《Head First 设计模式》学习笔记——复合模式

控制器是视图的行为。假设你希望有不同的行为。能够直接换一个控制器。

JSP的唯一工作就是产生页面表现模型的视图，以及进一步动作所须要的全部控件。

//MVC
//模型
public interface BeatModelInterface {
	//这些方法让控制器调用。控制器依据用户的操作对模型做出适当的处理
	void initialize();
	void on();
	void off();
	void setBPM(int bpm);

	//这些方法同意视图和控制器取得状态，而且成为观察者。
	int getBPM();
	void registerObserver(BeatObserver o);
	void removeObserver(BeatObserver o);
	void registerObserver(BPMObserver o);
	void removeObserver(BPMObserver o);
}

public class BeatModel implements BeatModelInterface, MetaEventListener {
	Sequencer sequencer;
	//两种观察者。一种观察节拍，一种观察BPM变化
	ArrayList<BeatObserver> beatObservers = new ArrayList<BeatObserver>();
	ArrayList<BPMObserver> bpmObservers = new ArrayList<BPMObserver>();
	int bpm = 90;
	Sequence sequence;
	Track track;

	public void initialize() {
		setUpMidi();
		buildTrackAndStart();
	}

	public void on() {
		sequencer.start();
		setBPM(90);
	}

	public void off() {
		setBPM(0);
		sequencer.stop();
	}

	public void setBPM(int bpm) {
		this.bpm = bpm;
		sequencer.setTempoInBPM(getBPM());
		notifyBPMObservers();
	}

	public int getBPM() {
		return bpm;
	}

	void beatEvent() {
		notifyBeatObservers();
	}

	//注冊观察者、通知观察者的代码
	
	//处理节拍的MIDI代码
}

//视图
public class DJView implements ActionListener, BeatObserver, BPMObserver {
	//视图持有模型和控制器的引用
	BeatModelInterface model;
	ControllerInterface controller;
	//显示控制button
	JFrame viewFrame;
	JPanel viewPanel;
	BeatBar beatBar;
	JLabel bpmOutputLabel;
	JFrame controlFrame;
	JPanel controlPanel;
	JLabel bpmLabel;
	JTextField bpmTextField;
	JButton setBPMButton;
	JButton increaseBPMButton;
	JButton decreaseBPMButton;
	JMenuBar menuBar;
	JMenu menu;
	JMenuItem startMenuItem;
	JMenuItem stopMenuItem;

	public DJView(ControllerInterface controller, BeatModelInterface model) {
		this.controller = controller;
		this.model = model;
		model.registerObserver((BeatObserver) this);
		model.registerObserver((BPMObserver) this);
	}

	public void createView() {
		// Create all Swing components here
		
	}

	//模型发生变化是，updateBPM()方法会被调用
	public void updateBPM() {
		if (model != null) {
			int bpm = model.getBPM();
			if (bpm == 0) {
				if (bpmOutputLabel != null) {
					bpmOutputLabel.setText("offline");
				}
			} else {
				if (bpmOutputLabel != null) {
					bpmOutputLabel.setText("Current BPM: " + model.getBPM());
				}
			}
		}
	}

	public void updateBeat() {
		if (beatBar != null) {
			beatBar.setValue(100);
		}
	}
}

//控制器
public interface ControllerInterface {
	//视图能调用全部的控制器方法都在丽丽
	void start();
	void stop();
	void increaseBPM();
	void decreaseBPM();
	void setBPM(int bpm);
}

//实现ControllerInterface接口
public class BeatController implements ControllerInterface {
	BeatModelInterface model;
	DJView view;

	public BeatController(BeatModelInterface model) {
		this.model = model;
		
		//把控制器当參数传入创建视图的构造器中
		view = new DJView(this, model);
		view.createView();
		view.createControls();
		view.disableStopMenuItem();
		view.enableStartMenuItem();
		model.initialize();
	}

	public void start() {
		model.on();
		view.disableStartMenuItem();
		view.enableStopMenuItem();
	}

	public void stop() {
		model.off();
		view.disableStopMenuItem();
		view.enableStartMenuItem();
	}

	public void increaseBPM() {
		int bpm = model.getBPM();
		model.setBPM(bpm + 1);
	}

	public void decreaseBPM() {
		int bpm = model.getBPM();
		model.setBPM(bpm - 1);
	}

	public void setBPM(int bpm) {
		model.setBPM(bpm);
	}
}

public class DJTestDrive {

	public static void main(String[] args) {
		BeatModelInterface model = new BeatModel();
		//由控制器创建视图
		ControllerInterface controller = new BeatController(model);
	}
}