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      1 /*
      2  * Copyright (C) 2017 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.setupwizardlib.view;
     18 
     19 import android.content.Context;
     20 import android.content.res.TypedArray;
     21 import android.util.AttributeSet;
     22 import android.view.View;
     23 import android.widget.FrameLayout;
     24 
     25 import com.android.setupwizardlib.R;
     26 
     27 /**
     28  * A layout that will measure its children size based on the space it is given, by using its
     29  * {@code android:minWidth}, {@code android:minHeight}, {@code android:maxWidth}, and
     30  * {@code android:maxHeight} values.
     31  *
     32  * <p>Typically this is used to show an illustration image or video on the screen. For optimal UX,
     33  * those assets typically want to occupy the remaining space available on screen within a certain
     34  * range, and then stop scaling beyond the min/max size attributes. Therefore this view is typically
     35  * used inside a ScrollView with {@code fillViewport} set to true, together with a linear layout
     36  * weight or relative layout to fill the remaining space visible on screen.
     37  *
     38  * <p>When measuring, this view ignores its children and simply layout according to the minWidth /
     39  * minHeight given. Therefore it is common for children of this layout to have width / height set to
     40  * {@code match_parent}. The maxWidth / maxHeight values will then be applied to the children to
     41  * make sure they are not too big.
     42  */
     43 public class FillContentLayout extends FrameLayout {
     44 
     45     private int mMaxWidth;
     46     private int mMaxHeight;
     47 
     48     public FillContentLayout(Context context) {
     49         this(context, null);
     50     }
     51 
     52     public FillContentLayout(Context context, AttributeSet attrs) {
     53         this(context, attrs, R.attr.suwFillContentLayoutStyle);
     54     }
     55 
     56     public FillContentLayout(Context context, AttributeSet attrs, int defStyleAttr) {
     57         super(context, attrs, defStyleAttr);
     58         init(context, attrs, defStyleAttr);
     59     }
     60 
     61     private void init(Context context, AttributeSet attrs, int defStyleAttr) {
     62         TypedArray a = context.obtainStyledAttributes(
     63                 attrs,
     64                 R.styleable.SuwFillContentLayout,
     65                 defStyleAttr,
     66                 0);
     67 
     68         mMaxHeight = a.getDimensionPixelSize(
     69                 R.styleable.SuwFillContentLayout_android_maxHeight, -1);
     70         mMaxWidth = a.getDimensionPixelSize(R.styleable.SuwFillContentLayout_android_maxWidth, -1);
     71 
     72         a.recycle();
     73     }
     74 
     75     @Override
     76     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     77         // Measure this view with the minWidth and minHeight, without asking the children.
     78         // (Children size is the drawable's intrinsic size, and we don't want that to influence
     79         // the size of the illustration).
     80         setMeasuredDimension(
     81                 getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),
     82                 getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));
     83 
     84         int childCount = getChildCount();
     85         for (int i = 0; i < childCount; i++) {
     86             measureIllustrationChild(getChildAt(i), getMeasuredWidth(), getMeasuredHeight());
     87         }
     88     }
     89 
     90     private void measureIllustrationChild(View child, int parentWidth, int parentHeight) {
     91         // Modified from ViewGroup#measureChildWithMargins
     92         final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
     93 
     94         // Create measure specs that are no bigger than min(parentSize, maxSize)
     95 
     96         int childWidthMeasureSpec = getMaxSizeMeasureSpec(
     97                 Math.min(mMaxWidth, parentWidth),
     98                 getPaddingLeft() + getPaddingRight() + lp.leftMargin + lp.rightMargin,
     99                 lp.width);
    100         int childHeightMeasureSpec = getMaxSizeMeasureSpec(
    101                 Math.min(mMaxHeight, parentHeight),
    102                 getPaddingTop() + getPaddingBottom() + lp.topMargin + lp.bottomMargin,
    103                 lp.height);
    104 
    105         child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
    106     }
    107 
    108     private static int getMaxSizeMeasureSpec(int maxSize, int padding, int childDimension) {
    109         // Modified from ViewGroup#getChildMeasureSpec
    110         int size = Math.max(0, maxSize - padding);
    111 
    112         if (childDimension >= 0) {
    113             // Child wants a specific size... so be it
    114             return MeasureSpec.makeMeasureSpec(childDimension, MeasureSpec.EXACTLY);
    115         } else if (childDimension == LayoutParams.MATCH_PARENT) {
    116             // Child wants to be our size. So be it.
    117             return MeasureSpec.makeMeasureSpec(size, MeasureSpec.EXACTLY);
    118         } else if (childDimension == LayoutParams.WRAP_CONTENT) {
    119             // Child wants to determine its own size. It can't be
    120             // bigger than us.
    121             return MeasureSpec.makeMeasureSpec(size, MeasureSpec.AT_MOST);
    122         }
    123         return 0;
    124     }
    125 }
    126