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XML attribute for overscrolling behavior

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This commit is contained in:
Adam Powell
2010-02-16 17:16:19 -08:00
parent 0f5a434c54
commit c9fbaabc1b
5 changed files with 106 additions and 36 deletions
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114
core/java/android/view/View.java
View File

@@ -1504,6 +1504,31 @@ public class View implements Drawable.Callback, KeyEvent.Callback, Accessibility
* @hide
*/
private static final int PREPRESSED = 0x02000000;
/**
* Always allow a user to overscroll this view, provided it is a
* view that can scroll.
*/
private static final int OVERSCROLL_ALWAYS = 0;
/**
* Allow a user to overscroll this view only if the content is large
* enough to meaningfully scroll, provided it is a view that can scroll.
*/
private static final int OVERSCROLL_IF_CONTENT_SCROLLS = 1;
/**
* Never allow a user to overscroll this view.
*/
private static final int OVERSCROLL_NEVER = 2;
/**
* Controls the overscroll mode for this view.
* See {@link #overscrollBy(int, int, int, int, int, int, int, int)},
* {@link #OVERSCROLL_ALWAYS}, {@link #OVERSCROLL_IF_CONTENT_SCROLLS},
* and {@link #OVERSCROLL_NEVER}.
*/
private int mOverscrollMode = OVERSCROLL_ALWAYS;
/**
* The parent this view is attached to.
@@ -2053,6 +2078,9 @@ public class View implements Drawable.Callback, KeyEvent.Callback, Accessibility
});
}
break;
case R.styleable.View_overscrollMode:
mOverscrollMode = a.getInt(attr, OVERSCROLL_ALWAYS);
break;
}
}
@@ -8573,43 +8601,59 @@ public class View implements Drawable.Callback, KeyEvent.Callback, Accessibility
int scrollX, int scrollY,
int scrollRangeX, int scrollRangeY,
int maxOverscrollX, int maxOverscrollY) {
// Scale the scroll amount if we're in the dropoff zone
final int dropoffX = maxOverscrollX / 2;
final int dropoffLeft = -dropoffX;
final int dropoffRight = dropoffX + scrollRangeX;
int newScrollX;
if ((scrollX < dropoffLeft && deltaX < 0) ||
(scrollX > dropoffRight && deltaX > 0)) {
newScrollX = scrollX + deltaX / 2;
} else {
newScrollX = scrollX + deltaX;
if (newScrollX > dropoffRight && deltaX > 0) {
int extra = newScrollX - dropoffRight;
newScrollX = dropoffRight + extra / 2;
} else if (newScrollX < dropoffLeft && deltaX < 0) {
int extra = newScrollX - dropoffLeft;
newScrollX = dropoffLeft + extra / 2;
}
}
final int overscrollMode = mOverscrollMode;
final boolean canScrollHorizontal =
computeHorizontalScrollRange() > computeHorizontalScrollExtent();
final boolean canScrollVertical =
computeVerticalScrollRange() > computeVerticalScrollExtent();
final boolean overscrollHorizontal = overscrollMode == OVERSCROLL_ALWAYS ||
(overscrollMode == OVERSCROLL_IF_CONTENT_SCROLLS && canScrollHorizontal);
final boolean overscrollVertical = overscrollMode == OVERSCROLL_ALWAYS ||
(overscrollMode == OVERSCROLL_IF_CONTENT_SCROLLS && canScrollVertical);
final int dropoffY = maxOverscrollY / 2;
final int dropoffTop = -dropoffY;
final int dropoffBottom = dropoffY + scrollRangeY;
int newScrollY;
if ((scrollY < dropoffTop && deltaY < 0) ||
(scrollY > dropoffBottom && deltaY > 0)) {
newScrollY = scrollY + deltaY / 2;
} else {
newScrollY = scrollY + deltaY;
if (newScrollY > dropoffBottom && deltaY > 0) {
int extra = newScrollY - dropoffBottom;
newScrollY = dropoffBottom + extra / 2;
} else if (newScrollY < dropoffTop && deltaY < 0) {
int extra = newScrollY - dropoffTop;
newScrollY = dropoffTop + extra / 2;
int newScrollX = scrollX + deltaX;
if (overscrollHorizontal) {
// Scale the scroll amount if we're in the dropoff zone
final int dropoffX = maxOverscrollX / 2;
final int dropoffLeft = -dropoffX;
final int dropoffRight = dropoffX + scrollRangeX;
if ((scrollX < dropoffLeft && deltaX < 0) ||
(scrollX > dropoffRight && deltaX > 0)) {
newScrollX = scrollX + deltaX / 2;
} else {
if (newScrollX > dropoffRight && deltaX > 0) {
int extra = newScrollX - dropoffRight;
newScrollX = dropoffRight + extra / 2;
} else if (newScrollX < dropoffLeft && deltaX < 0) {
int extra = newScrollX - dropoffLeft;
newScrollX = dropoffLeft + extra / 2;
}
}
} else {
maxOverscrollX = 0;
}
int newScrollY = scrollY + deltaY;
if (overscrollVertical) {
final int dropoffY = maxOverscrollY / 2;
final int dropoffTop = -dropoffY;
final int dropoffBottom = dropoffY + scrollRangeY;
if ((scrollY < dropoffTop && deltaY < 0) ||
(scrollY > dropoffBottom && deltaY > 0)) {
newScrollY = scrollY + deltaY / 2;
} else {
if (newScrollY > dropoffBottom && deltaY > 0) {
int extra = newScrollY - dropoffBottom;
newScrollY = dropoffBottom + extra / 2;
} else if (newScrollY < dropoffTop && deltaY < 0) {
int extra = newScrollY - dropoffTop;
newScrollY = dropoffTop + extra / 2;
}
}
} else {
maxOverscrollY = 0;
}
// Clamp values if at the limits and record
final int left = -maxOverscrollX;
final int right = maxOverscrollX + scrollRangeX;
@@ -8636,8 +8680,8 @@ public class View implements Drawable.Callback, KeyEvent.Callback, Accessibility
// Bump the device with some haptic feedback if we're at the edge
// and didn't start there.
if ((clampedX && scrollX != left && scrollX != right) ||
(clampedY && scrollY != top && scrollY != bottom)) {
if ((overscrollHorizontal && clampedX && scrollX != left && scrollX != right) ||
(overscrollVertical && clampedY && scrollY != top && scrollY != bottom)) {
performHapticFeedback(HapticFeedbackConstants.SCROLL_BARRIER);
}

3
core/java/android/widget/AbsListView.java
View File

@@ -2589,7 +2589,8 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
if (trackMotionScroll(delta, delta)) {
if (motionView != null) {
// Tweak the scroll for how far we overshot
mScrollY -= delta - (motionView.getTop() - oldTop);
int overshoot = -(delta - (motionView.getTop() - oldTop));
overscrollBy(0, overshoot, 0, mScrollY, 0, 0, 0, getOverscrollMax());
}
float vel = scroller.getCurrVelocity();
if (delta > 0) {