TwsScrollBarDrawable.java

package com.tencent.tws.assistant.drawable;

import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.Log;
import android.widget.ScrollBarDrawable;

import com.tencent.tws.assistant.utils.ReflectUtils;

public class TwsScrollBarDrawable extends ScrollBarDrawable {
	private static final String TAG = "com.tencent.tws.assistant.drawable.TwsScrollBarDrawable";

	private int twsViewLength, twsViewStart, twsViewEnd;

	public void twsSetParameters(int viewLength, int viewStart, int viewEnd) {
		Log.d(TAG, "twsSetParameters|len=" + viewLength + "startt=" + viewStart + ",end=" + viewEnd);

		twsViewLength = viewLength;
		twsViewStart = viewStart;
		twsViewEnd = viewEnd;
	}

	protected void twsDrawThumb(Canvas canvas, Rect bounds, int offset, int length, boolean vertical) {
		try {
			final Rect thumbRect = (Rect) getField("mTempBounds");
			final boolean changed = (Boolean) getField("mRangeChanged") || (Boolean) getField("mChanged");
			if (changed) {
				if (vertical) {
					if (twsViewLength == 0)
						twsViewLength = 1;
					float factor = ((float) (offset + length) / (float) twsViewLength) > 1.0f ? 1.0f
							: ((float) (offset + length) / (float) twsViewLength);
					thumbRect.set(bounds.left, bounds.top + offset
							+ ((int) ((0 - twsViewStart - twsViewEnd) * factor + twsViewStart)), bounds.right,
							bounds.top + offset + ((int) ((0 - twsViewStart - twsViewEnd) * factor + twsViewStart))
									+ length);
				} else {
					thumbRect.set(bounds.left + offset, bounds.top, bounds.left + offset + length, bounds.bottom);
				}
			}

			if (vertical) {
				final Drawable thumb = (Drawable) getField("mVerticalThumb");
				if (changed)
					thumb.setBounds(thumbRect);
				thumb.draw(canvas);
			} else {
				final Drawable thumb = (Drawable) getField("mHorizontalThumb");
				if (changed)
					thumb.setBounds(thumbRect);
				thumb.draw(canvas);
			}
		} catch (Exception e) {
			Log.e(TAG, "twsDrawThumb|exp:" + e.getMessage());
		}
	}

	@Override
	public void draw(Canvas canvas) {
		final boolean vertical = (Boolean) getField("mVertical");
		final int extent = (Integer) getField("mExtent");
		final int range = (Integer) getField("mRange");

		boolean drawTrack = true;
		boolean drawThumb = true;
		if (extent <= 0 || range <= extent) {
			drawTrack = vertical ? (Boolean) getField("mAlwaysDrawVerticalTrack")
					: (Boolean) getField("mAlwaysDrawHorizontalTrack");
			drawThumb = false;
		}

		Rect r = getBounds();
		if (canvas.quickReject(r.left, r.top, r.right, r.bottom, Canvas.EdgeType.AA)) {
			return;
		}
		if (drawTrack) {
			drawTrack(canvas, r, vertical);
		}

		if (drawThumb) {
			int size = vertical ? r.height() : r.width();
			int thickness = vertical ? r.width() : r.height();
			int length = Math.round((float) size * extent / range);
			int offset = Math.round((float) (size - length) * (Integer) getField("mOffset") / (range - extent));

			// avoid the tiny thumb
			int minLength = thickness * 2;
			if (length < minLength) {
				length = minLength;
			}
			// avoid the too-big thumb
			if (offset + length > size) {
				offset = size - length;
			}

			// tws-start recalculate scroll params::2015-1-9
			twsDrawThumb(canvas, r, offset, length, vertical);
			// tws-end recalculate scroll params::2015-1-9
		}
	}

	private Object getField(String fieldName) {
		Object value = null;
		try {
			Class<?> clz = ReflectUtils.forClassName("android.widget.ScrollBarDrawable");
			value = ReflectUtils.getFieldValue(fieldName, this, clz);
		} catch (Exception e) {
			Log.e(TAG, "twsSetParameters exp:" + e.getMessage());
		}

		return value;
	}
}