51.自定義佈局-SlidingLayout

涉及知識點：

1.View繪製三部曲（onMeasure、onLayout、Draw）(第一步和第三步本控件未作處理)

2.ScrollBy相對滾動、ScrollTo絕對滾動、Scroller滾動器的應用

3.TouchEvent處理三部曲（dispatch分發、intercept攔截、onTouchEvent處理）（第一步本控件未作處理）

4.自定義回調接口

---

效果圖：

---

控件源碼：

public class SlidingLayout extends RelativeLayout {
    private Scroller scroller;//滾動器

    /**
     * 構造器
     *
     * @param context
     * @param attrs
     */
    public SlidingLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        mLog.setLogFlag(false);
        initView();
    }

    /**
     * 初始化視圖
     */
    private void initView() {
        scroller = new Scroller(getContext(), new DecelerateInterpolator());
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        screenWidth = getMeasuredWidth();
    }

    List<Integer> childLeft;//記錄每一個子視圖的左邊界

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
        childLeft = new ArrayList<Integer>();

        int left = 0;
        for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            childLeft.add(left);
            child.layout(left, 0, left + child.getMeasuredWidth(), child.getMeasuredHeight());
            left += child.getMeasuredWidth();//寬度累加
        }
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        return super.dispatchTouchEvent(ev);
    }

    float downX, downY, moveX, moveY, upX, upY;
    int disX, disY;//絕對偏移值（move相對於down）

    float lastX, lastY;
    int disOffX, disOffY;//相對偏移值(move相對於上一次move)


    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                downX = event.getX();
                downY = event.getY();
                mLog.e("ACTION_DOWN:downX=" + downX + "\tdownY=" + downY);
                doDown();
                break;

            case MotionEvent.ACTION_MOVE:
                moveX = event.getX();
                moveY = event.getY();
                disX = (int) (moveX - downX);
                disY = (int) (moveY - downY);
                //若是是左右滑動就攔截
                if (Math.abs(disX) > Math.abs(disY)) {
                    return true;
                }
        }
        return super.onInterceptTouchEvent(event);
    }


    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                downX = event.getX();
                downY = event.getY();
                mLog.e("ACTION_DOWN:downX=" + downX + "\tdownY=" + downY);
                doDown();
                break;

            case MotionEvent.ACTION_MOVE:
                moveX = event.getX();
                moveY = event.getY();
                disX = (int) (moveX - downX);
                disY = (int) (moveY - downY);

                if (lastX != 0 && lastY != 0) {
                    disOffX = (int) (moveX - lastX);
                    disOffY = (int) (moveY - lastY);
                }
                lastX = moveX;
                lastY = moveY;
                mLog.e("ACTION_MOVE:moveX=" + moveX + "\tmoveY=" + moveY + "\tdisX=" + disX + "\tdisY=" + disY + "\tdisOffX=" + disOffX + "\tdisOffY=" + disOffY);
                doMove();
                break;

            case MotionEvent.ACTION_UP:
                upX = event.getX();
                upY = event.getY();
                disX = (int) (upX - downX);
                disY = (int) (upY - downY);
                lastX = 0;
                lastY = 0;
                mLog.e("ACTION_UP:upX=" + upX + "\tupY=" + upY + "\tdisX=" + disX + "\tdisY=" + disY);
                doUp();
                break;

        }

        return true;
    }

    private void doDown() {
    }

    int screenIndex;//記錄當前是哪個子視圖

    private void doMove() {
        mLog.e("doMove：disOffX=" + disOffX + "\tgetScrollX=" + getScrollX());


        //若是是第一屏，而且偏移值向右,就什麼都不作
        if (screenIndex == 0 && disOffX - getScrollX() > 0) {

            return;
        }
        //若是是最後一屏，而且偏移值向左,就什麼都不作
        if (screenIndex == getChildCount() - 1 && disOffX - getScrollX() < -childLeft.get(getChildCount() - 1)) {
            return;
        }
        /**
         * 特別注意：視圖的滑動值和手勢的偏移值是相反的！！！
         */
        scrollBy(-disOffX, 0);
    }

    private void doUp() {
        mLog.e("doUp:disOffX=" + disOffX + "\tgetMeasuredWidth/2=" + getMeasuredWidth() / 2);

//        //向右偏移==向左滑動，大於半屏時，跳到上一屏
        if (disX >= getMeasuredWidth() / 2 && screenIndex > 0) {
            mLog.e("跳到上一屏");
            screenIndex--;
        }
//        //向左偏移==向右滑動，大於半屏時，跳到下一屏
        else if (disX <= -getMeasuredWidth() / 2 && screenIndex < getChildCount() - 1) {
            mLog.e("跳到下一屏");
            screenIndex++;
        }

        //只有滑動過，才恢復屏幕(避免啓動無用的scroller)
        if (getScrollX() > 0) {
            scrollerScreen();
        }

    }

    int scrollTime = 500;

    /**
     * 使用scroller換屏（啓動滑動動畫，具體滑動須要到computeScroll裏面執行）
     */
    private void scrollerScreen() {
        //啓動滑動（默認時間爲250ms,此處我自定義爲1000ms）
        scroller.startScroll(getScrollX(), getScrollY(), childLeft.get(screenIndex) - getScrollX(), 0, scrollTime);
        invalidate();
    }


    float screenIndexF;
    int screenWidth;

    /**
     * 絕對滑動（相對於零點的滑動值）
     */
    @Override
    public void scrollTo(int x, int y) {
        super.scrollTo(x, y);
        mLog.e("scrollTo：x=" + x + "\ty=" + y);

    }


    /**
     * 相對滑動（相對於上一位置的滑動值）
     */
    @Override
    public void scrollBy(int x, int y) {
        super.scrollBy(x, y);
        mLog.e("scrollBy：x=" + x + "\ty=" + y);


    }

    /**
     * 計算滑動值（每一次重繪會自動調用此方法）
     */
    @Override
    public void computeScroll() {
        super.computeScroll();
        mLog.e("computeScroll");

        //當滑動完成時，computeScrollOffset()返回false
        if (scroller.computeScrollOffset()) {
            scrollTo(scroller.getCurrX(), 0);
            invalidate();
        }

        screenIndexF = getScrollX() / (float) screenWidth;
        iScreenIndexListener.currentScreenIndex(screenIndexF);
        mLog.e("screenIndexF=" + screenIndexF);
    }

    /**
     * 自定義回調接口,回調當前的屏幕下標數
     */
    interface IScreenIndexListener {
        void currentScreenIndex(float screenIndexF);
    }

    IScreenIndexListener iScreenIndexListener;

    public void setiScreenIndexListener(IScreenIndexListener iScreenIndexListener) {
        this.iScreenIndexListener = iScreenIndexListener;
    }
}

---

應用實例：

Java:

Xml：

來自爲知筆記(Wiz)