Question

在我的Android中，我正在使用内容解析器阅读联系人。但是内容解析器未初始化，它提供NullPointerException。我想在另一个类中使用字符串数组并获取它们中的值我必须查询数据库并从手机中读取联系人，但是如代码中所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。

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();

        ...

    }
}

Answer 2

应该在Activity的实现中调用

getContentResolver() - 尝试重写onCreate（）。如果你在活动中将其称为this.getContentResolver() =更容易阅读，那就更清楚了。

结帐this example code（在“绑定到数据”部分之后）。

您可以在每个其他应用程序组件中使用ContentResolver，只需要一个Context。对于Activity，您将自动使用Activity的上下文。您也可以使用Application Context - 它们的生命周期基本不同。

实例化内容解析器时是否有空指针异常？

2 个答案: