Android中ListView组件的Item拖动（Item改变顺序）

http://blog.csdn.net/mayingcai1987/archive/2011/04/25/6362325.aspx

/*
*
* Licensed under the Apache License, Version 2.0 (the “License”);
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an “AS IS” BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.flora;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.PixelFormat;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.GestureDetector;
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.view.GestureDetector.SimpleOnGestureListener;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.ListView;
public class DragAndDropListView extends ListView {
private ImageView mDragView;
private WindowManager mWindowManager;
private WindowManager.LayoutParams mWindowParams;
/**
* At which position is the item currently being dragged. Note that this
* takes in to account header items.
*/
private int mDragPos;
/**
* At which position was the item being dragged originally
*/
private int mSrcDragPos;
private int mDragPointX; // at what x offset inside the item did the user grab it
private int mDragPointY; // at what y offset inside the item did the user grab it
private int mXOffset; // the difference between screen coordinates and coordinates in this view
private int mYOffset; // the difference between screen coordinates and coordinates in this view
private DragListener mDragListener;
private DropListener mDropListener;
private RemoveListener mRemoveListener;
private int mUpperBound;
private int mLowerBound;
private int mHeight;
private GestureDetector mGestureDetector;
private static final int FLING = 0;
private static final int SLIDE = 1;
private static final int TRASH = 2;
private int mRemoveMode = -1;
private Rect mTempRect = new Rect();
private Bitmap mDragBitmap;
private final int mTouchSlop;
private int mItemHeightNormal;
private int mItemHeightExpanded;
private int mItemHeightHalf;
private Drawable mTrashcan;
public DragAndDropListView(Context context, AttributeSet attrs) {
super(context, attrs);
SharedPreferences pref = context.getSharedPreferences(“Music”, 3);
mRemoveMode = pref.getInt(“deletemode”, -1);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
Resources res = getResources();
mItemHeightNormal = res.getDimensionPixelSize(R.dimen.normal_height);
mItemHeightHalf = mItemHeightNormal / 2;
mItemHeightExpanded = res.getDimensionPixelSize(R.dimen.expanded_height);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if (mRemoveListener != null && mGestureDetector == null) {
if (mRemoveMode == FLING) {
mGestureDetector = new GestureDetector(getContext(), new SimpleOnGestureListener() {
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
if (mDragView != null) {
if (velocityX > 1000) {
Rect r = mTempRect;
mDragView.getDrawingRect(r);
if ( e2.getX() > r.right * 2 / 3) {
// fast fling right with release near the right edge of the screen
stopDragging();
mRemoveListener.remove(mSrcDragPos);
unExpandViews(true);
}
}
// flinging while dragging should have no effect
return true;
}
return false;
}
});
}
}
if (mDragListener != null || mDropListener != null) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
int x = (int) ev.getX();
int y = (int) ev.getY();
int itemnum = pointToPosition(x, y);
if (itemnum == AdapterView.INVALID_POSITION) {
break;
}
ViewGroup item = (ViewGroup) getChildAt(itemnum – getFirstVisiblePosition());
mDragPointX = x – item.getLeft();
mDragPointY = y – item.getTop();
mXOffset = ((int)ev.getRawX()) – x;
mYOffset = ((int)ev.getRawY()) – y;
// The left side of the item is the grabber for dragging the item
if (x < 64) {
item.setDrawingCacheEnabled(true);
// Create a copy of the drawing cache so that it does not get recycled
// by the framework when the list tries to clean up memory
Bitmap bitmap = Bitmap.createBitmap(item.getDrawingCache());
startDragging(bitmap, x, y);
mDragPos = itemnum;
mSrcDragPos = mDragPos;
mHeight = getHeight();
int touchSlop = mTouchSlop;
mUpperBound = Math.min(y – touchSlop, mHeight / 3);
mLowerBound = Math.max(y + touchSlop, mHeight * 2 /3);
return false;
}
stopDragging();
break;
}
}
return super.onInterceptTouchEvent(ev);
}
/*
* pointToPosition() doesn’t consider invisible views, but we
* need to, so implement a slightly different version.
*/
private int myPointToPosition(int x, int y) {
if (y < 0) {
// when dragging off the top of the screen, calculate position
// by going back from a visible item
int pos = myPointToPosition(x, y + mItemHeightNormal);
if (pos > 0) {
return pos – 1;
}
}
Rect frame = mTempRect;
final int count = getChildCount();
for (int i = count – 1; i >= 0; i–) {
final View child = getChildAt(i);
child.getHitRect(frame);
if (frame.contains(x, y)) {
return getFirstVisiblePosition() + i;
}
}
return INVALID_POSITION;
}
private int getItemForPosition(int y) {
int adjustedy = y – mDragPointY – mItemHeightHalf;
int pos = myPointToPosition(0, adjustedy);
if (pos >= 0) {
if (pos <= mSrcDragPos) {
pos += 1;
}
} else if (adjustedy < 0) {
// this shouldn’t happen anymore now that myPointToPosition deals
// with this situation
pos = 0;
}
return pos;
}
private void adjustScrollBounds(int y) {
if (y >= mHeight / 3) {
mUpperBound = mHeight / 3;
}
if (y <= mHeight * 2 / 3) {
mLowerBound = mHeight * 2 / 3;
}
}
/*
* Restore size and visibility for all listitems
*/
private void unExpandViews(boolean deletion) {
for (int i = 0;; i++) {
View v = getChildAt(i);
if (v == null) {
if (deletion) {
// HACK force update of mItemCount
int position = getFirstVisiblePosition();
int y = getChildAt(0).getTop();
setAdapter(getAdapter());
setSelectionFromTop(position, y);
// end hack
}
try {
layoutChildren(); // force children to be recreated where needed
v = getChildAt(i);
} catch (IllegalStateException ex) {
// layoutChildren throws this sometimes, presumably because we’re
// in the process of being torn down but are still getting touch
// events
}
if (v == null) {
return;
}
}
ViewGroup.LayoutParams params = v.getLayoutParams();
params.height = mItemHeightNormal;
v.setLayoutParams(params);
v.setVisibility(View.VISIBLE);
}
}
/* Adjust visibility and size to make it appear as though
* an item is being dragged around and other items are making
* room for it:
* If dropping the item would result in it still being in the
* same place, then make the dragged listitem’s size normal,
* but make the item invisible.
* Otherwise, if the dragged listitem is still on screen, make
* it as small as possible and expand the item below the insert
* point.
* If the dragged item is not on screen, only expand the item
* below the current insertpoint.
*/
private void doExpansion() {
int childnum = mDragPos – getFirstVisiblePosition();
if (mDragPos > mSrcDragPos) {
childnum++;
}
int numheaders = getHeaderViewsCount();
View first = getChildAt(mSrcDragPos – getFirstVisiblePosition());
for (int i = 0;; i++) {
View vv = getChildAt(i);
if (vv == null) {
break;
}
int height = mItemHeightNormal;
int visibility = View.VISIBLE;
if (mDragPos < numheaders && i == numheaders) {
// dragging on top of the header item, so adjust the item below
// instead
if (vv.equals(first)) {
visibility = View.INVISIBLE;
} else {
height = mItemHeightExpanded;
}
} else if (vv.equals(first)) {
// processing the item that is being dragged
if (mDragPos == mSrcDragPos || getPositionForView(vv) == getCount() – 1) {
// hovering over the original location
visibility = View.INVISIBLE;
} else {
// not hovering over it
// Ideally the item would be completely gone, but neither
// setting its size to 0 nor settings visibility to GONE
// has the desired effect.
height = 1;
}
} else if (i == childnum) {
if (mDragPos >= numheaders && mDragPos < getCount() – 1) {
height = mItemHeightExpanded;
}
}
ViewGroup.LayoutParams params = vv.getLayoutParams();
params.height = height;
vv.setLayoutParams(params);
vv.setVisibility(visibility);
}
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (mGestureDetector != null) {
mGestureDetector.onTouchEvent(ev);
}
if ((mDragListener != null || mDropListener != null) && mDragView != null) {
int action = ev.getAction();
switch (action) {
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
Rect r = mTempRect;
mDragView.getDrawingRect(r);
stopDragging();
if (mRemoveMode == SLIDE && ev.getX() > r.right * 3 / 4) {
if (mRemoveListener != null) {
mRemoveListener.remove(mSrcDragPos);
}
unExpandViews(true);
} else {
if (mDropListener != null && mDragPos >= 0 && mDragPos < getCount()) {
mDropListener.drop(mSrcDragPos, mDragPos);
}
unExpandViews(false);
}
break;
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
int x = (int) ev.getX();
int y = (int) ev.getY();
dragView(x, y);
int itemnum = getItemForPosition(y);
if (itemnum >= 0) {
if (action == MotionEvent.ACTION_DOWN || itemnum != mDragPos) {
if (mDragListener != null) {
mDragListener.drag(mDragPos, itemnum);
}
mDragPos = itemnum;
doExpansion();
}
int speed = 0;
adjustScrollBounds(y);
if (y > mLowerBound) {
// scroll the list up a bit
if (getLastVisiblePosition() < getCount() – 1) {
speed = y > (mHeight + mLowerBound) / 2 ? 16 : 4;
} else {
speed = 1;
}
} else if (y < mUpperBound) {
// scroll the list down a bit
speed = y < mUpperBound / 2 ? -16 : -4;
if (getFirstVisiblePosition() == 0
&& getChildAt(0).getTop() >= getPaddingTop()) {
// if we’re already at the top, don’t try to scroll, because
// it causes the framework to do some extra drawing that messes
// up our animation
speed = 0;
}
}
if (speed != 0) {
smoothScrollBy(speed, 30);
}
}
break;
}
return true;
}
return super.onTouchEvent(ev);
}
private void startDragging(Bitmap bm, int x, int y) {
stopDragging();
mWindowParams = new WindowManager.LayoutParams();
mWindowParams.gravity = Gravity.TOP | Gravity.LEFT;
mWindowParams.x = x – mDragPointX + mXOffset;
mWindowParams.y = y – mDragPointY + mYOffset;
mWindowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
mWindowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
mWindowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
| WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS;
mWindowParams.format = PixelFormat.TRANSLUCENT;
mWindowParams.windowAnimations = 0;
Context context = getContext();
ImageView v = new ImageView(context);
v.setBackgroundResource(R.drawable.drag_and_drop_image);
v.setPadding(0, 0, 0, 0);
v.setImageBitmap(bm);
mDragBitmap = bm;
mWindowManager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
mWindowManager.addView(v, mWindowParams);
mDragView = v;
}
private void dragView(int x, int y) {
if (mRemoveMode == SLIDE) {
float alpha = 1.0f;
int width = mDragView.getWidth();
if (x > width / 2) {
alpha = ((float)(width – x)) / (width / 2);
}
mWindowParams.alpha = alpha;
}
if (mRemoveMode == FLING || mRemoveMode == TRASH) {
mWindowParams.x = x – mDragPointX + mXOffset;
} else {
mWindowParams.x = 0;
}
mWindowParams.y = y – mDragPointY + mYOffset;
mWindowManager.updateViewLayout(mDragView, mWindowParams);
if (mTrashcan != null) {
int width = mDragView.getWidth();
if (y > getHeight() * 3 / 4) {
mTrashcan.setLevel(2);
} else if (width > 0 && x > width / 4) {
mTrashcan.setLevel(1);
} else {
mTrashcan.setLevel(0);
}
}
}
private void stopDragging() {
if (mDragView != null) {
mDragView.setVisibility(GONE);
WindowManager wm = (WindowManager)getContext().getSystemService(Context.WINDOW_SERVICE);
wm.removeView(mDragView);
mDragView.setImageDrawable(null);
mDragView = null;
}
if (mDragBitmap != null) {
mDragBitmap.recycle();
mDragBitmap = null;
}
if (mTrashcan != null) {
mTrashcan.setLevel(0);
}
}
public void setTrashcan(Drawable trash) {
mTrashcan = trash;
mRemoveMode = TRASH;
}
public void setDragListener(DragListener l) {
mDragListener = l;
}
public void setDropListener(DropListener l) {
mDropListener = l;
}
public void setRemoveListener(RemoveListener l) {
mRemoveListener = l;
}
public interface DragListener {
void drag(int from, int to);
}
public interface DropListener {
void drop(int from, int to);
}
public interface RemoveListener {
void remove(int which);
}
}

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