效果視頻

剖析Android坐標系

滑動的本質是移動，滑動的原理就是通過不斷的改變View的坐標而實作，

Android系統提供了很多方法獲取坐標值，可以將其分為兩種類別，具體如下：
View 提供的獲取坐標的方法
getTop()：獲取到的是View自身的頂邊到其父布局頂邊的距離
getLeft()：獲取到的是View自身的左邊到其父布局左邊的距離
getRight()：獲取到的是View自身的右邊到其父布局左邊的距離
getBottom()：獲取到的是View自身的底邊到其父布局頂邊的距離
MotionEvent 提供的方法
getX()：獲取點擊事件距離控制元件左邊的距離，即視圖坐標
getY()：獲取點擊事件距離控制元件頂邊的距離，即視圖坐標
getRawX()：獲取點擊事件距離整個螢屏左邊的距離，即絕對坐標
getRawY()：獲取點擊事件距離整個螢屏頂邊的距離，即絕對坐標

六種方式

layout

使用絕對坐標系，每次執行移動邏輯后需要重新設定初始化坐標

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int rawX = (int) (event.getRawX());
        int rawY = (int) (event.getRawY());
                switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                lastX = rawX;
                lastY = rawY;
                break;
            case MotionEvent.ACTION_MOVE:
                int offsetX = rawX - lastX;
                int offsetY = rawY - lastY;
               layout( getLeft()+offsetX,getTop()+offsetY,getRight()+offsetX,getBottom()+offsetY );
               lastX = rawX;
               lastY = rawY;
                break;
            case MotionEvent.ACTION_UP:
                break;

        }
        return true;
    }

scrollBy

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int x = (int) event.getX();
        int y = (int) event.getY();
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                lastX = x;
                lastY = y;
                break;
            case MotionEvent.ACTION_MOVE:
                int offsetX = x - lastX;
                int offsetY = y - lastY;
                ((View) getParent()).scrollBy( -offsetX, -offsetY );
                break;
            case MotionEvent.ACTION_UP:
                break;

        }
        return true;
    }

offsetLeftAndRight offsetTopAndButton

        @Override
    public boolean onTouchEvent(MotionEvent event) {
        int x = (int) event.getX();
        int y = (int) event.getY();
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                lastX = x;
                lastY = y;
                break;
            case MotionEvent.ACTION_MOVE:
                int offsetX = x - lastX;
                int offsetY = y - lastY;
               offsetLeftAndRight( offsetX );
               offsetTopAndBottom( offsetY );
                break;
            case MotionEvent.ACTION_UP:
                break;

        }
        return true;
    }

LayoutParams

通過getLayoutParams()獲取LayoutParams時，需要根據不同的父型別使用設定不同的型別，比如父布局為LinearLayout則設定型別為 LinearLayout.LayoutParams

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int x = (int) event.getX();
        int y = (int) event.getY();
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                lastX = x;
                lastY = y;
                break;
            case MotionEvent.ACTION_MOVE:
                int offsetX = x - lastX;
                int offsetY = y - lastY;
                LinearLayout.LayoutParams layoutParams = (LinearLayout.LayoutParams)getLayoutParams();
                layoutParams.leftMargin = getLeft()+offsetX;
                layoutParams.topMargin = getTop()+offsetY;
                setLayoutParams( layoutParams );
                break;
            case MotionEvent.ACTION_UP:
                break;

        }
        return true;
    }

更方便的是直接使用ViewGroup，不需要判斷父布局型別

  ViewGroup.MarginLayoutParams layoutParams = (ViewGroup.MarginLayoutParams)getLayoutParams();
                layoutParams.leftMargin = getLeft()+offsetX;
                layoutParams.topMargin = getTop()+offsetY;
                setLayoutParams( layoutParams );

Scroller

初始化Scroller

 scroller = new Scroller( context );

重寫computeScroll（）方法
使用computeScrollOffset（）判定是否完成了整個滑動

    @Override
    public void computeScroll() {
        if (scroller.computeScrollOffset()) {
            ((View) getParent()).scrollTo( scroller.getCurrX(), scroller.getCurrY() );
            invalidate();
        }
    super.computeScroll();
    }

  @Override
    public boolean onTouchEvent(MotionEvent mv) {
        View parent = (View) getParent();
        switch (mv.getAction()) {
            case MotionEvent.ACTION_DOWN:
                lastX = (int) mv.getX();
                lastY = (int) mv.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                int upX = (int) (mv.getX() - lastX);
                int upY = (int) (mv.getY() - lastY);
                parent.scrollBy( -upX, -upY );
                break;
            case MotionEvent.ACTION_UP:
                scroller.startScroll( parent.getScrollX(), parent.getScrollY(), -parent.getScrollX(), -parent.getScrollY(), 1000 );
                invalidate();
                break;
        }
        return super.onTouchEvent( mv );
    }

平移影片

效果視頻

private void InitAnimation(){
        animation = new TranslateAnimation( 0,200,0,200 );
        animation.setDuration( 1000 );
    }

 moveButton.startAnimation( animation );