之前的工作中，需要实现一个功能就是GridView中的item可以自由拖动， 思考了一下，其实实现起来不是很困难，主要工作就是交换节点，以及拖动时的移动效果，下面讲讲具体的实现：

首先声明一个BaseAdapter:

package com.dafasoft.dragablegridview;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.AbsListView;import android.widget.AdapterView;import android.widget.BaseAdapter;import java.util.ArrayList;import java.util.List;/*** Created by zhangyulong on 16/9/22.*/public abstract class BaseDragableAdapter<T> extends BaseAdapter {protected List<T> mList;protected Context mContext;protected LayoutInflater mInflater;//初始化需隐藏的位置信息protected int mHidePosition = AdapterView.INVALID_POSITION;public BaseDragableAdapter(Context context) {this.mContext = context;this.mInflater = LayoutInflater.from(context);mList = new ArrayList<T>();}@Overridepublic int getCount() {return mList == null ? 0 : mList.size();}@Overridepublic Object getItem(int i) {return mList == null ? 0 : mList.get(i);}@Overridepublic long getItemId(int i) {return i;}@Overridepublic abstract View getView(int i, View view, ViewGroup viewGroup);public void setList(List<T> list) {if (this.mList != null) this.mList.clear(); // 避免脏数据if (list == null) {return;}this.mList = list;}public void setList(T[] list){ArrayList<T> arrayList = new ArrayList<T>(list.length);for (T t : list) {arrayList.add(t);}setList(arrayList);}public List<T> getList() {return this.mList;}public void addAll(List<T> list) {if (list == null || list.size() == 0) return;this.mList.addAll(list);}public void addAll(int location, List<T> list) {if (list == null || list.size() == 0) return;this.mList.addAll(location, list);}public void clean() {if (getCount() == 0) return;mList.clear();}public void hideView(int position){mHidePosition = position;notifyDataSetChanged();}public void showHideView(){//重置hidepositionmHidePosition = AdapterView.INVALID_POSITION;notifyDataSetChanged();}/*** 交换节点* @param draggedPos 拖拽的起始节点* @param currentPos 拖拽的当前节点*/public void swapView(int draggedPos , int currentPos) {//从前往后拖if(draggedPos < currentPos){//将被拖拽的节点移动至当前节点mList.add(currentPos + 1 , mList.get(draggedPos));//删除拖拽前的节点mList.remove(draggedPos);}//从后往前拖else if (draggedPos > currentPos) {//将被拖拽的节点移动至当前节点mList.add(currentPos , mList.get(draggedPos));//删除拖拽前的节点mList.remove(draggedPos + 1);}mHidePosition = currentPos;notifyDataSetChanged();}}

其次实现DragableGridView:

package com.dafasoft.dragablegridview;import android.content.Context;import android.graphics.Bitmap;import android.graphics.PixelFormat;import android.util.AttributeSet;import android.util.Log;import android.view.Gravity;import android.view.MotionEvent;import android.view.View;import android.view.WindowManager;import android.widget.AdapterView;import android.widget.GridView;import android.widget.ImageView;/*** Created by zhangyulong on 16/9/22.*/public class DragableGridView extends GridView {private static final int DRAG_IMG_SHOW = 1;private static final int DRAG_IMG_NOT_SHOW = 0;private static final String LOG_TAG = "DragGridView";private static final float AMP_FACTOR = 1.2f;private ImageView dragImageView;private WindowManager.LayoutParams dragImageViewParams;private WindowManager windowManager;private boolean isViewOnDrag = false;/**previous dragged over position*/private int preDraggedOverPositon = AdapterView.INVALID_POSITION;private int downRawX;private int downRawY;public DragableGridView(Context context) {super(context);initView();}public DragableGridView(Context context, AttributeSet attrs) {super(context, attrs);initView();}public DragableGridView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);initView();}public void initView() {setOnItemLongClickListener(mOnItemLongClickListener);//setOnItemClickListener(onItemClickListener);//setOnItemSelectedListener(onItemSelectedListener);//初始化显示被拖动item的image viewdragImageView = new ImageView(getContext());dragImageView.setTag(DRAG_IMG_NOT_SHOW);//初始化用于设置dragImageView的参数对象dragImageViewParams = new WindowManager.LayoutParams();//获取窗口管理对象，用于后面向窗口中添加dragImageViewwindowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);}private OnItemLongClickListener mOnItemLongClickListener = new OnItemLongClickListener() {@Overridepublic boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {//记录长按item位置preDraggedOverPositon = position;//获取被长按item的drawing cacheview.destroyDrawingCache();view.setDrawingCacheEnabled(true);//通过被长按item，获取拖动item的bitmapBitmap dragBitmap = Bitmap.createBitmap(view.getDrawingCache());//设置拖动item的参数dragImageViewParams.gravity = Gravity.TOP | Gravity.LEFT;//设置拖动item为原item 1.2倍dragImageViewParams.width = (int)(AMP_FACTOR*dragBitmap.getWidth());dragImageViewParams.height = (int)(AMP_FACTOR*dragBitmap.getHeight());//设置触摸点为绘制拖动item的中心dragImageViewParams.x = (downRawX - dragImageViewParams.width/2);dragImageViewParams.y = (downRawY - dragImageViewParams.height/2);dragImageViewParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;//设置窗口支持透明度dragImageViewParams.format = PixelFormat.TRANSLUCENT;dragImageViewParams.windowAnimations = 0;//dragImageView为被拖动item的容器，清空上一次的显示if((int)dragImageView.getTag() == DRAG_IMG_SHOW) {windowManager.removeView(dragImageView);dragImageView.setTag(DRAG_IMG_NOT_SHOW);}//设置本次被长按的itemdragImageView.setImageBitmap(dragBitmap);//添加拖动item到屏幕windowManager.addView(dragImageView, dragImageViewParams);dragImageView.setTag(DRAG_IMG_SHOW);isViewOnDrag = true;//设置被长按item不显示((BaseDragableAdapter)getAdapter()).hideView(position);return true;}};@Overridepublic boolean onTouchEvent(MotionEvent ev) {//被按下时记录按下的坐标if(ev.getAction() == MotionEvent.ACTION_DOWN) {//获取触摸点相对于屏幕的坐标downRawX = (int)ev.getRawX();downRawY = (int)ev.getRawY();}//dragImageView处于被拖动时，更新dragImageView位置else if((ev.getAction() == MotionEvent.ACTION_MOVE) && (isViewOnDrag == true)) {Log.i(LOG_TAG, "" + ev.getRawX() + " " + ev.getRawY());//设置触摸点为dragImageView中心dragImageViewParams.x = (int)(ev.getRawX() - dragImageView.getWidth()/2);dragImageViewParams.y = (int)(ev.getRawY() - dragImageView.getHeight()/2);//更新窗口显示,移动dragImageView的位置windowManager.updateViewLayout(dragImageView, dragImageViewParams);//获取当前触摸点的item positionint currDraggedPosition = pointToPosition((int)ev.getX(), (int)ev.getY());//如果当前停留位置item不等于上次停留位置的item，交换本次和上次停留的itemif((currDraggedPosition != AdapterView.INVALID_POSITION) && (currDraggedPosition != preDraggedOverPositon)) {((BaseDragableAdapter)getAdapter()).swapView(preDraggedOverPositon, currDraggedPosition);preDraggedOverPositon = currDraggedPosition;}}//释放dragImageViewelse if((ev.getAction() == MotionEvent.ACTION_UP) && (isViewOnDrag == true)) {((BaseDragableAdapter)getAdapter()).showHideView();if((int)dragImageView.getTag() == DRAG_IMG_SHOW) {windowManager.removeView(dragImageView);dragImageView.setTag(DRAG_IMG_NOT_SHOW);}isViewOnDrag = false;}return super.onTouchEvent(ev);}}

实现一个adapter继承自BaseDragableAdapter:

package com.dafasoft.dragablegridview;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.TextView;/*** Created by zhangyulong on 16/9/22.*/public class MyAdapter extends BaseDragableAdapter<String> {public MyAdapter(Context context) {super(context);}@Overridepublic View getView(int i, View view, ViewGroup viewGroup) {ViewHolder viewHolder;if (view == null) {viewHolder = new ViewHolder();view = mInflater.inflate(R.layout.adapter_my , null);viewHolder.mItemTv = (TextView) view.findViewById(R.id.tv_item);view.setTag(viewHolder);} else {viewHolder = (ViewHolder)view.getTag();}if (mHidePosition == i) {view.setVisibility(View.GONE);} else {view.setVisibility(View.VISIBLE);}viewHolder.mItemTv.setText(mList.get(i));return view;}class ViewHolder{TextView mItemTv;}}

在activity中使用：

package com.dafasoft.dragablegridview;import android.app.Activity;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import java.util.ArrayList;import java.util.List;public class MainActivity extends Activity {private DragableGridView mDragableGv;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mDragableGv = (DragableGridView) findViewById(R.id.drag_grid_view);MyAdapter adapter = new MyAdapter(this);List<String> list = new ArrayList<String>();for (int i = 0 ; i < 30 ; i ++) {list.add("position" + i);}adapter.setList(list);mDragableGv.setAdapter(adapter);}}

以上所述是小编给大家介绍的Android实现GridView中的item自由拖动效果,实现一个模拟后台数据登入的效果，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网站的支持！