什么＆QUOT;这＆Q​​UOT;意味着？ [英] What does "this" mean?

问题描述

可能重复：
  的Java this.method（）与（）的方法

我一直在阅读一些事情，做一些教程关于Android的Java，但我还是不明白这个的意思，就像下面code。

I've been reading some things and doing some tutorials about android java but I still dont understand what "this" means, like in the following code.

    View continueButton = this.findViewById(R.id.continue_button);
    continueButton.setOnClickListener(this);
    View newButton = this.findViewById(R.id.new_button);
    newButton.setOnClickListener(this);

另外为什么会在这个例子中，一个按钮没有与按钮，但与景观的定义，有什么区别呢？

Also why is it in this example that a button is not defined with Button but with View, what is the difference?

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推荐答案

在这关键字的引用了当前对象。它被用来传递的的对象的此的实例，并且更

The this keyword is a reference to the current object. It is used to pass this instance of the object, and more.

例如，这两个分配是平等的：

For example, these two allocations are equal:

class Test{

    int a;

    public Test(){
        a = 5;
        this.a = 5;
    }

}

有时候，你有一个隐藏字段，你要访问：

Sometimes you have a hidden field you want to access:

class Test{

    int a;

    public Test(int a){
        this.a = a;
    }

}

在这里，您指定的字段 A 与参数的值 A 。

在这关键字以同样的方式与方法。再次，这两个是相同的：

The this keyword works the same way with methods. Again, these two are the same:

this.findViewById(R.id.myid);
findViewById(R.id.myid);

最后，说你有一个类为MyObject，有一个方法，需要一个为MyObject参数：

Finally, say you have a class MyObject that has a method which takes a MyObject parameter:

class MyObject{

    public static void myMethod(MyObject object){
        //Do something
    }

    public MyObject(){
        myMethod(this);
    }

}

在最后这个例子中，你通过了当前对象的引用静态方法。

In this last example you passed a reference of the current object to a static method.

另外为什么会在这个例子中，一个按钮没有与按钮，但与景观的定义，有什么区别呢？

Also why is it in this example that a button is not defined with Button but with View, what is the difference?

在Android SDK中，一个按钮是的的查看子类。您可以要求按钮为查看和投中的查看到按钮：

In Android SDK, a Button is a subclass of View. You can request the Button as a View and cast the View to a Button:

Button newButton = (Button) this.findViewById(R.id.new_button);

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