DraggableGridView可拖动的GridView

//TO DO:
//
// - improve timer performance (especially on Eee Pad)
// - improve child rearranging

package com.animoto.android.views;

import android.app.Activity;
import android.content.Context;
import android.graphics.Point;
import android.os.Handler;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.*;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ImageView;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class DraggableGridView extends ViewGroup implements View.OnTouchListener, View.OnClickListener, View.OnLongClickListener {


    private static final String TAG = "DraggableGridView";
    //layout vars
    public static float childRatio = .9f;
    //anim vars
    public static int animT = 150;
    protected int colCount;
    protected int childSize;
    protected int padding;
    protected int dpi;
    protected int scroll = 0;
    protected float lastDelta = 0;
    protected Handler handler = new Handler();
    /** * 正在拖动的项目index */
    protected int mDragged = -1;


    //dragging vars begin +++++++++++++++++++++++++++++++++++++++++++
    protected int lastX = -1;
    protected int lastY = -1;
    protected int mLastTarget = -1;
    protected boolean mEnabled = true;
    protected boolean touching = false;
    //dragging vars end +++++++++++++++++++++++++++++++++++++++++++


    protected ArrayList<Integer> mNewPositions = new ArrayList<Integer>();
    //listeners
    protected OnRearrangeListener onRearrangeListener;
    protected OnClickListener secondaryOnClickListener;
    protected Runnable updateTask = new Runnable() {
        public void run() {
            if (mDragged != -1) {
                if (lastY < padding * 3 && scroll > 0)
                    scroll -= 20;
                else if (lastY > getBottom() - getTop() - (padding * 3) && scroll < getMaxScroll())
                    scroll += 20;
            } else if (lastDelta != 0 && !touching) {
                scroll += lastDelta;
                lastDelta *= .9;
                if (Math.abs(lastDelta) < .25)
                    lastDelta = 0;
            }
            clampScroll();
            onLayout(true, getLeft(), getTop(), getRight(), getBottom());

            handler.postDelayed(this, 25);
        }
    };
    /** * 不可更改的item */
    private List<Integer> mImmutableItemIndex = new ArrayList<Integer>();
    private OnItemClickListener onItemClickListener;

    //CONSTRUCTOR AND HELPERS
    public DraggableGridView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setListeners();
        handler.removeCallbacks(updateTask);
        handler.postAtTime(updateTask, SystemClock.uptimeMillis() + 500);
        setChildrenDrawingOrderEnabled(true);

        DisplayMetrics metrics = new DisplayMetrics();
        ((Activity) context).getWindowManager().getDefaultDisplay().getMetrics(metrics);
        dpi = metrics.densityDpi;
    }


    public void setImmutableItems(Integer... indexs) {
        for (Integer index : indexs) {
            mImmutableItemIndex.add(index);
        }
    }

    protected void setListeners() {
        setOnTouchListener(this);
        super.setOnClickListener(this);
        setOnLongClickListener(this);
    }

    @Override
    public void setOnClickListener(OnClickListener l) {
        secondaryOnClickListener = l;
    }

    //OVERRIDES
    @Override
    public void addView(View child) {
        super.addView(child);
        mNewPositions.add(-1);
    }

    ;

    @Override
    public void removeViewAt(int index) {
        super.removeViewAt(index);
        mNewPositions.remove(index);
    }

    ;

    //LAYOUT
    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        //compute width of view, in dp
        float w = (right - left) / (dpi / 160f);

        //determine number of columns, at least 2
        colCount = 2;
        int sub = 240;
        w -= 280;
        while (w > 0) {
            colCount++;
            w -= sub;
            sub += 40;
        }

        //determine childSize and padding, in px
        childSize = (right - left) / colCount;
        childSize = Math.round(childSize * childRatio);
        padding = ((right - left) - (childSize * colCount)) / (colCount + 1);

        for (int i = 0; i < getChildCount(); i++)
            if (i != mDragged) {
                Point xy = getCoorFromIndex(i);
                getChildAt(i).layout(xy.x, xy.y, xy.x + childSize, xy.y + childSize);
            }
    }

    @Override
    protected int getChildDrawingOrder(int childCount, int i) {
        if (mDragged == -1)
            return i;
        else if (i == childCount - 1)
            return mDragged;
        else if (i >= mDragged)
            return i + 1;
        return i;
    }

    public int getIndexFromCoor(int x, int y) {
        int col = getColOrRowFromCoor(x), row = getColOrRowFromCoor(y + scroll);
        if (col == -1 || row == -1) //touch is between columns or rows
            return -1;
        int index = row * colCount + col;
        if (index >= getChildCount())
            return -1;
        return index;
    }

    /** * 根据所在区域，获取其所在行或列 * * @param coor * @return */
    protected int getColOrRowFromCoor(int coor) {
        coor -= padding;
        for (int i = 0; coor > 0; i++) {
            if (coor < childSize)
                return i;
            coor -= (childSize + padding);
        }
        return -1;
    }

    /** * 根据所在坐标，得到正在操作的是哪个项目 */
    protected int getTargetFromCoor(int x, int y) {
        if (getColOrRowFromCoor(y + scroll) == -1) //touch is between rows
            return -1;
        //if (getIndexFromCoor(x, y) != -1) //touch on top of another visual
        //return -1;

        int leftPos = getIndexFromCoor(x - (childSize / 4), y);
        int rightPos = getIndexFromCoor(x + (childSize / 4), y);
        if (leftPos == -1 && rightPos == -1) //touch is in the middle of nowhere
            return -1;
        if (leftPos == rightPos) //touch is in the middle of a visual
            return -1;

        int target = -1;
        if (rightPos > -1)
            target = rightPos;
        else if (leftPos > -1)
            target = leftPos + 1;
        if (mDragged < target)
            return target - 1;

        //Toast.makeText(getContext(), "Target: " + target + ".", Toast.LENGTH_SHORT).show();
        return target;
    }


    /** * 从所在的index，得到当前所在的区域 */
    protected Point getCoorFromIndex(int index) {
        int col = index % colCount;
        int row = index / colCount;
        return new Point(padding + (childSize + padding) * col,
                padding + (childSize + padding) * row - scroll);
    }


    public int getIndexOf(View child) {
        for (int i = 0; i < getChildCount(); i++)
            if (getChildAt(i) == child)
                return i;
        return -1;
    }

    //EVENT HANDLERS
    public void onClick(View view) {
        if (mEnabled) {
            if (secondaryOnClickListener != null)
                secondaryOnClickListener.onClick(view);
            if (onItemClickListener != null && getLastIndex() != -1)
                onItemClickListener.onItemClick(null, getChildAt(getLastIndex()), getLastIndex(), getLastIndex() / colCount);
        }
    }

    /** * 判断是否是 不可更改的 */
    private boolean isImmutable(int index) {
        if (mImmutableItemIndex == null || mImmutableItemIndex.size() == 0) {
            return false;
        }

        if (mImmutableItemIndex.contains(index)) {
            return true;
        } else {
            return false;
        }
    }

    public boolean onLongClick(View view) {
        if (!mEnabled)
            return false;
        int index = getLastIndex();
        if (index != -1) {
            Log.d(TAG, "长按的index" + index);
            if (!isImmutable(index)) {
                mDragged = index;
                animateDragged();
                return true;
            }
            return false;
        }
        return false;
    }

    public boolean onTouch(View view, MotionEvent event) {
        int action = event.getAction();
        switch (action & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                mEnabled = true;
                lastX = (int) event.getX();
                lastY = (int) event.getY();
                touching = true;
                break;
            case MotionEvent.ACTION_MOVE:
                int delta = lastY - (int) event.getY();
                if (mDragged != -1) {
                    //拖动了

                    //change draw location of ddragged visual
                    int x = (int) event.getX();
                    int y = (int) event.getY();
                    int left = x - (3 * childSize / 4);
                    int top = y - (3 * childSize / 4);
                    getChildAt(mDragged).layout(left, top, left + (childSize * 3 / 2), top + (childSize * 3 / 2));

                    //check for new target hover
                    int target = getTargetFromCoor(x, y);
                    Log.d(TAG, "target>>>" + target);

                    if (mLastTarget != target) {
                        if (target != -1) {
                            animateGap(target);
                        }
                    }

                    Log.d(TAG, "target>>" + target);
                    Log.d(TAG, "lastTargets>>" + mLastTarget);
                } else {
                    scroll += delta;
                    clampScroll();
                    if (Math.abs(delta) > 2)
                        mEnabled = false;
                    onLayout(true, getLeft(), getTop(), getRight(), getBottom());
                }
                lastX = (int) event.getX();
                lastY = (int) event.getY();
                lastDelta = delta;
                break;
            case MotionEvent.ACTION_UP:
                if (mDragged != -1) {
                    View v = getChildAt(mDragged);
                    if (mLastTarget != -1)
                        reorderChildren();
                    else {
                        Point xy = getCoorFromIndex(mDragged);
                        v.layout(xy.x, xy.y, xy.x + childSize, xy.y + childSize);
                    }
                    v.clearAnimation();
                    if (v instanceof ImageView)
                        ((ImageView) v).setAlpha(255);
                    mLastTarget = -1;
                    mDragged = -1;
                }
                touching = false;
                break;
        }
        if (mDragged != -1)
            return true;
        return false;
    }

    //EVENT HELPERS
    protected void animateDragged() {
        View draggingView = getChildAt(mDragged);
        int x = getCoorFromIndex(mDragged).x + childSize;
        int y = getCoorFromIndex(mDragged).y + childSize / 2;
        int l = x - (3 * childSize / 4);
        int t = y - (3 * childSize / 4);
        draggingView.layout(l, t, l + (childSize * 3 / 2), t + (childSize * 3 / 2));
        AnimationSet animSet = new AnimationSet(true);
        ScaleAnimation scale = new ScaleAnimation(.667f, 1, .667f, 1, childSize * 3 / 4, childSize * 3 / 4);
        scale.setDuration(animT);
        AlphaAnimation alpha = new AlphaAnimation(1, .5f);
        alpha.setDuration(animT);

        animSet.addAnimation(scale);
        animSet.addAnimation(alpha);
        animSet.setFillEnabled(true);
        animSet.setFillAfter(true);

        draggingView.clearAnimation();
        draggingView.startAnimation(animSet);
    }


    /** * 动态排列视图的顺序 */
    protected void animateGap(int target) {
        mLastTarget = target;

        for (int i = 0; i < getChildCount(); i++) {
            View childrenView = getChildAt(i);
            if (i == mDragged || isImmutable(i))
                continue;
            int newPos = i;
            if (mDragged < target && i >= mDragged + 1 && i <= target)
                newPos--;
            else if (target < mDragged && i >= target && i < mDragged)
                newPos++;



            //animate
            int oldPos = i;
            if (mNewPositions.get(i) != -1)
                oldPos = mNewPositions.get(i);
            //如果当前位置和上次位置一样，则不处理
            if (oldPos == newPos )
                continue;


            //yee
            if (isImmutable(newPos)) {
                if (newPos > i) {
                    newPos++;
                }else if (newPos < i) {
                    newPos--;
                }
            }

            Point oldXY = getCoorFromIndex(oldPos);
            Point newXY = getCoorFromIndex(newPos);
            Point oldOffset = new Point(oldXY.x - childrenView.getLeft(), oldXY.y - childrenView.getTop());
            Point newOffset = new Point(newXY.x - childrenView.getLeft(), newXY.y - childrenView.getTop());

            TranslateAnimation translate = new TranslateAnimation(Animation.ABSOLUTE, oldOffset.x,
                    Animation.ABSOLUTE, newOffset.x,
                    Animation.ABSOLUTE, oldOffset.y,
                    Animation.ABSOLUTE, newOffset.y);
            translate.setDuration(animT);
            translate.setFillEnabled(true);
            translate.setFillAfter(true);
            childrenView.clearAnimation();
            childrenView.startAnimation(translate);

            mNewPositions.set(i, newPos);
        }
    }

    /** * 动画结束后，重新排列item（将视图数据列表中的位置更改） */
    protected void reorderChildren() {
        //FIGURE OUT HOW TO REORDER CHILDREN WITHOUT REMOVING THEM ALL AND RECONSTRUCTING THE LIST!!!
// if (onRearrangeListener != null)
// onRearrangeListener.onRearrange(mDragged, dlastTarget);

        if (isImmutable(mLastTarget) || isImmutable(mDragged)) {
            return;
        }

        ArrayList<View> children = new ArrayList<View>();
        for (int i = 0; i < getChildCount(); i++) {
            getChildAt(i).clearAnimation();
            children.add(getChildAt(i));
        }
        removeAllViews();
        while (mDragged != mLastTarget){
            if (mLastTarget == children.size()) {
                // ddragged and dropped to the right of the last element
                children.add(children.remove(mDragged));
                mDragged = mLastTarget;
            } else if (mDragged < mLastTarget) {
                // shift to the right
                swapWithNext(children, mDragged, 1);
            } else if (mDragged > mLastTarget) {
                swapWithPrev(children, mDragged, 1);
            }
            if (mDragged < 0) {
                break;
            }
        }
        for (int i = 0; i < children.size(); i++) {
            mNewPositions.set(i, -1);
            addView(children.get(i));
        }
        onLayout(true, getLeft(), getTop(), getRight(), getBottom());
    }


    private void swapWithNext(ArrayList<View> childrenViews,int itemIndex, int offset) {

        if (isImmutable(itemIndex + offset)) {
            offset++;
            swapWithNext(childrenViews, mDragged, offset);
            return;
        }

        swap(childrenViews, itemIndex, itemIndex + offset);
        for (int i = 0; i < offset; i++) {
            mDragged++;
        }
    }

    private void swapWithPrev(ArrayList<View> childrenViews,int itemIndex, int offset) {

        if (isImmutable(itemIndex - offset) && (itemIndex - offset) >= 0) {
            offset++;
            swapWithPrev(childrenViews, mDragged, offset);
            return;
        }

        swap(childrenViews, itemIndex, itemIndex - offset);
        for (int i = 0; i < offset; i++) {
            mDragged--;
        }
    }

    private void swap(ArrayList<View> childrenViews, int firstItem, int secondItem) {
        int childViewSize = childrenViews.size();
        if (firstItem < 0 || secondItem < 0) {
            Log.d("swap", "first>" + firstItem + "; second>>" + secondItem);
            return;
        }

        if (firstItem >= childViewSize || secondItem >= childViewSize) {
            Log.d("swap", "size>>" + childViewSize + ";然而first>" + firstItem + "; second>>" + secondItem);
            return;
        }

        Collections.swap(childrenViews, firstItem, secondItem);
        if (onRearrangeListener != null)
            onRearrangeListener.onRearrange(firstItem, secondItem);
    }

    public void scrollToTop() {
        scroll = 0;
    }

    public void scrollToBottom() {
        scroll = Integer.MAX_VALUE;
        clampScroll();
    }

    protected void clampScroll() {
        int stretch = 3, overreach = getHeight() / 2;
        int max = getMaxScroll();
        max = Math.max(max, 0);

        if (scroll < -overreach) {
            scroll = -overreach;
            lastDelta = 0;
        } else if (scroll > max + overreach) {
            scroll = max + overreach;
            lastDelta = 0;
        } else if (scroll < 0) {
            if (scroll >= -stretch)
                scroll = 0;
            else if (!touching)
                scroll -= scroll / stretch;
        } else if (scroll > max) {
            if (scroll <= max + stretch)
                scroll = max;
            else if (!touching)
                scroll += (max - scroll) / stretch;
        }
    }

    protected int getMaxScroll() {
        int rowCount = (int) Math.ceil((double) getChildCount() / colCount), max = rowCount * childSize + (rowCount + 1) * padding - getHeight();
        return max;
    }

    public int getLastIndex() {
        return getIndexFromCoor(lastX, lastY);
    }

    //OTHER METHODS
    public void setOnRearrangeListener(OnRearrangeListener l) {
        this.onRearrangeListener = l;
    }

    public void setOnItemClickListener(OnItemClickListener l) {
        this.onItemClickListener = l;
    }
}