A, introducing

In fact, I always thought that the animation of adding goods to shopping cart like ele. me or Meituan takeout would be difficult, but it is not as difficult as I thought.
The layout mainly uses CoordinatorLayout+AppBarLayout+CollapsingToolbarLayout+TabLayout+ViewPager
Animation mainly uses second-order Bezier curve and attribute animation
The messaging uses the EventBus common event

Second, the general idea

As shown in the figure, there are three main points, starting point, ending point, and control point of Bezier curve
The starting point is the position of the View to be clicked, which can generally be obtained as follows. StartPosition [0] is the start coordinate of x axis, startPosition[1] is the end coordinate of Y axis, two points can be regarded as the two endpoints above the diagonal (x coordinate of upper left corner, Y coordinate of lower right corner)
```
// Start bezier data point
int[] startPosition = new int[2];
view.getLocationOnScreen(startPosition);
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```
The destination is the position of the shopping cart basket, similar to the starting point
```
mShoppingCart.getLocationInWindow(endPosition);
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```
The control point, the control point I chose is C in the figure above, which is the y coordinate of A and the X coordinate of B
```
controlPosition[0] = endPosition[0];
controlPosition[1] = startPosition[1];
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```

What needs to be noted is that I am not sure whether it is because of my layout problem, the point A that I click always has an offset. Later, after my colleague reminded me, I subtracted the Y-axis coordinate of TabLayout, namely the position.

/ / starting point
int[] startPosition;
/ / the end
int[] endPosition = new int[2];
// Bezier control point
int[] controlPosition = new int[2];
/ / tablayout position
int[] tablayoutPosition = new int[2];

startPosition = data.getStartPosition();
mShoppingCart.getLocationInWindow(endPosition);
mTabLayout.getLocationInWindow(tablayoutPosition);
// Handle the y offset of the starting point
startPosition[1] = startPosition[1] - tablayoutPosition[1] - mTabLayout.getHeight();
// The endpoint is centered
endPosition[0] = endPosition[0] + (mShoppingCart.getWidth() / 2);
controlPosition[0] = endPosition[0];
controlPosition[1] = startPosition[1];
Copy the code

Draw bezier curves using Path’s quadTo method, using PathMeasure to get coordinates of points (with valueanimator.offloat () and getPosTan() to get coordinates)

Path path = new Path();
path.moveTo(startPosition[0], startPosition[1]);
path.quadTo(controlPosition[0], controlPosition[1], endPosition[0], endPosition[1]);
PathMeasure pathMeasure = new PathMeasure();
// false indicates that path is not closed
pathMeasure.setPath(path, false);

// ofFloat is a generator
ValueAnimator valueAnimator = ValueAnimator.ofFloat(0, pathMeasure.getLength());
// Constant linear interpolator
valueAnimator.setInterpolator(new LinearInterpolator());
valueAnimator.setDuration(800);
valueAnimator.addUpdateListener(animation -> {
    float value = (Float) animation.getAnimatedValue();
    pathMeasure.getPosTan(value, currentPosition, null);
    imageView.setX(currentPosition[0]);
    imageView.setY(currentPosition[1]);
});
valueAnimator.start();
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Here is a zooming in and out animation of the shopping cart basket using the properties animation

/ / mShoppingCart is the View
ObjectAnimator shoppingCartX = ObjectAnimator.ofFloat(mShoppingCart, "scaleX".1.0 f.1.3 f.1.0 f);
ObjectAnimator shoppingCartY = ObjectAnimator.ofFloat(mShoppingCart, "scaleY".1.0 f.1.3 f.1.0 f);
shoppingCartX.setInterpolator(new AccelerateInterpolator());
shoppingCartY.setInterpolator(new AccelerateInterpolator());
AnimatorSet shoppingCart = new AnimatorSet();
shoppingCart
        .play(shoppingCartX)
        .with(shoppingCartY);
shoppingCart.setDuration(800);
shoppingCart.start();
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Third, a slightly complete majority of the code

private void AddAnimation(AddEventBean data) {
    / / starting point
    int[] startPosition;
    / / the end
    int[] endPosition = new int[2];
    // Bezier control point
    int[] controlPosition = new int[2];
    // The current position
    float[] currentPosition = new float[2];
    / / tablayout position
    int[] tablayoutPosition = new int[2];

    startPosition = data.getStartPosition();
    mShoppingCart.getLocationInWindow(endPosition);
    mTabLayout.getLocationInWindow(tablayoutPosition);
    // Handle the y offset of the starting point
    startPosition[1] = startPosition[1] - tablayoutPosition[1] - mTabLayout.getHeight();
    // The endpoint is centered
    endPosition[0] = endPosition[0] + (mShoppingCart.getWidth() / 2);
    controlPosition[0] = endPosition[0];
    controlPosition[1] = startPosition[1];


    final ImageView imageView = new ImageView(this);
    mConView.addView(imageView);
    imageView.setImageResource(R.drawable.specialadd);
    imageView.getLayoutParams().width = getResources().getDimensionPixelSize(R.dimen.dp_px_30);
    imageView.getLayoutParams().height = getResources().getDimensionPixelSize(R.dimen.dp_px_30);
    imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
    imageView.setVisibility(View.VISIBLE);
    imageView.setX(startPosition[0]);
    imageView.setY(startPosition[1]);

    Path path = new Path();
    path.moveTo(startPosition[0], startPosition[1]);
    path.quadTo(controlPosition[0], controlPosition[1], endPosition[0], endPosition[1]);
    PathMeasure pathMeasure = new PathMeasure();
    // false indicates that path is not closed
    pathMeasure.setPath(path, false);

    // ofFloat is a generator
    ValueAnimator valueAnimator = ValueAnimator.ofFloat(0, pathMeasure.getLength());
    // Constant linear interpolator
    valueAnimator.setInterpolator(new LinearInterpolator());
    valueAnimator.setDuration(800);
    valueAnimator.addUpdateListener(animation -> {
        float value = (Float) animation.getAnimatedValue();
        pathMeasure.getPosTan(value, currentPosition, null);
        imageView.setX(currentPosition[0]);
        imageView.setY(currentPosition[1]);
    });
    valueAnimator.start();

    ObjectAnimator shoppingCartX = ObjectAnimator.ofFloat(mShoppingCart, "scaleX".1.0 f.1.3 f.1.0 f);
    ObjectAnimator shoppingCartY = ObjectAnimator.ofFloat(mShoppingCart, "scaleY".1.0 f.1.3 f.1.0 f);
    shoppingCartX.setInterpolator(new AccelerateInterpolator());
    shoppingCartY.setInterpolator(new AccelerateInterpolator());
    AnimatorSet shoppingCart = new AnimatorSet();
    shoppingCart
            .play(shoppingCartX)
            .with(shoppingCartY);
    shoppingCart.setDuration(800);
    shoppingCart.start();

    valueAnimator.addListener(new Animator.AnimatorListener() {
        @Override
        public void onAnimationStart(Animator animation) {}// When the animation ends:
        @Override
        public void onAnimationEnd(Animator animation) {
            goodsChange(data);
        }

        @Override
        public void onAnimationCancel(Animator animation) {}@Override
        public void onAnimationRepeat(Animator animation) {}}); }Copy the code

Four, roughly write down the layout (also counted as a backup)

<?xml version="1.0" encoding="utf-8"? >
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    . .>

    <RelativeLayout
        . .>Top resident toolbar</RelativeLayout>

    <android.support.design.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1">

        <android.support.design.widget.AppBarLayout
            . .>

            <android.support.design.widget.CollapsingToolbarLayout
                . .
                app:layout_scrollFlags="scroll|exitUntilCollapsed">

                <LinearLayout
                    . .>View above TabLayout</LinearLayout>

            </android.support.design.widget.CollapsingToolbarLayout>

            <android.support.design.widget.TabLayout
                . . />

        </android.support.design.widget.AppBarLayout>

        <RelativeLayout
            . .
            android:fillViewport="true"
            app:layout_behavior="@string/appbar_scrolling_view_behavior">

            <android.support.v4.view.ViewPager
                android:id="@+id/view_pager"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />
        </RelativeLayout>

    </android.support.design.widget.CoordinatorLayout>

    <LinearLayout
        . .>Bottom of the shopping cart</LinearLayout>
</LinearLayout>
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5. Recommended resources

View position argument
Bezier curve of Path

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Add a shopping cart animation using a second-order Bezier curve

A, introducing

Second, the general idea

Third, a slightly complete majority of the code

Four, roughly write down the layout (also counted as a backup)

5. Recommended resources

Add a shopping cart animation using a second-order Bezier curve

A, introducing

Second, the general idea

Third, a slightly complete majority of the code

Four, roughly write down the layout (also counted as a backup)

5. Recommended resources

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