/* * Copyright (C) 2006 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 com.android.internal.R; import android.content.Context; import android.content.res.Resources; import android.content.res.TypedArray; import android.graphics.Canvas; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.os.StrictMode; import android.util.AttributeSet; import android.view.FocusFinder; import android.view.InputDevice; import android.view.KeyEvent; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewDebug; import android.view.ViewGroup; import android.view.ViewParent; import android.view.animation.AnimationUtils; 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 ScrollView * 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 vertical orientation, presenting a vertical * array of top-level items that the user can scroll through. * *
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. * *
ScrollView only supports vertical scrolling. * * @attr ref android.R.styleable#ScrollView_fillViewport */ public class ScrollView extends FrameLayout { static final int ANIMATED_SCROLL_GAP = 250; static final float MAX_SCROLL_FACTOR = 0.5f; private long mLastScroll; private final Rect mTempRect = new Rect(); private OverScroller mScroller; private EdgeGlow mEdgeGlowTop; private EdgeGlow mEdgeGlowBottom; /** * Position of the last motion event. */ private float mLastMotionY; /** * 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. */ @ViewDebug.ExportedProperty(category = "layout") private boolean mFillViewport; /** * Whether arrow scrolling is animated. */ private boolean mSmoothScrollingEnabled = true; private int mTouchSlop; private int mMinimumVelocity; private int mMaximumVelocity; private int mOverscrollDistance; private int mOverflingDistance; /** * ID of the active pointer. This is used to retain consistency during * drags/flings if multiple pointers are used. */ private int mActivePointerId = INVALID_POINTER; /** * The StrictMode "critical time span" objects to catch animation * stutters. Non-null when a time-sensitive animation is * in-flight. Must call finish() on them when done animating. * These are no-ops on user builds. */ private StrictMode.Span mScrollStrictSpan = null; // aka "drag" private StrictMode.Span mFlingStrictSpan = null; /** * Sentinel value for no current active pointer. * Used by {@link #mActivePointerId}. */ private static final int INVALID_POINTER = -1; public ScrollView(Context context) { this(context, null); } public ScrollView(Context context, AttributeSet attrs) { this(context, attrs, com.android.internal.R.attr.scrollViewStyle); } public ScrollView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); initScrollView(); TypedArray a = context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); a.recycle(); } @Override protected float getTopFadingEdgeStrength() { if (getChildCount() == 0) { return 0.0f; } final int length = getVerticalFadingEdgeLength(); if (mScrollY < length) { return mScrollY / (float) length; } return 1.0f; } @Override protected float getBottomFadingEdgeStrength() { if (getChildCount() == 0) { return 0.0f; } final int length = getVerticalFadingEdgeLength(); final int bottomEdge = getHeight() - mPaddingBottom; final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 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 * (mBottom - mTop)); } private void initScrollView() { mScroller = new OverScroller(getContext()); setFocusable(true); setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); setWillNotDraw(false); final ViewConfiguration configuration = ViewConfiguration.get(mContext); mTouchSlop = configuration.getScaledTouchSlop(); mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); mOverscrollDistance = configuration.getScaledOverscrollDistance(); mOverflingDistance = configuration.getScaledOverflingDistance(); } @Override public void addView(View child) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child); } @Override public void addView(View child, int index) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView 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("ScrollView 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("ScrollView can host only one direct child"); } super.addView(child, index, params); } /** * @return Returns true this ScrollView can be scrolled */ private boolean canScroll() { View child = getChildAt(0); if (child != null) { int childHeight = child.getHeight(); return getHeight() < childHeight + mPaddingTop + mPaddingBottom; } return false; } /** * Indicates whether this ScrollView's content is stretched to fill the viewport. * * @return True if the content fills the viewport, false otherwise. * * @attr ref android.R.styleable#ScrollView_fillViewport */ public boolean isFillViewport() { return mFillViewport; } /** * Indicates this ScrollView whether it should stretch its content height to fill * the viewport or not. * * @param fillViewport True to stretch the content's height to the viewport's * boundaries, false otherwise. * * @attr ref android.R.styleable#ScrollView_fillViewport */ 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 heightMode = MeasureSpec.getMode(heightMeasureSpec); if (heightMode == MeasureSpec.UNSPECIFIED) { return; } if (getChildCount() > 0) { final View child = getChildAt(0); int height = getMeasuredHeight(); if (child.getMeasuredHeight() < height) { final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft + mPaddingRight, lp.width); height -= mPaddingTop; height -= mPaddingBottom; int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } } } @Override public boolean dispatchKeyEvent(KeyEvent event) { // Let the focused view and/or our descendants get the key first return super.dispatchKeyEvent(event) || 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() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { View currentFocused = findFocus(); if (currentFocused == this) currentFocused = null; View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, View.FOCUS_DOWN); return nextFocused != null && nextFocused != this && nextFocused.requestFocus(View.FOCUS_DOWN); } return false; } boolean handled = false; if (event.getAction() == KeyEvent.ACTION_DOWN) { switch (event.getKeyCode()) { case KeyEvent.KEYCODE_DPAD_UP: if (!event.isAltPressed()) { handled = arrowScroll(View.FOCUS_UP); } else { handled = fullScroll(View.FOCUS_UP); } break; case KeyEvent.KEYCODE_DPAD_DOWN: if (!event.isAltPressed()) { handled = arrowScroll(View.FOCUS_DOWN); } else { handled = fullScroll(View.FOCUS_DOWN); } break; case KeyEvent.KEYCODE_SPACE: pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); break; } } return handled; } private boolean inChild(int x, int y) { if (getChildCount() > 0) { final int scrollY = mScrollY; final View child = getChildAt(0); return !(y < child.getTop() - scrollY || y >= child.getBottom() - scrollY || x < child.getLeft() || x >= child.getRight()); } return false; } @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; } 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. mLastMotionY is set to the y value * of the down event. */ final int activePointerId = mActivePointerId; if (activePointerId == INVALID_POINTER) { // If we don't have a valid id, the touch down wasn't on content. break; } final int pointerIndex = ev.findPointerIndex(activePointerId); final float y = ev.getY(pointerIndex); final int yDiff = (int) Math.abs(y - mLastMotionY); if (yDiff > mTouchSlop) { mIsBeingDragged = true; mLastMotionY = y; if (mScrollStrictSpan == null) { mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); } } break; } case MotionEvent.ACTION_DOWN: { final float y = ev.getY(); if (!inChild((int) ev.getX(), (int) y)) { mIsBeingDragged = false; break; } /* * Remember location of down touch. * ACTION_DOWN always refers to pointer index 0. */ mLastMotionY = y; mActivePointerId = ev.getPointerId(0); /* * If being flinged and user touches the screen, initiate drag; * otherwise don't. mScroller.isFinished should be false when * being flinged. */ mIsBeingDragged = !mScroller.isFinished(); if (mIsBeingDragged && mScrollStrictSpan == null) { mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); } break; } case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: /* Release the drag */ mIsBeingDragged = false; mActivePointerId = INVALID_POINTER; if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { invalidate(); } 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 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 (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(ev); final int action = ev.getAction(); switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: { mIsBeingDragged = getChildCount() != 0; if (!mIsBeingDragged) { return false; } /* * If being flinged and user touches, stop the fling. isFinished * will be false if being flinged. */ if (!mScroller.isFinished()) { mScroller.abortAnimation(); if (mFlingStrictSpan != null) { mFlingStrictSpan.finish(); mFlingStrictSpan = null; } } // Remember where the motion event started mLastMotionY = ev.getY(); mActivePointerId = ev.getPointerId(0); break; } case MotionEvent.ACTION_MOVE: if (mIsBeingDragged) { // Scroll to follow the motion event final int activePointerIndex = ev.findPointerIndex(mActivePointerId); final float y = ev.getY(activePointerIndex); final int deltaY = (int) (mLastMotionY - y); mLastMotionY = y; final int oldX = mScrollX; final int oldY = mScrollY; final int range = getScrollRange(); if (overScrollBy(0, deltaY, 0, mScrollY, 0, range, 0, mOverscrollDistance, true)) { // Break our velocity if we hit a scroll barrier. mVelocityTracker.clear(); } onScrollChanged(mScrollX, mScrollY, oldX, oldY); final int overscrollMode = getOverScrollMode(); if (overscrollMode == OVER_SCROLL_ALWAYS || (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { final int pulledToY = oldY + deltaY; if (pulledToY < 0) { mEdgeGlowTop.onPull((float) deltaY / getHeight()); if (!mEdgeGlowBottom.isFinished()) { mEdgeGlowBottom.onRelease(); } } else if (pulledToY > range) { mEdgeGlowBottom.onPull((float) deltaY / getHeight()); if (!mEdgeGlowTop.isFinished()) { mEdgeGlowTop.onRelease(); } } if (mEdgeGlowTop != null && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { invalidate(); } } } break; case MotionEvent.ACTION_UP: if (mIsBeingDragged) { final VelocityTracker velocityTracker = mVelocityTracker; velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); if (getChildCount() > 0) { if ((Math.abs(initialVelocity) > mMinimumVelocity)) { fling(-initialVelocity); } else { final int bottom = getScrollRange(); if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, bottom)) { invalidate(); } } } mActivePointerId = INVALID_POINTER; endDrag(); } break; case MotionEvent.ACTION_CANCEL: if (mIsBeingDragged && getChildCount() > 0) { if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { invalidate(); } mActivePointerId = INVALID_POINTER; endDrag(); } break; case MotionEvent.ACTION_POINTER_DOWN: { final int index = ev.getActionIndex(); final float y = ev.getY(index); mLastMotionY = y; mActivePointerId = ev.getPointerId(index); break; } case MotionEvent.ACTION_POINTER_UP: onSecondaryPointerUp(ev); mLastMotionY = ev.getY(ev.findPointerIndex(mActivePointerId)); break; } return true; } private void onSecondaryPointerUp(MotionEvent ev) { final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; final int pointerId = ev.getPointerId(pointerIndex); if (pointerId == mActivePointerId) { // This was our active pointer going up. Choose a new // active pointer and adjust accordingly. // TODO: Make this decision more intelligent. final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mLastMotionY = ev.getY(newPointerIndex); mActivePointerId = ev.getPointerId(newPointerIndex); if (mVelocityTracker != null) { mVelocityTracker.clear(); } } } @Override public boolean onGenericMotionEvent(MotionEvent event) { if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) { switch (event.getAction()) { case MotionEvent.ACTION_SCROLL: { if (!mIsBeingDragged) { final float vscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL); if (vscroll != 0) { final int delta = (int) (vscroll * getVerticalScrollFactor()); final int range = getScrollRange(); int oldScrollY = mScrollY; int newScrollY = oldScrollY - delta; if (newScrollY < 0) { newScrollY = 0; } else if (newScrollY > range) { newScrollY = range; } if (newScrollY != oldScrollY) { super.scrollTo(mScrollX, newScrollY); return true; } } } } } } return super.onGenericMotionEvent(event); } @Override protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY) { // Treat animating scrolls differently; see #computeScroll() for why. if (!mScroller.isFinished()) { mScrollX = scrollX; mScrollY = scrollY; invalidateParentIfNeeded(); if (clampedY) { mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); } } else { super.scrollTo(scrollX, scrollY); } awakenScrollBars(); } private int getScrollRange() { int scrollRange = 0; if (getChildCount() > 0) { View child = getChildAt(0); scrollRange = Math.max(0, child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); } return scrollRange; } /** *
* Finds the next focusable component that fits in this View's bounds * (excluding fading edges) pretending that this View's top is located at * the parameter top. *
* * @param topFocus look for a candidate at the top of the bounds if topFocus is true, * or at the bottom of the bounds if topFocus is false * @param top the top 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 topFocus, final int top, 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 = getVerticalFadingEdgeLength() / 2; final int topWithoutFadingEdge = top + fadingEdgeLength; final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; if ((preferredFocusable != null) && (preferredFocusable.getTop() < bottomWithoutFadingEdge) && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { return preferredFocusable; } return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, bottomWithoutFadingEdge); } /** ** Finds the next focusable component that fits in the specified bounds. *
* * @param topFocus look for a candidate is the one at the top of the bounds * if topFocus is true, or at the bottom of the bounds if topFocus is * false * @param top the top offset of the bounds in which a focusable must be * found * @param bottom the bottom 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 topFocus, int top, int bottom) { ListHandles scrolling in response to a "page up/down" shortcut press. This * method will scroll the view by one page up or down and give the focus * to the topmost/bottommost component in the new visible area. If no * component is a good candidate for focus, this scrollview reclaims the * focus.
* * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} * to go one page up or * {@link android.view.View#FOCUS_DOWN} to go one page down * @return true if the key event is consumed by this method, false otherwise */ public boolean pageScroll(int direction) { boolean down = direction == View.FOCUS_DOWN; int height = getHeight(); if (down) { mTempRect.top = getScrollY() + height; int count = getChildCount(); if (count > 0) { View view = getChildAt(count - 1); if (mTempRect.top + height > view.getBottom()) { mTempRect.top = view.getBottom() - height; } } } else { mTempRect.top = getScrollY() - height; if (mTempRect.top < 0) { mTempRect.top = 0; } } mTempRect.bottom = mTempRect.top + height; return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); } /** *Handles scrolling in response to a "home/end" shortcut press. This * method will scroll the view to the top or bottom and give the focus * to the topmost/bottommost component in the new visible area. If no * component is a good candidate for focus, this scrollview reclaims the * focus.
* * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} * to go the top of the view or * {@link android.view.View#FOCUS_DOWN} to go the bottom * @return true if the key event is consumed by this method, false otherwise */ public boolean fullScroll(int direction) { boolean down = direction == View.FOCUS_DOWN; int height = getHeight(); mTempRect.top = 0; mTempRect.bottom = height; if (down) { int count = getChildCount(); if (count > 0) { View view = getChildAt(count - 1); mTempRect.bottom = view.getBottom(); mTempRect.top = mTempRect.bottom - height; } } return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); } /** *Scrolls the view to make the area defined by top
and
* bottom
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.
The scroll range of a scroll view is the overall height of all of its * children.
*/ @Override protected int computeVerticalScrollRange() { final int count = getChildCount(); final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; if (count == 0) { return contentHeight; } int scrollRange = getChildAt(0).getBottom(); final int scrollY = mScrollY; final int overscrollBottom = Math.max(0, scrollRange - contentHeight); if (scrollY < 0) { scrollRange -= scrollY; } else if (scrollY > overscrollBottom) { scrollRange += scrollY - overscrollBottom; } return scrollRange; } @Override protected int computeVerticalScrollOffset() { return Math.max(0, super.computeVerticalScrollOffset()); } @Override protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { ViewGroup.LayoutParams lp = child.getLayoutParams(); int childWidthMeasureSpec; int childHeightMeasureSpec; childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft + mPaddingRight, lp.width); childHeightMeasureSpec = 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 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin + widthUsed, lp.width); final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( lp.topMargin + lp.bottomMargin, 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 (oldX != x || oldY != y) { overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 0, mOverflingDistance, false); onScrollChanged(mScrollX, mScrollY, oldX, oldY); final int range = getScrollRange(); final int overscrollMode = getOverScrollMode(); if (overscrollMode == OVER_SCROLL_ALWAYS || (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { if (y < 0 && oldY >= 0) { mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); } else if (y > range && oldY <= range) { mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); } } } awakenScrollBars(); // Keep on drawing until the animation has finished. postInvalidate(); } else { if (mFlingStrictSpan != null) { mFlingStrictSpan.finish(); mFlingStrictSpan = null; } } } /** * 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(0, scrollDelta); } } /** * 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(0, delta); } else { smoothScrollBy(0, delta); } } return scroll; } /** * Compute the amount to scroll in the Y 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) { if (getChildCount() == 0) return 0; int height = getHeight(); int screenTop = getScrollY(); int screenBottom = screenTop + height; int fadingEdge = getVerticalFadingEdgeLength(); // leave room for top fading edge as long as rect isn't at very top if (rect.top > 0) { screenTop += fadingEdge; } // leave room for bottom fading edge as long as rect isn't at very bottom if (rect.bottom < getChildAt(0).getHeight()) { screenBottom -= fadingEdge; } int scrollYDelta = 0; if (rect.bottom > screenBottom && rect.top > screenTop) { // need to move down to get it in view: move down just enough so // that the entire rectangle is in view (or at least the first // screen size chunk). if (rect.height() > height) { // just enough to get screen size chunk on scrollYDelta += (rect.top - screenTop); } else { // get entire rect at bottom of screen scrollYDelta += (rect.bottom - screenBottom); } // make sure we aren't scrolling beyond the end of our content int bottom = getChildAt(0).getBottom(); int distanceToBottom = bottom - screenBottom; scrollYDelta = Math.min(scrollYDelta, distanceToBottom); } else if (rect.top < screenTop && rect.bottom < screenBottom) { // need to move up to get it in view: move up just enough so that // entire rectangle is in view (or at least the first screen // size chunk of it). if (rect.height() > height) { // screen size chunk scrollYDelta -= (screenBottom - rect.bottom); } else { // entire rect at top scrollYDelta -= (screenTop - rect.top); } // make sure we aren't scrolling any further than the top our content scrollYDelta = Math.max(scrollYDelta, -getScrollY()); } return scrollYDelta; } @Override public void requestChildFocus(View child, View focused) { 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_DOWN; } else if (direction == View.FOCUS_BACKWARD) { direction = View.FOCUS_UP; } 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 onDetachedFromWindow() { super.onDetachedFromWindow(); if (mScrollStrictSpan != null) { mScrollStrictSpan.finish(); mScrollStrictSpan = null; } if (mFlingStrictSpan != null) { mFlingStrictSpan.finish(); mFlingStrictSpan = null; } } @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; // If the currently-focused view was visible on the screen when the // screen was at the old height, then scroll the screen to make that // view visible with the new screen height. if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { currentFocused.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(currentFocused, mTempRect); int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); doScrollY(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 velocityY The initial velocity in the Y direction. Positive * numbers mean that the finger/cursor is moving down the screen, * which means we want to scroll towards the top. */ public void fling(int velocityY) { if (getChildCount() > 0) { int height = getHeight() - mPaddingBottom - mPaddingTop; int bottom = getChildAt(0).getHeight(); mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, Math.max(0, bottom - height), 0, height/2); final boolean movingDown = velocityY > 0; View currentFocused = findFocus(); View newFocused = findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), currentFocused); if (newFocused == null) { newFocused = this; } if (newFocused != currentFocused) { newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP); } if (mFlingStrictSpan == null) { mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling"); } invalidate(); } } private void endDrag() { mIsBeingDragged = false; if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } if (mEdgeGlowTop != null) { mEdgeGlowTop.onRelease(); mEdgeGlowBottom.onRelease(); } if (mScrollStrictSpan != null) { mScrollStrictSpan.finish(); mScrollStrictSpan = null; } } /** * {@inheritDoc} * *This version also clamps the scrolling to the bounds of our child. */ @Override 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); } } } @Override public void setOverScrollMode(int mode) { if (mode != OVER_SCROLL_NEVER) { if (mEdgeGlowTop == null) { Context context = getContext(); final Resources res = context.getResources(); final Drawable edge = res.getDrawable(R.drawable.overscroll_edge); final Drawable glow = res.getDrawable(R.drawable.overscroll_glow); mEdgeGlowTop = new EdgeGlow(context, edge, glow); mEdgeGlowBottom = new EdgeGlow(context, edge, glow); } } else { mEdgeGlowTop = null; mEdgeGlowBottom = null; } super.setOverScrollMode(mode); } @Override public void draw(Canvas canvas) { super.draw(canvas); if (mEdgeGlowTop != null) { final int scrollY = mScrollY; if (!mEdgeGlowTop.isFinished()) { final int restoreCount = canvas.save(); final int width = getWidth() - mPaddingLeft - mPaddingRight; canvas.translate(mPaddingLeft, Math.min(0, scrollY)); mEdgeGlowTop.setSize(width, getHeight()); if (mEdgeGlowTop.draw(canvas)) { invalidate(); } canvas.restoreToCount(restoreCount); } if (!mEdgeGlowBottom.isFinished()) { final int restoreCount = canvas.save(); final int width = getWidth() - mPaddingLeft - mPaddingRight; final int height = getHeight(); canvas.translate(-width + mPaddingLeft, Math.max(getScrollRange(), scrollY) + height); canvas.rotate(180, width, 0); mEdgeGlowBottom.setSize(width, height); if (mEdgeGlowBottom.draw(canvas)) { invalidate(); } canvas.restoreToCount(restoreCount); } } } private int clamp(int n, int my, int child) { if (my >= child || n < 0) { /* my >= child is this case: * |--------------- me ---------------| * |------ child ------| * or * |--------------- me ---------------| * |------ child ------| * or * |--------------- me ---------------| * |------ child ------| * * n < 0 is this case: * |------ me ------| * |-------- child --------| * |-- mScrollX --| */ return 0; } if ((my+n) > child) { /* this case: * |------ me ------| * |------ child ------| * |-- mScrollX --| */ return child-my; } return n; } }