package com.example.draglistview;
import com.example.draglistview.MainActivity.DragListAdapter;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
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.ViewConfiguration;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.Toast;
public class DragView extends ListView{
private ImageView imageView; //被拖動(dòng)的圖片
private int scaledTouchSlop; //判斷拖動(dòng)的距離

private int dragSrcPosition; //手指在touch事件觸摸時(shí)候的原始位置
private int dragPosition; //手指拖動(dòng)列表項(xiàng)時(shí)候的位置

private int dragPoint; //手指點(diǎn)擊位置在當(dāng)前數(shù)據(jù)項(xiàng)item中的位置,只有Y坐標(biāo)
private int dragOffset; //當(dāng)前視圖listview在屏幕中的位置，只有Y坐標(biāo)

private int upScrollBounce; //向上滑動(dòng)的邊界
private int downScrollBounce; //拖動(dòng)的時(shí)候向下滑動(dòng)的邊界

private WindowManager windowManager = null; //窗口管理類
//窗口參數(shù)類
private WindowManager.LayoutParams layoutParams = null;



//注意該View如果在Layout xml 注冊(cè)使用的話必須使用下面的這個(gè)構(gòu)造進(jìn)行初始化
public DragView(Context context, AttributeSet attrs) {
super(context, attrs);
//觸發(fā)移動(dòng)事件的最小距離
scaledTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
}
//重寫(xiě)于absListView
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {

if(ev.getAction() == MotionEvent.ACTION_DOWN){
//獲取的該touch事件的x坐標(biāo)和y坐標(biāo)，該坐標(biāo)是相對(duì)于組件的左上角的位置
int x = (int) ev.getX();
int y = (int) ev.getY();
//賦值手指點(diǎn)擊時(shí)候的開(kāi)始坐標(biāo)
dragSrcPosition = dragPosition = this.pointToPosition(x, y);
//如果點(diǎn)擊在列表之外，也就是不允許的位置
if(dragPosition == AdapterView.INVALID_POSITION){
//直接執(zhí)行父類，不做任何操作
return super.onInterceptTouchEvent(ev);
}

/***
* 鎖定手指touch的列表item,
* 參數(shù)為屏幕的touch坐標(biāo)減去listview左上角的坐標(biāo)
* 這里的getChildAt方法參數(shù)為相對(duì)于組件左上角坐標(biāo)為00的情況
* 故有下面的這種參數(shù)算法
*/
ViewGroup itemView = (ViewGroup) this.getChildAt(dragPosition-this.getFirstVisiblePosition());
/****
* 說(shuō)明：getX Y為touch點(diǎn)相對(duì)于組件左上角的距離
* getRawX 、Y 為touch點(diǎn)相對(duì)于屏幕左上角的距離
* 參考http://blog.csdn.net/love_world_/article/details/8164293
*/
//touch點(diǎn)的view相對(duì)于該childitem的top坐標(biāo)的距離
dragPoint = y-itemView.getTop();
//為距離屏幕左上角的Y減去距離組件左上角的Y，其實(shí)就是
//組件上方的view+標(biāo)題欄+狀態(tài)欄的Y
dragOffset = (int) (ev.getRawY()-y);

//拿到拖動(dòng)的imageview對(duì)象
View drager = itemView.findViewById(R.id.imageView1);

//判斷條件為拖動(dòng)touch圖片是否為null和touch的位置，是否符合
if(drager != null && x>drager.getLeft()-20){

//判斷得出向上滑動(dòng)和向下滑動(dòng)的值
upScrollBounce = Math.min(y-scaledTouchSlop, getHeight()/3);
downScrollBounce = Math.max(y+scaledTouchSlop, getHeight()*2/3);
//啟用繪圖緩存
itemView.setDrawingCacheEnabled(true);
//根據(jù)圖像緩存拿到對(duì)應(yīng)位圖
Bitmap bm = Bitmap.createBitmap(itemView.getDrawingCache());
startDrag(bm, y);
}
return false;
}
return super.onInterceptTouchEvent(ev);
}


//重寫(xiě)OnTouchEvent,觸摸事件
@Override
public boolean onTouchEvent(MotionEvent ev) {
if(imageView != null && dragPosition != INVALID_POSITION){
int currentAction = ev.getAction();

switch (currentAction) {
case MotionEvent.ACTION_UP:
int upY = (int) ev.getY();
//還有一些操作
stopDrag();
onDrop(upY);
break;
case MotionEvent.ACTION_MOVE:
Log.v("move", "move---------");
int moveY = (int) ev.getY();
onDrag(moveY);
break;
default:
break;
}
return true;
}
//決定了選中的效果
return super.onTouchEvent(ev);
}



/****
* 準(zhǔn)備拖動(dòng)，初始化拖動(dòng)時(shí)的影像，和一些window參數(shù)
* @param bm 拖動(dòng)緩存位圖
* @param y 拖動(dòng)之前touch的位置
*/
public void startDrag(Bitmap bm,int y){
stopDrag();
layoutParams = new WindowManager.LayoutParams();
//設(shè)置重力
layoutParams.gravity = Gravity.TOP;
//橫軸坐標(biāo)不變
layoutParams.x = 0;
/**
*
* y軸坐標(biāo)為 視圖相對(duì)于自身左上角的Y-touch點(diǎn)在列表項(xiàng)中的y
* +視圖相對(duì)于屏幕左上角的Y，=
* 該view相對(duì)于屏幕左上角的位置
*/
layoutParams.y = y-dragPoint+dragOffset;
/****
* 寬度和高度都為wrapContent
*/
layoutParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
layoutParams.height = WindowManager.LayoutParams.WRAP_CONTENT;

/****
* 設(shè)置該layout參數(shù)的一些flags參數(shù)
*/
layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
//設(shè)置該window項(xiàng)是半透明的格式
layoutParams.format = PixelFormat.TRANSLUCENT;
//設(shè)置沒(méi)有動(dòng)畫(huà)
layoutParams.windowAnimations = 0;

//配置一個(gè)影像ImageView
ImageView imageViewForDragAni = new ImageView(getContext());
imageViewForDragAni.setImageBitmap(bm);
//配置該windowManager
windowManager = (WindowManager) this.getContext().getSystemService("window");
windowManager.addView(imageViewForDragAni, layoutParams);
imageView = imageViewForDragAni;
}

/***
* 停止拖動(dòng)，去掉拖動(dòng)時(shí)候的影像
*/
public void stopDrag(){
if(imageView != null){
windowManager.removeView(imageView);
imageView = null;
}
}


/****
* 拖動(dòng)方法
* @param y
*/
public void onDrag(int y){

if(imageView != null){
//透明度
layoutParams.alpha = 0.8f;
layoutParams.y = y-this.dragPoint+this.dragOffset;
windowManager.updateViewLayout(imageView, layoutParams);
}


//避免拖動(dòng)到分割線返回-1
int tempPosition = this.pointToPosition(0, y);
if(tempPosition != this.INVALID_POSITION){
this.dragPosition = tempPosition;
}


int scrollHeight = 0;
if(y<upScrollBounce){
scrollHeight = 8;//定義向上滾動(dòng)8個(gè)像素，如果可以向上滾動(dòng)的話
}else if(y>downScrollBounce){
scrollHeight = -8;//定義向下滾動(dòng)8個(gè)像素，，如果可以向上滾動(dòng)的話
}

if(scrollHeight!=0){
//真正滾動(dòng)的方法setSelectionFromTop()
setSelectionFromTop(dragPosition, getChildAt(dragPosition-getFirstVisiblePosition()).getTop()+scrollHeight);
}
}


/***
* 拖動(dòng)放下的時(shí)候
* param : y
*/
public void onDrop(int y){
int tempPosition = this.pointToPosition(0, y);
if(tempPosition != this.INVALID_POSITION){
this.dragPosition = tempPosition;
}

//超出邊界處理
if(y<getChildAt(1).getTop()){
//超出上邊界
dragPosition = 1;
}else if(y>getChildAt(getChildCount()-1).getBottom()){
//超出下邊界
dragPosition = getAdapter().getCount()-1;
//
}
//數(shù)據(jù)交換
if(dragPosition>0&&dragPosition<getAdapter().getCount()){
@SuppressWarnings("unchecked")
DragListAdapter adapter = (DragListAdapter)getAdapter();
//原始位置的item
String dragItem = adapter.getItem(dragSrcPosition);
adapter.remove(dragItem);
adapter.insert(dragItem, dragPosition);
Toast.makeText(getContext(), adapter.getList().toString(), Toast.LENGTH_SHORT).show();
}
}
}