Home | History | Annotate | Download | only in list 
      1 /*
      2  * Copyright (C) 2014 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.contacts.common.list;
     18 
     19 import android.content.Context;
     20 import android.content.res.Resources;
     21 import android.graphics.Canvas;
     22 import android.graphics.Paint;
     23 import android.util.AttributeSet;
     24 import android.view.View;
     25 import android.widget.LinearLayout;
     26 
     27 import com.android.contacts.common.R;
     28 
     29 public class ViewPagerTabStrip extends LinearLayout {
     30     private int mSelectedUnderlineThickness;
     31     private final Paint mSelectedUnderlinePaint;
     32 
     33     private int mIndexForSelection;
     34     private float mSelectionOffset;
     35 
     36     public ViewPagerTabStrip(Context context) {
     37         this(context, null);
     38     }
     39 
     40     public ViewPagerTabStrip(Context context, AttributeSet attrs) {
     41         super(context, attrs);
     42 
     43         final Resources res = context.getResources();
     44 
     45         mSelectedUnderlineThickness =
     46                 res.getDimensionPixelSize(R.dimen.tab_selected_underline_height);
     47         int underlineColor = res.getColor(R.color.tab_selected_underline_color);
     48         int backgroundColor = res.getColor(R.color.actionbar_background_color);
     49 
     50         mSelectedUnderlinePaint = new Paint();
     51         mSelectedUnderlinePaint.setColor(underlineColor);
     52 
     53         setBackgroundColor(backgroundColor);
     54         setWillNotDraw(false);
     55     }
     56 
     57     /**
     58      * Notifies this view that view pager has been scrolled. We save the tab index
     59      * and selection offset for interpolating the position and width of selection
     60      * underline.
     61      */
     62     void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
     63         mIndexForSelection = position;
     64         mSelectionOffset = positionOffset;
     65         invalidate();
     66     }
     67 
     68     @Override
     69     protected void onDraw(Canvas canvas) {
     70         int childCount = getChildCount();
     71 
     72         // Thick colored underline below the current selection
     73         if (childCount > 0) {
     74             View selectedTitle = getChildAt(mIndexForSelection);
     75             int selectedLeft = selectedTitle.getLeft();
     76             int selectedRight = selectedTitle.getRight();
     77             final boolean isRtl = isRtl();
     78             final boolean hasNextTab = isRtl ? mIndexForSelection > 0
     79                     : (mIndexForSelection < (getChildCount() - 1));
     80             if ((mSelectionOffset > 0.0f) && hasNextTab) {
     81                 // Draw the selection partway between the tabs
     82                 View nextTitle = getChildAt(mIndexForSelection + (isRtl ? -1 : 1));
     83                 int nextLeft = nextTitle.getLeft();
     84                 int nextRight = nextTitle.getRight();
     85 
     86                 selectedLeft = (int) (mSelectionOffset * nextLeft +
     87                         (1.0f - mSelectionOffset) * selectedLeft);
     88                 selectedRight = (int) (mSelectionOffset * nextRight +
     89                         (1.0f - mSelectionOffset) * selectedRight);
     90             }
     91 
     92             int height = getHeight();
     93             canvas.drawRect(selectedLeft, height - mSelectedUnderlineThickness,
     94                     selectedRight, height, mSelectedUnderlinePaint);
     95         }
     96     }
     97 
     98     private boolean isRtl() {
     99         return getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
    100     }
    101 }