このガイドでは、タップズーム アニメーションを実装する方法について説明します。タップズームを使用すると、フォト ギャラリーなどのアプリで、サムネイルから画面全体に広がるビューをアニメーション化できます。
サムネイルが画面全体に広がるタップズーム アニメーションの例を以下に示します。
完全に動作するサンプルについては、GitHub の WearSpeakerSample プロジェクトの UIAnimation クラスをご覧ください。
ビューを作成する
ズームするコンテンツの小さいバージョンと大きいバージョンを含むレイアウト ファイルを作成します。タップ可能な画像サムネイル用の ImageButton と、拡大後の画像のビューを表示する ImageView を作成する例を以下に示します。
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="16dp">
<ImageButton
android:id="@+id/thumb_button_1"
android:layout_width="100dp"
android:layout_height="75dp"
android:layout_marginRight="1dp"
android:src="@drawable/thumb1"
android:scaleType="centerCrop"
android:contentDescription="@string/description_image_1" />
</LinearLayout>
<!-- This initially hidden ImageView holds the zoomed version of
the preceding images. Without transformations applied, it fills the entire
screen. To achieve the zoom animation, this view's bounds are animated
from the bounds of the preceding thumbnail button to its final laid-out
bounds.
-->
<ImageView
android:id="@+id/expanded_image"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:visibility="invisible"
android:contentDescription="@string/description_zoom_touch_close" />
</FrameLayout>
ズーム アニメーションを設定する
レイアウトを適用したら、ズーム アニメーションをトリガーするイベント ハンドラをセットアップします。次の例では、View.OnClickListener を ImageButton に追加して、ユーザーが画像ボタンをタップしたときにズーム アニメーションを実行します。
Kotlin
class ZoomActivity : FragmentActivity() {
// Hold a reference to the current animator so that it can be canceled
// midway.
private var currentAnimator: Animator? = null
// The system "short" animation time duration in milliseconds. This duration
// is ideal for subtle animations or animations that occur frequently.
private var shortAnimationDuration: Int = 0
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_zoom)
// Hook up taps on the thumbnail views.
binding.thumbButton1.setOnClickListener {
zoomImageFromThumb(thumb1View, R.drawable.image1)
}
// Retrieve and cache the system's default "short" animation time.
shortAnimationDuration = resources.getInteger(android.R.integer.config_shortAnimTime)
}
...
}
Java
public class ZoomActivity extends FragmentActivity {
// Hold a reference to the current animator so that it can be canceled
// mid-way.
private Animator currentAnimator;
// The system "short" animation time duration in milliseconds. This duration
// is ideal for subtle animations or animations that occur frequently.
private int shortAnimationDuration;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_zoom);
// Hook up taps on the thumbnail views.
binding.thumbButton1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
zoomImageFromThumb(thumb1View, R.drawable.image1);
}
});
// Retrieve and cache the system's default "short" animation time.
shortAnimationDuration = getResources().getInteger(
android.R.integer.config_shortAnimTime);
}
...
}
ビューをズームする
必要に応じて、標準サイズビューからズームビューにアニメーションします。一般的に、標準サイズビューの境界から拡大サイズビューの境界にアニメーションする必要があります。以下に、サムネイルから拡大ビューにズームするズーム アニメーションを実装する方法を示します。これを行うには、高解像度画像を、非表示の「ズームイン」（拡大）ImageView に割り当てます。
下記のサンプルでは、わかりやすくするために、大きい画像リソースを UI スレッドにロードしています。UI スレッドのブロックを回避するために、この読み込みは別のスレッドで行い、その後でビットマップの設定を UI スレッドで行うことをおすすめします。通常、ビットマップは画面サイズ以下である必要があります。次に、ImageView の開始境界と終了境界を計算します。
Kotlin
private fun zoomImageFromThumb(thumbView: View, imageResId: Int) {
// If there's an animation in progress, cancel it immediately and
// proceed with this one.
currentAnimator?.cancel()
// Load the high-resolution "zoomed-in" image.
binding.expandedImage.setImageResource(imageResId)
// Calculate the starting and ending bounds for the zoomed-in image.
val startBoundsInt = Rect()
val finalBoundsInt = Rect()
val globalOffset = Point()
// The start bounds are the global visible rectangle of the thumbnail,
// and the final bounds are the global visible rectangle of the
// container view. Set the container view's offset as the origin for the
// bounds, since that's the origin for the positioning animation
// properties (X, Y).
thumbView.getGlobalVisibleRect(startBoundsInt)
binding.container.getGlobalVisibleRect(finalBoundsInt, globalOffset)
startBoundsInt.offset(-globalOffset.x, -globalOffset.y)
finalBoundsInt.offset(-globalOffset.x, -globalOffset.y)
val startBounds = RectF(startBoundsInt)
val finalBounds = RectF(finalBoundsInt)
// Using the "center crop" technique, adjust the start bounds to be the
// same aspect ratio as the final bounds. This prevents unwanted
// stretching during the animation. Calculate the start scaling factor.
// The end scaling factor is always 1.0.
val startScale: Float
if ((finalBounds.width() / finalBounds.height() > startBounds.width() / startBounds.height())) {
// Extend start bounds horizontally.
startScale = startBounds.height() / finalBounds.height()
val startWidth: Float = startScale * finalBounds.width()
val deltaWidth: Float = (startWidth - startBounds.width()) / 2
startBounds.left -= deltaWidth.toInt()
startBounds.right += deltaWidth.toInt()
} else {
// Extend start bounds vertically.
startScale = startBounds.width() / finalBounds.width()
val startHeight: Float = startScale * finalBounds.height()
val deltaHeight: Float = (startHeight - startBounds.height()) / 2f
startBounds.top -= deltaHeight.toInt()
startBounds.bottom += deltaHeight.toInt()
}
// Hide the thumbnail and show the zoomed-in view. When the animation
// begins, it positions the zoomed-in view in the place of the
// thumbnail.
thumbView.alpha = 0f
animateZoomToLargeImage(startBounds, finalBounds, startScale)
setDismissLargeImageAnimation(thumbView, startBounds, startScale)
}
Java
private void zoomImageFromThumb(final View thumbView, int imageResId) {
// If there's an animation in progress, cancel it immediately and
// proceed with this one.
if (currentAnimator != null) {
currentAnimator.cancel();
}
// Load the high-resolution "zoomed-in" image.
binding.expandedImage.setImageResource(imageResId);
// Calculate the starting and ending bounds for the zoomed-in image.
final Rect startBounds = new Rect();
final Rect finalBounds = new Rect();
final Point globalOffset = new Point();
// The start bounds are the global visible rectangle of the thumbnail,
// and the final bounds are the global visible rectangle of the
// container view. Set the container view's offset as the origin for the
// bounds, since that's the origin for the positioning animation
// properties (X, Y).
thumbView.getGlobalVisibleRect(startBounds);
findViewById(R.id.container)
.getGlobalVisibleRect(finalBounds, globalOffset);
startBounds.offset(-globalOffset.x, -globalOffset.y);
finalBounds.offset(-globalOffset.x, -globalOffset.y);
// Using the "center crop" technique, adjust the start bounds to be the
// same aspect ratio as the final bounds. This prevents unwanted
// stretching during the animation. Calculate the start scaling factor.
// The end scaling factor is always 1.0.
float startScale;
if ((float) finalBounds.width() / finalBounds.height()
> (float) startBounds.width() / startBounds.height()) {
// Extend start bounds horizontally.
startScale = (float) startBounds.height() / finalBounds.height();
float startWidth = startScale * finalBounds.width();
float deltaWidth = (startWidth - startBounds.width()) / 2;
startBounds.left -= deltaWidth;
startBounds.right += deltaWidth;
} else {
// Extend start bounds vertically.
startScale = (float) startBounds.width() / finalBounds.width();
float startHeight = startScale * finalBounds.height();
float deltaHeight = (startHeight - startBounds.height()) / 2;
startBounds.top -= deltaHeight;
startBounds.bottom += deltaHeight;
}
// Hide the thumbnail and show the zoomed-in view. When the animation
// begins, it positions the zoomed-in view in the place of the
// thumbnail.
thumbView.setAlpha(0f);
animateZoomToLargeImage(startBounds, finalBounds, startScale);
setDismissLargeImageAnimation(thumbView, startBounds, startScale);
}
4 つの位置設定 / サイズ設定プロパティ（X、Y、SCALE_X、SCALE_Y）を、開始境界から終了境界まで同時にアニメーション化します。4 つのアニメーションを AnimatorSet に追加して、同時に開始できるようにします。
Kotlin
private fun animateZoomToLargeImage(startBounds: RectF, finalBounds: RectF, startScale: Float) {
binding.expandedImage.visibility = View.VISIBLE
// Set the pivot point for SCALE_X and SCALE_Y transformations to the
// top-left corner of the zoomed-in view. The default is the center of
// the view.
binding.expandedImage.pivotX = 0f
binding.expandedImage.pivotY = 0f
// Construct and run the parallel animation of the four translation and
// scale properties: X, Y, SCALE_X, and SCALE_Y.
currentAnimator = AnimatorSet().apply {
play(
ObjectAnimator.ofFloat(
binding.expandedImage,
View.X,
startBounds.left,
finalBounds.left)
).apply {
with(ObjectAnimator.ofFloat(binding.expandedImage, View.Y, startBounds.top, finalBounds.top))
with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_X, startScale, 1f))
with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_Y, startScale, 1f))
}
duration = shortAnimationDuration.toLong()
interpolator = DecelerateInterpolator()
addListener(object : AnimatorListenerAdapter() {
override fun onAnimationEnd(animation: Animator) {
currentAnimator = null
}
override fun onAnimationCancel(animation: Animator) {
currentAnimator = null
}
})
start()
}
}
Java
private void animateZoomToLargeImage(Rect startBounds, Rect finalBounds, Float startScale) {
binding.expandedImage.setVisibility(View.VISIBLE);
// Set the pivot point for SCALE_X and SCALE_Y transformations to the
// top-left corner of the zoomed-in view. The default is the center of
// the view.
binding.expandedImage.setPivotX(0f);
binding.expandedImage.setPivotY(0f);
// Construct and run the parallel animation of the four translation and
// scale properties: X, Y, SCALE_X, and SCALE_Y.
AnimatorSet set = new AnimatorSet();
set
.play(ObjectAnimator.ofFloat(binding.expandedImage, View.X,
startBounds.left, finalBounds.left))
.with(ObjectAnimator.ofFloat(binding.expandedImage, View.Y,
startBounds.top, finalBounds.top))
.with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_X,
startScale, 1f))
.with(ObjectAnimator.ofFloat(binding.expandedImage,
View.SCALE_Y, startScale, 1f));
set.setDuration(shortAnimationDuration);
set.setInterpolator(new DecelerateInterpolator());
set.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
currentAnimator = null;
}
@Override
public void onAnimationCancel(Animator animation) {
currentAnimator = null;
}
});
set.start();
currentAnimator = set;
}
画像がズームインしているときにユーザーが画面をタップした場合は、同じアニメーションを逆向きに実行してズームアウトします。View.OnClickListener を ImageView に追加します。タップすると、ImageView が画像サムネイルのサイズまで小さくなり、表示設定が GONE に設定されて非表示になります。
Kotlin
private fun setDismissLargeImageAnimation(thumbView: View, startBounds: RectF, startScale: Float) {
// When the zoomed-in image is tapped, it zooms down to the original
// bounds and shows the thumbnail instead of the expanded image.
binding.expandedImage.setOnClickListener {
currentAnimator?.cancel()
// Animate the four positioning and sizing properties in parallel,
// back to their original values.
currentAnimator = AnimatorSet().apply {
play(ObjectAnimator.ofFloat(binding.expandedImage, View.X, startBounds.left)).apply {
with(ObjectAnimator.ofFloat(binding.expandedImage, View.Y, startBounds.top))
with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_X, startScale))
with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_Y, startScale))
}
duration = shortAnimationDuration.toLong()
interpolator = DecelerateInterpolator()
addListener(object : AnimatorListenerAdapter() {
override fun onAnimationEnd(animation: Animator) {
thumbView.alpha = 1f
binding.expandedImage.visibility = View.GONE
currentAnimator = null
}
override fun onAnimationCancel(animation: Animator) {
thumbView.alpha = 1f
binding.expandedImage.visibility = View.GONE
currentAnimator = null
}
})
start()
}
}
}
Java
private void setDismissLargeImageAnimation(View thumbView, Rect startBounds, Float startScale) {
// When the zoomed-in image is tapped, it zooms down to the original
// bounds and shows the thumbnail instead of the expanded image.
final float startScaleFinal = startScale;
binding.expandedImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (currentAnimator != null) {
currentAnimator.cancel();
}
// Animate the four positioning and sizing properties in
// parallel, back to their original values.
AnimatorSet set = new AnimatorSet();
set.play(ObjectAnimator
.ofFloat(binding.expandedImage, View.X, startBounds.left))
.with(ObjectAnimator
.ofFloat(binding.expandedImage,
View.Y,startBounds.top))
.with(ObjectAnimator
.ofFloat(binding.expandedImage,
View.SCALE_X, startScaleFinal))
.with(ObjectAnimator
.ofFloat(binding.expandedImage,
View.SCALE_Y, startScaleFinal));
set.setDuration(shortAnimationDuration);
set.setInterpolator(new DecelerateInterpolator());
set.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
thumbView.setAlpha(1f);
binding.expandedImage.setVisibility(View.GONE);
currentAnimator = null;
}
@Override
public void onAnimationCancel(Animator animation) {
thumbView.setAlpha(1f);
binding.expandedImage.setVisibility(View.GONE);
currentAnimator = null;
}
});
set.start();
currentAnimator = set;
}
});
}