我想实现一个允许用户将项目拖出的Gallery。这不应该妨碍滚动/投掷。
鉴于界面布局，用户只能在垂直路径中将项目拖出图库，并水平滚动图库。
这可行吗？有没有一种简单的方法来检测水平移动，并将它们推迟到画廊的事件处理程序，并拦截垂直移动？或者我是否必须覆盖onInterceptTouchEvent()并自己进行数学计算？
（编辑：我正在尝试使用GestureListener，覆盖onFling和onScroll，并在垂直滚动距离低于阈值时将事件传递给图库）
答案 0 :(得分：3)
我继承了Gallery，并覆盖了onScroll方法。我还没有实现拖放逻辑，但是拖动和滚动工作。
当我可以节省时间时，我会在我的博客中写一篇完整的帖子，其中包含更多详细信息和删除机制。现在，只要有人在将来到达此页面，就可以进行简单的复制粘贴。
为了保持它所属的行为，我创建了这个DraggableView接口：
public interface DraggableView {
public void beforeDrag();
public DragView createDragView();
public Object getDraggedInfo();
public void afterDrop();
}
如果图库中的视图实现此视图，则可以将其拖出图库区域。他们会在之前和之后得到通知，并且必须实施两种方法：
createDragView()返回一个DragView对象。基本上，一个透明的悬停位图伴随着用户的移动。
getDraggedInfo()返回应该到达放置目标的信息。
这是DragView类：
public class DragView extends ImageView {
private final LayoutParams mLayoutParams;
public DragView(Context context, Bitmap bitmap) {
super(context);
mLayoutParams = new LayoutParams();
mLayoutParams.gravity = Gravity.TOP | Gravity.LEFT;
mLayoutParams.height = LayoutParams.WRAP_CONTENT;
mLayoutParams.width = LayoutParams.WRAP_CONTENT;
mLayoutParams.flags = LayoutParams.FLAG_NOT_FOCUSABLE
| LayoutParams.FLAG_NOT_TOUCHABLE;
mLayoutParams.format = PixelFormat.TRANSLUCENT;
mLayoutParams.windowAnimations = 0;
mLayoutParams.alpha = 0.5f;
setImageBitmap(bitmap);
setLayoutParams(mLayoutParams);
}
public void move(int x, int y) {
mLayoutParams.x = x;
mLayoutParams.y = y;
}
}
如您所见，构建中需要Bitmap，并创建一个悬停ImageView。最后，这里是（刚刚实现的并不是很干净的）Gallery代码，以实现这一切：
public class DraggableItemGallery extends Gallery {
private boolean mDragging;
private DragView mDragView;
private DraggableView mDragViewOwner;
private WindowManager mWindowManager;
private boolean mScrollStarted;
public DraggableItemGallery(Context context) {
super(context);
initialize();
}
public DraggableItemGallery(Context context, AttributeSet attrs) {
super(context, attrs);
initialize();
}
public DraggableItemGallery(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initialize();
}
public void initialize() {
mWindowManager = (WindowManager)
getContext().getSystemService("window");
}
private void startDraggingItem(DraggableView view, int x, int y) {
mDragging = true;
mDragViewOwner = view;
mDragView = view.createDragView();
mDragView.move(x, y);
mWindowManager.addView(mDragView, mDragView.getLayoutParams());
}
private void continueDraggingItem(int x, int y) {
DragView dragView = getDragView();
dragView.move(x, y);
mWindowManager.updateViewLayout(dragView, dragView.getLayoutParams());
}
private void stopDraggingItem() {
mDragging = false;
mWindowManager.removeView(mDragView);
mDragViewOwner.afterDrop();
mDragView = null;
mDragViewOwner = null;
}
private DraggableView getDraggedItem() {
return mDragViewOwner;
}
private DragView getDragView() {
return mDragView;
}
private boolean isDraggingItem() {
return (mDragging);
}
private void setScrolling(boolean scrolling) {
mScrollStarted = scrolling;
System.out.println("Scrolling " + scrolling);
}
private boolean isScrolling() {
return mScrollStarted;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if ((event.getAction() & ACTION_MASK) == ACTION_UP) {
setScrolling(false);
if (isDraggingItem())
stopDraggingItem();
}
return super.onTouchEvent(event);
}
final Rect onScroll_tempRect = new Rect();
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
if (isScrolling()) {
if (isDraggingItem()) {
int x = (int) e2.getX(),
y = (int) e2.getY();
System.out.println("Moving to " + x + " " + y);
continueDraggingItem(x, y);
return true;
} else {
/* Not dragging, let the Gallery handle the event */
return super.onScroll(e1, e2, distanceX, distanceY);
}
} else {
setScrolling(true);
boolean isVertical = (Math.abs(distanceY) > Math.abs(distanceX));
if (isVertical) {
int x = (int) e1.getX(),
y = (int) e1.getY();
View hitChild = null;
// A tiny optimization, declared above this method
final Rect hitRect = onScroll_tempRect;
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
child.getHitRect(hitRect);
if (hitRect.contains(x, y)) {
hitChild = child;
break;
}
}
if (hitChild instanceof DraggableView) {
startDraggingItem((DraggableView) hitChild, x, y);
return true;
}
}
/* Either the scroll is not vertical, or the point
* of origin is not above a DraggableView. Again,
* we let the Gallery handle the event.
*/
return super.onScroll(e1, e2, distanceX, distanceY);
}
}
}
希望它有所帮助。
答案 1 :(得分：2)
我正是这样做的。这只是活动的代码......你需要一些布局和其他res文件......
每个列表项都有一个随机匹配的图标和名称。
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Rect;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.widget.FrameLayout.LayoutParams;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.*;
import java.util.ArrayList;
import java.util.Arrays;
public class DragActivity extends Activity implements View.OnTouchListener, AdapterView.OnItemLongClickListener
{
private static final String TAG="DragActivity";
private static final int NOT_DRAGGING = 0;
private static final int DRAGGING = 1;
private int state=NOT_DRAGGING;
private ImageView draggable =null;
private int dragged_position;
float current_x, current_y;
int current_icon = R.drawable.notepad;
private ArrayList<String> names = new ArrayList<String>(Arrays.asList("John", "Mark", "Mathew", "Luke", "Bob", "Will", "Brian", "Mike"));
private ArrayList<Integer> icons = new ArrayList<Integer>(Arrays.asList( R.drawable.glasses, R.drawable.monkey, R.drawable.normal, R.drawable.smile, R.drawable.wink));
private ArrayList<Integer> matching;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setupListContent();
ListView list = (ListView) findViewById(R.id.main_list);
list.setAdapter(new DragListAdapter());
list.setOnItemLongClickListener(this);
list.setOnTouchListener(this);
// need to use the same view for the both listeners, as described in Android documentation :
// http://developer.android.com/guide/topics/ui/ui-events.html
// onTouch() - This returns a boolean to indicate whether your listener consumes this event. The important thing
// is that this event can have multiple actions that follow each other. So, if you return false when the down action
// event is received, you indicate that you have not consumed the event and are also not interested in subsequent
// actions from this event. Thus, you will not be called for any other actions within the event, such as a finger
// gesture, or the eventual up action event.
ImageView image = (ImageView) findViewById(R.id.main_image);
image.setImageResource(current_icon);
}
private void setupListContent() {
matching = new ArrayList<Integer>();
for (int i=0; i<names.size(); i++) {
matching.add((int) (icons.size() * Math.random()));
}
}
@SuppressWarnings("unchecked")
private class DragListAdapter extends ArrayAdapter {
public DragListAdapter() {
super(DragActivity.this, R.layout.list_item, names);
}
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
if (row == null) {
LayoutInflater inflater = getLayoutInflater();
row = inflater.inflate(R.layout.list_item, parent, false);
}
row.setDrawingCacheEnabled(true);
TextView name = (TextView) row.findViewById(R.id.item_text);
ImageView icon = (ImageView) row.findViewById(R.id.item_icon);
name.setText(names.get(position));
icon.setImageResource(icons.get(matching.get(position)));
return row;
}
}
private boolean checkOnDropIcon(MotionEvent me) {
ImageView drop_icon = (ImageView) findViewById(R.id.main_image);
Rect icon_rect = new Rect();
drop_icon.getGlobalVisibleRect(icon_rect);
Log.d(TAG, "icon at " + icon_rect.left + "<- ->" + icon_rect.right + ", " +
icon_rect.top + " ^ v" + icon_rect.bottom);
if ((me.getRawX()<icon_rect.left) || (me.getRawX()>icon_rect.right) ||
(me.getRawY()<icon_rect.top) || (me.getRawY()>icon_rect.bottom)) {
return false;
}
else {
return true;
}
}
private void checkOnDrop(MotionEvent me) {
boolean onDropIcon = checkOnDropIcon(me);
ImageView image = (ImageView) findViewById(R.id.main_image);
if ((onDropIcon) && (current_icon==R.drawable.notepad)) {
current_icon = R.drawable.exit;
image.setImageResource(current_icon);
image.invalidate();
return;
}
if ((!onDropIcon) && (current_icon==R.drawable.exit)) {
current_icon = R.drawable.notepad;
image.setImageResource(current_icon);
image.invalidate();
return;
}
}
public boolean onTouch(View view, MotionEvent me) {
if (state == NOT_DRAGGING) {
// get the position of the touch so we know where to place the dragging item if it is a long press
current_x = me.getRawX();
current_y = me.getRawY();
return false;
}
else {
FrameLayout frame = (FrameLayout) findViewById(R.id.drag_space);
if (me.getAction()==MotionEvent.ACTION_UP) {
frame.removeAllViews();
draggable=null;
frame.setVisibility(View.GONE);
state=NOT_DRAGGING;
// check if we dropped a name
if (checkOnDropIcon(me)) {
names.remove(dragged_position);
matching.remove(dragged_position);
ListView list = (ListView) findViewById(R.id.main_list);
DragListAdapter adapter = (DragListAdapter) list.getAdapter();
adapter.notifyDataSetChanged();
}
// restore the icon
ImageView image = (ImageView) findViewById(R.id.main_image);
current_icon = R.drawable.notepad;
image.setImageResource(current_icon);
image.invalidate();
}
if (me.getAction()==MotionEvent.ACTION_MOVE) {
int frame_position[] = new int[2];
frame.getLocationOnScreen(frame_position);
draggable.setPadding(
(int) me.getRawX()-frame_position[0]-(draggable.getDrawable().getIntrinsicWidth()/2),
(int) me.getRawY()-frame_position[1]-(draggable.getDrawable().getIntrinsicHeight()/2),
0, 0);
draggable.invalidate();
checkOnDrop(me);
}
return true;
}
}
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
if (state == DRAGGING) {
Log.d(TAG, "already have an object moving... ?");
return false;
}
FrameLayout frame = (FrameLayout) findViewById(R.id.drag_space);
int frame_position[] = new int[2];
frame.getLocationOnScreen(frame_position);
// setup everything for dragging
state = DRAGGING;
dragged_position = i;
draggable = new ImageView(this);
Bitmap bm = view.getDrawingCache();
draggable.setImageBitmap(bm);
draggable.setAlpha(150);
draggable.setScaleType(ImageView.ScaleType.CENTER);
draggable.setDrawingCacheEnabled(true);
draggable.setPadding((int) current_x-frame_position[0]-(bm.getWidth()/2), (int) current_y-frame_position[1]-(bm.getHeight()/2), 0, 0);
frame.setVisibility(View.VISIBLE);
frame.addView(draggable, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
return true;
}
}