使用动画显示或隐藏视图

试用 Compose 方式

Jetpack Compose 是推荐在 Android 设备上使用的界面工具包。了解如何在 Compose 中使用动画。

<ph type="x-smartling-placeholder"></ph> 淡入淡出 →

在使用应用的过程中，屏幕上会显示新信息以及旧信息 信息。你可以立即更改屏幕上显示的内容 令人不悦，并且用户可能会错过突然出现的新内容。动画播放速度缓慢 向下移动并用运动吸引用户的注意力 更加明显

注意 ：Jetpack Compose 是构建 Android 的首选方式 。请参阅 Compose 动画文档。

有三种常见的动画可用于显示或隐藏视图：显示 动画、淡入淡出动画和卡片翻转动画

创建淡入淡出动画

淡入淡出动画（也称为渐隐）会逐渐淡出 一个 View 或 ViewGroup（同时启用） 慢慢地淡入另一个此动画适合在以下情形下 切换内容或视图。此处显示的淡入淡出动画使用了 ViewPropertyAnimator、 适用于 Android 3.1（API 级别 12）及更高版本。

以下是从进度指示器切换到文本内容的淡入淡出示例：

<ph type="x-smartling-placeholder">

图 1.淡入淡出动画。

创建视图

创建两个您想要淡入淡出的视图。以下示例创建了一个 进度指示器和可滚动文本视图：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView style="?android:textAppearanceMedium"
            android:lineSpacingMultiplier="1.2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/lorem_ipsum"
            android:padding="16dp" />

    </ScrollView>

    <ProgressBar android:id="@+id/loading_spinner"
        style="?android:progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center" />

</FrameLayout>

设置淡入淡出动画

如需设置淡入淡出动画，请执行以下操作：

1. 为想要淡入淡出的视图创建成员变量。您需要 这些引用。
2. 将淡入视图的可见性设置为 GONE。这会阻止视图 并将其从布局计算中省略， 正在处理
3. 缓存 config_shortAnimTime 系统属性。该属性定义了一个标准的“简短” 动画时长该时长非常适合用于精细动画或 频繁出现的动画效果 config_longAnimTime 和 config_mediumAnimTime 。

以下示例使用上一个代码段中的布局作为 活动内容视图：

Kotlin

class CrossfadeActivity : Activity() {

    private lateinit var contentView: View
    private lateinit var loadingView: View
    private var shortAnimationDuration: Int = 0
    ...
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_crossfade)

        contentView = findViewById(R.id.content)
        loadingView = findViewById(R.id.loading_spinner)

        // Initially hide the content view.
        contentView.visibility = View.GONE

        // Retrieve and cache the system's default "short" animation time.
        shortAnimationDuration = resources.getInteger(android.R.integer.config_shortAnimTime)
    }
    ...
}

Java

public class CrossfadeActivity extends Activity {

    private View contentView;
    private View loadingView;
    private int shortAnimationDuration;
    ...
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_crossfade);

        contentView = findViewById(R.id.content);
        loadingView = findViewById(R.id.loading_spinner);

        // Initially hide the content view.
        contentView.setVisibility(View.GONE);

        // Retrieve and cache the system's default "short" animation time.
        shortAnimationDuration = getResources().getInteger(
                android.R.integer.config_shortAnimTime);
    }
    ...
}

淡入淡出视图

正确设置视图后，可通过执行以下操作实现淡入淡出：

1. 对于淡入的视图，请将 alpha 值设置为 0，并将可见性设置为 从初始值更改为 VISIBLE 设置为 GONE。这会使视图可见但处于透明状态。
2. 对于淡入的视图，以动画形式呈现其 0 到 1 的 Alpha 值。对于 视图，以动画方式将 alpha 值从 1 到 0。
3. 使用 onAnimationEnd() 以 Animator.AnimatorListener, 将淡出视图的可见性设置为 GONE。虽然 alpha 值为 0，将视图的可见性设置为 GONE 会阻止视图 并将其从布局计算中省略， 处理。

以下方法通过示例说明了如何执行此操作：

Kotlin

class CrossfadeActivity : Activity() {

    private lateinit var contentView: View
    private lateinit var loadingView: View
    private var shortAnimationDuration: Int = 0
    ...
    private fun crossfade() {
        contentView.apply {
            // Set the content view to 0% opacity but visible, so that it is
            // visible but fully transparent during the animation.
            alpha = 0f
            visibility = View.VISIBLE

            // Animate the content view to 100% opacity and clear any animation
            // listener set on the view.
            animate()
                    .alpha(1f)
                    .setDuration(shortAnimationDuration.toLong())
                    .setListener(null)
        }
        // Animate the loading view to 0% opacity. After the animation ends,
        // set its visibility to GONE as an optimization step so it doesn't
        // participate in layout passes.
        loadingView.animate()
                .alpha(0f)
                .setDuration(shortAnimationDuration.toLong())
                .setListener(object : AnimatorListenerAdapter() {
                    override fun onAnimationEnd(animation: Animator) {
                        loadingView.visibility = View.GONE
                    }
                })
    }
}

Java

public class CrossfadeActivity extends Activity {

    private View contentView;
    private View loadingView;
    private int shortAnimationDuration;
    ...
    private void crossfade() {

        // Set the content view to 0% opacity but visible, so that it is
        // visible but fully transparent during the animation.
        contentView.setAlpha(0f);
        contentView.setVisibility(View.VISIBLE);

        // Animate the content view to 100% opacity and clear any animation
        // listener set on the view.
        contentView.animate()
                .alpha(1f)
                .setDuration(shortAnimationDuration)
                .setListener(null);

        // Animate the loading view to 0% opacity. After the animation ends,
        // set its visibility to GONE as an optimization step so it doesn't
        // participate in layout passes.
        loadingView.animate()
                .alpha(0f)
                .setDuration(shortAnimationDuration)
                .setListener(new AnimatorListenerAdapter() {
                    @Override
                    public void onAnimationEnd(Animator animation) {
                        loadingView.setVisibility(View.GONE);
                    }
                });
    }
}

创建卡片翻转动画

卡片翻转操作通过显示模拟动画，在内容视图之间切换 翻转卡片此处显示的卡片翻转动画使用了 FragmentTransaction。

卡片翻转的效果如下：

<ph type="x-smartling-placeholder">

图 2.卡片翻转动画。

创建 animator 对象

如需创建卡片翻转动画，您需要四个 Animator。两个 Animator 当卡片正面以动画形式呈现出来时，向左侧以动画形式呈现，以及当卡片以动画形式呈现时 左边和左边。另外两个 Animator 适用于在卡背面 分别以动画方式移入和移出右侧元素，以及向右侧以动画形式呈现。

card_flip_left_in.xml

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- Before rotating, immediately set the alpha to 0. -->
    <objectAnimator
        android:valueFrom="1.0"
        android:valueTo="0.0"
        android:propertyName="alpha"
        android:duration="0" />

    <!-- Rotate. -->
    <objectAnimator
        android:valueFrom="-180"
        android:valueTo="0"
        android:propertyName="rotationY"
        android:interpolator="@android:interpolator/accelerate_decelerate"
        android:duration="@integer/card_flip_time_full" />

    <!-- Halfway through the rotation, set the alpha to 1. See startOffset. -->
    <objectAnimator
        android:valueFrom="0.0"
        android:valueTo="1.0"
        android:propertyName="alpha"
        android:startOffset="@integer/card_flip_time_half"
        android:duration="1" />
</set>

card_flip_left_out.xml

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- Rotate. -->
    <objectAnimator
        android:valueFrom="0"
        android:valueTo="180"
        android:propertyName="rotationY"
        android:interpolator="@android:interpolator/accelerate_decelerate"
        android:duration="@integer/card_flip_time_full" />

    <!-- Halfway through the rotation, set the alpha to 0. See startOffset. -->
    <objectAnimator
        android:valueFrom="1.0"
        android:valueTo="0.0"
        android:propertyName="alpha"
        android:startOffset="@integer/card_flip_time_half"
        android:duration="1" />
</set>

card_flip_right_in.xml

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- Before rotating, immediately set the alpha to 0. -->
    <objectAnimator
        android:valueFrom="1.0"
        android:valueTo="0.0"
        android:propertyName="alpha"
        android:duration="0" />

    <!-- Rotate. -->
    <objectAnimator
        android:valueFrom="180"
        android:valueTo="0"
        android:propertyName="rotationY"
        android:interpolator="@android:interpolator/accelerate_decelerate"
        android:duration="@integer/card_flip_time_full" />

    <!-- Halfway through the rotation, set the alpha to 1. See startOffset. -->
    <objectAnimator
        android:valueFrom="0.0"
        android:valueTo="1.0"
        android:propertyName="alpha"
        android:startOffset="@integer/card_flip_time_half"
        android:duration="1" />
</set>

card_flip_right_out.xml

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- Rotate. -->
    <objectAnimator
        android:valueFrom="0"
        android:valueTo="-180"
        android:propertyName="rotationY"
        android:interpolator="@android:interpolator/accelerate_decelerate"
        android:duration="@integer/card_flip_time_full" />

    <!-- Halfway through the rotation, set the alpha to 0. See startOffset. -->
    <objectAnimator
        android:valueFrom="1.0"
        android:valueTo="0.0"
        android:propertyName="alpha"
        android:startOffset="@integer/card_flip_time_half"
        android:duration="1" />
</set>

创建视图

卡片的每一面都是一个单独的布局，可以包含您在 例如要翻转的两个文本视图、两张图片或任意视图组合 。使用您稍后要添加动画效果的 fragment 中的两个布局。通过 以下布局会创建卡片的一侧（显示文本）：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#a6c"
    android:padding="16dp"
    android:gravity="bottom">

    <TextView android:id="@android:id/text1"
        style="?android:textAppearanceLarge"
        android:textStyle="bold"
        android:textColor="#fff"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/card_back_title" />

    <TextView style="?android:textAppearanceSmall"
        android:textAllCaps="true"
        android:textColor="#80ffffff"
        android:textStyle="bold"
        android:lineSpacingMultiplier="1.2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/card_back_description" />

</LinearLayout>

下一个布局会创建卡片的另一面， ImageView:

<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:src="@drawable/image1"
    android:scaleType="centerCrop"
    android:contentDescription="@string/description_image_1" />

创建 Fragment

为卡片的正面和背面创建 Fragment 类。在 fragment 中 类，则返回从 onCreateView() 方法。然后，您可以在父 activity 中创建此 fragment 的实例 卡片的显示位置

以下示例展示了父 activity 中的嵌套 fragment 类 使用它们：

Kotlin

class CardFlipActivity : FragmentActivity() {
    ...
    /**

                    *   A fragment representing the front of the card.
     */
    class CardFrontFragment : Fragment() {

    override fun onCreateView(
                inflater: LayoutInflater,
                container: ViewGroup?,
                savedInstanceState: Bundle?
    ): View = inflater.inflate(R.layout.fragment_card_front, container, false)
    }

    /**
    *   A fragment representing the back of the card.
    */
    class CardBackFragment : Fragment() {

    override fun onCreateView(
                inflater: LayoutInflater,
                container: ViewGroup?,
                savedInstanceState: Bundle?
    ): View = inflater.inflate(R.layout.fragment_card_back, container, false)
    }
}

Java

public class CardFlipActivity extends FragmentActivity {
    ...
    /**
    *   A fragment representing the front of the card.
    */
    public class CardFrontFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            return inflater.inflate(R.layout.fragment_card_front, container, false);
    }
    }

    /**
    *   A fragment representing the back of the card.
    */
    public class CardBackFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            return inflater.inflate(R.layout.fragment_card_back, container, false);
    }
    }
}

为卡片翻转添加动画

显示父 activity 内的 fragment。为此，请创建布局 以下示例创建了一个 您可以添加的FrameLayout fragment 在运行时：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

在 activity 代码中，将内容视图设置为您创建的布局。 最好在创建 activity 时显示默认 fragment。通过 以下示例 activity 展示了如何按照 默认值：

Kotlin

class CardFlipActivity : FragmentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_activity_card_flip)
        if (savedInstanceState == null) {
            supportFragmentManager.beginTransaction()
                    .add(R.id.container, CardFrontFragment())
                    .commit()
        }
    }
    ...
}

Java

public class CardFlipActivity extends FragmentActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_activity_card_flip);

        if (savedInstanceState == null) {
            getSupportFragmentManager()
                    .beginTransaction()
                    .add(R.id.container, new CardFrontFragment())
                    .commit();
        }
    }
    ...
}

在显示卡片正面时，您可以同时显示卡片背面和 在适当的时间播放翻转动画。创建方法以显示 可执行以下操作的卡片：

• 设置您为 Fragment 转换创建的自定义动画。
• 将显示的 fragment 替换为新的 fragment，并为此事件添加动画效果 自定义动画效果
• 将之前显示的 fragment 添加到 fragment 返回堆栈中，这样当 当用户点按“返回”按钮时，卡片会翻转回来。

Kotlin

class CardFlipActivity : FragmentActivity() {
    ...
    private fun flipCard() {
        if (showingBack) {
            supportFragmentManager.popBackStack()
            return
        }

        // Flip to the back.

        showingBack = true

        // Create and commit a new fragment transaction that adds the fragment
        // for the back of the card, uses custom animations, and is part of the
        // fragment manager's back stack.

        supportFragmentManager.beginTransaction()

                // Replace the default fragment animations with animator
                // resources representing rotations when switching to the back
                // of the card, as well as animator resources representing
                // rotations when flipping back to the front, such as when the
                // system Back button is tapped.
                .setCustomAnimations(
                        R.animator.card_flip_right_in,
                        R.animator.card_flip_right_out,
                        R.animator.card_flip_left_in,
                        R.animator.card_flip_left_out
                )

                // Replace any fragments in the container view with a fragment
                // representing the next page, indicated by the just-incremented
                // currentPage variable.
                .replace(R.id.container, CardBackFragment())

                // Add this transaction to the back stack, letting users press
                // the Back button to get to the front of the card.
                .addToBackStack(null)

                // Commit the transaction.
                .commit()
    }
}

Java

public class CardFlipActivity extends FragmentActivity {
    ...
    private void flipCard() {
        if (showingBack) {
            getSupportFragmentManager().popBackStack();
            return;
        }

        // Flip to the back.

        showingBack = true;

        // Create and commit a new fragment transaction that adds the fragment
        // for the back of the card, uses custom animations, and is part of the
        // fragment manager's back stack.

        getSupportFragmentManager()
                .beginTransaction()

                // Replace the default fragment animations with animator
                // resources representing rotations when switching to the back
                // of the card, as well as animator resources representing
                // rotations when flipping back to the front, such as when the
                // system Back button is pressed.
                .setCustomAnimations(
                        R.animator.card_flip_right_in,
                        R.animator.card_flip_right_out,
                        R.animator.card_flip_left_in,
                        R.animator.card_flip_left_out)

                // Replace any fragments in the container view with a fragment
                // representing the next page, indicated by the just-incremented
                // currentPage variable.
                .replace(R.id.container, new CardBackFragment())

                // Add this transaction to the back stack, letting users press
                // Back to get to the front of the card.
                .addToBackStack(null)

                // Commit the transaction.
                .commit();
    }
}

创建圆形揭露动画

当您显示或隐藏组时，揭露动画可为用户提供视觉连续性 界面元素组成元素通过 ViewAnimationUtils.createCircularReveal() 方法，您可以通过动画方式呈现裁剪圆形来显示或隐藏视图。这个 中提供了 ViewAnimationUtils 类， 适用于 Android 5.0（API 级别 21）及更高版本。

以下示例展示了如何揭露之前不可见的视图：

Kotlin

// A previously invisible view.
val myView: View = findViewById(R.id.my_view)

// Check whether the runtime version is at least Android 5.0.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    // Get the center for the clipping circle.
    val cx = myView.width / 2
    val cy = myView.height / 2

    // Get the final radius for the clipping circle.
    val finalRadius = Math.hypot(cx.toDouble(), cy.toDouble()).toFloat()

    // Create the animator for this view. The start radius is 0.
    val anim = ViewAnimationUtils.createCircularReveal(myView, cx, cy, 0f, finalRadius)
    // Make the view visible and start the animation.
    myView.visibility = View.VISIBLE
    anim.start()
} else {
    // Set the view to invisible without a circular reveal animation below
    // Android 5.0.
    myView.visibility = View.INVISIBLE
}

Java

// A previously invisible view.
View myView = findViewById(R.id.my_view);

// Check whether the runtime version is at least Android 5.0.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    // Get the center for the clipping circle.
    int cx = myView.getWidth() / 2;
    int cy = myView.getHeight() / 2;

    // Get the final radius for the clipping circle.
    float finalRadius = (float) Math.hypot(cx, cy);

    // Create the animator for this view. The start radius is 0.
    Animator anim = ViewAnimationUtils.createCircularReveal(myView, cx, cy, 0f, finalRadius);

    // Make the view visible and start the animation.
    myView.setVisibility(View.VISIBLE);
    anim.start();
} else {
    // Set the view to invisible without a circular reveal animation below
    // Android 5.0.
    myView.setVisibility(View.INVISIBLE);
}

ViewAnimationUtils.createCircularReveal() 动画采用五个参数。 第一个参数是要在屏幕上隐藏或显示的视图。通过 接下来的两个参数是裁剪中心的 X 和 Y 坐标。 圆圈。这通常是视图的中心，但您也可以使用 用户点按的点，以便动画从用户选择的位置开始。通过 第四个参数是裁剪圆形的起始半径。

在前面的示例中，初始半径设置为零，使视图 正在显示的圆圈被圆圈隐藏了。最后一个参数是 圆圈。显示视图时，使最终半径大于 视图，以便在动画播放完毕之前完全显示视图。

如需隐藏之前可见的视图，请执行以下操作：

Kotlin

// A previously visible view.
val myView: View = findViewById(R.id.my_view)

// Check whether the runtime version is at least Android 5.0.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    // Get the center for the clipping circle.
    val cx = myView.width / 2
    val cy = myView.height / 2

    // Get the initial radius for the clipping circle.
    val initialRadius = Math.hypot(cx.toDouble(), cy.toDouble()).toFloat()

    // Create the animation. The final radius is 0.
    val anim = ViewAnimationUtils.createCircularReveal(myView, cx, cy, initialRadius, 0f)

    // Make the view invisible when the animation is done.
    anim.addListener(object : AnimatorListenerAdapter() {

        override fun onAnimationEnd(animation: Animator) {
            super.onAnimationEnd(animation)
            myView.visibility = View.INVISIBLE
        }
    })

    // Start the animation.
    anim.start()
} else {
    // Set the view to visible without a circular reveal animation below
    // Android 5.0.
    myView.visibility = View.VISIBLE
}

Java

// A previously visible view.
final View myView = findViewById(R.id.my_view);

// Check whether the runtime version is at least Android 5.0.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    // Get the center for the clipping circle.
    int cx = myView.getWidth() / 2;
    int cy = myView.getHeight() / 2;

    // Get the initial radius for the clipping circle.
    float initialRadius = (float) Math.hypot(cx, cy);

    // Create the animation. The final radius is 0.
    Animator anim = ViewAnimationUtils.createCircularReveal(myView, cx, cy, initialRadius, 0f);

    // Make the view invisible when the animation is done.
    anim.addListener(new AnimatorListenerAdapter() {
        @Override
        public void onAnimationEnd(Animator animation) {
            super.onAnimationEnd(animation);
            myView.setVisibility(View.INVISIBLE);
        }
    });

    // Start the animation.
    anim.start();
} else {
    // Set the view to visible without a circular reveal animation below Android
    // 5.0.
    myView.setVisibility(View.VISIBLE);
}

在本例中，裁剪圆形的初始半径设置为 视图，使视图在动画开始播放前可见。最后一个 radius 设置为 0，以便在动画播放完毕时隐藏视图。 为动画添加监听器，以便将视图的可见性设置为 INVISIBLE 。

其他资源

• 使用 Jetpack Compose 实现动画。
• Jetpack Compose 的手势。