如何在相对布局的中心放置一个按钮

Question

我正在尝试在中心应用程序上放一个按钮...有人可以向我解释这个代码到底在做什么？

RelativeLayout.LayoutParams BD = new RelativeLayout.LayoutParams(
            RelativeLayout.LayoutParams.WRAP_CONTENT,
            RelativeLayout.LayoutParams.WRAP_CONTENT
    );
    BD.addRule(RelativeLayout.CENTER_HORIZONTAL);
    BD.addRule(RelativeLayout.CENTER_VERTICAL);

Answer 1

此代码的作用是

RelativeLayout.LayoutParams BD = new RelativeLayout.LayoutParams(
        RelativeLayout.LayoutParams.WRAP_CONTENT,
        RelativeLayout.LayoutParams.WRAP_CONTENT
);

上线告诉视图仅占据所需的空间。

BD.addRule(RelativeLayout.CENTER_HORIZONTAL);
BD.addRule(RelativeLayout.CENTER_VERTICAL);

上面的两行告诉Layoutmanager将此视图保持在水平和垂直方向。

您应该阅读有关Relativelayout和Relativelayoutparams。

Answer 2

RelativeLayout relativeLayout;
Button btnNewButton;
relativeLayout = new RelativeLayout(getApplicationContext());
    btnNewButton = new Button(getApplicationContext());
    btnNewButton.setText("Button Text");
    RelativeLayout.LayoutParams BD = new RelativeLayout.LayoutParams(
            RelativeLayout.LayoutParams.WRAP_CONTENT,
            RelativeLayout.LayoutParams.WRAP_CONTENT
    );
    BD.addRule(RelativeLayout.CENTER_HORIZONTAL);
    BD.addRule(RelativeLayout.CENTER_VERTICAL);
    btnNewButton.setLayoutParams(BD);
    relativeLayout.addView(btnNewButton);
    setContentView(relativeLayout);

我希望它能帮助您