Android自定义gridView仿头条频道拖动管理功能

项目中遇到这样个需求：app的功能导航需要可拖动排序，类似头条中的频道拖动管理。效果如下，gif不是很顺畅，真机会好很多。

虽然类似的文章网上搜一下有很多，但写的都不令人满意，注释不清晰，而且动画还不够流畅。经本人整理优化后，拿出来供后续有需要的使用。

实现原理：

gridView作为基本控件
WindowManager.addView的方式实现可拖动的view
TranslateAnimation实现移动动画，动画完后更新adapter即可

主要的实现原理上面已经说明，源码中关键的地点也有注释，因此下面直接上源码。

package com.hai.draggrid;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.PixelFormat;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.view.animation.Animation;
import android.view.animation.TranslateAnimation;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
/**
 * 长按拖动图标可以调整item位置的Gridview
 * Created by huanghp on 2019/10/15.
 * Email h1132760021@sina.com
 */
public class DragGridView extends GridView {
 private static final String TAG = "DragGridView";
 private int downX, downY;
 private int rawX, rawY;
 private int lastPosition = INVALID_POSITION;
 private int viewL, viewT;
 private int itemHeight, itemWidth;
 private int itemCount;
 private double dragScale = 1.2D;//拖动view的放大比例
 private ImageView dragImageView;
 private WindowManager windowManager = null;
 private WindowManager.LayoutParams windowParams = null;
 private boolean isMoving = false;
 private Animation lastAnimation;
 private static final long TIME_ANIMATE = 300;
 public DragGridView(Context context, AttributeSet attrs) {
  this(context, attrs, 0);
 }
 public DragGridView(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  setOnItemLongClickListener(new OnItemLongClickListener() {
   @Override
   public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
    lastPosition = position;
    View dragView = getChildAt(lastPosition - getFirstVisiblePosition());
    itemHeight = dragView.getHeight();
    itemWidth = dragView.getWidth();
    itemCount = getCount();
    int rows = itemCount / getNumColumns();// 算出行数
    int left = (itemCount % getNumColumns());// 算出最后一行多余的数量
    if (lastPosition != INVALID_POSITION) {
     viewL = downX - dragView.getLeft();
     viewT = downY - dragView.getTop();
     dragView.destroyDrawingCache();
     dragView.setDrawingCacheEnabled(true);
     Bitmap bitmap = Bitmap.createBitmap(dragView.getDrawingCache());
     startDrag(bitmap);
     dragView.setVisibility(INVISIBLE);
     isMoving = false;
     ((Adapter) getAdapter()).setIsDrag(true);
     requestDisallowInterceptTouchEvent(true);
     return true;
    }
    return false;
   }
  });
 }
 private void startDrag(Bitmap dragBitmap) {
  stopDrag();
  windowParams = new WindowManager.LayoutParams();
  windowParams.gravity = Gravity.TOP | Gravity.LEFT;
  //得到preview左上角相对于屏幕的坐标
  windowParams.x = rawX - viewL;
  windowParams.y = rawY - viewT;
  //设置拖拽item的宽和高
  windowParams.width = (int) (dragScale * dragBitmap.getWidth());// 放大dragScale倍，可以设置拖动后的倍数
  windowParams.height = (int) (dragScale * dragBitmap.getHeight());// 放大dragScale倍，可以设置拖动后的倍数
  this.windowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
    | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
    | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
    | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
  this.windowParams.format = PixelFormat.TRANSLUCENT;
  this.windowParams.windowAnimations = 0;
  ImageView iv = new ImageView(getContext());
  iv.setImageBitmap(dragBitmap);
  windowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
  windowManager.addView(iv, windowParams);
  dragImageView = iv;
 }
 private void stopDrag() {
  if (dragImageView != null && windowManager != null) {
   windowManager.removeView(dragImageView);
   dragImageView = null;
  }
 }
 @Override
 public boolean onTouchEvent(MotionEvent ev) {
  int x = (int) ev.getX();
  int y = (int) ev.getY();
  switch (ev.getAction()) {
   case MotionEvent.ACTION_DOWN:
    downX = x;
    downY = y;
    rawX = (int) ev.getRawX();
    rawY = (int) ev.getRawY();
    break;
   case MotionEvent.ACTION_MOVE:
    if (dragImageView != null && lastPosition != INVALID_POSITION) {
     updateDrag((int) ev.getRawX(), (int) ev.getRawY());
     if (!isMoving) onMove(x, y, false);
    }
    break;
   case MotionEvent.ACTION_UP:
//    Log.e(TAG, "dragImageView is null=" + (dragImageView == null) + ",lastposition=" + lastPosition
//      + ",pointToPosition=" + pointToPosition(x, y) + ",ismove=" + isMoving);
    if (dragMK