android - BottomSheet 动画持续时间

Question

我正在为我的一种布局使用 BottomSheet View 。对于一个非常具体的情况，我需要 BottomSheet 的动画持续时间，它通过 setState(...) 方法在布局中滑动。它应该在 400 毫秒左右，但我不希望在这种情况下使用“神奇”数字。

Answer 1

BottomSheetBehavior 的持续时间由 setState 触发的动画或触摸事件取决于各种条件。

BottomSheetBehavior 内部使用 ViewDragHelper这决定了 computeAxisDuration() 内的动画持续时间私有(private)方法。这个持续时间取决于一些任意值，不能通过官方 API 更改:

public class ViewDragHelper {
    ...
    private static final int BASE_SETTLE_DURATION = 256; // ms
    private static final int MAX_SETTLE_DURATION = 6000; // ms
    ...
}

更改显示/隐藏动画时间的 hack 解决方案是...

• 将整个 BottomSheetBehavior 和 ViewDragHelper 类源代码复制到您的项目中(使用不同的包名称)
• 在您的文件 BottomSheetBehavior.java 中 - 更改 import ViewDragHelper 以使用您的 ViewDragHelper 而不是原始的 Android API 类。
• 在文件 ViewDragHelper.java 中 - 更改 computeAxisDuration 返回的持续时间以满足您的要求，例如正好返回 400 毫秒。
• 使用您的 BottomSheetBehavior 类代替原来的类。

这是一个非常糟糕的解决方案，但它在我的项目中有效。详情如下。

文件ViewDragHelper.java

public class ViewDragHelper {
    // Additional fields and methods defined.
    private int mSettleDuration = BASE_SETTLE_DURATION;
    public void setDurationSpeedFactor(final float factor) {
        mSettleDuration = (int)(factor * BASE_SETTLE_DURATION);
    }
    private boolean mSkipAnimation = false;
    public void setSkipAnimation(final boolean skipAnimation) {
        this.mSkipAnimation = skipAnimation;
    }
    // Modified version of private function.
    private int computeAxisDuration(int delta, int velocity, int motionRange) {
        if (delta == 0) {
            return 0;
        }
    
        final int width = mParentView.getWidth();
        final int halfWidth = width / 2;
        final float distanceRatio = Math.min(1f, (float) Math.abs(delta) / width);
        final float distance = halfWidth + halfWidth
            * distanceInfluenceForSnapDuration(distanceRatio);
        
        int duration;
        velocity = Math.abs(velocity);
        if (velocity > 0) {
            duration = 4 * Math.round(1000 * Math.abs(distance / velocity));
        } else {
            final float range = (float) Math.abs(delta) / motionRange;
            duration = (int) ((range + 1) * mSettleDuration);
        }
        return Math.min(duration, MAX_SETTLE_DURATION);
    }
    // Rest of original class body here...
}

文件 BottomSheetBehavior.java

// Comment out original ViewDragHelper and use above modified version.
//import androidx.customview.widget.ViewDragHelper;
import your.custom.ViewDragHelper;

public class BottomSheetBehavior<V extends View> extends CoordinatorLayout.Behavior<V> {

    /**
     * Allows to set up ViewDragHelper immediately or when it is created.
     */
    public interface IDragHelperConfig {
        void onDragHelperCreated(ViewDragHelper viewDragHelper);
    }
    private IDragHelperConfig iDragHelperConfig;
    public void setIDragHelperConfig(IDragHelperConfig iDragHelperConfig) {
        this.iDragHelperConfig = iDragHelperConfig;
        if (viewDragHelper != null) {
            iDragHelperConfig.onDragHelperCreated(viewDragHelper);
        }
    }
    //...
    public boolean onLayoutChild(...) {
        if (viewDragHelper == null) {
            viewDragHelper = ViewDragHelper.create(parent, dragCallback);
            if (iDragHelperConfig != null) {
                iDragHelperConfig.onDragHelperCreated(viewDragHelper);
            }
        }
    }
    //...
}

任何android View 初始化中的示例代码

    val params: CoordinatorLayout.LayoutParams = myLayout.layoutParams as CoordinatorLayout.LayoutParams
    val behavior = BottomSheetBehavior<FrameLayout>(myLayout.context, null)
    // Optionally, set the height of the bottom sheet when it is collapsed (usefull for experiments).
    // behavior.peekHeight = 20
    
    // Configure bottom sheet behavior.
    behavior.setIDragHelperConfig {
        // Set how many times to slow the speed of the animation
        // (relative to original Android animation speed).
        it.setDurationSpeedFactor(20f)

        // Optionally, turn off animation
        // Useful when entering a new activity and 
        // initial animation is not desired.
        it.setSkipAnimation(false)
    }
    params.behavior = behavior