1/*
2 * Copyright (C) 2015 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.internal.widget;
18
19import android.content.Context;
20import android.content.res.TypedArray;
21import android.util.AttributeSet;
22import android.view.Gravity;
23import android.view.View;
24import android.widget.LinearLayout;
25
26import com.android.internal.R;
27
28/**
29 * An extension of LinearLayout that automatically switches to vertical
30 * orientation when it can't fit its child views horizontally.
31 */
32public class ButtonBarLayout extends LinearLayout {
33    /** Minimum screen height required for button stacking. */
34    private static final int ALLOW_STACKING_MIN_HEIGHT_DP = 320;
35
36    /** Amount of the second button to "peek" above the fold when stacked. */
37    private static final int PEEK_BUTTON_DP = 16;
38
39    /** Whether the current configuration allows stacking. */
40    private boolean mAllowStacking;
41
42    private int mLastWidthSize = -1;
43
44    private int mMinimumHeight = 0;
45
46    public ButtonBarLayout(Context context, AttributeSet attrs) {
47        super(context, attrs);
48
49        final boolean allowStackingDefault =
50                context.getResources().getConfiguration().screenHeightDp
51                        >= ALLOW_STACKING_MIN_HEIGHT_DP;
52        final TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ButtonBarLayout);
53        mAllowStacking = ta.getBoolean(R.styleable.ButtonBarLayout_allowStacking,
54                allowStackingDefault);
55        ta.recycle();
56    }
57
58    public void setAllowStacking(boolean allowStacking) {
59        if (mAllowStacking != allowStacking) {
60            mAllowStacking = allowStacking;
61            if (!mAllowStacking && getOrientation() == LinearLayout.VERTICAL) {
62                setStacked(false);
63            }
64            requestLayout();
65        }
66    }
67
68    @Override
69    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
70        final int widthSize = MeasureSpec.getSize(widthMeasureSpec);
71
72        if (mAllowStacking) {
73            if (widthSize > mLastWidthSize && isStacked()) {
74                // We're being measured wider this time, try un-stacking.
75                setStacked(false);
76            }
77
78            mLastWidthSize = widthSize;
79        }
80
81        boolean needsRemeasure = false;
82
83        // If we're not stacked, make sure the measure spec is AT_MOST rather
84        // than EXACTLY. This ensures that we'll still get TOO_SMALL so that we
85        // know to stack the buttons.
86        final int initialWidthMeasureSpec;
87        if (!isStacked() && MeasureSpec.getMode(widthMeasureSpec) == MeasureSpec.EXACTLY) {
88            initialWidthMeasureSpec = MeasureSpec.makeMeasureSpec(widthSize, MeasureSpec.AT_MOST);
89
90            // We'll need to remeasure again to fill excess space.
91            needsRemeasure = true;
92        } else {
93            initialWidthMeasureSpec = widthMeasureSpec;
94        }
95
96        super.onMeasure(initialWidthMeasureSpec, heightMeasureSpec);
97
98        if (mAllowStacking && !isStacked()) {
99            final int measuredWidth = getMeasuredWidthAndState();
100            final int measuredWidthState = measuredWidth & MEASURED_STATE_MASK;
101            if (measuredWidthState == MEASURED_STATE_TOO_SMALL) {
102                setStacked(true);
103
104                // Measure again in the new orientation.
105                needsRemeasure = true;
106            }
107        }
108
109        if (needsRemeasure) {
110            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
111        }
112
113        // Compute minimum height such that, when stacked, some portion of the
114        // second button is visible.
115        int minHeight = 0;
116        final int firstVisible = getNextVisibleChildIndex(0);
117        if (firstVisible >= 0) {
118            final View firstButton = getChildAt(firstVisible);
119            final LayoutParams firstParams = (LayoutParams) firstButton.getLayoutParams();
120            minHeight += getPaddingTop() + firstButton.getMeasuredHeight()
121                    + firstParams.topMargin + firstParams.bottomMargin;
122            if (isStacked()) {
123                final int secondVisible = getNextVisibleChildIndex(firstVisible + 1);
124                if (secondVisible >= 0) {
125                    minHeight += getChildAt(secondVisible).getPaddingTop()
126                            + PEEK_BUTTON_DP * getResources().getDisplayMetrics().density;
127                }
128            } else {
129                minHeight += getPaddingBottom();
130            }
131        }
132
133        if (getMinimumHeight() != minHeight) {
134            setMinimumHeight(minHeight);
135        }
136    }
137
138    private int getNextVisibleChildIndex(int index) {
139        for (int i = index, count = getChildCount(); i < count; i++) {
140            if (getChildAt(i).getVisibility() == View.VISIBLE) {
141                return i;
142            }
143        }
144        return -1;
145    }
146
147    @Override
148    public int getMinimumHeight() {
149        return Math.max(mMinimumHeight, super.getMinimumHeight());
150    }
151
152    private void setStacked(boolean stacked) {
153        setOrientation(stacked ? LinearLayout.VERTICAL : LinearLayout.HORIZONTAL);
154        setGravity(stacked ? Gravity.RIGHT : Gravity.BOTTOM);
155
156        final View spacer = findViewById(R.id.spacer);
157        if (spacer != null) {
158            spacer.setVisibility(stacked ? View.GONE : View.INVISIBLE);
159        }
160
161        // Reverse the child order. This is specific to the Material button
162        // bar's layout XML and will probably not generalize.
163        final int childCount = getChildCount();
164        for (int i = childCount - 2; i >= 0; i--) {
165            bringChildToFront(getChildAt(i));
166        }
167    }
168
169    private boolean isStacked() {
170        return getOrientation() == LinearLayout.VERTICAL;
171    }
172}
173