EffectDemo/app/src/main/java/com/xunao/effectdemo/DragGridView.java

package com.xunao.effectdemo;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.PixelFormat;
import android.graphics.Rect;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.GridView;
import android.widget.ImageView;

/**
 * @创建者 Demon
 * @创建时间 2018/5/2 16:28
 * @描述 ${TODO}
 */

public class DragGridView extends GridView {
    //拖拽响应的时间 默认为1s
    private long mDragResponseMs = 1000;
    //是否支持拖拽，默认不支持
    private boolean isDrag = true;
    //振动器，用于提示替换
//    private Vibrator mVibrator;
    //拖拽的item的position
    private int      mDragPosition;
    //拖拽的item对应的View
    private View mDragView;

    //窗口管理器，用于为Activity上添加拖拽的View
    private WindowManager mWindowManager;
    //item镜像的布局参数
    private WindowManager.LayoutParams mLayoutParams;

    //item镜像的 显示镜像，这里用ImageView显示
    private ImageView mDragMirrorView;
    //item镜像的bitmap
    private Bitmap mDragBitmap;

    //按下的点到所在item的左边缘距离
    private int mPoint2ItemLeft;
    private int mPoint2ItemTop;

    //DragView到上边缘的距离
    private int mOffset2Top;
    private int mOffset2Left;

    //按下时x,y
    private int mDownX;
    private int mDownY;
    //移动的时x.y
    private int mMoveX;
    private int mMoveY;

    //状态栏高度
    private int mStatusHeight;

    //XGridView向下滚动的边界值
    private int mDownScrollBorder;
    //XGridView向上滚动的边界值
    private int mUpScrollBorder;
    //滚动的速度
    private int mSpeed = 20;

    //item发生变化的回调接口
    private OnItemChangeListener changeListener;

    private Handler mHandler;

    private Context mContext;

    /**
     * 长按的Runnable
     */
    private Runnable mLongClickRunable = new Runnable() {
        @Override
        public void run() {

            isDrag = true;
//            mVibrator.vibrate(200);
            //隐藏该item
            mDragView.setVisibility(INVISIBLE);

            //在点击的地方创建并显示item镜像
            createDragView(mDragBitmap, mDownX, mDownY);
        }
    };

    /**
     * 当moveY的值大于向上滚动的边界值，触发GridView自动向上滚动
     * 当moveY的值小于向下滚动的边界值，触犯GridView自动向下滚动
     * 否则不进行滚动
     */
    private Runnable mScrollRunbale = new Runnable() {
        @Override
        public void run() {
            int scrollY = 0;
            if (mMoveY > mUpScrollBorder){
                scrollY = mSpeed;
                mHandler.postDelayed(mScrollRunbale,25);
            }else if (mMoveY < mDownScrollBorder){
                scrollY = -mSpeed;
                mHandler.postDelayed(mScrollRunbale,25);
            }else {
                scrollY = 0;
                mHandler.removeCallbacks(mScrollRunbale);
            }
            smoothScrollBy(scrollY,10);
        }
    };


    public DragGridView(Context context) {
        this(context,null);
    }

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

    public DragGridView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mContext = context;
//        mVibrator = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);
        mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
        mHandler = new Handler();
        mStatusHeight = getStatusHeight(context);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        switch (ev.getAction()){
            case MotionEvent.ACTION_DOWN:
                mDownX = (int)ev.getX();
                mDownY = (int)ev.getY();

                //获取按下的position
                mDragPosition = pointToPosition(mDownX, mDownY);
                if (mDragPosition == INVALID_POSITION){     //无效就返回
                    return super.dispatchTouchEvent(ev);
                }

                //延时长按执行mLongClickRunable
                mHandler.postDelayed(mLongClickRunable, mDragResponseMs);
                //获取按下的item对应的View 由于存在复用机制，所以需要 处理FirstVisiblePosition
                mDragView = getChildAt(mDragPosition - getFirstVisiblePosition());
                if (mDragView == null){
                    return super.dispatchTouchEvent(ev);
                }

                //计算按下的点到所在item的left top 距离
                mPoint2ItemLeft = mDownX - mDragView.getLeft();
                mPoint2ItemTop = mDownY - mDragView.getTop();
                //计算GridView的left top 偏移量：原始距离 - 相对距离就是偏移量
                mOffset2Left = (int)ev.getRawX() - mDownX;
                mOffset2Top = (int)ev.getRawY() - mDownY;

                //获取GridView自动向下滚动的偏移量，小于这个值，DragGridView向下滚动
                mDownScrollBorder = getHeight() / 4;
                //获取GridView自动向上滚动的偏移量，大于这个值，DragGridView向上滚动
                mUpScrollBorder = getHeight() * 3 / 4;

                //开启视图缓存
                mDragView.setDrawingCacheEnabled(true);
                //获取缓存的中的bitmap镜像 包含了item中的ImageView和TextView
                mDragBitmap = Bitmap.createBitmap(mDragView.getDrawingCache());
                //释放视图缓存 避免出现重复的镜像
                mDragView.destroyDrawingCache();

                break;
            case MotionEvent.ACTION_MOVE:

                mMoveX = (int)ev.getX();
                mMoveY = (int)ev.getY();

                //如果只在按下的item上移动，未超过边界，就不移除mLongClickRunable
                if (!isTouchInItem(mDragView, mMoveX, mMoveY)) {
                    mHandler.removeCallbacks(mLongClickRunable);
                }

                break;
            case MotionEvent.ACTION_UP:
                mHandler.removeCallbacks(mLongClickRunable);
                mHandler.removeCallbacks(mScrollRunbale);
                break;
            default:
                break;
        }
        return super.dispatchTouchEvent(ev);
    }



    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if (isDrag && mDragMirrorView != null){
            switch (ev.getAction()){
                case MotionEvent.ACTION_DOWN:
                    break;
                case MotionEvent.ACTION_MOVE:
                    mMoveX = (int)ev.getX();
                    mMoveY = (int)ev.getY();
                    onDragItem(mMoveX, mMoveY);
                    break;
                case MotionEvent.ACTION_UP:
                    onStopDrag();
                    isDrag = false;
                    break;
                default:
                    break;
            }
            return true;
        }
        return super.onTouchEvent(ev);
    }


    /************************对外提供的接口***************************************/

    public boolean isDrag() {
        return isDrag;
    }

    //设置是否可拖拽
    public void setDrag(boolean drag) {
        isDrag = drag;
    }

    public long getDragResponseMs() {
        return mDragResponseMs;
    }

    //设置长按响应时长
    public void setDragResponseMs(long mDragResponseMs) {
        this.mDragResponseMs = mDragResponseMs;
    }

    public void setOnItemChangeListener(OnItemChangeListener changeListener) {
        this.changeListener = changeListener;
    }
    /******************************************************************************/


    /**
     * 点是否在该View上面
     * @param view
     * @param x
     * @param y
     * @return
     */
    private boolean isTouchInItem(View view, int x, int y) {
        if (view == null){
            return false;
        }
        if (view.getLeft() < x  && x < view.getRight()
                && view.getTop() < y && y < view.getBottom()){
            return true;
        }else {
            return false;
        }
    }

    /**
     * 获取状态栏的高度
     * @param context
     * @return
     */
    private static int getStatusHeight(Context context){
        int statusHeight = 0;
        Rect localRect = new Rect();
        ((Activity) context).getWindow().getDecorView().getWindowVisibleDisplayFrame(localRect);
        statusHeight = localRect.top;
        if (0 == statusHeight){
            Class<?> localClass;
            try {
                localClass = Class.forName("com.android.internal.R$dimen");
                Object localObject = localClass.newInstance();
                int height = Integer.parseInt(localClass.getField("status_bar_height").get(localObject).toString());
                statusHeight = context.getResources().getDimensionPixelSize(height);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return statusHeight;
    }

    /**
     * 停止拖动
     */
    private void onStopDrag() {
        View view = getChildAt(mDragPosition - getFirstVisiblePosition());
        if (view != null){
            view.setVisibility(VISIBLE);
        }
        changeListener.onStop();
        removeDragImage();
    }

    /**
     * WindowManager 移除镜像
     */
    private void removeDragImage() {
        if (mDragMirrorView != null){
            mWindowManager.removeView(mDragMirrorView);
            mDragMirrorView = null;
        }
    }

    /**
     * 拖动item到指定位置
     * @param x
     * @param y
     */
    private void onDragItem(int x, int y) {
        mLayoutParams.x = x - mPoint2ItemLeft + mOffset2Left;
        mLayoutParams.y = y - mPoint2ItemTop + mOffset2Top - mStatusHeight;
        //更新镜像位置
        mWindowManager.updateViewLayout(mDragMirrorView,mLayoutParams);

        onSwapItem(x,y);

        mHandler.post(mScrollRunbale);
    }

    /**
     * 交换 item 并且控制 item之间的显示与隐藏
     * @param x
     * @param y
     */
    private void onSwapItem(int x, int y) {
        //获取我们手指移动到那个item
        int tmpPosition = pointToPosition(x, y);
        if (tmpPosition != INVALID_POSITION && tmpPosition != mDragPosition){
            if (changeListener != null){
                changeListener.onChange(mDragPosition, tmpPosition);
            }
            //隐藏tmpPosition
            getChildAt(tmpPosition - getFirstVisiblePosition()).setVisibility(INVISIBLE);
            //显示之前的item
            getChildAt(mDragPosition - getFirstVisiblePosition()).setVisibility(VISIBLE);

            mDragPosition = tmpPosition;
        }

    }

    /**
     * 创建拖动的镜像
     * @param bitmap
     * @param downX
     * @param downY
     */
    private void createDragView(Bitmap bitmap, int downX, int downY) {
        mLayoutParams = new WindowManager.LayoutParams();
        mLayoutParams.format = PixelFormat.TRANSLUCENT; //图片之外其他地方透明
        mLayoutParams.gravity = Gravity.TOP | Gravity.LEFT; //左 上
        //指定位置 其实就是 该 item 对应的 rawX rawY 因为Window 添加View是需要知道 raw x ,y的
        mLayoutParams.x = mOffset2Left + (downX - mPoint2ItemLeft);
        mLayoutParams.y = downY - mPoint2ItemTop + mOffset2Top - mStatusHeight;
        //指定布局大小
        mLayoutParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
        mLayoutParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
        //透明度
        mLayoutParams.alpha = 0.4f;
        //指定标志 不能获取焦点和触摸
        mLayoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;

        mDragMirrorView = new ImageView(getContext());
        mDragMirrorView.setImageBitmap(bitmap);
        //添加View到窗口中
        mWindowManager.addView(mDragMirrorView,mLayoutParams);
    }


    /**
     * item 交换时的回调接口
     */
    public interface OnItemChangeListener{
        void onChange(int from, int to);
        void onStop();
    }
}