/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.widget;
import android.util.AttributeSet;
import android.graphics.Rect;
import android.view.View;
import android.view.VelocityTracker;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.KeyEvent;
import android.view.FocusFinder;
import android.view.MotionEvent;
import android.view.ViewParent;
import android.view.animation.AnimationUtils;
import android.content.Context;
import android.content.res.TypedArray;
import java.util.List;
/**
* Layout container for a view hierarchy that can be scrolled by the user,
* allowing it to be larger than the physical display. A HorizontalScrollView
* is a {@link FrameLayout}, meaning you should place one child in it
* containing the entire contents to scroll; this child may itself be a layout
* manager with a complex hierarchy of objects. A child that is often used
* is a {@link LinearLayout} in a horizontal orientation, presenting a horizontal
* array of top-level items that the user can scroll through.
*
* <p>You should never use a HorizontalScrollView with a {@link ListView}, since
* ListView takes care of its own scrolling. Most importantly, doing this
* defeats all of the important optimizations in ListView for dealing with
* large lists, since it effectively forces the ListView to display its entire
* list of items to fill up the infinite container supplied by HorizontalScrollView.
*
* <p>The {@link TextView} class also
* takes care of its own scrolling, so does not require a ScrollView, but
* using the two together is possible to achieve the effect of a text view
* within a larger container.
*
* <p>HorizontalScrollView only supports horizontal scrolling.
*/
public class HorizontalScrollView extends FrameLayout {
private static final int ANIMATED_SCROLL_GAP = ScrollView.ANIMATED_SCROLL_GAP;
private static final float MAX_SCROLL_FACTOR = ScrollView.MAX_SCROLL_FACTOR;
private long mLastScroll;
private final Rect mTempRect = new Rect();
private Scroller mScroller;
/**
* Flag to indicate that we are moving focus ourselves. This is so the
* code that watches for focus changes initiated outside this ScrollView
* knows that it does not have to do anything.
*/
private boolean mScrollViewMovedFocus;
/**
* Position of the last motion event.
*/
private float mLastMotionX;
/**
* True when the layout has changed but the traversal has not come through yet.
* Ideally the view hierarchy would keep track of this for us.
*/
private boolean mIsLayoutDirty = true;
/**
* The child to give focus to in the event that a child has requested focus while the
* layout is dirty. This prevents the scroll from being wrong if the child has not been
* laid out before requesting focus.
*/
private View mChildToScrollTo = null;
/**
* True if the user is currently dragging this ScrollView around. This is
* not the same as 'is being flinged', which can be checked by
* mScroller.isFinished() (flinging begins when the user lifts his finger).
*/
private boolean mIsBeingDragged = false;
/**
* Determines speed during touch scrolling
*/
private VelocityTracker mVelocityTracker;
/**
* When set to true, the scroll view measure its child to make it fill the currently
* visible area.
*/
private boolean mFillViewport;
/**
* Whether arrow scrolling is animated.
*/
private boolean mSmoothScrollingEnabled = true;
private int mTouchSlop;
public HorizontalScrollView(Context context) {
this(context, null);
}
public HorizontalScrollView(Context context, AttributeSet attrs) {
this(context, attrs, com.android.internal.R.attr.horizontalScrollViewStyle);
}
public HorizontalScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initScrollView();
TypedArray a = context.obtainStyledAttributes(attrs,
android.R.styleable.HorizontalScrollView, defStyle, 0);
setFillViewport(a.getBoolean(android.R.styleable.HorizontalScrollView_fillViewport, false));
a.recycle();
}
@Override
protected float getLeftFadingEdgeStrength() {
if (getChildCount() == 0) {
return 0.0f;
}
final int length = getHorizontalFadingEdgeLength();
if (mScrollX < length) {
return mScrollX / (float) length;
}
return 1.0f;
}
@Override
protected float getRightFadingEdgeStrength() {
if (getChildCount() == 0) {
return 0.0f;
}
final int length = getHorizontalFadingEdgeLength();
final int rightEdge = getWidth() - mPaddingRight;
final int span = getChildAt(0).getRight() - mScrollX - rightEdge;
if (span < length) {
return span / (float) length;
}
return 1.0f;
}
/**
* @return The maximum amount this scroll view will scroll in response to
* an arrow event.
*/
public int getMaxScrollAmount() {
return (int) (MAX_SCROLL_FACTOR * (mRight - mLeft));
}
private void initScrollView() {
mScroller = new Scroller(getContext());
setFocusable(true);
setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
setWillNotDraw(false);
mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
}
@Override
public void addView(View child) {
if (getChildCount() > 0) {
throw new IllegalStateException("HorizontalScrollView can host only one direct child");
}
super.addView(child);
}
@Override
public void addView(View child, int index) {
if (getChildCount() > 0) {
throw new IllegalStateException("HorizontalScrollView can host only one direct child");
}
super.addView(child, index);
}
@Override
public void addView(View child, ViewGroup.LayoutParams params) {
if (getChildCount() > 0) {
throw new IllegalStateException("HorizontalScrollView can host only one direct child");
}
super.addView(child, params);
}
@Override
public void addView(View child, int index, ViewGroup.LayoutParams params) {
if (getChildCount() > 0) {
throw new IllegalStateException("HorizontalScrollView can host only one direct child");
}
super.addView(child, index, params);
}
/**
* @return Returns true this HorizontalScrollView can be scrolled
*/
private boolean canScroll() {
View child = getChildAt(0);
if (child != null) {
int childWidth = child.getWidth();
return getWidth() < childWidth + mPaddingLeft + mPaddingRight ;
}
return false;
}
/**
* Indicates whether this ScrollView's content is stretched to fill the viewport.
*
* @return True if the content fills the viewport, false otherwise.
*/
public boolean isFillViewport() {
return mFillViewport;
}
/**
* Indicates this ScrollView whether it should stretch its content width to fill
* the viewport or not.
*
* @param fillViewport True to stretch the content's width to the viewport's
* boundaries, false otherwise.
*/
public void setFillViewport(boolean fillViewport) {
if (fillViewport != mFillViewport) {
mFillViewport = fillViewport;
requestLayout();
}
}
/**
* @return Whether arrow scrolling will animate its transition.
*/
public boolean isSmoothScrollingEnabled() {
return mSmoothScrollingEnabled;
}
/**
* Set whether arrow scrolling will animate its transition.
* @param smoothScrollingEnabled whether arrow scrolling will animate its transition
*/
public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) {
mSmoothScrollingEnabled = smoothScrollingEnabled;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (!mFillViewport) {
return;
}
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
if (widthMode == MeasureSpec.UNSPECIFIED) {
return;
}
final View child = getChildAt(0);
int width = getMeasuredWidth();
if (child.getMeasuredHeight() < width) {
final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams();
int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec, mPaddingTop
+ mPaddingBottom, lp.height);
width -= mPaddingLeft;
width -= mPaddingRight;
int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);
child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}
}
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
// Let the focused view and/or our descendants get the key first
boolean handled = super.dispatchKeyEvent(event);
if (handled) {
return true;
}
return executeKeyEvent(event);
}
/**
* You can call this function yourself to have the scroll view perform
* scrolling from a key event, just as if the event had been dispatched to
* it by the view hierarchy.
*
* @param event The key event to execute.
* @return Return true if the event was handled, else false.
*/
public boolean executeKeyEvent(KeyEvent event) {
mTempRect.setEmpty();
if (!canScroll()) {
if (isFocused()) {
View currentFocused = findFocus();
if (currentFocused == this) currentFocused = null;
View nextFocused = FocusFinder.getInstance().findNextFocus(this,
currentFocused, View.FOCUS_RIGHT);
return nextFocused != null && nextFocused != this &&
nextFocused.requestFocus(View.FOCUS_RIGHT);
}
return false;
}
boolean handled = false;
if (event.getAction() == KeyEvent.ACTION_DOWN) {
switch (event.getKeyCode()) {
case KeyEvent.KEYCODE_DPAD_LEFT:
if (!event.isAltPressed()) {
handled = arrowScroll(View.FOCUS_LEFT);
} else {
handled = fullScroll(View.FOCUS_LEFT);
}
break;
case KeyEvent.KEYCODE_DPAD_RIGHT:
if (!event.isAltPressed()) {
handled = arrowScroll(View.FOCUS_RIGHT);
} else {
handled = fullScroll(View.FOCUS_RIGHT);
}
break;
case KeyEvent.KEYCODE_SPACE:
pageScroll(event.isShiftPressed() ? View.FOCUS_LEFT : View.FOCUS_RIGHT);
break;
}
}
return handled;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
/*
* This method JUST determines whether we want to intercept the motion.
* If we return true, onMotionEvent 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) && (mIsBeingDragged)) {
return true;
}
if (!canScroll()) {
mIsBeingDragged = false;
return false;
}
final float x = ev.getX();
switch (action) {
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 x value
* of the down event.
*/
final int xDiff = (int) Math.abs(x - mLastMotionX);
if (xDiff > mTouchSlop) {
mIsBeingDragged = true;
if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true);
}
break;
case MotionEvent.ACTION_DOWN:
/* Remember location of down touch */
mLastMotionX = x;
/*
* If being flinged and user touches the screen, initiate drag;
* otherwise don't. mScroller.isFinished should be false when
* being flinged.
*/
mIsBeingDragged = !mScroller.isFinished();
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
/* Release the drag */
mIsBeingDragged = false;
break;
}
/*
* The only time we want to intercept motion events is if we are in the
* drag mode.
*/
return mIsBeingDragged;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) {
// Don't handle edge touches immediately -- they may actually belong to one of our
// descendants.
return false;
}
if (!canScroll()) {
return false;
}
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
final int action = ev.getAction();
final float x = ev.getX();
switch (action) {
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 = x;
break;
case MotionEvent.ACTION_MOVE:
// Scroll to follow the motion event
final int deltaX = (int) (mLastMotionX - x);
mLastMotionX = x;
if (deltaX < 0) {
if (mScrollX > 0) {
scrollBy(deltaX, 0);
}
} else if (deltaX > 0) {
final int rightEdge = getWidth() - mPaddingRight;
final int availableToScroll = getChildAt(0).getRight() - mScrollX - rightEdge;
if (availableToScroll > 0) {
scrollBy(Math.min(availableToScroll, deltaX), 0);
}
}
break;
case MotionEvent.ACTION_UP:
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000);
int initialVelocity = (int) velocityTracker.getXVelocity();
if ((Math.abs(initialVelocity) >
ViewConfiguration.get(mContext).getScaledMinimumFlingVelocity()) &&
getChildCount() > 0) {
fling(-initialVelocity);
}
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
return true;
}
/**
* <p>
* Finds the next focusable component that fits in this View's bounds
* (excluding fading edges) pretending that this View's left is located at
* the parameter left.
* </p>
*
* @param leftFocus look for a candidate is the one at the left of the bounds
* if leftFocus is true, or at the right of the bounds if leftFocus
* is false
* @param left the left offset of the bounds in which a focusable must be
* found (the fading edge is assumed to start at this position)
* @param preferredFocusable the View that has highest priority and will be
* returned if it is within my bounds (null is valid)
* @return the next focusable component in the bounds or null if none can be found
*/
private View findFocusableViewInMyBounds(final boolean leftFocus,
final int left, View preferredFocusable) {
/*
* The fading edge's transparent side should be considered for focus
* since it's mostly visible, so we divide the actual fading edge length
* by 2.
*/
final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2;
final int leftWithoutFadingEdge = left + fadingEdgeLength;
final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength;
if ((preferredFocusable != null)
&& (preferredFocusable.getLeft() < rightWithoutFadingEdge)
&& (preferredFocusable.getRight() > leftWithoutFadingEdge)) {
return preferredFocusable;
}
return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge,
rightWithoutFadingEdge);
}
/**
* <p>
* Finds the next focusable component that fits in the specified bounds.
* </p>
*
* @param leftFocus look for a candidate is the one at the left of the bounds
* if leftFocus is true, or at the right of the bounds if
* leftFocus is false
* @param left the left offset of the bounds in which a focusable must be
* found
* @param right the right offset of the bounds in which a focusable must
* be found
* @return the next focusable component in the bounds or null if none can
* be found
*/
private View findFocusableViewInBounds(boolean leftFocus, int left, int right) {
List<View> focusables = getFocusables(View.FOCUS_FORWARD);
View focusCandidate = null;
/*
* A fully contained focusable is one where its left is below the bound's
* left, and its right is above the bound's right. A partially
* contained focusable is one where some part of it is within the
* bounds, but it also has some part that is not within bounds. A fully contained
* focusable is preferred to a partially contained focusable.
*/
boolean foundFullyContainedFocusable = false;
int count = focusables.size();
for (int i = 0; i < count; i++) {
View view = focusables.get(i);
int viewLeft = view.getLeft();
int viewRight = view.getRight();
if (left < viewRight && viewLeft < right) {
/*
* the focusable is in the target area, it is a candidate for
* focusing
*/
final boolean viewIsFullyContained = (left < viewLeft) &&
(viewRight < right);
if (focusCandidate == null) {
/* No candidate, take this one */
focusCandidate = view;
foundFullyContainedFocusable = viewIsFullyContained;
} else {
final boolean viewIsCloserToBoundary =
(leftFocus && viewLeft < focusCandidate.getLeft()) ||
(!leftFocus && viewRight > focusCandidate.getRight());
if (foundFullyContainedFocusable) {
if (viewIsFullyContained && viewIsCloserToBoundary) {
/*
* We're dealing with only fully contained views, so
* it has to be closer to the boundary to beat our
* candidate
*/
focusCandidate = view;
}
} else {
if (viewIsFullyContained) {
/* Any fully contained view beats a partially contained view */
focusCandidate = view;
foundFullyContainedFocusable = true;
} else if (viewIsCloserToBoundary) {
/*
* Partially contained view beats another partially
* contained view if it's closer
*/
focusCandidate = view;
}
}
}
}
}
return focusCandidate;
}
/**
* <p>Handles scrolling in response to a "page up/down" shortcut press. This
* method will scroll the view by one page left or right and give the focus
* to the leftmost/rightmost component in the new visible area. If no
* component is a good candidate for focus, this scrollview reclaims the
* focus.</p>
*
* @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT}
* to go one page left or {@link android.view.View#FOCUS_RIGHT}
* to go one page right
* @return true if the key event is consumed by this method, false otherwise
*/
public boolean pageScroll(int direction) {
boolean right = direction == View.FOCUS_RIGHT;
int width = getWidth();
if (right) {
mTempRect.left = getScrollX() + width;
int count = getChildCount();
if (count > 0) {
View view = getChildAt(count - 1);
if (mTempRect.left + width > view.getRight()) {
mTempRect.left = view.getRight() - width;
}
}
} else {
mTempRect.left = getScrollX() - width;
if (mTempRect.left < 0) {
mTempRect.left = 0;
}
}
mTempRect.right = mTempRect.left + width;
return scrollAndFocus(direction, mTempRect.left, mTempRect.right);
}
/**
* <p>Handles scrolling in response to a "home/end" shortcut press. This
* method will scroll the view to the left or right and give the focus
* to the leftmost/rightmost component in the new visible area. If no
* component is a good candidate for focus, this scrollview reclaims the
* focus.</p>
*
* @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT}
* to go the left of the view or {@link android.view.View#FOCUS_RIGHT}
* to go the right
* @return true if the key event is consumed by this method, false otherwise
*/
public boolean fullScroll(int direction) {
boolean right = direction == View.FOCUS_RIGHT;
int width = getWidth();
mTempRect.left = 0;
mTempRect.right = width;
if (right) {
int count = getChildCount();
if (count > 0) {
View view = getChildAt(count - 1);
mTempRect.right = view.getRight();
mTempRect.left = mTempRect.right - width;
}
}
return scrollAndFocus(direction, mTempRect.left, mTempRect.right);
}
/**
* <p>Scrolls the view to make the area defined by <code>left</code> and
* <code>right</code> visible. This method attempts to give the focus
* to a component visible in this area. If no component can be focused in
* the new visible area, the focus is reclaimed by this scrollview.</p>
*
* @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT}
* to go left {@link android.view.View#FOCUS_RIGHT} to right
* @param left the left offset of the new area to be made visible
* @param right the right offset of the new area to be made visible
* @return true if the key event is consumed by this method, false otherwise
*/
private boolean scrollAndFocus(int direction, int left, int right) {
boolean handled = true;
int width = getWidth();
int containerLeft = getScrollX();
int containerRight = containerLeft + width;
boolean goLeft = direction == View.FOCUS_LEFT;
View newFocused = findFocusableViewInBounds(goLeft, left, right);
if (newFocused == null) {
newFocused = this;
}
if (left >= containerLeft && right <= containerRight) {
handled = false;
} else {
int delta = goLeft ? (left - containerLeft) : (right - containerRight);
doScrollX(delta);
}
if (newFocused != findFocus() && newFocused.requestFocus(direction)) {
mScrollViewMovedFocus = true;
mScrollViewMovedFocus = false;
}
return handled;
}
/**
* Handle scrolling in response to a left or right arrow click.
*
* @param direction The direction corresponding to the arrow key that was
* pressed
* @return True if we consumed the event, false otherwise
*/
public boolean arrowScroll(int direction) {
View currentFocused = findFocus();
if (currentFocused == this) currentFocused = null;
View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);
final int maxJump = getMaxScrollAmount();
if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) {
nextFocused.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(nextFocused, mTempRect);
int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
doScrollX(scrollDelta);
nextFocused.requestFocus(direction);
} else {
// no new focus
int scrollDelta = maxJump;
if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) {
scrollDelta = getScrollX();
} else if (direction == View.FOCUS_RIGHT) {
int daRight = getChildAt(getChildCount() - 1).getRight();
int screenRight = getScrollX() + getWidth();
if (daRight - screenRight < maxJump) {
scrollDelta = daRight - screenRight;
}
}
if (scrollDelta == 0) {
return false;
}
doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta);
}
if (currentFocused != null && currentFocused.isFocused()
&& isOffScreen(currentFocused)) {
// previously focused item still has focus and is off screen, give
// it up (take it back to ourselves)
// (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are
// sure to
// get it)
final int descendantFocusability = getDescendantFocusability(); // save
setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS);
requestFocus();
setDescendantFocusability(descendantFocusability); // restore
}
return true;
}
/**
* @return whether the descendant of this scroll view is scrolled off
* screen.
*/
private boolean isOffScreen(View descendant) {
return !isWithinDeltaOfScreen(descendant, 0);
}
/**
* @return whether the descendant of this scroll view is within delta
* pixels of being on the screen.
*/
private boolean isWithinDeltaOfScreen(View descendant, int delta) {
descendant.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(descendant, mTempRect);
return (mTempRect.right + delta) >= getScrollX()
&& (mTempRect.left - delta) <= (getScrollX() + getWidth());
}
/**
* Smooth scroll by a X delta
*
* @param delta the number of pixels to scroll by on the X axis
*/
private void doScrollX(int delta) {
if (delta != 0) {
if (mSmoothScrollingEnabled) {
smoothScrollBy(delta, 0);
} else {
scrollBy(delta, 0);
}
}
}
/**
* Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
*
* @param dx the number of pixels to scroll by on the X axis
* @param dy the number of pixels to scroll by on the Y axis
*/
public final void smoothScrollBy(int dx, int dy) {
long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll;
if (duration > ANIMATED_SCROLL_GAP) {
mScroller.startScroll(mScrollX, mScrollY, dx, dy);
invalidate();
} else {
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
scrollBy(dx, dy);
}
mLastScroll = AnimationUtils.currentAnimationTimeMillis();
}
/**
* Like {@link #scrollTo}, but scroll smoothly instead of immediately.
*
* @param x the position where to scroll on the X axis
* @param y the position where to scroll on the Y axis
*/
public final void smoothScrollTo(int x, int y) {
smoothScrollBy(x - mScrollX, y - mScrollY);
}
/**
* <p>The scroll range of a scroll view is the overall width of all of its
* children.</p>
*/
@Override
protected int computeHorizontalScrollRange() {
int count = getChildCount();
return count == 0 ? getWidth() : getChildAt(0).getRight();
}
@Override
protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) {
ViewGroup.LayoutParams lp = child.getLayoutParams();
int childWidthMeasureSpec;
int childHeightMeasureSpec;
childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop
+ mPaddingBottom, lp.height);
childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}
@Override
protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed,
int parentHeightMeasureSpec, int heightUsed) {
final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,
mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin
+ heightUsed, lp.height);
final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED);
child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}
@Override
public void computeScroll() {
if (mScroller.computeScrollOffset()) {
// This is called at drawing time by ViewGroup. We don't want to
// re-show the scrollbars at this point, which scrollTo will do,
// so we replicate most of scrollTo here.
//
// It's a little odd to call onScrollChanged from inside the drawing.
//
// It is, except when you remember that computeScroll() is used to
// animate scrolling. So unless we want to defer the onScrollChanged()
// until the end of the animated scrolling, we don't really have a
// choice here.
//
// I agree. The alternative, which I think would be worse, is to post
// something and tell the subclasses later. This is bad because there
// will be a window where mScrollX/Y is different from what the app
// thinks it is.
//
int oldX = mScrollX;
int oldY = mScrollY;
int x = mScroller.getCurrX();
int y = mScroller.getCurrY();
if (getChildCount() > 0) {
View child = getChildAt(0);
mScrollX = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth());
mScrollY = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight());
} else {
mScrollX = x;
mScrollY = y;
}
if (oldX != mScrollX || oldY != mScrollY) {
onScrollChanged(mScrollX, mScrollY, oldX, oldY);
}
// Keep on drawing until the animation has finished.
postInvalidate();
}
}
/**
* Scrolls the view to the given child.
*
* @param child the View to scroll to
*/
private void scrollToChild(View child) {
child.getDrawingRect(mTempRect);
/* Offset from child's local coordinates to ScrollView coordinates */
offsetDescendantRectToMyCoords(child, mTempRect);
int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
if (scrollDelta != 0) {
scrollBy(scrollDelta, 0);
}
}
/**
* If rect is off screen, scroll just enough to get it (or at least the
* first screen size chunk of it) on screen.
*
* @param rect The rectangle.
* @param immediate True to scroll immediately without animation
* @return true if scrolling was performed
*/
private boolean scrollToChildRect(Rect rect, boolean immediate) {
final int delta = computeScrollDeltaToGetChildRectOnScreen(rect);
final boolean scroll = delta != 0;
if (scroll) {
if (immediate) {
scrollBy(delta, 0);
} else {
smoothScrollBy(delta, 0);
}
}
return scroll;
}
/**
* Compute the amount to scroll in the X direction in order to get
* a rectangle completely on the screen (or, if taller than the screen,
* at least the first screen size chunk of it).
*
* @param rect The rect.
* @return The scroll delta.
*/
protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) {
int width = getWidth();
int screenLeft = getScrollX();
int screenRight = screenLeft + width;
int fadingEdge = getHorizontalFadingEdgeLength();
// leave room for left fading edge as long as rect isn't at very left
if (rect.left > 0) {
screenLeft += fadingEdge;
}
// leave room for right fading edge as long as rect isn't at very right
if (rect.right < getChildAt(0).getWidth()) {
screenRight -= fadingEdge;
}
int scrollXDelta = 0;
if (rect.right > screenRight && rect.left > screenLeft) {
// need to move right to get it in view: move right just enough so
// that the entire rectangle is in view (or at least the first
// screen size chunk).
if (rect.width() > width) {
// just enough to get screen size chunk on
scrollXDelta += (rect.left - screenLeft);
} else {
// get entire rect at right of screen
scrollXDelta += (rect.right - screenRight);
}
// make sure we aren't scrolling beyond the end of our content
int right = getChildAt(getChildCount() - 1).getRight();
int distanceToRight = right - screenRight;
scrollXDelta = Math.min(scrollXDelta, distanceToRight);
} else if (rect.left < screenLeft && rect.right < screenRight) {
// need to move right to get it in view: move right just enough so that
// entire rectangle is in view (or at least the first screen
// size chunk of it).
if (rect.width() > width) {
// screen size chunk
scrollXDelta -= (screenRight - rect.right);
} else {
// entire rect at left
scrollXDelta -= (screenLeft - rect.left);
}
// make sure we aren't scrolling any further than the left our content
scrollXDelta = Math.max(scrollXDelta, -getScrollX());
}
return scrollXDelta;
}
@Override
public void requestChildFocus(View child, View focused) {
if (!mScrollViewMovedFocus) {
if (!mIsLayoutDirty) {
scrollToChild(focused);
} else {
// The child may not be laid out yet, we can't compute the scroll yet
mChildToScrollTo = focused;
}
}
super.requestChildFocus(child, focused);
}
/**
* When looking for focus in children of a scroll view, need to be a little
* more careful not to give focus to something that is scrolled off screen.
*
* This is more expensive than the default {@link android.view.ViewGroup}
* implementation, otherwise this behavior might have been made the default.
*/
@Override
protected boolean onRequestFocusInDescendants(int direction,
Rect previouslyFocusedRect) {
// convert from forward / backward notation to up / down / left / right
// (ugh).
if (direction == View.FOCUS_FORWARD) {
direction = View.FOCUS_RIGHT;
} else if (direction == View.FOCUS_BACKWARD) {
direction = View.FOCUS_LEFT;
}
final View nextFocus = previouslyFocusedRect == null ?
FocusFinder.getInstance().findNextFocus(this, null, direction) :
FocusFinder.getInstance().findNextFocusFromRect(this,
previouslyFocusedRect, direction);
if (nextFocus == null) {
return false;
}
if (isOffScreen(nextFocus)) {
return false;
}
return nextFocus.requestFocus(direction, previouslyFocusedRect);
}
@Override
public boolean requestChildRectangleOnScreen(View child, Rect rectangle,
boolean immediate) {
// offset into coordinate space of this scroll view
rectangle.offset(child.getLeft() - child.getScrollX(),
child.getTop() - child.getScrollY());
return scrollToChildRect(rectangle, immediate);
}
@Override
public void requestLayout() {
mIsLayoutDirty = true;
super.requestLayout();
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
mIsLayoutDirty = false;
// Give a child focus if it needs it
if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) {
scrollToChild(mChildToScrollTo);
}
mChildToScrollTo = null;
// Calling this with the present values causes it to re-clam them
scrollTo(mScrollX, mScrollY);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
View currentFocused = findFocus();
if (null == currentFocused || this == currentFocused)
return;
final int maxJump = mRight - mLeft;
if (isWithinDeltaOfScreen(currentFocused, maxJump)) {
currentFocused.getDrawingRect(mTempRect);
offsetDescendantRectToMyCoords(currentFocused, mTempRect);
int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
doScrollX(scrollDelta);
}
}
/**
* Return true if child is an descendant of parent, (or equal to the parent).
*/
private boolean isViewDescendantOf(View child, View parent) {
if (child == parent) {
return true;
}
final ViewParent theParent = child.getParent();
return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent);
}
/**
* Fling the scroll view
*
* @param velocityX The initial velocity in the X direction. Positive
* numbers mean that the finger/curor is moving down the screen,
* which means we want to scroll towards the left.
*/
public void fling(int velocityX) {
int width = getWidth() - mPaddingRight - mPaddingLeft;
int right = getChildAt(0).getWidth();
mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, right - width, 0, 0);
final boolean movingRight = velocityX > 0;
View newFocused = findFocusableViewInMyBounds(movingRight,
mScroller.getFinalX(), findFocus());
if (newFocused == null) {
newFocused = this;
}
if (newFocused != findFocus()
&& newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT)) {
mScrollViewMovedFocus = true;
mScrollViewMovedFocus = false;
}
invalidate();
}
/**
* {@inheritDoc}
*
* <p>This version also clamps the scrolling to the bounds of our child.
*/
public void scrollTo(int x, int y) {
// we rely on the fact the View.scrollBy calls scrollTo.
if (getChildCount() > 0) {
View child = getChildAt(0);
x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth());
y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight());
if (x != mScrollX || y != mScrollY) {
super.scrollTo(x, y);
}
}
}
private int clamp(int n, int my, int child) {
if (my >= child || n < 0) {
return 0;
}
if ((my + n) > child) {
return child - my;
}
return n;
}
}
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