OnCreate 中未正确设置全局变量

Question

我试图从用户的 phone 中提取联系人，然后将这些与我在解析后端中的 phone 号码进行匹配，然后在自定义列表视图中显示匹配项。我已经设法完成了几乎所有事情，但是我无法正确设置全局变量 mBinderPhoneNumber。根据 logcat 无论出于何种原因，该变量首先显示为 null，然后才获得正确的值，即使我在需要使用它之前正确设置了该变量。

这是 logcat ，它显示变量最初显示为空，然后才正确设置：

12-31 15:17:12.242 27804-27935/com.rileymacdonaldapps.binder D/TAG: mBinderPhoneNumbers from AddContactsInList:null
12-31 15:17:12.902 27804-27804/com.rileymacdonaldapps.binder D/TAG: mBinderPhoneNumbers from onCreate: [CORRECT PARSE USER1, CORRECT PARSE USER2]

有好心人可以帮帮我吗？

这是 activity:

public class AddContactsActivity extends Activity {
    public List mBinderPhoneNumbers;
    Context context = null;
    ContactsAdapter objAdapter;
    ListView lv = null;
    EditText edtSearch = null;
    LinearLayout llContainer = null;
    Button btnOK = null;
    RelativeLayout rlPBContainer = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        context = this;
        setContentView(R.layout.activity_add_contacts);
        rlPBContainer = (RelativeLayout) findViewById(R.id.pbcontainer);
        edtSearch = (EditText) findViewById(R.id.input_search);
        llContainer = (LinearLayout) findViewById(R.id.data_container);
        btnOK = (Button) findViewById(R.id.ok_button);


        btnOK.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                getSelectedContacts();
            }
        });

        edtSearch.addTextChangedListener(new TextWatcher() {

            @Override
            public void onTextChanged(CharSequence cs, int arg1, int arg2,
                                      int arg3) {
                // When user changed the Text
                String text = edtSearch.getText().toString()
                        .toLowerCase(Locale.getDefault());
                objAdapter.filter(text);
            }

            @Override
            public void beforeTextChanged(CharSequence arg0, int arg1,
                                          int arg2, int arg3) {
                // TODO Auto-generated method stub

            }

            @Override
            public void afterTextChanged(Editable arg0) {
                // TODO Auto-generated method stub
            }
        });
        // Get parse users
        String [] phoneNumberList = {"DUMMY NUMBER1", "DUMMY NUMBER2", "DUMMY NUMBER3", "DUMMY NUMBER4"};
        ParseQuery<ParseUser> query = ParseUser.getQuery(); {
            query.whereContainedIn("username", Arrays.asList(phoneNumberList));
            query.findInBackground(new FindCallback<ParseUser>() {
                public void done (List<ParseUser> list, ParseException e){
                    if (e == null) {
                        mBinderPhoneNumbers = list;
                        Log.d("TAG", "mBinderPhoneNumbers from onCreate: " + mBinderPhoneNumbers);
                    } else {
                        // Something went wrong.
                        Log.e("TAG", "User query error: " + e);
                    }
                }
            });
        }
        addContactsInList();
    }

    private void getSelectedContacts() {
        // TODO Auto-generated method stub

        StringBuffer sb = new StringBuffer();

        for (ContactObject bean : ContactsListClass.phoneList) {

            if (bean.isSelected()) {
                sb.append(bean.getName());
                sb.append(",");
            }
        }

        String s = sb.toString().trim();

        if (TextUtils.isEmpty(s)) {
            Toast.makeText(context, "Select at least one Contact",
                    Toast.LENGTH_SHORT).show();
        } else {

            s = s.substring(0, s.length() - 1);
            Toast.makeText(context, "Selected Contacts: " + s,
                    Toast.LENGTH_SHORT).show();
        }

    }

    private void addContactsInList() {
        // TODO Auto-generated method stub


        Thread thread = new Thread() {
            @Override
            public void run() {

                showPB();

                try {

                    Cursor phones = getContentResolver().query(
                            ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
                            null, null, null, null);

                    try {
                        ContactsListClass.phoneList.clear();
                    } catch (Exception e) {

                    }


                    while (phones.moveToNext()) {


                        Log.d("TAG", "mBinderPhoneNumbers from AddContactsInList:" + mBinderPhoneNumbers);
                        if (Arrays.asList(mBinderPhoneNumbers).contains(phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NORMALIZED_NUMBER)))) {
                            String phoneName = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
                            String phoneNumber = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NORMALIZED_NUMBER));
                            String phoneImage = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.CONTACT_ID));
                            ContactObject cp = new ContactObject();
                            cp.setName(phoneName);
                            cp.setNumber(phoneNumber);
                            cp.setImage(phoneImage);
                            ContactsListClass.phoneList.add(cp);
                        }
                    }
                    phones.close();
                    lv = new ListView(context);
                    lv.setLayoutParams(new LayoutParams(
                            LayoutParams.MATCH_PARENT,
                            LayoutParams.MATCH_PARENT));

                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            // TODO Auto-generated method stub
                            llContainer.addView(lv);
                        }
                    });

                    Collections.sort(ContactsListClass.phoneList,
                            new Comparator<ContactObject>() {
                                @Override
                                public int compare(ContactObject lhs,
                                                   ContactObject rhs) {
                                    return lhs.getName().compareTo(
                                            rhs.getName());
                                }
                            });

                    objAdapter = new ContactsAdapter(AddContactsActivity.this,
                            ContactsListClass.phoneList);
                    lv.setAdapter(objAdapter);
                    lv.setOnItemClickListener(new OnItemClickListener() {

                        @Override
                        public void onItemClick(AdapterView<?> parent,
                                                View view, int position, long id) {

                            CheckBox chk = (CheckBox) view
                                    .findViewById(R.id.contactcheck);
                            ContactObject bean = ContactsListClass.phoneList
                                    .get(position);
                            if (bean.isSelected()) {
                                bean.setSelected(false);
                                chk.setChecked(false);
                            } else {
                                bean.setSelected(true);
                                chk.setChecked(true);
                            }

                        }
                    });

                } catch (Exception e) {

                    e.printStackTrace();

                }

                hidePB();

            }
        };

        thread.start();

    }

    void showPB() {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                // TODO Auto-generated method stub
                rlPBContainer.setVisibility(View.VISIBLE);
                edtSearch.setVisibility(View.GONE);
                btnOK.setVisibility(View.GONE);
            }
        });
    }

    void hidePB() {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                // TODO Auto-generated method stub
                rlPBContainer.setVisibility(View.GONE);
                edtSearch.setVisibility(View.VISIBLE);
                btnOK.setVisibility(View.VISIBLE);
            }
        });
    }

}

Answer 1

     query.findInBackground(new FindCallback<ParseUser>() {
                    public void done (List<ParseUser> list, ParseException e){
                        if (e == null) {
                            mBinderPhoneNumbers = list;
                            addContactsInList();// call here
                            Log.d("TAG", "mBinderPhoneNumbers from onCreate: " + mBinderPhoneNumbers);
                        } else {
                            // Something went wrong.
                            Log.e("TAG", "User query error: " + e);
                        }
                    }
                });

最好这样使用。由于您使用的是 findInBackground，因此会有延迟。该列表仅在调用 done 后可用。

Answer 2

query.findInBackground() 和 addContactsInList() 都异步执行工作。一旦你打电话给他们，他们就会启动一个后台线程来完成工作。因为您按顺序调用这两个方法，所以两个线程大约同时启动。您无法保证任何一种方法相对于另一种方法何时完成。

听起来您想要的是仅在 query.findInBackground() 完成后才调用 addContactsInList()。将该调用移动到 findInBackground() 的 done() 回调应该会达到预期的结果。

Answer 3

问题是，query.findInBackground() 正在它自己的线程中执行。由于它不是阻塞调用，主线程不会等待 query.findInBackground() 完成。因此，addContactsInList() 甚至会在 mBinderPhoneNumbers 初始化之前开始执行。

更好的解决方案是在 done() 中调用 addContactsInList()。像这样，

query.findInBackground(new FindCallback<ParseUser>() {
    public void done (List<ParseUser> list, ParseException e){
        if (e == null) {
            mBinderPhoneNumbers = list;
            addContactsInList();
            .....
        }
    }
});

OnCreate 中未正确设置全局变量

Global Variable Not Being Set Correctly in OnCreate

android

android-activity

android-runonuithread