AndroidICS4.0版本的launcher拖拽的流程,基本和2.3的相似。就是比2.3寫的封裝的接口多了一些,比如刪除類的寫法就多了個類。等等。4.0的改變有一些,但是不是特別大。這個月一直在改動Launcher的縮略圖的效果,4.0的縮略圖的功能沒有實現,還得從2.3的Launcher中摘出來。通過做這個縮略圖對Launcher的模塊有一點點了解,拿來分享一下Launcher拖拽的工作流程。有圖有真相!
轉載請標明出處:http://blog.csdn.net/wdaming1986/article/details/7671318
(1) 先來看看類之間的繼承關係
圖(1)
(2)再來看看Launcher拖拽流程的時序圖
圖(2)
下面咱們分步來解析Launcher拖拽的詳細過程:
step 1 :先來看看Launcher.java這個類的onCreate()方法中的setupViews()方法中的一部分代碼:
// Setup the workspace
mWorkspace.setHapticFeedbackEnabled(false);
mWorkspace.setOnLongClickListener(this);
mWorkspace.setup(dragController);
dragController.addDragListener(mWorkspace);
Workspace設置長按事件的監聽交給了Launcher.java這個類了。所以在主屏上長按事件會走到Launcher.java----->
onLongClick()這個方法中去;
step 2 :接着我們來看看Launcher.java中onLongClick()的代碼:
public boolean onLongClick(View v) {
··············
// The hotseat touch handling does not go through Workspace, and we always allow long press
// on hotseat items.
final View itemUnderLongClick = longClickCellInfo.cell;
boolean allowLongPress = isHotseatLayout(v) || mWorkspace.allowLongPress();
if (allowLongPress && !mDragController.isDragging()) {
if (itemUnderLongClick == null) {
// User long pressed on empty space
mWorkspace.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS,
HapticFeedbackConstants.FLAG_IGNORE_VIEW_SETTING);
startWallpaper();
} else {
if (!(itemUnderLongClick instanceof Folder)) {
// User long pressed on an item
mWorkspace.startDrag(longClickCellInfo);
}
}
}
return true;
}
通過itemUnderLongClick == null 來判斷,在屏幕上觸發長按事件是否選中了shortcut或者widget。如果爲空,就啓動桌面的壁紙,else,就把拖拽事件往Workspace.java這個類傳遞。
Step 3 :通過mWorkspace.startDrag(longClickCellInfo),把長按事件傳遞給workspace來處理,具體來看代碼:
void startDrag(CellLayout.CellInfo cellInfo) {
View child = cellInfo.cell;
// Make sure the drag was started by a long press as opposed to a long click.
if (!child.isInTouchMode()) {
return;
}
mDragInfo = cellInfo;
//隱藏拖拽的child
child.setVisibility(GONE);
child.clearFocus();
child.setPressed(false);
final Canvas canvas = new Canvas();
// We need to add extra padding to the bitmap to make room for the glow effect
final int bitmapPadding = HolographicOutlineHelper.MAX_OUTER_BLUR_RADIUS;
// The outline is used to visualize where the item will land if dropped
mDragOutline = createDragOutline(child, canvas, bitmapPadding);
beginDragShared(child, this);
}
上面的代碼主要做的工作是:把正在拖拽的這個view隱藏掉,在主屏幕上繪製一個藍色的,大小和圖標相似的一個邊框,以表示能在主屏的這個位置放置。
Step 4 :接着調用beginDragShared(child, this)這個方法,代碼如下:
public void beginDragShared(View child, DragSource source) {
··· ···
// Clear the pressed state if necessary
if (child instanceof BubbleTextView) {
BubbleTextView icon = (BubbleTextView) child;
icon.clearPressedOrFocusedBackground();
}
mDragController.startDrag(b, dragLayerX, dragLayerY, source, child.getTag(),
DragController.DRAG_ACTION_MOVE, dragVisualizeOffset, dragRect);
b.recycle();
}
這個方法做的工作是:開始進行拖拽,繪製正在拖拽的圖片,把拖拽的事件交給DragController來處理。
Step 5 :接着來看看mDragController.startDrag(b, dragLayerX, dragLayerY, source, child.getTag(), DragController.DRAG_ACTION_MOVE, dragVisualizeOffset, dragRect)這個方法,代碼如下:
public void startDrag(Bitmap b, int dragLayerX, int dragLayerY,
DragSource source, Object dragInfo, int dragAction, Point dragOffset, Rect dragRegion) {
··· ···
mDragObject.dragComplete = false;
mDragObject.xOffset = mMotionDownX - (dragLayerX + dragRegionLeft);
mDragObject.yOffset = mMotionDownY - (dragLayerY + dragRegionTop);
mDragObject.dragSource = source;
mDragObject.dragInfo = dragInfo;
mVibrator.vibrate(VIBRATE_DURATION);
final DragView dragView = mDragObject.dragView = new DragView(mLauncher, b, registrationX,
registrationY, 0, 0, b.getWidth(), b.getHeight());
if (dragOffset != null) {
dragView.setDragVisualizeOffset(new Point(dragOffset));
}
if (dragRegion != null) {
dragView.setDragRegion(new Rect(dragRegion));
}
dragView.show(mMotionDownX, mMotionDownY);
handleMoveEvent(mMotionDownX, mMotionDownY);
}
這個方法的作用是:計算要拖拽的view的大小,顯示在workspace上,dragView.show(mMotionDownX, mMotionDownY);這個show()會根據手指的移動而移動的。然後在通過handleMoveEvent()方法來分發拖拽的目標到底在哪個目標上。DropTarget一共有3個:workspace,ButtonDropTarget(刪除類),Folder;他們分別實現了DropTarget這個接口。
下面來看看這個接口有一下幾個方法:
boolean isDropEnabled();
void onDrop(DragObject dragObject);
void onDragEnter(DragObject dragObject);
void onDragOver(DragObject dragObject);
void onDragExit(DragObject dragObject);
DropTarget getDropTargetDelegate(DragObject dragObject);
boolean acceptDrop(DragObject dragObject);
// These methods are implemented in Views
void getHitRect(Rect outRect);
void getLocationInDragLayer(int[] loc);
int getLeft();
int getTop();
這些方法不是每個類繼承了DropTarget的接口,都要把每個方法都實現,這要看具體的需要來定。
另外這個接口中有個內部類-----DragObject:如下
class DragObject {
public int x = -1;
public int y = -1;
/** X offset from the upper-left corner of the cell to where we touched. */
public int xOffset = -1;
/** Y offset from the upper-left corner of the cell to where we touched. */
public int yOffset = -1;
/** This indicates whether a drag is in final stages, either drop or cancel. It
* differentiates onDragExit, since this is called when the drag is ending, above
* the current drag target, or when the drag moves off the current drag object.
*/
public boolean dragComplete = false;
/** The view that moves around while you drag. */
public DragView dragView = null;
/** The data associated with the object being dragged */
public Object dragInfo = null;
/** Where the drag originated */
public DragSource dragSource = null;
/** Post drag animation runnable */
public Runnable postAnimationRunnable = null;
/** Indicates that the drag operation was cancelled */
public boolean cancelled = false;
public DragObject() {
}
}
這個類的作用是存儲一些座標,拖拽點距離整個view左上角x軸上的距離,y軸上的距離,還有一些拖拽的信息都保存在這個類中,還有動畫線程類等等。在拖拽過程中這些信息都是會用到的。
Step 6 :接着來看看handleMoveEvent()這個類,這個類頻繁被調用,因爲在DragLayer.java這個類中onTouchEvent()方法,最後調用的是 mDragController.onTouchEvent(ev)這個方法,長按後,移動的事件就傳遞到了DragController中的onTouchEvent()方法中,先來看看mDragController.onTouchEvent(ev)這個方法,代碼如下:
/**
* Call this from a drag source view.
*/
public boolean onTouchEvent(MotionEvent ev) {
if (!mDragging) {
return false;
}
final int action = ev.getAction();
final int[] dragLayerPos = getClampedDragLayerPos(ev.getX(), ev.getY());
final int dragLayerX = dragLayerPos[0];
final int dragLayerY = dragLayerPos[1];
switch (action) {
case MotionEvent.ACTION_DOWN:
// Remember where the motion event started
mMotionDownX = dragLayerX;
mMotionDownY = dragLayerY;
if ((dragLayerX < mScrollZone) || (dragLayerX > mScrollView.getWidth() - mScrollZone)) {
mScrollState = SCROLL_WAITING_IN_ZONE;
mHandler.postDelayed(mScrollRunnable, SCROLL_DELAY);
} else {
mScrollState = SCROLL_OUTSIDE_ZONE;
}
break;
case MotionEvent.ACTION_MOVE:
handleMoveEvent(dragLayerX, dragLayerY);
break;
case MotionEvent.ACTION_UP:
// Ensure that we've processed a move event at the current pointer location.
handleMoveEvent(dragLayerX, dragLayerY);
mHandler.removeCallbacks(mScrollRunnable);
if (mDragging) {
drop(dragLayerX, dragLayerY);
}
endDrag();
break;
case MotionEvent.ACTION_CANCEL:
cancelDrag();
break;
}
return true;
}
在這個方法中清楚的可以看見handleMoveEvent()這個方法會在move,up的時候頻繁地調用。
現在再來看看這個handleMoveEvent()方法,看看它的廬山真面目:
private void handleMoveEvent(int x, int y) {
mDragObject.dragView.move(x, y);
// Drop on someone?
final int[] coordinates = mCoordinatesTemp;
DropTarget dropTarget = findDropTarget(x, y, coordinates);
mDragObject.x = coordinates[0];
mDragObject.y = coordinates[1];
if (dropTarget != null) {
DropTarget delegate = dropTarget.getDropTargetDelegate(mDragObject);
if (delegate != null) {
dropTarget = delegate;
}
if (mLastDropTarget != dropTarget) {
if (mLastDropTarget != null) {
mLastDropTarget.onDragExit(mDragObject);
}
dropTarget.onDragEnter(mDragObject);
}
dropTarget.onDragOver(mDragObject);
} else {
if (mLastDropTarget != null) {
mLastDropTarget.onDragExit(mDragObject);
}
}
mLastDropTarget = dropTarget;
··· ···
}
這個方法的作用:通過findDropTarget(x, y, coordinates),來判斷在哪個拖拽目標裏面,然後通過下面的if判斷來執行不同的onDragOver,onDragExit等的方法。這樣就在相應的類中去做處理,以後的事情就明朗了。這就是Launcher的拖拽事件的分發與處理,用到了MVC的思想,代碼閱讀起來還是比較順利的。有圖有真相。
歡迎大家留言討論相關問題。