DragStartHelper
public class DragStartHelper
DragStartHelper is a utility class for implementing drag and drop support.
It detects gestures commonly used to start drag (long click for any input source, click and drag for mouse).
It also keeps track of the screen location where the drag started, and helps determining the hot spot position for a drag shadow.
Implement DragStartHelper.OnDragStartListener to start the drag operation:
DragStartHelper.OnDragStartListener listener = new DragStartHelper.OnDragStartListener {
protected void onDragStart(View view, DragStartHelper helper) {
View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view) {
public void onProvideShadowMetrics(Point shadowSize, Point shadowTouchPoint) {
super.onProvideShadowMetrics(shadowSize, shadowTouchPoint);
helper.getTouchPosition(shadowTouchPoint);
}
};
view.startDrag(mClipData, shadowBuilder, mLocalState, mDragFlags);
}
};
mDragStartHelper = new DragStartHelper(mDraggableView, listener);mDragStartHelper.attach();
public boolean onTouch(View view, MotionEvent event) {
if (mDragStartHelper.onTouch(view, event)) {
return true;
}
return handleTouchEvent(view, event);
}
public boolean onLongClick(View view) {
if (mDragStartHelper.onLongClick(view)) {
return true;
}
return handleLongClickEvent(view);
}Summary
Nested types |
|---|
public interface DragStartHelper.OnDragStartListenerInterface definition for a callback to be invoked when a drag start gesture is detected. |
Public constructors |
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DragStartHelper(Create a DragStartHelper associated with the specified view. |
Public methods |
|
|---|---|
void |
attach()Attach the helper to the view. |
void |
detach()Detach the helper from the view. |
void |
getTouchPosition(@NonNull Point point)Compute the position of the touch event that started the drag operation. |
boolean |
onLongClick(@NonNull View v)Handle a long click event. |
boolean |
onTouch(@NonNull View v, @NonNull MotionEvent event)Handle a touch event. |
Public constructors
DragStartHelper
public DragStartHelper(
@NonNull View view,
@NonNull DragStartHelper.OnDragStartListener listener
)
Create a DragStartHelper associated with the specified view. The newly created helper is not initially attached to the view, attach must be called explicitly.
| Parameters | |
|---|---|
@NonNull View view |
A View |
@NonNull DragStartHelper.OnDragStartListener listener |
listener for the drag events. |
Public methods
attach
public void attach()
Attach the helper to the view.
This will replace previously existing touch and long click listeners.
detach
public void detach()
Detach the helper from the view.
This will reset touch and long click listeners to null.
getTouchPosition
public void getTouchPosition(@NonNull Point point)
Compute the position of the touch event that started the drag operation.
onLongClick
public boolean onLongClick(@NonNull View v)
Handle a long click event.
| Returns | |
|---|---|
boolean |
true if the callback consumed the long click, false otherwise. |
onTouch
public boolean onTouch(@NonNull View v, @NonNull MotionEvent event)
Handle a touch event.
| Parameters | |
|---|---|
@NonNull View v |
The view the touch event has been dispatched to. |
@NonNull MotionEvent event |
The MotionEvent object containing full information about the event. |
| Returns | |
|---|---|
boolean |
True if the listener has consumed the event, false otherwise. |