hi, i am a new android developer, and recently I was doing a
horizontal scrolling menu. the follow is xml doc:
<com.kingkong.gallery.GalleryHorizontalView
android:id="@+id/HorizontalScrollView01"
android:layout_width="fill_parent" android:scrollbars="none"
android:layout_height="wrap_content">
<LinearLayout android:id="@+id/ourlayout"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#ffffff">
</LinearLayout>
</com.kingkong.gallery.GalleryHorizontalView>
class GalleryHorizontalView is defined by myself, it is extends from
HorizontalScrollView.
in GalleryHorizontalView, I made the following changes ( changes in
method onTouchEvent(MotionEvent ev) ):
case MotionEvent.ACTION_MOVE:
// x == ev.getX();
final int deltaX = (int) (mLastMotionX - x);
mLastMotionX = x;
// i want to let the child
view's ( LinearLayout ) horizontal padding change,so change
//the child view's x
coordinate, x coordinate is change by deltaX;
if (deltaX < 0) {
if (getScrollX() >= 0) {
getChildAt(0).scrollBy(deltaX, 0);
}
} else if (deltaX > 0) {
final int rightEdge = getWidth() -
getPaddingRight();
final int availableToScroll =
getChildAt(0).getRight()
- getScrollX() - rightEdge;
if (availableToScroll > 0) {
getChildAt(0).scrollBy(Math.min(availableToScroll, deltaX),
0);
}
}
break;
case MotionEvent.ACTION_UP:
int menuItemWidth =
80;
int temp = getChildAt(0).getScrollX();
int remainder = temp %menuItemWidth;
int scrollToCoords = 0;
// if temp <0 or temp == the child view's left
coordinate, scrollToCoords =0;
//scrollToCoords's value is x coordinate when the child
view end its scrolling.
//the follow calculation is to ensure that each option can
be displayed properly
if (temp < 0 || temp == getChildAt(0).getLeft()) {
scrollToCoords = 0;
} else if (temp >= getChildAt(0).getRight() / 2) {
scrollToCoords = getChildAt(0).getWidth() / 2;
} else if (temp < getChildAt(0).getRight()
&& temp > getChildAt(0).getLeft()) {
if (remainder == 0) {
scrollToCoords = temp;
} else {
if (remainder > menuItemWidth/2) {
scrollToCoords =
temp - remainder + menuItemWidth;
}
if (remainder <= menuItemWidth/2) {
scrollToCoords = temp -
remainder;
}
}
}
float mDeltaX = mLastMotionX - x;
mScroller.startScroll((int)mLastMotionX, 0, (int)x, 0,
1000);
this.invalidate();
getChildAt(0).scrollBy((int) mDeltaX, 0);
getChildAt(0).scrollTo(scrollToCoords, 0);
i run my app after made this change,the child view LinearLayout can
scroll with the order, but it looks like jump,
not smooth scrolling, how can make the scroll smooth.
thanks very much.
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