Android Open Source - muzei Scrollbar

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License

The source code is released under:
Apache License
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Java Source Code

/*
 * Copyright 2014 Google Inc.// ww w.  j a v a2  s  .c  o m
 *
 * 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 com.google.android.apps.muzei.util;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.View;

import net.nurik.roman.muzei.R;

public class Scrollbar extends View {
    private boolean mHidden = true;

    private final int mAnimationDuration;

    private int mIndicatorColor = 0xff000000;
    private int mBackgroundColor = 0x80000000;

    private float mIndicatorWidth;
    private Paint mBackgroundPaint;
    private Paint mIndicatorPaint;

    private Path mTempPath = new Path();
    private RectF mTempRectF = new RectF();

    private int mWidth;
    private int mHeight;

    private int mScrollRange;
    private int mViewportWidth;
    private float mPosition;

    public Scrollbar(Context context) {
        this(context, null, 0);
    }

    public Scrollbar(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public Scrollbar(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        mAnimationDuration = getResources().getInteger(android.R.integer.config_shortAnimTime);

        final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.Scrollbar);
        mBackgroundColor = a.getColor(R.styleable.Scrollbar_backgroundColor, mBackgroundColor);
        mIndicatorColor = a.getColor(R.styleable.Scrollbar_indicatorColor, mIndicatorColor);
        a.recycle();

        mBackgroundPaint = new Paint();
        mBackgroundPaint.setColor(mBackgroundColor);
        mBackgroundPaint.setAntiAlias(true);

        mIndicatorPaint = new Paint();
        mIndicatorPaint.setColor(mIndicatorColor);
        mIndicatorPaint.setAntiAlias(true);

        setAlpha(0);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (mScrollRange <= mViewportWidth) {
            return;
        }

        mTempRectF.top = 0;
        mTempRectF.bottom = mHeight;
        mTempRectF.left = 0;
        mTempRectF.right = mWidth;

        drawPill(canvas, mTempRectF, mBackgroundPaint);

        mTempRectF.top = 0;
        mTempRectF.bottom = mHeight;
        mTempRectF.left = mPosition * 1f / (mScrollRange - mViewportWidth)
                * mWidth * (1 - mIndicatorWidth);
        mTempRectF.right = mTempRectF.left + mIndicatorWidth * mWidth;

        drawPill(canvas, mTempRectF, mIndicatorPaint);
    }

    private void drawPill(Canvas canvas, RectF rectF, Paint paint) {
        float radius = rectF.height() / 2;
        float temp;

        mTempPath.reset();
        mTempPath.moveTo(rectF.left + radius, rectF.top);
        mTempPath.lineTo(rectF.right - radius, rectF.top);

        temp = rectF.left;
        rectF.left = rectF.right - 2 * radius;
        mTempPath.arcTo(rectF, 270, 180);
        rectF.left = temp;

        mTempPath.lineTo(rectF.left + radius, rectF.bottom);

        temp = rectF.right;
        rectF.right = rectF.left + rectF.height();
        mTempPath.arcTo(rectF, 90, 180);
        rectF.right = temp;

        mTempPath.close();
        canvas.drawPath(mTempPath, paint);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        setMeasuredDimension(
                View.resolveSize(0, widthMeasureSpec),
                View.resolveSize(0, heightMeasureSpec));
    }

    public void setScrollPosition(int position) {
        mPosition = MathUtil.constrain(0, mScrollRange, position);
        postInvalidateOnAnimation();
    }

    public void setScrollRangeAndViewportWidth(int scrollRange, int viewportWidth) {
        mScrollRange = scrollRange;
        mViewportWidth = viewportWidth;
        mIndicatorWidth = 0.1f;
        if (mScrollRange > 0) {
            mIndicatorWidth = MathUtil.constrain(mIndicatorWidth, 1f,
                    mViewportWidth * 1f / mScrollRange);
        }
        postInvalidateOnAnimation();
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mHeight = h;
        mWidth = w;
    }

    public void show() {
        if (!mHidden) {
            return;
        }

        mHidden = false;
        animate().cancel();
        animate().alpha(1f).setDuration(mAnimationDuration);
    }

    public void hide() {
        if (mHidden) {
            return;
        }

        mHidden = true;
        animate().cancel();
        animate().alpha(0f).setDuration(mAnimationDuration);
    }
}
Java Source Code List
