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/*
* Copyright (C) 2016 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.view;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
/**
* Helper class for drawing round scroll bars on round Wear devices.
*/
class RoundScrollbarRenderer {
// The range of the scrollbar position represented as an angle in degrees.
private static final int SCROLLBAR_ANGLE_RANGE = 90;
private static final int MAX_SCROLLBAR_ANGLE_SWIPE = 16;
private static final int MIN_SCROLLBAR_ANGLE_SWIPE = 6;
private static final float WIDTH_PERCENTAGE = 0.02f;
private static final int DEFAULT_THUMB_COLOR = 0xFFE8EAED;
private static final int DEFAULT_TRACK_COLOR = 0x4CFFFFFF;
private final Paint mThumbPaint = new Paint();
private final Paint mTrackPaint = new Paint();
private final RectF mRect = new RectF();
private final View mParent;
private final int mMaskThickness;
public RoundScrollbarRenderer(View parent) {
// Paints for the round scrollbar.
// Set up the thumb paint
mThumbPaint.setAntiAlias(true);
mThumbPaint.setStrokeCap(Paint.Cap.ROUND);
mThumbPaint.setStyle(Paint.Style.STROKE);
// Set up the track paint
mTrackPaint.setAntiAlias(true);
mTrackPaint.setStrokeCap(Paint.Cap.ROUND);
mTrackPaint.setStyle(Paint.Style.STROKE);
mParent = parent;
// Fetch the resource indicating the thickness of CircularDisplayMask, rounding in the same
// way WindowManagerService.showCircularMask does. The scroll bar is inset by this amount so
// that it doesn't get clipped.
mMaskThickness = parent.getContext().getResources().getDimensionPixelSize(
com.android.internal.R.dimen.circular_display_mask_thickness);
}
public void drawRoundScrollbars(Canvas canvas, float alpha, Rect bounds) {
if (alpha == 0) {
return;
}
// Get information about the current scroll state of the parent view.
float maxScroll = mParent.computeVerticalScrollRange();
float scrollExtent = mParent.computeVerticalScrollExtent();
if (scrollExtent <= 0 || maxScroll <= scrollExtent) {
return;
}
float currentScroll = Math.max(0, mParent.computeVerticalScrollOffset());
float linearThumbLength = mParent.computeVerticalScrollExtent();
float thumbWidth = mParent.getWidth() * WIDTH_PERCENTAGE;
mThumbPaint.setStrokeWidth(thumbWidth);
mTrackPaint.setStrokeWidth(thumbWidth);
setThumbColor(applyAlpha(DEFAULT_THUMB_COLOR, alpha));
setTrackColor(applyAlpha(DEFAULT_TRACK_COLOR, alpha));
// Normalize the sweep angle for the scroll bar.
float sweepAngle = (linearThumbLength / maxScroll) * SCROLLBAR_ANGLE_RANGE;
sweepAngle = clamp(sweepAngle, MIN_SCROLLBAR_ANGLE_SWIPE, MAX_SCROLLBAR_ANGLE_SWIPE);
// Normalize the start angle so that it falls on the track.
float startAngle = (currentScroll * (SCROLLBAR_ANGLE_RANGE - sweepAngle))
/ (maxScroll - linearThumbLength) - SCROLLBAR_ANGLE_RANGE / 2;
startAngle = clamp(startAngle, -SCROLLBAR_ANGLE_RANGE / 2,
SCROLLBAR_ANGLE_RANGE / 2 - sweepAngle);
// Draw the track and the thumb.
float inset = thumbWidth / 2 + mMaskThickness;
mRect.set(
bounds.left + inset,
bounds.top + inset,
bounds.right - inset,
bounds.bottom - inset);
canvas.drawArc(mRect, -SCROLLBAR_ANGLE_RANGE / 2, SCROLLBAR_ANGLE_RANGE, false,
mTrackPaint);
canvas.drawArc(mRect, startAngle, sweepAngle, false, mThumbPaint);
}
private static float clamp(float val, float min, float max) {
if (val < min) {
return min;
} else if (val > max) {
return max;
} else {
return val;
}
}
private static int applyAlpha(int color, float alpha) {
int alphaByte = (int) (Color.alpha(color) * alpha);
return Color.argb(alphaByte, Color.red(color), Color.green(color), Color.blue(color));
}
private void setThumbColor(int thumbColor) {
if (mThumbPaint.getColor() != thumbColor) {
mThumbPaint.setColor(thumbColor);
}
}
private void setTrackColor(int trackColor) {
if (mTrackPaint.getColor() != trackColor) {
mTrackPaint.setColor(trackColor);
}
}
}
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