java - 以编程方式向按钮添加描边

Question

有什么方法可以使用 java 而不是 XML 向按钮添加笔划/轮廓？我一直在努力研究它，我遇到的一切都是 XML。

我想要做的是让按钮默认带有黑色边框。然后在按下后颜色会变成红色。

Answer 1

在Java中你可以这样实现，

    public Drawable getMyDrawable() {
        StateListDrawable states = new StateListDrawable();

//        states.addState(new int[]{
//                -android.R.attr.state_enabled,
//        }, getDisableDrawable());

        states.addState(new int[]{
                android.R.attr.state_focused, -android.R.attr.state_pressed,
        }, getDrawable(true));
        states.addState(new int[]{
                android.R.attr.state_focused, android.R.attr.state_pressed,
        }, getDrawable(true));
        states.addState(new int[]{
                -android.R.attr.state_focused, android.R.attr.state_pressed,
        }, getDrawable(true));
        states.addState(new int[]{
                android.R.attr.state_enabled
        }, getDrawable(false));

        return states;
    }

    public Drawable getDrawable(boolean pressed) {
        Drawable[] normalDrawable = new Drawable[2];
        normalDrawable[0] = getRectBorder(pressed);
        normalDrawable[1] = getRectBG();

        LayerDrawable layerDrawable = new LayerDrawable(normalDrawable);
        layerDrawable.setLayerInset(1, 2, 2, 2, 2);

        return layerDrawable.mutate();
    }

    public Drawable getRectBorder(boolean pressed) {
        RectShape rectShape = new RectShape();
        ShapeDrawable shapeDrawable = new ShapeDrawable(rectShape);
        shapeDrawable.getPaint().setColor(pressed ? Color.RED : Color.BLACK);
        shapeDrawable.getPaint().setStyle(Paint.Style.STROKE);
        shapeDrawable.getPaint().setStrokeWidth(2);
        shapeDrawable.getPaint().setAntiAlias(true);
        shapeDrawable.getPaint().setFlags(Paint.ANTI_ALIAS_FLAG);
        return shapeDrawable.mutate();
    }

    public Drawable getRectBG() {
        RectShape rectShape = new RectShape();
        ShapeDrawable shapeDrawable = new ShapeDrawable(rectShape);
        shapeDrawable.getPaint().setColor(Color.WHITE);
        shapeDrawable.getPaint().setStyle(Paint.Style.FILL);
        shapeDrawable.getPaint().setAntiAlias(true);
        shapeDrawable.getPaint().setFlags(Paint.ANTI_ALIAS_FLAG);
        return shapeDrawable.mutate();
    }

最后在你的按钮中你可以这样设置，

Button button = (Button) findViewById(R.id.button);

if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
    button.setBackgroundDrawable(getMyDrawable());
} else {
    button.setBackground(getMyDrawable());
}