安卓實現任意控件view可拖拽，並監聽拖拽和點擊事件，可自動拉回屏幕邊緣

因爲項目中有需要實現控件可任意拖拽的需求，所以簡單寫了個自定義OnTouchListener，以作拋磚引玉，歡迎大家提議反饋。

完整實現類如下，代碼中有詳細註釋：
用戶可以決定是否開啓自動拖拽邊緣功能，可以監聽控件的拖拽和點擊事件

public class OnDragTouchListener implements View.OnTouchListener {

    private int mScreenWidth, mScreenHeight;//屏幕寬高
    private float mOriginalX, mOriginalY;//手指按下時的初始位置
    private float mDistanceX, mDistanceY;//記錄手指與view的左上角的距離
    private int left, top, right, bottom;
    private OnDraggableClickListener mListener;
    private boolean hasAutoPullToBorder;//標記是否開啓自動拉到邊緣功能

    public OnDragTouchListener() {
    }

    public OnDragTouchListener(boolean isAutoPullToBorder) {
        hasAutoPullToBorder = isAutoPullToBorder;
    }

    @Override
    public boolean onTouch(final View v, MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mScreenWidth = v.getResources().getDisplayMetrics().widthPixels;
                mScreenHeight = v.getResources().getDisplayMetrics().heightPixels;
                mOriginalX = event.getRawX();
                mOriginalY = event.getRawY();
                mDistanceX = event.getRawX() - v.getLeft();
                mDistanceY = event.getRawY() - v.getTop();
                break;
            case MotionEvent.ACTION_MOVE:
                left = (int) (event.getRawX() - mDistanceX);
                top = (int) (event.getRawY() - mDistanceY);
                right = left + v.getWidth();
                bottom = top + v.getHeight();
                if (left < 0) {
                    left = 0;
                    right = left + v.getWidth();
                }
                if (top < 0) {
                    top = 0;
                    bottom = top + v.getHeight();
                }
                if (right > mScreenWidth) {
                    right = mScreenWidth;
                    left = right - v.getWidth();
                }
                if (bottom > mScreenHeight) {
                    bottom = mScreenHeight;
                    top = bottom - v.getHeight();
                }
                v.layout(left, top, right, bottom);
                break;
            case MotionEvent.ACTION_UP:
                //在拖動過按鈕後，如果其他view刷新導致重繪，會讓按鈕重回原點，所以需要更改佈局參數
                ViewGroup.MarginLayoutParams lp = (ViewGroup.MarginLayoutParams) v.getLayoutParams();
                startAutoPull(v, lp);
                //如果移動距離過小，則判定爲點擊
                if (Math.abs(event.getRawX() - mOriginalX) <
                        ScreenUtils.getPxFromDp(v.getResources(), 5) &&
                        Math.abs(event.getRawY() - mOriginalY) <
                                ScreenUtils.getPxFromDp(v.getResources(), 5)) {
                    if (mListener != null) {
                        mListener.onClick(v);
                    }
                }
                //消除警告
                v.performClick();
                break;
        }
        return true;
    }

    public OnDraggableClickListener getOnDraggableClickListener() {
        return mListener;
    }

    public void setOnDraggableClickListener(OnDraggableClickListener listener) {
        mListener = listener;
    }

    public boolean isHasAutoPullToBorder() {
        return hasAutoPullToBorder;
    }

    public void setHasAutoPullToBorder(boolean hasAutoPullToBorder) {
        this.hasAutoPullToBorder = hasAutoPullToBorder;
    }

    /**
     * 開啓自動拖拽
     *
     * @param v  拉動控件
     * @param lp 控件佈局參數
     */
    private void startAutoPull(final View v, final ViewGroup.MarginLayoutParams lp) {
        if (!hasAutoPullToBorder) {
            v.layout(left, top, right, bottom);
            lp.setMargins(left, top, 0, 0);
            v.setLayoutParams(lp);
            if (mListener != null) {
                mListener.onDragged(v, left, top);
            }
            return;
        }
        //當用戶拖拽完後，讓控件根據遠近距離回到最近的邊緣
        float end = 0;
        if ((left + v.getWidth() / 2) >= mScreenWidth / 2) {
            end = mScreenWidth - v.getWidth();
        }
        ValueAnimator animator = ValueAnimator.ofFloat(left, end);
        animator.setInterpolator(new DecelerateInterpolator());
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                int leftMargin = (int) ((float) animation.getAnimatedValue());
                v.layout(leftMargin, top, right, bottom);
                lp.setMargins(leftMargin, top, 0, 0);
                v.setLayoutParams(lp);
            }
        });
        final float finalEnd = end;
        animator.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                super.onAnimationEnd(animation);
                if (mListener != null) {
                    mListener.onDragged(v, (int) finalEnd, top);
                }
            }
        });
        animator.setDuration(400);
        animator.start();
    }

    /**
     * 控件拖拽監聽器
     */
    public interface OnDraggableClickListener {

        /**
         * 當控件拖拽完後回調
         *
         * @param v    拖拽控件
         * @param left 控件左邊距
         * @param top  控件右邊距
         */
        void onDragged(View v, int left, int top);

        /**
         * 當可拖拽控件被點擊時回調
         *
         * @param v 拖拽控件
         */
        void onClick(View v);
    }
}

後期有時間會做更多優化和擴展功能，如果有什麼更好的方式或建議，歡迎大家反饋。