android之luncher滑动效果

Java代码：

importandroid.content.Context;
importandroid.util.Log;
importandroid.content.res.TypedArray;
importandroid.util.AttributeSet;
importandroid.view.MotionEvent;
importandroid.view.VelocityTracker;
importandroid.view.View;
importandroid.view.ViewGroup;
importandroid.view.ViewConfiguration;
importandroid.widget.Scroller;
publicclassDragableSpaceextendsViewGroup{
privateScrollermScroller;
privateVelocityTrackermVelocityTracker;
privateintmScrollX=0;
privateintmCurrentScreen=0;
privatefloatmLastMotionX;
privatestaticfinalStringLOG_TAG="DragableSpace";
privatestaticfinalintSNAP_VELOCITY=1000;
privatefinalstaticintTOUCH_STATE_REST=0;
privatefinalstaticintTOUCH_STATE_SCROLLING=1;
privateintmTouchState=TOUCH_STATE_REST;
privateintmTouchSlop=0;
publicDragableSpace(Contextcontext){
super(context);
mScroller=newScroller(context);
mTouchSlop=ViewConfiguration.get(getContext()).getScaledTouchSlop();
this.setLayoutParams(newViewGroup.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.FILL_PARENT));
}
publicDragableSpace(Contextcontext,AttributeSetattrs){
super(context,attrs);
mScroller=newScroller(context);
mTouchSlop=ViewConfiguration.get(getContext()).getScaledTouchSlop();
this.setLayoutParams(newViewGroup.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.FILL_PARENT));
TypedArraya=getContext().obtainStyledAttributes(attrs,R.styleable.DragableSpace);
mCurrentScreen=a.getInteger(R.styleable.DragableSpace_default_screen,0);
}
@Override
publicbooleanonInterceptTouchEvent(MotionEventev){
finalintaction=ev.getAction();
if((action==MotionEvent.ACTION_MOVE)
&&(mTouchState!=TOUCH_STATE_REST)){
returntrue;
}
finalfloatx=ev.getX();
switch(action){
caseMotionEvent.ACTION_MOVE:
finalintxDiff=(int)Math.abs(x-mLastMotionX);
booleanxMoved=xDiff>mTouchSlop;
if(xMoved){
//ScrolliftheusermovedfarenoughalongtheXaxis
mTouchState=TOUCH_STATE_SCROLLING;
}
break;
caseMotionEvent.ACTION_DOWN:
//Rememberlocationofdowntouch
mLastMotionX=x;
mTouchState=mScroller.isFinished()?TOUCH_STATE_REST:TOUCH_STATE_SCROLLING;
break;
caseMotionEvent.ACTION_CANCEL:
caseMotionEvent.ACTION_UP:
//Releasethedrag
mTouchState=TOUCH_STATE_REST;
break;
}
returnmTouchState!=TOUCH_STATE_REST;
}
@Override
publicbooleanonTouchEvent(MotionEventevent){
if(mVelocityTracker==null){
mVelocityTracker=VelocityTracker.obtain();
}
mVelocityTracker.addMovement(event);
finalintaction=event.getAction();
finalfloatx=event.getX();
switch(action){
caseMotionEvent.ACTION_DOWN:
Log.i(LOG_TAG,"event:down");
if(!mScroller.isFinished()){
mScroller.abortAnimation();
}
//Rememberwherethemotioneventstarted
mLastMotionX=x;
break;
caseMotionEvent.ACTION_MOVE:
//Log.i(LOG_TAG,"event:move");
//if(mTouchState==TOUCH_STATE_SCROLLING){
//Scrolltofollowthemotionevent
finalintdeltaX=(int)(mLastMotionX-x);
mLastMotionX=x;
//Log.i(LOG_TAG,"event:move,deltaX"+deltaX+",mScrollX"+mScrollX);
if(deltaX<0){
if(mScrollX>0){
scrollBy(Math.max(-mScrollX,deltaX),0);
}
}elseif(deltaX>0){
finalintavailableToScroll=getChildAt(getChildCount()-1)
.getRight()
-mScrollX-getWidth();
if(availableToScroll>0){
scrollBy(Math.min(availableToScroll,deltaX),0);
}
}
//}
break;
caseMotionEvent.ACTION_UP:
Log.i(LOG_TAG,"event:up");
//if(mTouchState==TOUCH_STATE_SCROLLING){
finalVelocityTrackervelocityTracker=mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000);
intvelocityX=(int)velocityTracker.getXVelocity();
if(velocityX>SNAP_VELOCITY&&mCurrentScreen>0){
//Flinghardenoughtomoveleft
snapToScreen(mCurrentScreen-1);
}elseif(velocityX<-SNAP_VELOCITY
&&mCurrentScreen<getChildCount()-1){
//Flinghardenoughtomoveright
snapToScreen(mCurrentScreen+1);
}else{
snapToDestination();
}
if(mVelocityTracker!=null){
mVelocityTracker.recycle();
mVelocityTracker=null;
}
//}
mTouchState=TOUCH_STATE_REST;
break;
caseMotionEvent.ACTION_CANCEL:
Log.i(LOG_TAG,"event:cancel");
mTouchState=TOUCH_STATE_REST;
}
mScrollX=this.getScrollX();
returntrue;
}
privatevoidsnapToDestination(){
finalintscreenWidth=getWidth();
finalintwhichScreen=(mScrollX+(screenWidth/2))/screenWidth;
Log.i(LOG_TAG,"fromdes");
snapToScreen(whichScreen);
}
publicvoidsnapToScreen(intwhichScreen){
Log.i(LOG_TAG,"snapToScreen"+whichScreen);
mCurrentScreen=whichScreen;
finalintnewX=whichScreen*getWidth();
finalintdelta=newX-mScrollX;
mScroller.startScroll(mScrollX,0,delta,0,Math.abs(delta)*2);
invalidate();
}
publicvoidsetToScreen(intwhichScreen){
Log.i(LOG_TAG,"setToScreen"+whichScreen);
mCurrentScreen=whichScreen;
finalintnewX=whichScreen*getWidth();
mScroller.startScroll(newX,0,0,0,10);
invalidate();
}
@Override
protectedvoidonLayout(booleanchanged,intl,intt,intr,intb){
intchildLeft=0;
finalintcount=getChildCount();
for(inti=0;i<count;i++){
finalViewchild=getChildAt(i);
if(child.getVisibility()!=View.GONE){
finalintchildWidth=child.getMeasuredWidth();
child.layout(childLeft,0,childLeft+childWidth,child
.getMeasuredHeight());
childLeft+=childWidth;
}
}
}
@Override
protectedvoidonMeasure(intwidthMeasureSpec,intheightMeasureSpec){
super.onMeasure(widthMeasureSpec,heightMeasureSpec);
finalintwidth=MeasureSpec.getSize(widthMeasureSpec);
finalintwidthMode=MeasureSpec.getMode(widthMeasureSpec);
if(widthMode!=MeasureSpec.EXACTLY){
thrownewIllegalStateException("errormode.");
}
finalintheightMode=MeasureSpec.getMode(heightMeasureSpec);
if(heightMode!=MeasureSpec.EXACTLY){
thrownewIllegalStateException("errormode.");
}
//Thechildrenaregiventhesamewidthandheightastheworkspace
finalintcount=getChildCount();
for(inti=0;i<count;i++){
getChildAt(i).measure(widthMeasureSpec,heightMeasureSpec);
}
Log.i(LOG_TAG,"movingtoscreen"+mCurrentScreen);
scrollTo(mCurrentScreen*width,0);
}
@Override
publicvoidcomputeScroll(){
if(mScroller.computeScrollOffset()){
mScrollX=mScroller.getCurrX();
scrollTo(mScrollX,0);
postInvalidate();
}
}
}
Java代码：

<?xmlversion= "1.0" encoding= "utf-8" ?>
<com.matthieu.launcher.DragableSpacexmlns:app= "http://schemas.android.com/apk/res/com.matthieu.launcher"
xmlns:android= "http://schemas.android.com/apk/res/android"
android:id= "@+id/space"
android:layout_width= "fill_parent"
android:layout_height= "fill_parent"
app:default_screen= "1"
>
<includeandroid:id= "@+id/left" layout= "@layout/left_screen" />
<includeandroid:id= "@+id/center" layout= "@layout/initial_screen" />
<includeandroid:id= "@+id/right" layout= "@layout/right_screen" />
</com.matthieu.launcher.DragableSpace>

values/attrs.xml

<?xml version="1.0" encoding="utf-8"?> <resources>   <declare-styleable name="DragableSpace">     <attr name="default_screen" format="integer"/>   </declare-styleable> </resources>

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