如何在循环上向按钮添加动作侦听器？ [英] How would I add an action listener to buttons on a loop?

问题描述

我希望每次在我的4x4网格中按下按钮时，它会增加将移动1。这是创建4x4按钮布局。每次按下任何按钮，我都希望移动来增加。基本上我正在创建记忆游戏，你翻转卡片以相互匹配。我只需要计算一个玩家解决这个难题的移动的总金额。

I want it so every time a button is pressed in my 4x4 grid, that it increments moves by 1 . This is creating a 4x4 layout of buttons. Each time any of those buttons are pressed, I want moves to increment. Basically I'm creating the memory game, where you flip cards over to match each other. I just have to keep count of the total amount of moves a player does to solve the puzzle.

private int moves = 0;

private GridPane makeGridPane(){
    ConcentrationModel c = new ConcentrationModel();
    GridPane grid = new GridPane();

    ColumnConstraints col1 = new ColumnConstraints();
    col1.setPercentWidth( 50 );

    grid.getColumnConstraints().addAll(col1, col1, col1, col1);
    RowConstraints row1 = new RowConstraints();
    row1.setPercentHeight( 50 );
    grid.getRowConstraints().addAll(row1, row1, row1, row1);


    for(int row = 0; row < 4; row ++){
        for(int col = 0; col < 4; col++){
            Button btn = new Button();
            ImageView image = new ImageView(c.getCards().get(0).getImage());
            image.setFitWidth(WIDTH/4);
            image.setFitHeight(HEIGHT/4);
            btn.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
            btn.setGraphic(image);
            grid.add(btn, col, row);


        }
    }
    return grid;
}

推荐答案

这实际上非常简单。您所要做的就是在 grid.add（...）之前添加这段代码：

This is actually pretty simple. All you have to do is add this bit of code just before your grid.add(...):

btn.setOnAction(new EventHandler<ActionEvent>() {
    @Override public void handle(ActionEvent event) {
        moves++;
    }
});

或者，相当于Java 8版本：

Or, equivalently, the Java 8 version:

btn.setOnAction((ActionEvent e) -> {moves++;});

^{（我目前无法对此进行测试，但应 >工作。如果没有，lemme知道，我会尝试解决它。​​）}

^{(I can't currently test this, but it should work. If not, lemme know and I'll try to fix it.)}

如果你担心记忆，基督徒指出以下这会为每个按钮创建一个 EventHandler 的新实例。虽然这可能不是太可怕，但这可能是一个坏习惯。处理（没有双关语）的最佳方法是在之前为循环创建一个对象：

If you're concerned about memory, Christian points out below that this creates a new instance of EventHandler for every button. While this may not be too terrible, it's probably a bad habit to get into. The best way to handle (no pun intended) this is by making an object before your for loop:

EventHandler<ActionEvent> eh = new EventHandler<>() {
    @Override public void handle(ActionEvent event) {
        moves++;
    }
};

然后，对于每个按钮，而不是最顶层的代码，你只需写：

Then, for each of your buttons, instead of the top-most code, you'd simply write:

btn.setOnAction(eh);

这样，单个 EventHandler 正在创建并用于处理所有事件。如果你需要创建的不仅仅是几个按钮，你会想要使用这个，因为它更快（不需要为每个对象分配内存）和更高的内存效率（...它，呃，没有不需要为每个对象分配内存。在这种情况下，我认为这是微不足道的，但尽管如此，我还是很高兴。

That way, a single EventHandler is being created and used to handle all the events. You'll want to use this one if you need to create more than just a few buttons, both because it's faster (doesn't need to allocate memory for each object) and more memory-efficient (...it, uh, doesn't need to allocate the memory for each object). In this case, I think it's pretty trivial, but it's good to know nonetheless.

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