从现有方法来讲为了实现桌面的3D转屏效果主要是通过Launcher中的workspace实现（现有的有源码的方法），具体实现见：
???? http://www.eoeandroid.com/viewthread.php?tid=27079&extra=&page=1 （写这篇文章也是为了“报答”该作者开源的贡献，共同学习）
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???? 不过该方法存在以下几个问题：
???? 转载请注明http://ishelf.javaeye.com/admin/blogs/836929
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???? 依据以上问题本文从每个屏的dispatchDraw入手，修改CellLayout的dispatchDraw方法，这篇文章先给出2D的实现方式（利用Matrix实现）：
????? 由于代码过多，本文只给出做过修改的代码
///CellLayout.java
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@Override
public void dispatchDraw(Canvas canvas) {
long start_time = System.currentTimeMillis();
startRotate(canvas, currentX, canvas.getWidth(), canvas.getHeight());
super.dispatchDraw(canvas);
canvas.restore();
long end_time = System.currentTimeMillis();
Log.d("CellLayout" + currentScrenn, (end_time - start_time) + " ms");
}
// 上面的Log信息是用来对比用opengl实现两者效率
//startRotate使用来计算该屏显示的位置以及显示的大小，xCor是手指移动的位置大小
public void startRotate(Canvas mCanvas, float xCor, int width, int height) {
boolean flag = true;
if (isCurrentScrenn && xCor < 0) {
xCor = width + xCor;
flag = false;
} else if (isCurrentScrenn && xCor >= 0) {
// xCor = width - xCor;
} else if (!isCurrentScrenn && xCor < 0) {
xCor = width + xCor;
} else if (!isCurrentScrenn && xCor >= 0) {
flag = false;
}
final float SPAN = 0.000424f;
float f = xCor - 10;
if (f <= 0) {
f = 0;
xCor = 10;
}// the maximum left
float value = f * SPAN;
if (f > width) {
xCor = width - 10;
value = 0.127225f;
}// the maximum right
if (isBorder) {
doDraw(mCanvas, new float[] {
0, 0, width, 0, width, height, 0, height
}, new float[] {
0, 0, width, 0, width, height, 0, height
});
} else if (!flag) {
doDraw(mCanvas, new float[] {
0, 0, width, 0, width, height, 0, height
}, new float[] {
0, 0, xCor, height * (1 / 7.0f - value), xCor, height * (6 / 7.0f + value), 0,
height
});
} else {
doDraw(mCanvas, new float[] {
0, 0, width, 0, width, height, 0, height
}, new float[] {
xCor, height * (1 / 30.0f + value), width, 0, width, height, xCor,
height * (29 / 30.0f - value)
});
}
}
private Matrix mMatrix = new Matrix();
private int currentScrenn;
private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private boolean isBorder;
//doDraw使用计算该屏如何变形，这里使用matrix的polyToPoly来实现，具体描述见APIDemo
private void doDraw(Canvas canvas, float src[], float dst[]) {
canvas.save();
mMatrix.setPolyToPoly(src, 0, dst, 0, src.length >> 1);
canvas.concat(mMatrix);
switch (currentScrenn) {
case 0:
mPaint.setColor(Color.RED);
break;
case 1:
mPaint.setColor(Color.BLUE);
break;
case 2:
mPaint.setColor(Color.YELLOW);
break;
case 3:
mPaint.setColor(Color.CYAN);
break;
case 4:
mPaint.setColor(Color.GREEN);
break;
}
mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
canvas.drawRect(0, 0, src[4], src[5], mPaint);
}
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??? 以下是workspace，该类主要是要传给cellLayout移动的参数
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// 该方法用来画屏
protected void dispatchDraw(Canvas canvas) {
boolean restore = false;
int restoreCount = 0;
// ViewGroup.dispatchDraw() supports many features we don't need:
// clip to padding, layout animation, animation listener, disappearing
// children, etc. The following implementation attempts to fast-track
// the drawing dispatch by drawing only what we know needs to be drawn.
boolean fastDraw = mTouchState != TOUCH_STATE_SCROLLING && mNextScreen == INVALID_SCREEN;
Log.d("Scroller","dispatchDraw"+mScrollX);
// If we are not scrolling or flinging, draw only the current screen
if (fastDraw) {
((CellLayout) getChildAt(mCurrentScreen)).setPara(mCurrentScreen,
(mCurrentScreen - mCurrentScreen) >= 0 ? true : false, true,
mChangeMotionX - mLastMotionX);
drawChild(canvas, getChildAt(mCurrentScreen), getDrawingTime());
} else {
final long drawingTime = getDrawingTime();
final float scrollPos = (float) mScrollX / getWidth();
final int leftScreen = (int) scrollPos;
final int rightScreen = leftScreen + 1;
if (leftScreen >= 0) {
((CellLayout) getChildAt(leftScreen)).setPara(leftScreen,
(leftScreen - mCurrentScreen) >= 0 ? true : false, scrollPos == leftScreen,
mChangeMotionX - mLastMotionX);
drawChild(canvas, getChildAt(leftScreen), drawingTime);
}
if (scrollPos != leftScreen && rightScreen < getChildCount()) {
((CellLayout) getChildAt(rightScreen)).setPara(rightScreen, mCurrentScreen
- rightScreen >= 0 ? true : false, scrollPos == leftScreen, mChangeMotionX
- mLastMotionX);
drawChild(canvas, getChildAt(rightScreen), drawingTime);
}
}
if (restore) {
canvas.restoreToCount(restoreCount);
}
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (mLauncher.isWorkspaceLocked()) {
return false; // We don't want the events. Let them fall through to
// the all apps view.
}
if (mLauncher.isAllAppsVisible()) {
// Cancel any scrolling that is in progress.
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
snapToScreen(mCurrentScreen);
return false; // We don't want the events. Let them fall through to
// the all apps view.
}
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
final int action = ev.getAction();
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
/*
* If being flinged and user touches, stop the fling. isFinished
* will be false if being flinged.
*/
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
// Remember where the motion event started
mLastMotionX = ev.getX();
mChangeMotionX = mLastMotionX;
mActivePointerId = ev.getPointerId(0);
if (mTouchState == TOUCH_STATE_SCROLLING) {
enableChildrenCache(mCurrentScreen - 1, mCurrentScreen + 1);
}
break;
case MotionEvent.ACTION_MOVE:
if (mTouchState == TOUCH_STATE_SCROLLING) {
// Scroll to follow the motion event
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(pointerIndex);
final float deltaX = mLastMotionX - x;
mLastMotionX = x;
if (deltaX < 0) {
if (mTouchX > 0) {
mTouchX += Math.max(-mTouchX, deltaX);
mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
invalidate();
}
} else if (deltaX > 0) {
final float availableToScroll = getChildAt(getChildCount() - 1).getRight()
- mTouchX - getWidth();
if (availableToScroll > 0) {
mTouchX += Math.min(availableToScroll, deltaX);
mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
invalidate();
}
} else {
awakenScrollBars();
}
}
break;
case MotionEvent.ACTION_UP:
if (mTouchState == TOUCH_STATE_SCROLLING) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
final int velocityX = (int) velocityTracker.getXVelocity(mActivePointerId);
final int screenWidth = getWidth();
final int whichScreen = (mScrollX + (screenWidth / 2)) / screenWidth;
final float scrolledPos = (float) mScrollX / screenWidth;
mChangeMotionX = mLastMotionX;
if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {
// Fling hard enough to move left.
// Don't fling across more than one screen at a time.
final int bound = scrolledPos < whichScreen ? mCurrentScreen - 1
: mCurrentScreen;
snapToScreen(Math.min(whichScreen, bound), velocityX, true);
} else if (velocityX < -SNAP_VELOCITY && mCurrentScreen < getChildCount() - 1) {
// Fling hard enough to move right
// Don't fling across more than one screen at a time.
final int bound = scrolledPos > whichScreen ? mCurrentScreen + 1
: mCurrentScreen;
snapToScreen(Math.max(whichScreen, bound), velocityX, true);
} else {
snapToScreen(whichScreen, 0, true);
}
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
mTouchState = TOUCH_STATE_REST;
mActivePointerId = INVALID_POINTER;
break;
case MotionEvent.ACTION_CANCEL:
mTouchState = TOUCH_STATE_REST;
mActivePointerId = INVALID_POINTER;
break;
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
}
return true;
}
//修改该方法主要目的是记录滑动的距离
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
final boolean workspaceLocked = mLauncher.isWorkspaceLocked();
final boolean allAppsVisible = mLauncher.isAllAppsVisible();
if (workspaceLocked || allAppsVisible) {
return false; // We don't want the events. Let them fall through to
// the all apps view.
}
/*
* This method JUST determines whether we want to intercept the motion.
* If we return true, onTouchEvent will be called and we do the actual
* scrolling there.
*/
/*
* Shortcut the most recurring case: the user is in the dragging state
* and he is moving his finger. We want to intercept this motion.
*/
final int action = ev.getAction();
if ((action == MotionEvent.ACTION_MOVE) && (mTouchState != TOUCH_STATE_REST)) {
return true;
}
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_MOVE: {
/*
* mIsBeingDragged == false, otherwise the shortcut would have
* caught it. Check whether the user has moved far enough from
* his original down touch.
*/
/*
* Locally do absolute value. mLastMotionX is set to the y value
* of the down event.
*/
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(pointerIndex);
final float y = ev.getY(pointerIndex);
final int xDiff = (int) Math.abs(x - mLastMotionX);
final int yDiff = (int) Math.abs(y - mLastMotionY);
final int touchSlop = mTouchSlop;
boolean xMoved = xDiff > touchSlop;
boolean yMoved = yDiff > touchSlop;
if (xMoved || yMoved) {
if (xMoved) {
// Scroll if the user moved far enough along the X axis
mTouchState = TOUCH_STATE_SCROLLING;
mLastMotionX = x;
mTouchX = mScrollX;
mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
enableChildrenCache(mCurrentScreen - 1, mCurrentScreen + 1);
}
// Either way, cancel any pending longpress
if (mAllowLongPress) {
mAllowLongPress = false;
// Try canceling the long press. It could also have been
// scheduled
// by a distant descendant, so use the mAllowLongPress
// flag to block
// everything
final View currentScreen = getChildAt(mCurrentScreen);
currentScreen.cancelLongPress();
}
}
break;
}
case MotionEvent.ACTION_DOWN: {
final float x = ev.getX();
final float y = ev.getY();
// Remember location of down touch
mLastMotionX = x;
mChangeMotionX = x;
mLastMotionY = y;
mActivePointerId = ev.getPointerId(0);
mAllowLongPress = true;
/*
* If being flinged and user touches the screen, initiate drag;
* otherwise don't. mScroller.isFinished should be false when
* being flinged.
*/
mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;
break;
}
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
if (mTouchState != TOUCH_STATE_SCROLLING) {
final CellLayout currentScreen = (CellLayout) getChildAt(mCurrentScreen);
if (!currentScreen.lastDownOnOccupiedCell()) {
getLocationOnScreen(mTempCell);
// Send a tap to the wallpaper if the last down was on
// empty space
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
mWallpaperManager.sendWallpaperCommand(getWindowToken(),
"android.wallpaper.tap",
mTempCell[0] + (int) ev.getX(pointerIndex), mTempCell[1]
+ (int) ev.getY(pointerIndex), 0, null);
}
}
// Release the drag
clearChildrenCache();
mTouchState = TOUCH_STATE_REST;
mActivePointerId = INVALID_POINTER;
mAllowLongPress = false;
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
break;
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
}
/*
* The only time we want to intercept motion events is if we are in the
* drag mode.
*/
return mTouchState != TOUCH_STATE_REST;
}
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??? 这些类的修改特别是变换时一定要注意canvas的save和restore方法，不清楚的先百度一下，不然很容易就变形了。下篇讨论使用openGL实现的方法
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