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      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 
     17 package com.android.gallery3d.ui;
     18 
     19 import android.content.Context;
     20 import android.graphics.Rect;
     21 import android.util.TypedValue;
     22 
     23 import com.android.gallery3d.glrenderer.GLCanvas;
     24 import com.android.gallery3d.glrenderer.NinePatchTexture;
     25 
     26 public class ScrollBarView extends GLView {
     27     @SuppressWarnings("unused")
     28     private static final String TAG = "ScrollBarView";
     29 
     30     private int mBarHeight;
     31 
     32     private int mGripHeight;
     33     private int mGripPosition;  // left side of the grip
     34     private int mGripWidth;     // zero if the grip is disabled
     35     private int mGivenGripWidth;
     36 
     37     private int mContentPosition;
     38     private int mContentTotal;
     39 
     40     private NinePatchTexture mScrollBarTexture;
     41 
     42     public ScrollBarView(Context context, int gripHeight, int gripWidth) {
     43         TypedValue outValue = new TypedValue();
     44         context.getTheme().resolveAttribute(
     45                 android.R.attr.scrollbarThumbHorizontal, outValue, true);
     46         mScrollBarTexture = new NinePatchTexture(
     47                 context, outValue.resourceId);
     48         mGripPosition = 0;
     49         mGripWidth = 0;
     50         mGivenGripWidth = gripWidth;
     51         mGripHeight = gripHeight;
     52     }
     53 
     54     @Override
     55     protected void onLayout(
     56             boolean changed, int left, int top, int right, int bottom) {
     57         if (!changed) return;
     58         mBarHeight = bottom - top;
     59     }
     60 
     61     // The content position is between 0 to "total". The current position is
     62     // in "position".
     63     public void setContentPosition(int position, int total) {
     64         if (position == mContentPosition && total == mContentTotal) {
     65             return;
     66         }
     67 
     68         invalidate();
     69 
     70         mContentPosition = position;
     71         mContentTotal = total;
     72 
     73         // If the grip cannot move, don't draw it.
     74         if (mContentTotal <= 0) {
     75             mGripPosition = 0;
     76             mGripWidth = 0;
     77             return;
     78         }
     79 
     80         // Map from the content range to scroll bar range.
     81         //
     82         // mContentTotal --> getWidth() - mGripWidth
     83         // mContentPosition --> mGripPosition
     84         mGripWidth = mGivenGripWidth;
     85         float r = (getWidth() - mGripWidth) / (float) mContentTotal;
     86         mGripPosition = Math.round(r * mContentPosition);
     87     }
     88 
     89     @Override
     90     protected void render(GLCanvas canvas) {
     91         super.render(canvas);
     92         if (mGripWidth == 0) return;
     93         Rect b = bounds();
     94         int y = (mBarHeight - mGripHeight) / 2;
     95         mScrollBarTexture.draw(canvas, mGripPosition, y, mGripWidth, mGripHeight);
     96     }
     97 }
     98