java - 实例化内容解析器时出现空指针异常？

Question

在我的 Android 中，我正在使用内容解析器读取联系人。但是内容解析器没有得到初始化，它给出了 NullPointerException。我想在另一个类中使用字符串数组并获取其中的值我必须查询数据库并从电话中读取联系人，但如代码中指出的那样坚持该异常:

//this code is in some other class...     
et= (EditText) findViewById(R.id.searchcontact);
        et.addTextChangedListener(new TextWatcher() {

             public void onTextChanged(CharSequence s, int start, int before, int
             count) { // TODO Auto-generated method stub
                 lva.getFilter().filter(s);

RefreshListView rlv=new RefreshListView();<----class is getting called from here
                 lva.notifyDataSetInvalidated();
                 lva = new ListViewAdapterContacts(AllContactsActivity.this, rlv.names, rlv.types, rlv.phones, rlv.ids);

                 lv.setAdapter(lva);


             }

             public void beforeTextChanged(CharSequence s, int start, int count,
             int after) { // TODO Auto-generated method stub

             }

             public void afterTextChanged(Editable s) { 
                 // TODO Auto-generated  method stub


            // lva.notifyDataSetChanged();
             }
             });

...............********.........

public class RefreshListView extends ListActivity{

            String[] names,phones,types,ids;
            String name,id,phoneNumber;
            int type;
            ArrayList <String> newValues;

        public void onCreate(Bundle b){
        super.onCreate(b);

        newValues=SetNewList.getNames();
        getContacts();
    }



public void getContacts(){
                int foo = 0;


    ContentResolver cr = getContentResolver();<---//null pointer exception

    Cursor cur = cr.query(ContactsContract.Contacts.CONTENT_URI, null,
                        null, null, "UPPER(" + ContactsContract.Contacts.DISPLAY_NAME
                        + ") ASC");
                if (cur.getCount() > 0) {

                    names = new String[cur.getCount()];
                    phones = new String[cur.getCount()];
                    types = new String[cur.getCount()];
                    ids = new String[cur.getCount()];

                    while (cur.moveToNext()) {

                        name = cur
                        .getString(cur
                                .getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
                        for(int i=0;i<=newValues.size();i++){           
                            if(newValues.get(i).equalsIgnoreCase(name)) {
                                id = cur.getString(cur
                                        .getColumnIndex(ContactsContract.Contacts._ID));
                                String hasPhone = cur
                                .getString(cur
                                        .getColumnIndex(ContactsContract.Contacts.HAS_PHONE_NUMBER));

                                if (Integer.parseInt(hasPhone) == 1) {

                                    Cursor phones = getContentResolver().query(
                                            ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
                                            null,
                                            ContactsContract.CommonDataKinds.Phone.CONTACT_ID
                                            + " = " + id, null, null);

                                    while (phones.moveToNext()) {
                                        phoneNumber = phones
                                        .getString(phones
                                                .getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));

                                        type = phones.getInt(phones.getColumnIndex(Phone.TYPE));

                                    } // while

                                    phones.close();
                                }// if

                                else {
                                    phoneNumber = "unknown";
                                    type = 0;

                                }// else



                                phones[foo] = phoneNumber;
                                names[foo] = name;
                                ids[foo] = id;

                                if (type == 0) {
                                    String value = "unknown";
                                    types[foo] = value;
                                }

                                else if (type == 1) {
                                    String value = "home";
                                    types[foo] = value;
                                }// if

                                else if (type == 2) {
                                    String value = "mobile";
                                    types[foo] = value;
                                }// else if

                                else if (type == 3) {
                                    String value = "Work";
                                    types[foo] = value;
                                }

                                else if (type == 4) {
                                    String value = "Workfax";
                                    types[foo] = value;
                                }

                                else if (type == 5) {
                                    String value = "Home Fax";
                                    types[foo] = value;

                                } else if (type == 6) {
                                    String value = "Pager";
                                    types[foo] = value;
                                }

                                else {
                                    String value = "Other";

                                    types[foo] = value;
                                }

                                foo++;
                            }
                        }
                    }// while
                }// if


            }// get contacts

        }

Answer 1

不要这样做......

public class RefreshListView extends ListActivity{

    public RefreshListView() {

        ...

    }
}

不要为 Android Activity 使用构造函数!!!

您应该删除该构造函数并将代码放入 Activity onCreate(...) 方法中。

请参阅 Activity 的文档并阅读 Activities .

尝试这样的事情......

public class RefreshListView extends ListActivity{

    String[] names,phones,types,ids;
    String name,id,phoneNumber;
    int type;
    ArrayList <String> newValues;
    ContentResolver cr = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        cr = getContentResolver();
        newValues=SetNewList.getNames();//getnames is of static type
        getContacts();
    }

    public void getContacts() {
        int foo = 0;

        // REMOVE THE NEXT LINE !!!
        // ContentResolver cr = getContentResolver();

        ...

    }
}