Android 共享元素转换 : Transforming an ImageView from a circle to a rectangle and back again

Question

我正在尝试在两个 Activity 之间进行共享元素转换。

第一个 Activity 有一个圆形 ImageView ，第二个 Activity 有一个矩形 ImageView 。我只希望圆圈从第一个 Activity 过渡到第二个 Activity ，当我按回时它变成一个正方形并返回到圆圈。

我发现过渡不是那么整齐——在下面的动画中，你可以看到矩形 imageview 的大小似乎在缩小，直到它与圆的大小相匹配。方形 ImageView 出现片刻，然后出现圆圈。我想摆脱方形 ImageView ，使圆圈成为过渡的终点。

有人知道这是怎么做到的吗？

我创建了一个小型测试存储库，您可以在此处下载:https://github.com/Winghin2517/TransitionTest

我的第一个 Activity 的代码 - ImageView 位于我的第一个 Activity 的 MainFragment 中:

public class MainFragment extends android.support.v4.app.Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_view, container,false);
        final ImageView dot = (ImageView) view.findViewById(R.id.image_circle);
        Picasso.with(getContext()).load(R.drawable.snow).transform(new PureCircleTransformation()).into(dot);
        dot.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(getContext(), SecondActivity.class);
                View sharedView = dot;
                String transitionName = getString(R.string.blue_name);
                ActivityOptionsCompat transitionActivityOptions = ActivityOptionsCompat.makeSceneTransitionAnimation(getActivity(), sharedView, transitionName);
                startActivity(i, transitionActivityOptions.toBundle());
            }
        });
        return view;
    }
}

这是我的第二个包含矩形 ImageView 的 Activity :

public class SecondActivity extends AppCompatActivity {

    ImageView backdrop;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        backdrop = (ImageView) findViewById(R.id.picture);
        backdrop.setBackground(ContextCompat.getDrawable(this, R.drawable.snow));
    }

    @Override
    public void onBackPressed() {
        supportFinishAfterTransition();
        super.onBackPressed();

    }
}

这是我传递给 Picasso 以生成圆的 PureCircleTransformation 类:

package test.com.transitiontest;

import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Paint;

import com.squareup.picasso.Transformation;

public class PureCircleTransformation implements Transformation {

    private static final int STROKE_WIDTH = 6;

    @Override
    public Bitmap transform(Bitmap source) {
        int size = Math.min(source.getWidth(), source.getHeight());

        int x = (source.getWidth() - size) / 2;
        int y = (source.getHeight() - size) / 2;

        Bitmap squaredBitmap = Bitmap.createBitmap(source, x, y, size, size);
        if (squaredBitmap != source) {
            source.recycle();
        }

        Bitmap bitmap = Bitmap.createBitmap(size, size, source.getConfig());

        Canvas canvas = new Canvas(bitmap);

        Paint avatarPaint = new Paint();
        BitmapShader shader = new BitmapShader(squaredBitmap, BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP);
        avatarPaint.setShader(shader);

        float r = size / 2f;
        canvas.drawCircle(r, r, r, avatarPaint);

        squaredBitmap.recycle();
        return bitmap;
    }

    @Override
    public String key() {
        return "circleTransformation()";
    }
}

我明白，在我的第一个 Activity 中，圆圈只是通过应用 picasso 转换类被“剪切”出来的，并且 ImageView 只是一个方形布局，因此它显示为一个圆形。也许这就是我从矩形过渡到正方形时动画看起来像这样的原因，但我真的希望从矩形过渡到圆形。

我认为有办法做到这一点。在 whatsapp 应用程序中，我可以看到效果，但我似乎无法弄清楚他们是如何做到的 - 如果您在 whatsapp 上单击您 friend 的个人资料图片，该应用程序会将圆形 ImageView 扩展为正方形。单击返回将使正方形返回圆形。

Answer 1

我提议创建一个自定义 View ，它可以动画自己从圆形到矩形并返回，然后通过添加移动动画将自定义过渡包裹在它周围。

它的样子:

代码如下(有值(value)的部分)。
如需完整 sample ，请查看 my github .

CircleRectView.java:

public class CircleRectView extends ImageView {

private int circleRadius;
private float cornerRadius;

private RectF bitmapRect;
private Path clipPath;

private void init(TypedArray a) {
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR2
            && Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        setLayerType(LAYER_TYPE_SOFTWARE, null);
    }

    if (a.hasValue(R.styleable.CircleRectView_circleRadius)) {
        circleRadius = a.getDimensionPixelSize(R.styleable.CircleRectView_circleRadius, 0);
        cornerRadius = circleRadius;
    }
    clipPath = new Path();
    a.recycle();
}

public Animator animator(int startHeight, int startWidth, int endHeight, int endWidth) {
    AnimatorSet animatorSet = new AnimatorSet();

    ValueAnimator heightAnimator = ValueAnimator.ofInt(startHeight, endHeight);
    ValueAnimator widthAnimator = ValueAnimator.ofInt(startWidth, endWidth);

    heightAnimator.addUpdateListener(valueAnimator -> {
        int val = (Integer) valueAnimator.getAnimatedValue();
        ViewGroup.LayoutParams layoutParams = getLayoutParams();
        layoutParams.height = val;

        setLayoutParams(layoutParams);
        requestLayoutSupport();
    });

    widthAnimator.addUpdateListener(valueAnimator -> {
        int val = (Integer) valueAnimator.getAnimatedValue();
        ViewGroup.LayoutParams layoutParams = getLayoutParams();
        layoutParams.width = val;

        setLayoutParams(layoutParams);
        requestLayoutSupport();
    });

    ValueAnimator radiusAnimator;
    if (startWidth < endWidth) {
        radiusAnimator = ValueAnimator.ofFloat(circleRadius, 0);
    } else {
        radiusAnimator = ValueAnimator.ofFloat(cornerRadius, circleRadius);
    }

    radiusAnimator.setInterpolator(new AccelerateInterpolator());
    radiusAnimator.addUpdateListener(animator -> cornerRadius = (float) (Float) animator.getAnimatedValue());

    animatorSet.playTogether(heightAnimator, widthAnimator, radiusAnimator);

    return animatorSet;
}

/**
 * this needed because of that somehow {@link #onSizeChanged} NOT CALLED when requestLayout while activity transition end is running
 */
private void requestLayoutSupport() {
    View parent = (View) getParent();
    int widthSpec = View.MeasureSpec.makeMeasureSpec(parent.getWidth(), View.MeasureSpec.EXACTLY);
    int heightSpec = View.MeasureSpec.makeMeasureSpec(parent.getHeight(), View.MeasureSpec.EXACTLY);
    parent.measure(widthSpec, heightSpec);
    parent.layout(parent.getLeft(), parent.getTop(), parent.getRight(), parent.getBottom());
}

@Override
public void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    //This event-method provides the real dimensions of this custom view.

    Log.d("size changed", "w = " + w + " h = " + h);

    bitmapRect = new RectF(0, 0, w, h);
}

@Override
protected void onDraw(Canvas canvas) {

    Drawable drawable = getDrawable();

    if (drawable == null) {
        return;
    }

    if (getWidth() == 0 || getHeight() == 0) {
        return;
    }

    clipPath.reset();
    clipPath.addRoundRect(bitmapRect, cornerRadius, cornerRadius, Path.Direction.CW);
    canvas.clipPath(clipPath);
    super.onDraw(canvas);
}

}

@TargetApi(Build.VERSION_CODES.KITKAT)
public class CircleToRectTransition extends Transition {
private static final String TAG = CircleToRectTransition.class.getSimpleName();
private static final String BOUNDS = "viewBounds";
private static final String[] PROPS = {BOUNDS};

@Override
public String[] getTransitionProperties() {
    return PROPS;
}

private void captureValues(TransitionValues transitionValues) {
    View view = transitionValues.view;
    Rect bounds = new Rect();
    bounds.left = view.getLeft();
    bounds.right = view.getRight();
    bounds.top = view.getTop();
    bounds.bottom = view.getBottom();
    transitionValues.values.put(BOUNDS, bounds);
}

@Override
public void captureStartValues(TransitionValues transitionValues) {
    captureValues(transitionValues);
}

@Override
public void captureEndValues(TransitionValues transitionValues) {
    captureValues(transitionValues);
}

@Override
public Animator createAnimator(ViewGroup sceneRoot, TransitionValues startValues, TransitionValues endValues) {
    if (startValues == null || endValues == null) {
        return null;
    }

    if (!(startValues.view instanceof CircleRectView)) {
        Log.w(CircleToRectTransition.class.getSimpleName(), "transition view should be CircleRectView");
        return null;
    }

    CircleRectView view = (CircleRectView) (startValues.view);

    Rect startRect = (Rect) startValues.values.get(BOUNDS);
    final Rect endRect = (Rect) endValues.values.get(BOUNDS);

    Animator animator;

    //scale animator
    animator = view.animator(startRect.height(), startRect.width(), endRect.height(), endRect.width());

    //movement animators below
    //if some translation not performed fully, use it instead of start coordinate
    float startX = startRect.left + view.getTranslationX();
    float startY = startRect.top + view.getTranslationY();

    //somehow end rect returns needed value minus translation in case not finished transition available
    float moveXTo = endRect.left + Math.round(view.getTranslationX());
    float moveYTo = endRect.top + Math.round(view.getTranslationY());

    Animator moveXAnimator = ObjectAnimator.ofFloat(view, "x", startX, moveXTo);
    Animator moveYAnimator = ObjectAnimator.ofFloat(view, "y", startY, moveYTo);

    AnimatorSet animatorSet = new AnimatorSet();
    animatorSet.playTogether(animator, moveXAnimator, moveYAnimator);

    //prevent blinking when interrupt animation
    return new NoPauseAnimator(animatorSet);
}

MainActivity.java:

 view.setOnClickListener(v -> {
        Intent intent = new Intent(this, SecondActivity.class);
        ActivityOptionsCompat transitionActivityOptions = ActivityOptionsCompat.makeSceneTransitionAnimation(MainActivity.this, view, getString(R.string.circle));

        ActivityCompat.startActivity(MainActivity.this, intent , transitionActivityOptions.toBundle());
    });

SecondActivity.java :

@Override
protected void onCreate(Bundle savedInstanceState) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        getWindow().setSharedElementEnterTransition(new CircleToRectTransition().setDuration(1500));
        getWindow().setSharedElementExitTransition(new CircleToRectTransition().setDuration(1500));
    }

    super.onCreate(savedInstanceState);
    ...
 }
@Override
public void onBackPressed() {
    supportFinishAfterTransition();
}

已编辑:CircleToRectTransition 的先前变体并不通用，仅在特定情况下有效。检查没有那个缺点的修改示例

EDITED2:事实证明，您根本不需要自定义过渡，只需从 SecondActivity 中删除设置逻辑，它将以默认方式工作。使用这种方法，您可以设置转换持续时间 this way .

EDITED3:为 api < 18

提供反向移植

顺便说一句，您可以使用 such technique 将这些东西反向移植到 Lollipop 之前的设备上。 .已经创建了可以使用动画师的地方