Android 自定义侧滑面板

1、继承HorizontalScrollView，主要利用它水平滚动的特性scrollTo和smoothScrollTo方法
2、万能的onTouchEvent

public class SlidingMenu extends HorizontalScrollView
{
    /**
     * 屏幕宽度
     */
    private int mScreenWidth;
    /**
     * dp
     */
    private int mMenuRightPadding;
    /**
     * 菜单的宽度
     */
    private int mMenuWidth;
    private int mHalfMenuWidth;

    private boolean isOpen;

    private boolean once;

    public SlidingMenu(Context context, AttributeSet attrs)
    {
        this(context, attrs, 0);

    }

    public SlidingMenu(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
        mScreenWidth = ScreenUtils.getScreenWidth(context);

        TypedArray a = context.getTheme().obtainStyledAttributes(attrs,
                R.styleable.SlidingMenu, defStyle, 0);
        int n = a.getIndexCount();
        for (int i = 0; i < n; i++)
        {
            int attr = a.getIndex(i);
            switch (attr)
            {
            case R.styleable.SlidingMenu_rightPadding:
                // 默认50
                mMenuRightPadding = a.getDimensionPixelSize(attr,
                        (int) TypedValue.applyDimension(
                                TypedValue.COMPLEX_UNIT_DIP, 50f,
                                getResources().getDisplayMetrics()));// 默认为10DP
                break;
            }
        }
        a.recycle();
    }

    public SlidingMenu(Context context)
    {
        this(context, null, 0);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        /**
         * 显示的设置一个宽度
         */
        if (!once)
        {
            LinearLayout wrapper = (LinearLayout) getChildAt(0);
            ViewGroup menu = (ViewGroup) wrapper.getChildAt(0);
            ViewGroup content = (ViewGroup) wrapper.getChildAt(1);

            mMenuWidth = mScreenWidth - mMenuRightPadding;
            mHalfMenuWidth = mMenuWidth / 2;
            menu.getLayoutParams().width = mMenuWidth;
            content.getLayoutParams().width = mScreenWidth;

        }
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b)
    {
        super.onLayout(changed, l, t, r, b);
        if (changed)
        {
            // 将菜单隐藏
            this.scrollTo(mMenuWidth, 0);
            once = true;
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev)
    {
        int action = ev.getAction();
        switch (action)
        {
        // Up时，进行判断，如果显示区域大于菜单宽度一半则完全显示，否则隐藏
        case MotionEvent.ACTION_UP:
            int scrollX = getScrollX();
            if (scrollX > mHalfMenuWidth)
            {
                this.smoothScrollTo(mMenuWidth, 0);
                isOpen = false;
            } else
            {
                this.smoothScrollTo(0, 0);
                isOpen = true;
            }
            return true;
        }
        return super.onTouchEvent(ev);
    }

    /**
     * 打开菜单
     */
    public void openMenu()
    {
        if (isOpen)
            return;
        this.smoothScrollTo(0, 0);
        isOpen = true;
    }

    /**
     * 关闭菜单
     */
    public void closeMenu()
    {
        if (isOpen)
        {
            this.smoothScrollTo(mMenuWidth, 0);
            isOpen = false;
        }
    }

    /**
     * 切换菜单状态
     */
    public void toggle()
    {
        if (isOpen)
        {
            closeMenu();
        } else
        {
            openMenu();
        }
    }
}