之前的工作中，需要實現一個功能就是GridView中的item可以自由拖動， 思考了一下，其實實現起來不是很困難，主要工作就是交換節點，以及拖動時的移動效果，下面講講具體的實現：
首先聲明一個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;//初始化需隱藏的位置信息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(); // 避免臟數據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();}/*** 交換節點* @param draggedPos 拖拽的起始節點* @param currentPos 拖拽的當前節點*/public void swapView(int draggedPos , int currentPos) {//從前往后拖if(draggedPos < currentPos){//將被拖拽的節點移動至當前節點mList.add(currentPos + 1 , mList.get(draggedPos));//刪除拖拽前的節點mList.remove(draggedPos);}//從后往前拖else if (draggedPos > currentPos) {//將被拖拽的節點移動至當前節點mList.add(currentPos , mList.get(draggedPos));//刪除拖拽前的節點mList.remove(draggedPos + 1);}mHidePosition = currentPos;notifyDataSetChanged();}}其次實現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);//初始化顯示被拖動item的image viewdragImageView = new ImageView(getContext());dragImageView.setTag(DRAG_IMG_NOT_SHOW);//初始化用于設置dragImageView的參數對象dragImageViewParams = new WindowManager.LayoutParams();//獲取窗口管理對象，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) {//記錄長按item位置preDraggedOverPositon = position;//獲取被長按item的drawing cacheview.destroyDrawingCache();view.setDrawingCacheEnabled(true);//通過被長按item，獲取拖動item的bitmapBitmap dragBitmap = Bitmap.createBitmap(view.getDrawingCache());//設置拖動item的參數dragImageViewParams.gravity = Gravity.TOP | Gravity.LEFT;//設置拖動item為原item 1.2倍dragImageViewParams.width = (int)(AMP_FACTOR*dragBitmap.getWidth());dragImageViewParams.height = (int)(AMP_FACTOR*dragBitmap.getHeight());//設置觸摸點為繪制拖動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;//設置窗口支持透明度dragImageViewParams.format = PixelFormat.TRANSLUCENT;dragImageViewParams.windowAnimations = 0;//dragImageView為被拖動item的容器，清空上一次的顯示if((int)dragImageView.getTag() == DRAG_IMG_SHOW) {windowManager.removeView(dragImageView);dragImageView.setTag(DRAG_IMG_NOT_SHOW);}//設置本次被長按的itemdragImageView.setImageBitmap(dragBitmap);//添加拖動item到屏幕windowManager.addView(dragImageView, dragImageViewParams);dragImageView.setTag(DRAG_IMG_SHOW);isViewOnDrag = true;//設置被長按item不顯示((BaseDragableAdapter)getAdapter()).hideView(position);return true;}};@Overridepublic boolean onTouchEvent(MotionEvent ev) {//被按下時記錄按下的坐標if(ev.getAction() == MotionEvent.ACTION_DOWN) {//獲取觸摸點相對于屏幕的坐標downRawX = (int)ev.getRawX();downRawY = (int)ev.getRawY();}//dragImageView處于被拖動時，更新dragImageView位置else if((ev.getAction() == MotionEvent.ACTION_MOVE) && (isViewOnDrag == true)) {Log.i(LOG_TAG, "" + ev.getRawX() + " " + ev.getRawY());//設置觸摸點為dragImageView中心dragImageViewParams.x = (int)(ev.getRawX() - dragImageView.getWidth()/2);dragImageViewParams.y = (int)(ev.getRawY() - dragImageView.getHeight()/2);//更新窗口顯示,移動dragImageView的位置windowManager.updateViewLayout(dragImageView, dragImageViewParams);//獲取當前觸摸點的item positionint currDraggedPosition = pointToPosition((int)ev.getX(), (int)ev.getY());//如果當前停留位置item不等于上次停留位置的item，交換本次和上次停留的itemif((currDraggedPosition != AdapterView.INVALID_POSITION) && (currDraggedPosition != preDraggedOverPositon)) {((BaseDragableAdapter)getAdapter()).swapView(preDraggedOverPositon, currDraggedPosition);preDraggedOverPositon = currDraggedPosition;}}//釋放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);}}實現一個adapter繼承自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);}}以上所述是小編給大家介紹的Android實現GridView中的item自由拖動效果,實現一個模擬后臺數據登入的效果，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復大家的。在此也非常感謝大家對武林網網站的支持！
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