1 /*
2  * Copyright (C) 2020 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.systemui.util.animation
18 
19 import android.annotation.SuppressLint
20 import android.content.Context
21 import android.view.View
22 import android.view.ViewGroup
23 import android.widget.FrameLayout
24 import com.android.systemui.res.R
25 
26 /**
27  * A special view that is designed to host a single "unique object". The unique object is
28  * dynamically added and removed from this view and may transition to other UniqueObjectHostViews
29  * available in the system.
30  * This is useful to share a singular instance of a view that can transition between completely
31  * independent parts of the view hierarchy.
32  * If the view currently hosts the unique object, it's measuring it normally,
33  * but if it's not attached, it will obtain the size by requesting a measure, as if it were
34  * always attached.
35  */
36 class UniqueObjectHostView(
37     context: Context
38 ) : FrameLayout(context) {
39     lateinit var measurementManager: MeasurementManager
40 
41     @SuppressLint("DrawAllocation")
onMeasurenull42     override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
43         val paddingHorizontal = paddingStart + paddingEnd
44         val paddingVertical = paddingTop + paddingBottom
45         val width = MeasureSpec.getSize(widthMeasureSpec) - paddingHorizontal
46         val widthSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.getMode(widthMeasureSpec))
47         val height = MeasureSpec.getSize(heightMeasureSpec) - paddingVertical
48         val heightSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.getMode(heightMeasureSpec))
49         val measurementInput = MeasurementInput(widthSpec, heightSpec)
50 
51         // Let's make sure the measurementManager knows about our size, to ensure that we have
52         // a value available. This might perform a measure internally if we don't have a cached
53         // size.
54         val (cachedWidth, cachedHeight) = measurementManager.onMeasure(measurementInput)
55 
56         if (isCurrentHost()) {
57             super.onMeasure(widthMeasureSpec, heightMeasureSpec)
58             getChildAt(0)?.requiresRemeasuring = false
59         }
60         // The goal here is that the view will always have a consistent measuring, regardless
61         // if it's attached or not.
62         // The behavior is therefore very similar to the view being persistently attached to
63         // this host, which can prevent flickers. It also makes sure that we always know
64         // the size of the view during transitions even if it has never been attached here
65         // before.
66         // We previously still measured the size when the view was attached, but this doesn't
67         // work properly because we can set the measuredState while still attached to the
68         // old host, which will trigger an inconsistency in height
69         setMeasuredDimension(cachedWidth + paddingHorizontal, cachedHeight + paddingVertical)
70     }
71 
addViewnull72     override fun addView(child: View?, index: Int, params: ViewGroup.LayoutParams?) {
73         if (child == null) {
74             throw IllegalArgumentException("child must be non-null")
75         }
76         if (child.measuredWidth == 0 || measuredWidth == 0 || child.requiresRemeasuring == true) {
77             super.addView(child, index, params)
78             return
79         }
80         // Suppress layouts when adding a view. The view should already be laid out with the
81         // right size when being attached to this view
82         invalidate()
83         addViewInLayout(child, index, params, true /* preventRequestLayout */)
84         // RTL properties are normally resolved in onMeasure(), which we are intentionally skipping
85         child.resolveRtlPropertiesIfNeeded()
86         val left = paddingLeft
87         val top = paddingTop
88         val paddingHorizontal = paddingStart + paddingEnd
89         val paddingVertical = paddingTop + paddingBottom
90         child.layout(left,
91                 top,
92                 left + measuredWidth - paddingHorizontal,
93                 top + measuredHeight - paddingVertical)
94     }
95 
isCurrentHostnull96     private fun isCurrentHost() = childCount != 0
97 
98     interface MeasurementManager {
99         fun onMeasure(input: MeasurementInput): MeasurementOutput
100     }
101 }
102 
103 /**
104  * Does this view require remeasuring currently outside of the regular measure flow?
105  */
106 var View.requiresRemeasuring: Boolean
107     get() {
108         val required = getTag(R.id.requires_remeasuring)
109         return required?.equals(true) ?: false
110     }
111     set(value) {
112         setTag(R.id.requires_remeasuring, value)
113     }
114