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;

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 (dragImageView != null && lastPosition != INVALID_POSITION) {
//     if (isMoving) onMove(x, y, true);//动画还未执行完的情况下，重设动画会清除之前设置的动画。
     stopDrag();
     ((Adapter) getAdapter()).setIsDrag(false);
     ((BaseAdapter) getAdapter()).notifyDataSetChanged();
     requestDisallowInterceptTouchEvent(false);
    }
    break;
  }
  return super.onTouchEvent(ev);
 }
 private void onMove(int moveX, int moveY, boolean isMoveUp) {
  final int targetPosition = pointToPosition(moveX, moveY);
  if (targetPosition != INVALID_POSITION) {
   if (targetPosition == lastPosition) {
    //移动位置在还未到新item内
    return;
   }
   //移需要移动的动ITEM数量
   int moveCount = targetPosition - lastPosition;
   if (moveCount != 0) {
    if (isMoveUp) {//手指抬起时，不执行动画直接交换数据
     Adapter adapter = (Adapter) getAdapter();
     adapter.exchange(lastPosition, targetPosition);
     lastPosition = targetPosition;
     isMoving = false;
    } else {
     int moveCountAbs = Math.abs(moveCount);
     float toXvalue = 0, toYvalue = 0;
     //moveXP移动的距离百分比（相对于自己长度的百分比）
     float moveXP = ((float) getHorizontalSpacing() / (float) itemWidth) + 1.0f;
     float moveYP = ((float) getVerticalSpacing() / (float) itemHeight) + 1.0f;
     int holdPosition;
//     Log.d(TAG, "start annimation=" + moveCountAbs);
     for (int i = 0; i < moveCountAbs; i++) {
      //从左往右，或是从上往下
      if (moveCount > 0) {
       holdPosition = lastPosition + i + 1;
       //同一行
       if (lastPosition / getNumColumns() == holdPosition / getNumColumns()) {
        toXvalue = -moveXP;
        toYvalue = 0;
       } else if (holdPosition % getNumColumns() == 0) {
        toXvalue = (getNumColumns() - 1) * moveXP;
        toYvalue = -moveYP;
       } else {
        toXvalue = -moveXP;
        toYvalue = 0;
       }
      } else {
       //从右往左，或是从下往上
       holdPosition = lastPosition - i - 1;
       if (lastPosition / getNumColumns() == holdPosition / getNumColumns()) {
        toXvalue = moveXP;
        toYvalue = 0;
       } else if ((holdPosition + 1) % getNumColumns() == 0) {
        toXvalue = -(getNumColumns() - 1) * moveXP;
        toYvalue = moveYP;
       } else {
        toXvalue = moveXP;
        toYvalue = 0;
       }
      }
      View holdView = getChildAt(holdPosition);
      Animation moveAnimation = createAnimation(toXvalue, toYvalue);
      moveAnimation.setAnimationListener(new Animation.AnimationListener() {
       @Override
       public void onAnimationStart(Animation animation) {
        isMoving = true;
       }
       @Override
       public void onAnimationRepeat(Animation animation) {
       }
       @Override
       public void onAnimationEnd(Animation animation) {
        // 如果为最后个动画结束，那执行下面的方法
        if (animation == lastAnimation) {
         Adapter adapter = (Adapter) getAdapter();
         adapter.exchange(lastPosition, targetPosition);
         lastPosition = targetPosition;
         isMoving = false;
        }
       }
      });
      holdView.startAnimation(moveAnimation);
      if (holdPosition == targetPosition) {
       lastAnimation = moveAnimation;
      }
     }
    }
   }
  }
 }
 public Animation createAnimation(float toXValue, float toYValue) {
  TranslateAnimation mTranslateAnimation = new TranslateAnimation(
    Animation.RELATIVE_TO_SELF, 0.0F, Animation.RELATIVE_TO_SELF, toXValue,
    Animation.RELATIVE_TO_SELF, 0.0F, Animation.RELATIVE_TO_SELF, toYValue);
  mTranslateAnimation.setFillAfter(true);// 设置一个动画效果执行完毕后，View对象保留在终止的位置。
  mTranslateAnimation.setDuration(TIME_ANIMATE);
  return mTranslateAnimation;
 }
 private void updateDrag(int rawX, int rawY) {
  windowParams.alpha = 0.6f;
  windowParams.x = rawX - viewL;
  windowParams.y = rawY - viewT;
  windowManager.updateViewLayout(dragImageView, windowParams);
 }
 static abstract class Adapter extends BaseAdapter {
  protected boolean isDrag;
  protected int holdPosition = -1;
  public void setIsDrag(boolean isDrag) {
   this.isDrag = isDrag;
  }
  public void exchange(int startPosition, int endPositon) {
   holdPosition = endPositon;
  }
 }
}

主要的代码就是DragGridView，拿到此view实现起来就相当简单了。为了文章完整性，下面也贴上本效果图的主要使用代码。

String[] items = new String[]{"头条", "视频", "娱乐", "体育", "北京", "新时代"
      , "网易号", "段子", "冰雪运动", "科技", "汽车", "轻松一刻"
      , "时尚", "直播", "图片", "跟帖", "NBA", "态度公开课"
      , "推荐", "热点", "社会", "趣图", "美女", "军事"};
gridView.setAdapter(new DragGridView.Adapter() {
      @Override
      public void exchange(int startPosition, int endPositon) {
        super.exchange(startPosition, endPositon);
        String item = list.get(startPosition);
        if (startPosition < endPositon) {
          list.add(endPositon + 1, item);
          list.remove(startPosition);
        } else {
          list.add(endPositon, item);
          list.remove(startPosition + 1);
        }
        for (int i = 0; i < list.size(); i++) {
          Log.e(TAG, "exchange: =" + list.get(i));
        }
        notifyDataSetChanged();
      }
  ...省略部分代码
      @Override
      public View getView(int position, View convertView, ViewGroup parent) {
        //todo,这里需要优化，没有复用views。也不能按传统方式服用view，否则会造成拖动的view空白
//        if (convertView == null) {
        convertView = getLayoutInflater().inflate(R.layout.item, parent, false);
//        }
        ((TextView) convertView.findViewById(R.id.tv)).setText(getItem(position));
        if (isDrag && position == holdPosition) {
          convertView.setVisibility(View.INVISIBLE);
        } else convertView.setVisibility(View.VISIBLE);
        return convertView;
      }
    });

本文到这就结束了，有需要的同学拿到轮子就可以直接使用了，谢谢！

不知道有没有眼尖的同学发现Adapterd的getView方法中有个 todo需要优化。原因是这样：如果打开注释中的代码，复用convertView，会造成gridView释放后的新位置一片空白，不知道什么原因，因此折中的方法就是每次都是新生成一个convertView。
希

总结

以上所述是小编给大家介绍的Android自定义gridView仿头条频道拖动管理功能，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对编程网网站的支持！
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