Android：加载片段时开始动画

Question

I've trying to implement custom fragment with loading animation. Same code works fine with activity, but not works with fragment.

Here my fragment layout code:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="pw.osin.musicexpert.fragments.BusyFragment">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/fragment_animation_logo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginBottom="20dp"
        android:background="@drawable/vinyl" />

    <FrameLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="20dp"
        android:background="@color/colorPrimaryDark">

        <TextView
            android:id="@+id/fragment_animation_description"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="16dp"
            android:gravity="center_horizontal"
            android:text="@string/message_data_is_loading"
            android:textColor="@color/colorPrimaryYellow"
            android:textSize="20dp"
            android:textStyle="bold" />
    </FrameLayout>

</LinearLayout>

My methods which I invokes in OnCreate method in fragment

private fun setAnimation() {
    Log.i(TAG, "Установка анимации")
    val drawable = AnimationUtils.loadAnimation(this.context, R.anim.rotate_anim)
    mAnimationDescription?.setText(R.string.message_data_is_loading);
    mAnimationImage?.startAnimation(drawable)
}

private fun initViewItems(view: View?) {
    Log.i(TAG, "Поиск элементов View")
    mAnimationDescription = view?.findView<TextView>(R.id.animation_description);
    mAnimationImage = view?.findView<ImageView>(R.id.animation_logo);
}

My rotate animation code:

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <rotate
        android:duration="2000"
        android:fromDegrees="0"
        android:pivotX="50%"
        android:pivotY="50%"
        android:repeatCount="infinite"
        android:startOffset="0"
        android:toDegrees="360" />
</set>

Here I attach my animation fragment to activity in OnCreate method

private var mTransaction: FragmentTransaction? = null

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    attachFragment()
}

private fun attachFragment() {
    mTransaction = supportFragmentManager.beginTransaction()
    mTransaction?.add(R.id.main_activity_container, BusyFragment.newInstance("Получаем дату"))
    mTransaction?.commit()
}

Where I need to invoke my start animation method?

Thanks.

Answer 1

From the documentation of onResume :

Called when the fragment is visible to the user and actively running. This is generally tied to Activity.onResume of the containing Activity's lifecycle.

You want to run the animation when it can be visible in the first place, hence I suggest starting the animation in your fragment's onResume or override the onFragmentsResumed method in the activity that this fragment is attached to.