
            pDialog.dismiss();
        /**
         * Updating parsed JSON data into ListView
         */
        ListAdapter adapter = new SimpleAdapter(Student_data.this, studentList, R.layout.data_item,
                new String[] { TAG_NAME }, new int[] { R.id.name });

        setListAdapter(adapter);
    }

}

public class CheckBoxClick implements OnItemClickListener {

    @Override
    public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
        // TODO Auto-generated method stub
        CheckBox chkbox = (CheckBox) arg1;
        if (chkbox.isChecked()) {
            present[i] = arg2;
            i++;
        }
        if (chkbox.isChecked()) {
            absent[j] = arg2;
            j++;
        }
    }
}

public class ButtonClick implements OnClickListener {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        finish();
    }
}

}

data_item.xml ---＆GT;

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:padding="10dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:weightSum="2" >

<!-- Name Label -->

<TextView
    android:id="@+id/name"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_weight="2"
    android:paddingBottom="2dip"
    android:paddingTop="6dip"
    android:textColor="#000"
    android:textSize="16sp"
    android:textStyle="bold" />

    <CheckBox
    android:id="@+id/chkbox"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_weight="1" />

    </LinearLayout>

Answer 1

试试这个

if (((CheckBox) arg1).isChecked()) {
             //your code
 }

复选框isclicked给出null值

1 个答案: