package com.fengjian.test;
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.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;
import com.fengjian.test.DragListActivity.DragListAdapter;
public class DragListView extends ListView {
private ImageView dragImageView;//被拖拽的项,其实就是一个ImageView
private int dragSrcPosition;//手指拖动项原始在列表中的位置
private int dragPosition;//手指拖动的时候,当前拖动项在列表中的位置
private int dragPoint;//在当前数据项中的位置
private int dragOffset;//当前视图和屏幕的距离(这里只使用了y方向上)
private WindowManager windowManager;//windows窗口控制类
private WindowManager.LayoutParams windowParams;//用于控制拖拽项的显示的参数
private int scaledTouchSlop;//判断滑动的一个距离
private int upScrollBounce;//拖动的时候,开始向上滚动的边界
private int downScrollBounce;//拖动的时候,开始向下滚动的边界
public DragListView(Context context, AttributeSet attrs) {
super(context, attrs);
scaledTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
}
//拦截touch事件,其实就是加一层控制
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if(ev.getAction()==MotionEvent.ACTION_DOWN){
int x = (int)ev.getX();
int y = (int)ev.getY();
dragSrcPosition = dragPosition = pointToPosition(x, y);
if(dragPosition==AdapterView.INVALID_POSITION){
return super.onInterceptTouchEvent(ev);
}
ViewGroup itemView = (ViewGroup) getChildAt(dragPosition-getFirstVisiblePosition());
dragPoint = y - itemView.getTop();
dragOffset = (int) (ev.getRawY() - y);
View dragger = itemView.findViewById(R.id.drag_list_item_image);
if(dragger!=null&&x>dragger.getLeft()-20){
//
upScrollBounce = Math.min(y-scaledTouchSlop, getHeight()/3);
downScrollBounce = Math.max(y+scaledTouchSlop, getHeight()*2/3);
itemView.setDrawingCacheEnabled(true);
Bitmap bm = Bitmap.createBitmap(itemView.getDrawingCache());
startDrag(bm, y);
}
return false;
}
return super.onInterceptTouchEvent(ev);
}
/**
* 触摸事件
*/
@Override
public boolean onTouchEvent(MotionEvent ev) {
if(dragImageView!=null&&dragPosition!=INVALID_POSITION){
int action = ev.getAction();
switch(action){
case MotionEvent.ACTION_UP:
int upY = (int)ev.getY();
stopDrag();
onDrop(upY);
break;
case MotionEvent.ACTION_MOVE:
int moveY = (int)ev.getY();
onDrag(moveY);
break;
default:break;
}
return true;
}
//也决定了选中的效果
return super.onTouchEvent(ev);
}
/**
* 准备拖动,初始化拖动项的图像
* @param bm
* @param y
*/
public void startDrag(Bitmap bm ,int y){
stopDrag();
windowParams = new WindowManager.LayoutParams();
windowParams.gravity = Gravity.TOP;
windowParams.x = 0;
windowParams.y = y - dragPoint + dragOffset;
windowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
windowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
windowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
windowParams.format = PixelFormat.TRANSLUCENT;
windowParams.windowAnimations = 0;
ImageView imageView = new ImageView(getContext());
imageView.setImageBitmap(bm);
windowManager = (WindowManager)getContext().getSystemService("window");
windowManager.addView(imageView, windowParams);
dragImageView = imageView;
}
/**
* 停止拖动,去除拖动项的头像
*/
public void stopDrag(){
if(dragImageView!=null){
windowManager.removeView(dragImageView);
dragImageView = null;
}
}
/**
* 拖动执行,在Move方法中执行
* @param y
*/
public void onDrag(int y){
if(dragImageView!=null){
windowParams.alpha = 0.8f;
windowParams.y = y - dragPoint + dragOffset;
windowManager.updateViewLayout(dragImageView, windowParams);
}
//为了避免滑动到分割线的时候,返回-1的问题
int tempPosition = pointToPosition(0, y);
if(tempPosition!=INVALID_POSITION){
dragPosition = tempPosition;
}
//滚动
int scrollHeight = 0;
if(y<upScrollBounce){
scrollHeight = 8;//定义向上滚动8个像素,如果可以向上滚动的话
}else if(y>downScrollBounce){
scrollHeight = -8;//定义向下滚动8个像素,,如果可以向上滚动的话
}
if(scrollHeight!=0){
//真正滚动的方法setSelectionFromTop()
setSelectionFromTop(dragPosition, getChildAt(dragPosition-getFirstVisiblePosition()).getTop()+scrollHeight);
}
}
/**
* 拖动放下的时候
* @param y
*/
public void onDrop(int y){
//为了避免滑动到分割线的时候,返回-1的问题
int tempPosition = pointToPosition(0, y);
if(tempPosition!=INVALID_POSITION){
dragPosition = tempPosition;
}
//超出边界处理
if(y<getChildAt(1).getTop()){
//超出上边界
dragPosition = 1;
}else if(y>getChildAt(getChildCount()-1).getBottom()){
//超出下边界
dragPosition = getAdapter().getCount()-1;
}
//数据交换
if(dragPosition>0&&dragPosition<getAdapter().getCount()){
@SuppressWarnings("unchecked")
DragListAdapter adapter = (DragListAdapter)getAdapter();
String dragItem = adapter.getItem(dragSrcPosition);
adapter.remove(dragItem);
adapter.insert(dragItem, dragPosition);
Toast.makeText(getContext(), adapter.getList().toString(), Toast.LENGTH_SHORT).show();
}
}
}