Android水平和垂直方向的快速滑动条/快速滑块/快滑滚动条/快滑滚动块标准实现，Java
java
/*
* Copyright 2018 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 androidx.recyclerview.widget;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.animation.ValueAnimator.AnimatorUpdateListener;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.StateListDrawable;
import android.view.MotionEvent;
import androidx.annotation.IntDef;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.VisibleForTesting;
import androidx.core.view.ViewCompat;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
/**
* Class responsible to animate and provide a fast scroller.
*/
@VisibleForTesting
class FastScroller extends RecyclerView.ItemDecoration implements RecyclerView.OnItemTouchListener {
@IntDef({STATE_HIDDEN, STATE_VISIBLE, STATE_DRAGGING})
@Retention(RetentionPolicy.SOURCE)
private @interface State { }
// Scroll thumb not showing
private static final int STATE_HIDDEN = 0;
// Scroll thumb visible and moving along with the scrollbar
private static final int STATE_VISIBLE = 1;
// Scroll thumb being dragged by user
private static final int STATE_DRAGGING = 2;
@IntDef({DRAG_X, DRAG_Y, DRAG_NONE})
@Retention(RetentionPolicy.SOURCE)
private @interface DragState{ }
private static final int DRAG_NONE = 0;
private static final int DRAG_X = 1;
private static final int DRAG_Y = 2;
@IntDef({ANIMATION_STATE_OUT, ANIMATION_STATE_FADING_IN, ANIMATION_STATE_IN,
ANIMATION_STATE_FADING_OUT})
@Retention(RetentionPolicy.SOURCE)
private @interface AnimationState { }
private static final int ANIMATION_STATE_OUT = 0;
private static final int ANIMATION_STATE_FADING_IN = 1;
private static final int ANIMATION_STATE_IN = 2;
private static final int ANIMATION_STATE_FADING_OUT = 3;
private static final int SHOW_DURATION_MS = 500;
private static final int HIDE_DELAY_AFTER_VISIBLE_MS = 1500;
private static final int HIDE_DELAY_AFTER_DRAGGING_MS = 1200;
private static final int HIDE_DURATION_MS = 500;
private static final int SCROLLBAR_FULL_OPAQUE = 255;
private static final int[] PRESSED_STATE_SET = new int[]{android.R.attr.state_pressed};
private static final int[] EMPTY_STATE_SET = new int[]{};
private final int mScrollbarMinimumRange;
private final int mMargin;
// Final values for the vertical scroll bar
@SuppressWarnings("WeakerAccess") /* synthetic access */
final StateListDrawable mVerticalThumbDrawable;
@SuppressWarnings("WeakerAccess") /* synthetic access */
final Drawable mVerticalTrackDrawable;
private final int mVerticalThumbWidth;
private final int mVerticalTrackWidth;
// Final values for the horizontal scroll bar
private final StateListDrawable mHorizontalThumbDrawable;
private final Drawable mHorizontalTrackDrawable;
private final int mHorizontalThumbHeight;
private final int mHorizontalTrackHeight;
// Dynamic values for the vertical scroll bar
@VisibleForTesting int mVerticalThumbHeight;
@VisibleForTesting int mVerticalThumbCenterY;
@VisibleForTesting float mVerticalDragY;
// Dynamic values for the horizontal scroll bar
@VisibleForTesting int mHorizontalThumbWidth;
@VisibleForTesting int mHorizontalThumbCenterX;
@VisibleForTesting float mHorizontalDragX;
private int mRecyclerViewWidth = 0;
private int mRecyclerViewHeight = 0;
private RecyclerView mRecyclerView;
/**
* Whether the document is long/wide enough to require scrolling. If not, we don't show the
* relevant scroller.
*/
private boolean mNeedVerticalScrollbar = false;
private boolean mNeedHorizontalScrollbar = false;
@State private int mState = STATE_HIDDEN;
@DragState private int mDragState = DRAG_NONE;
private final int[] mVerticalRange = new int[2];
private final int[] mHorizontalRange = new int[2];
@SuppressWarnings("WeakerAccess") /* synthetic access */
final ValueAnimator mShowHideAnimator = ValueAnimator.ofFloat(0, 1);
@SuppressWarnings("WeakerAccess") /* synthetic access */
@AnimationState int mAnimationState = ANIMATION_STATE_OUT;
private final Runnable mHideRunnable = new Runnable() {
@Override
public void run() {
hide(HIDE_DURATION_MS);
}
};
private final RecyclerView.OnScrollListener
mOnScrollListener = new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
updateScrollPosition(recyclerView.computeHorizontalScrollOffset(),
recyclerView.computeVerticalScrollOffset());
}
};
FastScroller(RecyclerView recyclerView, StateListDrawable verticalThumbDrawable,
Drawable verticalTrackDrawable, StateListDrawable horizontalThumbDrawable,
Drawable horizontalTrackDrawable, int defaultWidth, int scrollbarMinimumRange,
int margin) {
mVerticalThumbDrawable = verticalThumbDrawable;
mVerticalTrackDrawable = verticalTrackDrawable;
mHorizontalThumbDrawable = horizontalThumbDrawable;
mHorizontalTrackDrawable = horizontalTrackDrawable;
mVerticalThumbWidth = Math.max(defaultWidth, verticalThumbDrawable.getIntrinsicWidth());
mVerticalTrackWidth = Math.max(defaultWidth, verticalTrackDrawable.getIntrinsicWidth());
mHorizontalThumbHeight = Math
.max(defaultWidth, horizontalThumbDrawable.getIntrinsicWidth());
mHorizontalTrackHeight = Math
.max(defaultWidth, horizontalTrackDrawable.getIntrinsicWidth());
mScrollbarMinimumRange = scrollbarMinimumRange;
mMargin = margin;
mVerticalThumbDrawable.setAlpha(SCROLLBAR_FULL_OPAQUE);
mVerticalTrackDrawable.setAlpha(SCROLLBAR_FULL_OPAQUE);
mShowHideAnimator.addListener(new AnimatorListener());
mShowHideAnimator.addUpdateListener(new AnimatorUpdater());
attachToRecyclerView(recyclerView);
}
public void attachToRecyclerView(@Nullable RecyclerView recyclerView) {
if (mRecyclerView == recyclerView) {
return; // nothing to do
}
if (mRecyclerView != null) {
destroyCallbacks();
}
mRecyclerView = recyclerView;
if (mRecyclerView != null) {
setupCallbacks();
}
}
private void setupCallbacks() {
mRecyclerView.addItemDecoration(this);
mRecyclerView.addOnItemTouchListener(this);
mRecyclerView.addOnScrollListener(mOnScrollListener);
}
private void destroyCallbacks() {
mRecyclerView.removeItemDecoration(this);
mRecyclerView.removeOnItemTouchListener(this);
mRecyclerView.removeOnScrollListener(mOnScrollListener);
cancelHide();
}
@SuppressWarnings("WeakerAccess") /* synthetic access */
void requestRedraw() {
mRecyclerView.invalidate();
}
void setState(@State int state) {
if (state == STATE_DRAGGING && mState != STATE_DRAGGING) {
mVerticalThumbDrawable.setState(PRESSED_STATE_SET);
cancelHide();
}
if (state == STATE_HIDDEN) {
requestRedraw();
} else {
show();
}
if (mState == STATE_DRAGGING && state != STATE_DRAGGING) {
mVerticalThumbDrawable.setState(EMPTY_STATE_SET);
resetHideDelay(HIDE_DELAY_AFTER_DRAGGING_MS);
} else if (state == STATE_VISIBLE) {
resetHideDelay(HIDE_DELAY_AFTER_VISIBLE_MS);
}
mState = state;
}
private boolean isLayoutRTL() {
return ViewCompat.getLayoutDirection(mRecyclerView) == ViewCompat.LAYOUT_DIRECTION_RTL;
}
public boolean isDragging() {
return mState == STATE_DRAGGING;
}
@VisibleForTesting boolean isVisible() {
return mState == STATE_VISIBLE;
}
public void show() {
switch (mAnimationState) {
case ANIMATION_STATE_FADING_OUT:
mShowHideAnimator.cancel();
// fall through
case ANIMATION_STATE_OUT:
mAnimationState = ANIMATION_STATE_FADING_IN;
mShowHideAnimator.setFloatValues((float) mShowHideAnimator.getAnimatedValue(), 1);
mShowHideAnimator.setDuration(SHOW_DURATION_MS);
mShowHideAnimator.setStartDelay(0);
mShowHideAnimator.start();
break;
}
}
@VisibleForTesting
void hide(int duration) {
switch (mAnimationState) {
case ANIMATION_STATE_FADING_IN:
mShowHideAnimator.cancel();
// fall through
case ANIMATION_STATE_IN:
mAnimationState = ANIMATION_STATE_FADING_OUT;
mShowHideAnimator.setFloatValues((float) mShowHideAnimator.getAnimatedValue(), 0);
mShowHideAnimator.setDuration(duration);
mShowHideAnimator.start();
break;
}
}
private void cancelHide() {
mRecyclerView.removeCallbacks(mHideRunnable);
}
private void resetHideDelay(int delay) {
cancelHide();
mRecyclerView.postDelayed(mHideRunnable, delay);
}
@Override
public void onDrawOver(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
if (mRecyclerViewWidth != mRecyclerView.getWidth()
|| mRecyclerViewHeight != mRecyclerView.getHeight()) {
mRecyclerViewWidth = mRecyclerView.getWidth();
mRecyclerViewHeight = mRecyclerView.getHeight();
// This is due to the different events ordering when keyboard is opened or
// retracted vs rotate. Hence to avoid corner cases we just disable the
// scroller when size changed, and wait until the scroll position is recomputed
// before showing it back.
setState(STATE_HIDDEN);
return;
}
if (mAnimationState != ANIMATION_STATE_OUT) {
if (mNeedVerticalScrollbar) {
drawVerticalScrollbar(canvas);
}
if (mNeedHorizontalScrollbar) {
drawHorizontalScrollbar(canvas);
}
}
}
private void drawVerticalScrollbar(Canvas canvas) {
int viewWidth = mRecyclerViewWidth;
int left = viewWidth - mVerticalThumbWidth;
int top = mVerticalThumbCenterY - mVerticalThumbHeight / 2;
mVerticalThumbDrawable.setBounds(0, 0, mVerticalThumbWidth, mVerticalThumbHeight);
mVerticalTrackDrawable
.setBounds(0, 0, mVerticalTrackWidth, mRecyclerViewHeight);
if (isLayoutRTL()) {
mVerticalTrackDrawable.draw(canvas);
canvas.translate(mVerticalThumbWidth, top);
canvas.scale(-1, 1);
mVerticalThumbDrawable.draw(canvas);
canvas.scale(-1, 1);
canvas.translate(-mVerticalThumbWidth, -top);
} else {
canvas.translate(left, 0);
mVerticalTrackDrawable.draw(canvas);
canvas.translate(0, top);
mVerticalThumbDrawable.draw(canvas);
canvas.translate(-left, -top);
}
}
private void drawHorizontalScrollbar(Canvas canvas) {
int viewHeight = mRecyclerViewHeight;
int top = viewHeight - mHorizontalThumbHeight;
int left = mHorizontalThumbCenterX - mHorizontalThumbWidth / 2;
mHorizontalThumbDrawable.setBounds(0, 0, mHorizontalThumbWidth, mHorizontalThumbHeight);
mHorizontalTrackDrawable
.setBounds(0, 0, mRecyclerViewWidth, mHorizontalTrackHeight);
canvas.translate(0, top);
mHorizontalTrackDrawable.draw(canvas);
canvas.translate(left, 0);
mHorizontalThumbDrawable.draw(canvas);
canvas.translate(-left, -top);
}
/**
* Notify the scroller of external change of the scroll, e.g. through dragging or flinging on
* the view itself.
*
* @param offsetX The new scroll X offset.
* @param offsetY The new scroll Y offset.
*/
void updateScrollPosition(int offsetX, int offsetY) {
int verticalContentLength = mRecyclerView.computeVerticalScrollRange();
int verticalVisibleLength = mRecyclerViewHeight;
mNeedVerticalScrollbar = verticalContentLength - verticalVisibleLength > 0
&& mRecyclerViewHeight >= mScrollbarMinimumRange;
int horizontalContentLength = mRecyclerView.computeHorizontalScrollRange();
int horizontalVisibleLength = mRecyclerViewWidth;
mNeedHorizontalScrollbar = horizontalContentLength - horizontalVisibleLength > 0
&& mRecyclerViewWidth >= mScrollbarMinimumRange;
if (!mNeedVerticalScrollbar && !mNeedHorizontalScrollbar) {
if (mState != STATE_HIDDEN) {
setState(STATE_HIDDEN);
}
return;
}
if (mNeedVerticalScrollbar) {
float middleScreenPos = offsetY + verticalVisibleLength / 2.0f;
mVerticalThumbCenterY =
(int) ((verticalVisibleLength * middleScreenPos) / verticalContentLength);
mVerticalThumbHeight = Math.min(verticalVisibleLength,
(verticalVisibleLength * verticalVisibleLength) / verticalContentLength);
}
if (mNeedHorizontalScrollbar) {
float middleScreenPos = offsetX + horizontalVisibleLength / 2.0f;
mHorizontalThumbCenterX =
(int) ((horizontalVisibleLength * middleScreenPos) / horizontalContentLength);
mHorizontalThumbWidth = Math.min(horizontalVisibleLength,
(horizontalVisibleLength * horizontalVisibleLength) / horizontalContentLength);
}
if (mState == STATE_HIDDEN || mState == STATE_VISIBLE) {
setState(STATE_VISIBLE);
}
}
@Override
public boolean onInterceptTouchEvent(@NonNull RecyclerView recyclerView,
@NonNull MotionEvent ev) {
final boolean handled;
if (mState == STATE_VISIBLE) {
boolean insideVerticalThumb = isPointInsideVerticalThumb(ev.getX(), ev.getY());
boolean insideHorizontalThumb = isPointInsideHorizontalThumb(ev.getX(), ev.getY());
if (ev.getAction() == MotionEvent.ACTION_DOWN
&& (insideVerticalThumb || insideHorizontalThumb)) {
if (insideHorizontalThumb) {
mDragState = DRAG_X;
mHorizontalDragX = (int) ev.getX();
} else if (insideVerticalThumb) {
mDragState = DRAG_Y;
mVerticalDragY = (int) ev.getY();
}
setState(STATE_DRAGGING);
handled = true;
} else {
handled = false;
}
} else if (mState == STATE_DRAGGING) {
handled = true;
} else {
handled = false;
}
return handled;
}
@Override
public void onTouchEvent(@NonNull RecyclerView recyclerView, @NonNull MotionEvent me) {
if (mState == STATE_HIDDEN) {
return;
}
if (me.getAction() == MotionEvent.ACTION_DOWN) {
boolean insideVerticalThumb = isPointInsideVerticalThumb(me.getX(), me.getY());
boolean insideHorizontalThumb = isPointInsideHorizontalThumb(me.getX(), me.getY());
if (insideVerticalThumb || insideHorizontalThumb) {
if (insideHorizontalThumb) {
mDragState = DRAG_X;
mHorizontalDragX = (int) me.getX();
} else if (insideVerticalThumb) {
mDragState = DRAG_Y;
mVerticalDragY = (int) me.getY();
}
setState(STATE_DRAGGING);
}
} else if (me.getAction() == MotionEvent.ACTION_UP && mState == STATE_DRAGGING) {
mVerticalDragY = 0;
mHorizontalDragX = 0;
setState(STATE_VISIBLE);
mDragState = DRAG_NONE;
} else if (me.getAction() == MotionEvent.ACTION_MOVE && mState == STATE_DRAGGING) {
show();
if (mDragState == DRAG_X) {
horizontalScrollTo(me.getX());
}
if (mDragState == DRAG_Y) {
verticalScrollTo(me.getY());
}
}
}
@Override
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) { }
private void verticalScrollTo(float y) {
final int[] scrollbarRange = getVerticalRange();
y = Math.max(scrollbarRange[0], Math.min(scrollbarRange[1], y));
if (Math.abs(mVerticalThumbCenterY - y) < 2) {
return;
}
int scrollingBy = scrollTo(mVerticalDragY, y, scrollbarRange,
mRecyclerView.computeVerticalScrollRange(),
mRecyclerView.computeVerticalScrollOffset(), mRecyclerViewHeight);
if (scrollingBy != 0) {
mRecyclerView.scrollBy(0, scrollingBy);
}
mVerticalDragY = y;
}
private void horizontalScrollTo(float x) {
final int[] scrollbarRange = getHorizontalRange();
x = Math.max(scrollbarRange[0], Math.min(scrollbarRange[1], x));
if (Math.abs(mHorizontalThumbCenterX - x) < 2) {
return;
}
int scrollingBy = scrollTo(mHorizontalDragX, x, scrollbarRange,
mRecyclerView.computeHorizontalScrollRange(),
mRecyclerView.computeHorizontalScrollOffset(), mRecyclerViewWidth);
if (scrollingBy != 0) {
mRecyclerView.scrollBy(scrollingBy, 0);
}
mHorizontalDragX = x;
}
private int scrollTo(float oldDragPos, float newDragPos, int[] scrollbarRange, int scrollRange,
int scrollOffset, int viewLength) {
int scrollbarLength = scrollbarRange[1] - scrollbarRange[0];
if (scrollbarLength == 0) {
return 0;
}
float percentage = ((newDragPos - oldDragPos) / (float) scrollbarLength);
int totalPossibleOffset = scrollRange - viewLength;
int scrollingBy = (int) (percentage * totalPossibleOffset);
int absoluteOffset = scrollOffset + scrollingBy;
if (absoluteOffset < totalPossibleOffset && absoluteOffset >= 0) {
return scrollingBy;
} else {
return 0;
}
}
@VisibleForTesting
boolean isPointInsideVerticalThumb(float x, float y) {
return (isLayoutRTL() ? x <= mVerticalThumbWidth
: x >= mRecyclerViewWidth - mVerticalThumbWidth)
&& y >= mVerticalThumbCenterY - mVerticalThumbHeight / 2
&& y <= mVerticalThumbCenterY + mVerticalThumbHeight / 2;
}
@VisibleForTesting
boolean isPointInsideHorizontalThumb(float x, float y) {
return (y >= mRecyclerViewHeight - mHorizontalThumbHeight)
&& x >= mHorizontalThumbCenterX - mHorizontalThumbWidth / 2
&& x <= mHorizontalThumbCenterX + mHorizontalThumbWidth / 2;
}
@VisibleForTesting
Drawable getHorizontalTrackDrawable() {
return mHorizontalTrackDrawable;
}
@VisibleForTesting
Drawable getHorizontalThumbDrawable() {
return mHorizontalThumbDrawable;
}
@VisibleForTesting
Drawable getVerticalTrackDrawable() {
return mVerticalTrackDrawable;
}
@VisibleForTesting
Drawable getVerticalThumbDrawable() {
return mVerticalThumbDrawable;
}
/**
* Gets the (min, max) vertical positions of the vertical scroll bar.
*/
private int[] getVerticalRange() {
mVerticalRange[0] = mMargin;
mVerticalRange[1] = mRecyclerViewHeight - mMargin;
return mVerticalRange;
}
/**
* Gets the (min, max) horizontal positions of the horizontal scroll bar.
*/
private int[] getHorizontalRange() {
mHorizontalRange[0] = mMargin;
mHorizontalRange[1] = mRecyclerViewWidth - mMargin;
return mHorizontalRange;
}
private class AnimatorListener extends AnimatorListenerAdapter {
private boolean mCanceled = false;
AnimatorListener() {
}
@Override
public void onAnimationEnd(Animator animation) {
// Cancel is always followed by a new directive, so don't update state.
if (mCanceled) {
mCanceled = false;
return;
}
if ((float) mShowHideAnimator.getAnimatedValue() == 0) {
mAnimationState = ANIMATION_STATE_OUT;
setState(STATE_HIDDEN);
} else {
mAnimationState = ANIMATION_STATE_IN;
requestRedraw();
}
}
@Override
public void onAnimationCancel(Animator animation) {
mCanceled = true;
}
}
private class AnimatorUpdater implements AnimatorUpdateListener {
AnimatorUpdater() {
}
@Override
public void onAnimationUpdate(ValueAnimator valueAnimator) {
int alpha = (int) (SCROLLBAR_FULL_OPAQUE * ((float) valueAnimator.getAnimatedValue()));
mVerticalThumbDrawable.setAlpha(alpha);
mVerticalTrackDrawable.setAlpha(alpha);
requestRedraw();
}
}
}Android官方快滑/快速滚动条源代码链接地址：
https://android.googlesource.com/platform/frameworks/support/+/androidx-main/recyclerview/recyclerview/src/main/java/androidx/recyclerview/widget/FastScroller.java