* View objects that receive a DragEvent call {@link #getAction()}, which returns * an action type that indicates the state of the drag and drop operation. This allows a View * object to react to a change in state by changing its appearance or performing other actions. * For example, a View can react to the {@link #ACTION_DRAG_ENTERED} action type by * by changing one or more colors in its displayed image. *
** During a drag and drop operation, the system displays an image that the user drags. This image * is called a drag shadow. Several action types reflect the position of the drag shadow relative * to the View receiving the event. *
** Most methods return valid data only for certain event actions. This is summarized in the * following table. Each possible {@link #getAction()} value is listed in the first column. The * other columns indicate which method or methods return valid data for that getAction() value: *
*| getAction() Value | *getClipDescription() | *getLocalState() | *getX() | *getY() | *getClipData() | *getResult() | *
|---|---|---|---|---|---|---|
| ACTION_DRAG_STARTED | *X | *X | *X | *X | ** | * |
| ACTION_DRAG_ENTERED | *X | *X | ** | * | * | * |
| ACTION_DRAG_LOCATION | *X | *X | *X | *X | ** | * |
| ACTION_DRAG_EXITED | *X | *X | ** | * | * | * |
| ACTION_DROP | *X | *X | *X | *X | *X | ** |
| ACTION_DRAG_ENDED | *X | *X | ** | * | * | X | *
* The {@link android.view.DragEvent#getAction()}, * {@link android.view.DragEvent#describeContents()}, * {@link android.view.DragEvent#writeToParcel(Parcel,int)}, and * {@link android.view.DragEvent#toString()} methods always return valid data. *
* *For a guide to implementing drag and drop features, read the * Drag and Drop developer guide.
** A View only receives further drag events if it returns {@code true} in response to * ACTION_DRAG_STARTED. *
* @see #ACTION_DRAG_ENDED */ public static final int ACTION_DRAG_STARTED = 1; /** * Action constant returned by {@link #getAction()}: Sent to a View after * {@link #ACTION_DRAG_ENTERED} if the drag shadow is still within the View object's bounding * box. The {@link #getX()} and {@link #getY()} methods supply * the X and Y position of of the drag point within the View object's bounding box. ** A View receives an {@link #ACTION_DRAG_ENTERED} event before receiving any * ACTION_DRAG_LOCATION events. *
** The system stops sending ACTION_DRAG_LOCATION events to a View once the user moves the * drag shadow out of the View object's bounding box. If the user moves the drag shadow back * into the View object's bounding box, the View receives an ACTION_DRAG_ENTERED again before * receiving any more ACTION_DRAG_LOCATION events. *
* @see #ACTION_DRAG_ENTERED * @see #getX() * @see #getY() */ public static final int ACTION_DRAG_LOCATION = 2; /** * Action constant returned by {@link #getAction()}: Signals to a View that the user * has released the drag shadow, and the drag point is within the bounding box of the View. * The View should retrieve the data from the DragEvent by calling {@link #getClipData()}. * The methods {@link #getX()} and {@link #getY()} return the X and Y position of the drop point * within the View object's bounding box. ** The View should return {@code true} from its {@link View#onDragEvent(DragEvent)} * handler or {@link View.View.OnDragListener#onDrag(View,DragEvent) OnDragListener.onDrag()} * listener if it accepted the drop, and {@code false} if it ignored the drop. *
** The View can also react to this action by changing its appearance. *
* @see #getClipData() * @see #getX() * @see #getY() */ public static final int ACTION_DROP = 3; /** * Action constant returned by {@link #getAction()}: Signals to a View that the drag and drop * operation has concluded. A View that changed its appearance during the operation should * return to its usual drawing state in response to this event. ** All views that received an ACTION_DRAG_STARTED event will receive the * ACTION_DRAG_ENDED event even if they are not currently visible when the drag ends. *
** The View object can call {@link #getResult()} to see the result of the operation. * If a View returned {@code true} in response to {@link #ACTION_DROP}, then * getResult() returns {@code true}, otherwise it returns {@code false}. *
* @see #ACTION_DRAG_STARTED * @see #getResult() */ public static final int ACTION_DRAG_ENDED = 4; /** * Action constant returned by {@link #getAction()}: Signals to a View that the drag point has * entered the bounding box of the View. ** If the View can accept a drop, it can react to ACTION_DRAG_ENTERED * by changing its appearance in a way that tells the user that the View is the current * drop target. *
* The system stops sending ACTION_DRAG_LOCATION events to a View once the user moves the * drag shadow out of the View object's bounding box. If the user moves the drag shadow back * into the View object's bounding box, the View receives an ACTION_DRAG_ENTERED again before * receiving any more ACTION_DRAG_LOCATION events. * * @see #ACTION_DRAG_ENTERED * @see #ACTION_DRAG_LOCATION */ public static final int ACTION_DRAG_ENTERED = 5; /** * Action constant returned by {@link #getAction()}: Signals that the user has moved the * drag shadow outside the bounding box of the View. * The View can react by changing its appearance in a way that tells the user that * View is no longer the immediate drop target. ** After the system sends an ACTION_DRAG_EXITED event to the View, the View receives no more * ACTION_DRAG_LOCATION events until the user drags the drag shadow back over the View. *
* */ public static final int ACTION_DRAG_EXITED = 6; private DragEvent() { } private void init(int action, float x, float y, ClipDescription description, ClipData data, Object localState, boolean result) { mAction = action; mX = x; mY = y; mClipDescription = description; mClipData = data; mLocalState = localState; mDragResult = result; } static DragEvent obtain() { return DragEvent.obtain(0, 0f, 0f, null, null, null, false); } /** @hide */ public static DragEvent obtain(int action, float x, float y, Object localState, ClipDescription description, ClipData data, boolean result) { final DragEvent ev; synchronized (gRecyclerLock) { if (gRecyclerTop == null) { ev = new DragEvent(); ev.init(action, x, y, description, data, localState, result); return ev; } ev = gRecyclerTop; gRecyclerTop = ev.mNext; gRecyclerUsed -= 1; } ev.mRecycledLocation = null; ev.mRecycled = false; ev.mNext = null; ev.init(action, x, y, description, data, localState, result); return ev; } /** @hide */ public static DragEvent obtain(DragEvent source) { return obtain(source.mAction, source.mX, source.mY, source.mLocalState, source.mClipDescription, source.mClipData, source.mDragResult); } /** * Inspect the action value of this event. * @return One of the following action constants, in the order in which they usually occur * during a drag and drop operation: ** This method returns valid data for all event actions. * @return The ClipDescription that was part of the ClipData sent to the system by startDrag(). */ public ClipDescription getClipDescription() { return mClipDescription; } /** * Returns the local state object sent to the system as part of the call to * {@link android.view.View#startDrag(ClipData,View.DragShadowBuilder,Object,int) startDrag()}. * The object is intended to provide local information about the drag and drop operation. For * example, it can indicate whether the drag and drop operation is a copy or a move. *
* This method returns valid data for all event actions. *
* @return The local state object sent to the system by startDrag(). */ public Object getLocalState() { return mLocalState; } /** ** Returns an indication of the result of the drag and drop operation. * This method only returns valid data if the action type is {@link #ACTION_DRAG_ENDED}. * The return value depends on what happens after the user releases the drag shadow. *
** If the user releases the drag shadow on a View that can accept a drop, the system sends an * {@link #ACTION_DROP} event to the View object's drag event listener. If the listener * returns {@code true}, then getResult() will return {@code true}. * If the listener returns {@code false}, then getResult() returns {@code false}. *
** Notice that getResult() also returns {@code false} if no {@link #ACTION_DROP} is sent. This * happens, for example, when the user releases the drag shadow over an area outside of the * application. In this case, the system sends out {@link #ACTION_DRAG_ENDED} for the current * operation, but never sends out {@link #ACTION_DROP}. *
* @return {@code true} if a drag event listener returned {@code true} in response to * {@link #ACTION_DROP}. If the system did not send {@link #ACTION_DROP} before * {@link #ACTION_DRAG_ENDED}, or if the listener returned {@code false} in response to * {@link #ACTION_DROP}, then {@code false} is returned. */ public boolean getResult() { return mDragResult; } /** * Recycle the DragEvent, to be re-used by a later caller. After calling * this function you must never touch the event again. * * @hide */ public final void recycle() { // Ensure recycle is only called once! if (TRACK_RECYCLED_LOCATION) { if (mRecycledLocation != null) { throw new RuntimeException(toString() + " recycled twice!", mRecycledLocation); } mRecycledLocation = new RuntimeException("Last recycled here"); } else { if (mRecycled) { throw new RuntimeException(toString() + " recycled twice!"); } mRecycled = true; } mClipData = null; mClipDescription = null; mLocalState = null; synchronized (gRecyclerLock) { if (gRecyclerUsed < MAX_RECYCLED) { gRecyclerUsed++; mNext = gRecyclerTop; gRecyclerTop = this; } } } /** * Returns a string containing a concise, human-readable representation of this DragEvent * object. * @return A string representation of the DragEvent object. */ @Override public String toString() { return "DragEvent{" + Integer.toHexString(System.identityHashCode(this)) + " action=" + mAction + " @ (" + mX + ", " + mY + ") desc=" + mClipDescription + " data=" + mClipData + " local=" + mLocalState + " result=" + mDragResult + "}"; } /* Parcelable interface */ /** * Returns information about the {@link android.os.Parcel} representation of this DragEvent * object. * @return Information about the {@link android.os.Parcel} representation. */ public int describeContents() { return 0; } /** * Creates a {@link android.os.Parcel} object from this DragEvent object. * @param dest A {@link android.os.Parcel} object in which to put the DragEvent object. * @param flags Flags to store in the Parcel. */ public void writeToParcel(Parcel dest, int flags) { dest.writeInt(mAction); dest.writeFloat(mX); dest.writeFloat(mY); dest.writeInt(mDragResult ? 1 : 0); if (mClipData == null) { dest.writeInt(0); } else { dest.writeInt(1); mClipData.writeToParcel(dest, flags); } if (mClipDescription == null) { dest.writeInt(0); } else { dest.writeInt(1); mClipDescription.writeToParcel(dest, flags); } } /** * A container for creating a DragEvent from a Parcel. */ public static final Parcelable.Creator