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Merge pull request android#5 from android/loading
List > Loading
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‎Motion/app/build.gradle

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@@ -56,7 +56,7 @@ dependencies {
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implementation 'androidx.appcompat:appcompat:1.1.0-rc01'
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implementation 'androidx.transition:transition:1.2.0-beta01'
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implementation 'androidx.dynamicanimation:dynamicanimation:1.1.0-alpha02'
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implementation 'androidx.recyclerview:recyclerview:1.1.0-beta02'
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implementation 'androidx.recyclerview:recyclerview:1.1.0-beta03'
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implementation 'androidx.constraintlayout:constraintlayout:2.0.0-beta2'
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@@ -65,6 +65,9 @@ dependencies {
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implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
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implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
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def paging_version = '2.1.0'
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implementation "androidx.paging:paging-runtime-ktx:$paging_version"
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implementation 'com.google.android.material:material:1.1.0-alpha09'
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implementation "androidx.navigation:navigation-fragment-ktx:$navigation_version"

‎Motion/app/src/main/AndroidManifest.xml

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@@ -117,6 +117,22 @@
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android:resource="@array/stagger_apis" />
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</activity>
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<activity
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android:name=".demo.loading.LoadingActivity"
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android:label="@string/loading_label">
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<intent-filter>
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<action android:name="android.intent.action.MAIN" />
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<category android:name="com.example.android.motion.intent.category.DEMO" />
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</intent-filter>
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<meta-data
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android:name="com.example.android.motion.demo.DESCRIPTION"
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android:value="@string/loading_description" />
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<meta-data
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android:name="com.example.android.motion.demo.APIS"
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android:resource="@array/loading_apis" />
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</activity>
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<activity
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android:name=".demo.oscillation.OscillationActivity"
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android:label="@string/oscillation_label"

‎Motion/app/src/main/java/com/example/android/motion/demo/loading/CheeseAdapter.kt

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/*
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* Copyright 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.android.motion.demo.loading
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import android.animation.ObjectAnimator
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import android.os.SystemClock
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import android.view.LayoutInflater
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import android.view.View
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import android.view.ViewGroup
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import android.widget.ImageView
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import android.widget.TextView
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import androidx.core.animation.doOnEnd
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import androidx.paging.PagedListAdapter
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import androidx.recyclerview.widget.RecyclerView
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import com.bumptech.glide.Glide
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import com.bumptech.glide.load.resource.bitmap.CircleCrop
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import com.example.android.motion.R
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import com.example.android.motion.model.Cheese
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internal class CheeseAdapter : PagedListAdapter<Cheese, CheeseViewHolder>(Cheese.DIFF_CALLBACK) {
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override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CheeseViewHolder {
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return CheeseViewHolder(parent)
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}
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override fun onBindViewHolder(holder: CheeseViewHolder, position: Int) {
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val cheese: Cheese? = getItem(position)
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if (cheese == null) {
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holder.showPlaceholder()
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} else {
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holder.bind(cheese)
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}
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}
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}
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/**
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* A dummy adapter that shows placeholders.
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*/
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internal class PlaceholderAdapter : RecyclerView.Adapter<CheeseViewHolder>() {
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override fun getItemCount(): Int {
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return Int.MAX_VALUE
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}
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override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CheeseViewHolder {
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return CheeseViewHolder(parent)
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}
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override fun onBindViewHolder(holder: CheeseViewHolder, position: Int) {
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// We have to call this method in onBindVH rather than onCreateVH because it uses the
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// adapterPosition of the ViewHolder.
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holder.showPlaceholder()
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}
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}
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private const val FADE_DURATION = 1000L
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internal class CheeseViewHolder(parent: ViewGroup) : RecyclerView.ViewHolder(
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LayoutInflater.from(parent.context).inflate(R.layout.cheese_list_item, parent, false)
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) {
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val image: ImageView = itemView.findViewById(R.id.image)
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val name: TextView = itemView.findViewById(R.id.name)
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/**
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* This is the animation we apply to each of the list items. It animates the alpha value from 1
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* to 0, then back to 1. The animation repeats infinitely until it is manually ended.
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*/
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private val animation = ObjectAnimator.ofFloat(itemView, View.ALPHA, 1f, 0f, 1f).apply {
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repeatCount = ObjectAnimator.INFINITE
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duration = FADE_DURATION
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// Reset the alpha on animation end.
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doOnEnd { itemView.alpha = 1f }
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}
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fun showPlaceholder() {
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// Shift the timing of fade-in/out for each item by its adapter position. We use the
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// elapsed real time to make this independent from the timing of method call.
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animation.currentPlayTime =
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(SystemClock.elapsedRealtime() - adapterPosition * 30L) % FADE_DURATION
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animation.start()
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// Show the placeholder UI.
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image.setImageResource(R.drawable.image_placeholder)
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name.text = null
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name.setBackgroundResource(R.drawable.text_placeholder)
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}
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fun bind(cheese: Cheese) {
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animation.end()
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Glide.with(image).load(cheese.image).transform(CircleCrop()).into(image)
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name.text = cheese.name
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name.setBackgroundResource(0)
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}
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}

‎Motion/app/src/main/java/com/example/android/motion/demo/loading/CheeseDataSource.kt

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/*
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* Copyright 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.android.motion.demo.loading
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import android.os.SystemClock
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import androidx.paging.DataSource
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import androidx.paging.PositionalDataSource
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import com.example.android.motion.model.Cheese
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class CheeseDataSource : PositionalDataSource<Cheese>() {
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companion object Factory : DataSource.Factory<Int, Cheese>() {
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override fun create(): DataSource<Int, Cheese> = CheeseDataSource()
28+
}
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override fun loadInitial(params: LoadInitialParams, callback: LoadInitialCallback<Cheese>) {
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// Simulate a slow network.
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SystemClock.sleep(3000L)
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callback.onResult(
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Cheese.ALL.subList(
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params.requestedStartPosition,
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params.requestedStartPosition + params.requestedLoadSize
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),
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params.requestedStartPosition,
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Cheese.ALL.size
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)
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}
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override fun loadRange(params: LoadRangeParams, callback: LoadRangeCallback<Cheese>) {
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// Simulate a slow network.
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SystemClock.sleep(3000L)
46+
callback.onResult(
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Cheese.ALL.subList(
48+
params.startPosition, params.startPosition + params.loadSize
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)
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)
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}
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}

‎Motion/app/src/main/java/com/example/android/motion/demo/loading/LoadingActivity.kt

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/*
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* Copyright 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
8+
* http://www.apache.org/licenses/LICENSE-2.0
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*
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+
*/
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package com.example.android.motion.demo.loading
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import android.os.Bundle
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import android.view.Menu
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import android.view.MenuItem
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import androidx.activity.viewModels
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import androidx.appcompat.app.AppCompatActivity
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import androidx.appcompat.widget.Toolbar
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import androidx.lifecycle.observe
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import androidx.recyclerview.widget.RecyclerView
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import androidx.transition.Fade
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import androidx.transition.Transition
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import androidx.transition.TransitionListenerAdapter
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import androidx.transition.TransitionManager
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import com.example.android.motion.R
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import com.example.android.motion.demo.FAST_OUT_SLOW_IN
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import com.example.android.motion.demo.LARGE_EXPAND_DURATION
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import com.example.android.motion.demo.plusAssign
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import com.example.android.motion.demo.transitionSequential
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import com.example.android.motion.ui.EdgeToEdge
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/**
39+
* Shows a list of cheeses. We use the Paging Library to load the list.
40+
*/
41+
class LoadingActivity : AppCompatActivity() {
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private val viewModel: LoadingViewModel by viewModels()
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private lateinit var list: RecyclerView
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private val fade = transitionSequential {
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duration = LARGE_EXPAND_DURATION
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interpolator = FAST_OUT_SLOW_IN
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this += Fade(Fade.OUT)
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this += Fade(Fade.IN)
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addListener(object : TransitionListenerAdapter() {
52+
override fun onTransitionEnd(transition: Transition) {
53+
if (savedItemAnimator != null) {
54+
list.itemAnimator = savedItemAnimator
55+
}
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}
57+
})
58+
}
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60+
private val placeholderAdapter = PlaceholderAdapter()
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private val cheeseAdapter = CheeseAdapter()
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private var savedItemAnimator: RecyclerView.ItemAnimator? = null
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override fun onCreate(savedInstanceState: Bundle?) {
66+
super.onCreate(savedInstanceState)
67+
setContentView(R.layout.loading_activity)
68+
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val toolbar: Toolbar = findViewById(R.id.toolbar)
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list = findViewById(R.id.list)
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setSupportActionBar(toolbar)
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EdgeToEdge.setUpRoot(findViewById(R.id.coordinator))
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EdgeToEdge.setUpAppBar(findViewById(R.id.app_bar), toolbar)
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EdgeToEdge.setUpScrollingContent(list)
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// Show the initial placeholders.
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// See the ViewHolder implementation for how to create the loading animation.
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list.adapter = placeholderAdapter
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viewModel.cheeses.observe(this) { cheeses ->
80+
if (list.adapter != cheeseAdapter) {
81+
list.adapter = cheeseAdapter
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savedItemAnimator = list.itemAnimator
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list.itemAnimator = null
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TransitionManager.beginDelayedTransition(list, fade)
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}
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cheeseAdapter.submitList(cheeses)
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}
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}
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override fun onCreateOptionsMenu(menu: Menu?): Boolean {
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menuInflater.inflate(R.menu.loading, menu)
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return super.onCreateOptionsMenu(menu)
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}
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override fun onOptionsItemSelected(item: MenuItem): Boolean {
96+
return when (item.itemId) {
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R.id.action_refresh -> {
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TransitionManager.beginDelayedTransition(list, fade)
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list.adapter = placeholderAdapter
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viewModel.refresh()
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true
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}
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else -> super.onOptionsItemSelected(item)
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}
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}
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}

‎Motion/app/src/main/java/com/example/android/motion/demo/loading/LoadingViewModel.kt

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/*
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* Copyright 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
8+
* http://www.apache.org/licenses/LICENSE-2.0
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*
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+
*/
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package com.example.android.motion.demo.loading
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import androidx.lifecycle.LiveData
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import androidx.lifecycle.MediatorLiveData
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import androidx.lifecycle.ViewModel
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import androidx.paging.PagedList
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import androidx.paging.toLiveData
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import com.example.android.motion.model.Cheese
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class LoadingViewModel : ViewModel() {
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private var source: LiveData<PagedList<Cheese>>? = null
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private val _cheeses = MediatorLiveData<PagedList<Cheese>>()
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val cheeses: LiveData<PagedList<Cheese>> = _cheeses
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init {
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refresh()
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}
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fun refresh() {
37+
source?.let { _cheeses.removeSource(it) }
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val s = CheeseDataSource.toLiveData(pageSize = 15)
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source = s
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_cheeses.addSource(s) { _cheeses.postValue(it) }
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}
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}

‎Motion/app/src/main/res/drawable/image_placeholder.xml

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<?xml version="1.0" encoding="utf-8"?>
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<!--
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~ Copyright 2019 The Android Open Source Project
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~
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~ Licensed under the Apache License, Version 2.0 (the "License");
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~ you may not use this file except in compliance with the License.
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~ You may obtain a copy of the License at
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~
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~ http://www.apache.org/licenses/LICENSE-2.0
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~
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~ Unless required by applicable law or agreed to in writing, software
12+
~ distributed under the License is distributed on an "AS IS" BASIS,
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~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14+
~ See the License for the specific language governing permissions and
15+
~ limitations under the License.
16+
-->
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<shape
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xmlns:android="http://schemas.android.com/apk/res/android"
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android:shape="oval">
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<solid android:color="@color/card_background" />
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</shape>

‎Motion/app/src/main/res/drawable/text_placeholder.xml

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<?xml version="1.0" encoding="utf-8"?>
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<!--
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~ Copyright 2019 The Android Open Source Project
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~
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~ Licensed under the Apache License, Version 2.0 (the "License");
6+
~ you may not use this file except in compliance with the License.
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~ You may obtain a copy of the License at
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~
9+
~ http://www.apache.org/licenses/LICENSE-2.0
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~
11+
~ Unless required by applicable law or agreed to in writing, software
12+
~ distributed under the License is distributed on an "AS IS" BASIS,
13+
~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14+
~ See the License for the specific language governing permissions and
15+
~ limitations under the License.
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-->
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<shape
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xmlns:android="http://schemas.android.com/apk/res/android"
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android:shape="rectangle">
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<size android:width="160dp" />
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<solid android:color="@color/card_background" />
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</shape>

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