问题

I followed this documentation: https://developer.android.com/training/transitions/start-activity#java .

First, I will show you my implementation. You will find my question at the end of this post.

Thus, I modified 4 files:

fade.xml, which defines the duration of the fade in transition.

<?xml version="1.0" encoding="utf-8"?>
<transitionSet xmlns:android="http://schemas.android.com/apk/res/android">
    <fade android:fadingMode="fade_in" android:duration="3000" />
</transitionSet>

values/styles.xml, which defines the windowEnterTransition thanks to fade.xml. Note that MainActivity's parent, AppTheme, has Material as parent.

<!-- Base application theme. -->
<style name="AppTheme" parent="android:Theme.Material">
    <!-- Customize your theme here. -->
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>

    <item name="android:windowActivityTransitions">true</item>
</style>

<style name="AppTheme.NoActionBar">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
</style>

<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />

<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />

<style name="MainActivityTheme" parent="AppTheme">
    <item name="android:windowEnterTransition">@transition/fade</item>
</style>

Since I created this new theme "MainActivityTheme", I also modified the Android Manifest to specify this new theme to this activity:

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity"
        android:theme="@style/MainActivityTheme">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Finally, I have set the enter transition in MainActivity.java:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getWindow().setEnterTransition(new Fade(Fade.IN));
    setContentView(R.layout.activity_main);
}

Emulator and Gradle build

build.gradle (Module: app)

apply plugin: 'com.android.application'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.example.."
        minSdkVersion 21
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.android.support:support-v4:27.1.1'
    implementation 'com.android.support:design:27.1.1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

Emulator

The version of Android installed within the emulator is: 5.1.1 (cf. "About phone" in the settings of Android, in the emulator).

Question

However, when I launch my application, the main activity's UI doesn't fade in. Do you know why ? In other words: Why the XML specified transition isn't executed? (or why its specified duration isn't taken account?)

I also tried to move <item name="android:windowActivityTransitions">true</item> from the theme MainActivityTheme (file: styles.xml) to the theme AppTheme (file: the same, i.e.: styles.xml). But it didn't fix this bug.

回答1:

Try This I hope its Work

Activity transitions in material design apps provide visual connections between different states through motion and transformations between common elements. You can specify custom animations for enter and exit transitions and for transitions of shared elements between activities.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);
    setContentView(R.layout.activity_main);
}

Also Read This Question This May helps You WindowEnterTransition Not Affecting Activity Transition

来源：https://stackoverflow.com/questions/52237312/why-the-xml-specified-transition-isnt-executed-or-why-its-specified-duration

标签

android

android-transitions