java-design-patterns/model-view-presenter/src/main/java/com/iluwatar/FileSelectorPresenter.java

package com.iluwatar;

/**
 * Every instance of this class represents the Presenter component
 * in the Model-View-Presenter architectural pattern.
 * 
 * It is responsible for reacting to the user's actions and update the View component.
 */
public class FileSelectorPresenter {
	
	/**
	 * The View component that the presenter interacts with.
	 */
	private FileSelectorView view;
	
	/**
	 * The Model component that the presenter interacts with.
	 */
	private FileLoader loader;
	
	/**
	 * Constructor
	 * 
	 * @param view The view component that the presenter will interact with.
	 */
	public FileSelectorPresenter(FileSelectorView view) {
		this.view = view;
	}
	
	/**
	 * Sets the FileLoader object, to the value given as parameter.
	 * 
	 * @param loader The new FileLoader object(the Model component).
	 */
	public void setLoader(FileLoader loader) {
		this.loader = loader;
	}
	
	/**
	 * Starts the presenter.
	 */
	public void start() {
		view.setPresenter(this);
		view.open();
	}
	
	/**
	 * An "event" that fires when the name of the file to be loaded changes.
	 */
	public void fileNameChanged() {
		loader.setFileName(view.getFileName());
	}
	
	public void confirmed() {
		if(loader.getFileName() == null || loader.getFileName().equals("")) {
			view.showMessage("Please give the name of the file first!");
			return;
		}
		
		if(loader.fileExists()) {
			String data = loader.loadData();
			view.displayData(data);
		} 
		
		else {
			view.showMessage("The file specified does not exist.");
		}
	}
	
	/**
	 * Cancels the file loading process.
	 */
	public void cancelled() {
		view.close();
	}	
}