设计模式之美学习-行为型-中介模式(三十六)

什么是中介模式

中介模式定义了一个单独的（中介）对象，来封装一组对象之间的交互。将这组对象之间的交互委派给与中介对象交互，来避免对象之间的直接交互。

需求

假设我们有一个比较复杂的对话框，对话框中有很多控件，比如按钮、文本框、下拉框等。当我们对某个控件进行操作的时候，其他控件会做出相应的反应，比如，我们在下拉框中选择“注册”，注册相关的控件就会显示在对话框中。如果我们在下拉框中选择“登陆”，登陆相关的控件就会显示在对话框中

未使用模式

public class UIControl {
    private static final String LOGIN_BTN_ID = "login_btn";
    private static final String REG_BTN_ID = "reg_btn";
    private static final String USERNAME_INPUT_ID = "username_input";
    private static final String PASSWORD_INPUT_ID = "pswd_input";
    private static final String REPEATED_PASSWORD_INPUT_ID = "repeated_pswd_input";
    private static final String HINT_TEXT_ID = "hint_text";
    private static final String SELECTION_ID = "selection";

    public static void main(String[] args) {
        Button loginButton = (Button)findViewById(LOGIN_BTN_ID);
        Button regButton = (Button)findViewById(REG_BTN_ID);
        Input usernameInput = (Input)findViewById(USERNAME_INPUT_ID);
        Input passwordInput = (Input)findViewById(PASSWORD_INPUT_ID);
        Input repeatedPswdInput = (Input)findViewById(REPEATED_PASSWORD_INPUT_ID);
        Text hintText = (Text)findViewById(HINT_TEXT_ID);
        Selection selection = (Selection)findViewById(SELECTION_ID);

        //登录按钮点击 
        loginButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                String username = usernameInput.text();
                String password = passwordInput.text();
                //校验数据...
                //做业务处理...
            }
        });
        //注册按钮点击
        regButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                //获取usernameInput、passwordInput、repeatedPswdInput数据...
                //校验数据...
                //做业务处理...
            }
        });

        //...省略selection下拉选择框相关代码....
    }
}

使用中介者模式实现

//抽象的中介者
public interface Mediator {
    void handleEvent(Component component, String event);
}

//具体中介者
public class LandingPageDialog implements Mediator {
    private Button loginButton;
    private Button regButton;
    private Selection selection;
    private Input usernameInput;
    private Input passwordInput;
    private Input repeatedPswdInput;
    private Text hintText;

    @Override
    public void handleEvent(Component component, String event) {
        //点击了login
        if (component.equals(loginButton)) {
            String username = usernameInput.text();
            String password = passwordInput.text();
            //校验数据...
            //做业务处理...
            //点击了regButton
        } else if (component.equals(regButton)) {
            //获取usernameInput、passwordInput、repeatedPswdInput数据...
            //校验数据...
            //做业务处理...
            //点解了选择则
        } else if (component.equals(selection)) {
            String selectedItem = selection.select();
            if (selectedItem.equals("login")) {
                usernameInput.show();
                passwordInput.show();
                repeatedPswdInput.hide();
                hintText.hide();
                //...省略其他代码
            } else if (selectedItem.equals("register")) {
                //....
            }
        }
    }
}

public class UIControl {
    private static final String LOGIN_BTN_ID = "login_btn";
    private static final String REG_BTN_ID = "reg_btn";
    private static final String USERNAME_INPUT_ID = "username_input";
    private static final String PASSWORD_INPUT_ID = "pswd_input";
    private static final String REPEATED_PASSWORD_INPUT_ID = "repeated_pswd_input";
    private static final String HINT_TEXT_ID = "hint_text";
    private static final String SELECTION_ID = "selection";

    public static void main(String[] args) {
        Button loginButton = (Button)findViewById(LOGIN_BTN_ID);
        Button regButton = (Button)findViewById(REG_BTN_ID);
        Input usernameInput = (Input)findViewById(USERNAME_INPUT_ID);
        Input passwordInput = (Input)findViewById(PASSWORD_INPUT_ID);
        Input repeatedPswdInput = (Input)findViewById(REPEATED_PASSWORD_INPUT_ID);
        Text hintText = (Text)findViewById(HINT_TEXT_ID);
        Selection selection = (Selection)findViewById(SELECTION_ID);

        //将按钮信息交给中介者
        Mediator dialog = new LandingPageDialog();
        dialog.setLoginButton(loginButton);
        dialog.setRegButton(regButton);
        dialog.setUsernameInput(usernameInput);
        dialog.setPasswordInput(passwordInput);
        dialog.setRepeatedPswdInput(repeatedPswdInput);
        dialog.setHintText(hintText);
        dialog.setSelection(selection);

        loginButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                //交个中介者处理
                dialog.handleEvent(loginButton, "click");
            }
        });

        regButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                //交个中介者处理
                dialog.handleEvent(regButton, "click");
            }
        });

        //....
    }
}