动态设置按钮背景

通过代码使用一份资源动态设置按钮按下效果

原理

使用 StateListDrawable 动态设置背景，并利用 normal 状态的 background 动态调整其 alpha 值，并将其设置为 pressed 的 drawable

设置背景为一个 Drawable

 public static void bkAutoAlpha(View view, @DrawableRes int resBackground, @FloatRange(from = 0, to = 1) float alpha) {
        final StateListDrawable stateListDrawable = new StateListDrawable();
        Drawable normal = view.getContext().getResources().getDrawable(resBackground);
        normal.mutate();
        Drawable pressed = view.getContext().getResources().getDrawable(resBackground);
        pressed.setAlpha(getAlpha(alpha));

        stateListDrawable.addState(new int[]{android.R.attr.state_pressed}, pressed);
        stateListDrawable.addState(new int[]{}, normal);

        view.setBackgroundDrawable(stateListDrawable);
        view.setClickable(true);
    }

    public static int getAlpha(@FloatRange(from = 0, to = 1) float alpha) {
        return (int) (255 * alpha);
    }

设置背景为颜色，并自动调整 Alpha

public static void bkAutoAlphaColor(View view,int resBackgroundColor,float alpha) {
    ColorDrawable colorDrawableNormal = new ColorDrawable();
    ColorDrawable colorDrawablePressed = new ColorDrawable();

    int normalColor = getColor(view.getContext(),resBackgroundColor);
    int pressedColor = alphaColor(normalColor, convertAlphaToInt(alpha));

    colorDrawableNormal.setColor(normalColor);
    colorDrawablePressed.setColor(pressedColor);

    final StateListDrawable stateListDrawable = new StateListDrawable();
    stateListDrawable.addState(new int[]{android.R.attr.state_pressed}, colorDrawablePressed);
    stateListDrawable.addState(new int[]{}, colorDrawableNormal);

    view.setBackgroundDrawable(stateListDrawable);
    view.setClickable(true);
}

private static int getColor(Context context,int resBackgroundColor){
    return context.getResources().getColor(resBackgroundColor);
}

private static int alphaColor(int color,int alpha){
    return Color.argb(alpha,Color.red(color),Color.green(color),Color.blue(color));
}

TODO

• 简单支持 enable 状态

Start with the Java snippets in this issue and Android's StateListDrawable state handling. The TODO requests support for the enabled state, but its expected appearance and exact scope are not specified; done should mean that enabled-state behavior is supported alongside the existing pressed and normal states.