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      1 /*
      2  * Copyright (C) 2016 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 android.support.design.internal;
     18 
     19 import android.content.Context;
     20 import android.util.AttributeSet;
     21 import android.view.View;
     22 import android.view.ViewGroup;
     23 
     24 /**
     25  * A simple ViewGroup that aligns all the views inside on a baseline. Note: bottom padding for this
     26  * view will be measured starting from the baseline.
     27  *
     28  * @hide
     29  */
     30 public class BaselineLayout extends ViewGroup {
     31     private int mBaseline = -1;
     32 
     33     public BaselineLayout(Context context) {
     34         super(context, null, 0);
     35     }
     36 
     37     public BaselineLayout(Context context, AttributeSet attrs) {
     38         super(context, attrs, 0);
     39     }
     40 
     41     public BaselineLayout(Context context, AttributeSet attrs, int defStyleAttr) {
     42         super(context, attrs, defStyleAttr);
     43     }
     44 
     45     @Override
     46     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     47         final int count = getChildCount();
     48         int maxWidth = 0;
     49         int maxHeight = 0;
     50         int maxChildBaseline = -1;
     51         int maxChildDescent = -1;
     52         int childState = 0;
     53 
     54         for (int i = 0; i < count; i++) {
     55             final View child = getChildAt(i);
     56             if (child.getVisibility() == GONE) {
     57                 continue;
     58             }
     59 
     60             measureChild(child, widthMeasureSpec, heightMeasureSpec);
     61             final int baseline = child.getBaseline();
     62             if (baseline != -1) {
     63                 maxChildBaseline = Math.max(maxChildBaseline, baseline);
     64                 maxChildDescent = Math.max(maxChildDescent, child.getMeasuredHeight() - baseline);
     65             }
     66             maxWidth = Math.max(maxWidth, child.getMeasuredWidth());
     67             maxHeight = Math.max(maxHeight, child.getMeasuredHeight());
     68             childState = View.combineMeasuredStates(childState, child.getMeasuredState());
     69         }
     70         if (maxChildBaseline != -1) {
     71             maxChildDescent = Math.max(maxChildDescent, getPaddingBottom());
     72             maxHeight = Math.max(maxHeight, maxChildBaseline + maxChildDescent);
     73             mBaseline = maxChildBaseline;
     74         }
     75         maxHeight = Math.max(maxHeight, getSuggestedMinimumHeight());
     76         maxWidth = Math.max(maxWidth, getSuggestedMinimumWidth());
     77         setMeasuredDimension(
     78                 View.resolveSizeAndState(maxWidth, widthMeasureSpec, childState),
     79                 View.resolveSizeAndState(maxHeight, heightMeasureSpec,
     80                         childState << MEASURED_HEIGHT_STATE_SHIFT));
     81     }
     82 
     83     @Override
     84     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
     85         final int count = getChildCount();
     86         final int parentLeft = getPaddingLeft();
     87         final int parentRight = right - left - getPaddingRight();
     88         final int parentContentWidth = parentRight - parentLeft;
     89         final int parentTop = getPaddingTop();
     90 
     91         for (int i = 0; i < count; i++) {
     92             final View child = getChildAt(i);
     93             if (child.getVisibility() == GONE) {
     94                 continue;
     95             }
     96 
     97             final int width = child.getMeasuredWidth();
     98             final int height = child.getMeasuredHeight();
     99 
    100             final int childLeft = parentLeft + (parentContentWidth - width) / 2;
    101             final int childTop;
    102             if (mBaseline != -1 && child.getBaseline() != -1) {
    103                 childTop = parentTop + mBaseline - child.getBaseline();
    104             } else {
    105                 childTop = parentTop;
    106             }
    107 
    108             child.layout(childLeft, childTop, childLeft + width, childTop + height);
    109         }
    110     }
    111 
    112     @Override
    113     public int getBaseline() {
    114         return mBaseline;
    115     }
    116 }
    117