ScrollBarView.java revision 2b3ee0ea07246b859a5b75d8a6102a7cce7ec838 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.gallery3d.ui;
18
19import android.content.Context;
20import android.graphics.Rect;
21import android.util.TypedValue;
22
23public class ScrollBarView extends GLView {
24    @SuppressWarnings("unused")
25    private static final String TAG = "ScrollBarView";
26
27    private int mBarHeight;
28
29    private int mGripHeight;
30    private int mGripPosition;  // left side of the grip
31    private int mGripWidth;     // zero if the grip is disabled
32    private int mGivenGripWidth;
33
34    private int mContentPosition;
35    private int mContentTotal;
36
37    private NinePatchTexture mScrollBarTexture;
38
39    public ScrollBarView(Context context, int gripHeight, int gripWidth) {
40        TypedValue outValue = new TypedValue();
41        context.getTheme().resolveAttribute(
42                android.R.attr.scrollbarThumbHorizontal, outValue, true);
43        mScrollBarTexture = new NinePatchTexture(
44                context, outValue.resourceId);
45        mGripPosition = 0;
46        mGripWidth = 0;
47        mGivenGripWidth = gripWidth;
48        mGripHeight = gripHeight;
49    }
50
51    @Override
52    protected void onLayout(
53            boolean changed, int left, int top, int right, int bottom) {
54        if (!changed) return;
55        mBarHeight = bottom - top;
56    }
57
58    // The content position is between 0 to "total". The current position is
59    // in "position".
60    public void setContentPosition(int position, int total) {
61        if (position == mContentPosition && total == mContentTotal) {
62            return;
63        }
64
65        invalidate();
66
67        mContentPosition = position;
68        mContentTotal = total;
69
70        // If the grip cannot move, don't draw it.
71        if (mContentTotal <= 0) {
72            mGripPosition = 0;
73            mGripWidth = 0;
74            return;
75        }
76
77        // Map from the content range to scroll bar range.
78        //
79        // mContentTotal --> getWidth() - mGripWidth
80        // mContentPosition --> mGripPosition
81        mGripWidth = mGivenGripWidth;
82        float r = (getWidth() - mGripWidth) / (float) mContentTotal;
83        mGripPosition = Math.round(r * mContentPosition);
84    }
85
86    @Override
87    protected void render(GLCanvas canvas) {
88        super.render(canvas);
89        if (mGripWidth == 0) return;
90        Rect b = bounds();
91        int y = (mBarHeight - mGripHeight) / 2;
92        mScrollBarTexture.draw(canvas, mGripPosition, y, mGripWidth, mGripHeight);
93    }
94}
95