使用okhttp连接网络，再把数据储存进Sqlite

这次会把所有之前学过的东西应用在一起，写一个登入的功能。

1. Activity调用CONFIG，获得URL后

2. Activity再调用Okhttp，从服务器返回JSON

3. Activity调用GsonTools，把JSON转换成<List>DTO

4. Activity调用DAO的get、set方法，把叁数<List>DTO传到方法

5. DAO继承DbHelper，把<List>DTO储存到Sqlite

以下是部份代码的精要

1. Activity初始化GsonTools、OkHttp、DAO。

    private OkHttp okhttp;
    private GsonTools gsonTools;
    private BitMap bitMap;
    private UserDAO userDAO;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        supportRequestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_login);

        okhttp = OkHttp.getInstance();
        gsonTools = GsonTools.getInstance();
        bitMap = BitMap.getInstance();
        userDAO = new UserDAO(this);

        initUI();
        isHavingUserInSqlite();
    }

2. 必须在新线程下调用Okhttp，而在该线程下想刷新UI，必须用runOnUiThread()。

        // Network thread
        new Thread(new Runnable() {
            @Override
            public void run() {

                // run your code here

                // UI Thread
                LoginActivity.this.runOnUiThread(new Runnable() {
                    public void run() {
                        // ui
                    }
                });

            }
        }).start();

3. 最核心的业务都在这里。

    private void validUser() {
        // Network thread
        new Thread(new Runnable() {
            @Override
            public void run() {
                ResultDTO resultDTO;

                // check weather user is exist?
                userExistURL = Configuration.isUserExistURL(userName, userPassword);
                userExistResult = okhttp.getResponse(userExistURL);
                resultDTO = gsonTools.getLogin(userExistResult);

                // get user info if user is exist
                if ( resultDTO.getResult().equals("1") ) {
                    userGetURL = Configuration.getUserURL(resultDTO.getId());
                    userResult = okhttp.getResponse(userGetURL);
                    userDTO = gsonTools.getUser(userResult);

                    // save user info into SQlite
                    if ( userDAO.setUser(userDTO) )
                    {
                        intent = new Intent(LoginActivity.this, MainActivity.class);
                        startActivity(intent);
                    }
                } else {
                    loginMsg = "密碼或帳號不正確";
                }

                // UI Thread
                LoginActivity.this.runOnUiThread(new Runnable() {
                    public void run() {
                        tvLoginResult.setText(loginMsg);
                    }
                });

            }
        }).start();
    }