使用MotionLayout实现高德地图bottomSheets效果

高德效果

• 搜到的一个效果，附上链接,用的behavior，我没下源码看，因为我只是想尝试另外一种方式。具体效果暂不知 Android 仿高德地图可拉伸的BottomSheet

以下是我用motionlayout实现的效果，没有达到丝滑流畅，优化就看小伙伴你了

缘由

• 使用高德地图的时候看着这种体验很好，随后就想试试怎么达到类似效果
• 最近正在看MotionLayout的东西，正好就尝试尝试

MotionLayout

• 「译」 MotionLayout 介绍 (Part I - IV) 系列教会你如何使用MotionLayout
• 这里不做过多描述，总结一下在xml文件夹下创建 xxscene.xml 主要用于描述场景动画的关键帧和view状态变化等
• xxscene.xml 内容包括 主要为3个关键内容：

1. Transition 过渡

constraintSetStart :启动约束场景

constraintSetEnd ：结束约束场景

app:dragDirection="dragUp" 拽动(拖拉)

2. KeyFrameSet 关键帧集合

KeyAttribute 关键帧

app:framePosition 位置，进度

app:target="@id/xxx 被描述的view id

3. ConstraintSet 约束集合

<Transition
        app:constraintSetEnd="@id/slideup_end"
        app:constraintSetStart="@id/slideup_start"
        app:duration="600"
        app:interpolator="easeIn">
        <OnSwipe
            app:dragDirection="dragUp"
            app:maxAcceleration="600"
            app:touchAnchorSide="top"
            app:touchAnchorId="@id/content"
           />
        <KeyFrameSet>
            <KeyAttribute
                android:alpha="0"
                app:framePosition="45"
                app:target="@id/sugar_title" />

            <KeyAttribute
                android:alpha="1"
                app:framePosition="90"
                app:target="@id/sugar_title" />
        ...
        </KeyFrameSet>
 </Transition>   
 
 <ConstraintSet android:id="@+id/slideup_start">

        <Constraint
        ···
        />
    ...
  </ConstraintSet>  
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拆解过程

• 高德地图是上拉之后是三段式的，如图所示

MotionLayout
MotionLayout

拆解完毕

实现过程

• 设置阀值

/**
     * 初始位置
     */
    public final static float PROGRESS_START = 0f;
    /**
     * 顶部阀值 
     */
    public final static float PROGRESS_TOP = 0.9f;
    /**
     * 低部阀值 
     */
    public final static float PROGRESS_BOTTOM = 0.1f;
    /**
     * 中间位置 
     */
    public final static float PROGRESS_MIDDLE = 0.6f;
    /**
     * 结束位置 
     */
    public final static float PROGRESS_END = 1.0f;
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• 重写 MotionLayout 的 onTouchEvent 事件 ,使用 hasMiddle 布尔值判断是否有中间状态

@Override
    public boolean onTouchEvent(MotionEvent event) {
        float progress = getProgress();
        View viewGroup = findViewById(R.id.content);
        Rect mRect = new Rect();
        if (!mTouchStared) {
            viewGroup.getHitRect(mRect);
            mTouchStared = mRect.contains((int) event.getX(), (int) event.getY());
        }
        float endY;
        if (hasMiddle) {
            switch (event.getActionMasked()) {
                case MotionEvent.ACTION_CANCEL:
                    mTouchStared = false;
                    break;
                case MotionEvent.ACTION_DOWN:
                    startY = event.getY();
                    break;
                case MotionEvent.ACTION_UP:
                    endY = event.getY();
                    //手势向下
                    if ((endY - startY) > 0) {
                        if (progress >= PROGRESS_TOP) {
                            mTouchStared = false;
                            handleProgress(PROGRESS_END);

                        }
                        if (progress < PROGRESS_TOP && progress >= PROGRESS_MIDDLE) {
                            handleProgress(PROGRESS_MIDDLE);
                        }
                        if (progress < PROGRESS_MIDDLE) {
                            handleProgress(PROGRESS_START);
                        }
                        //手势向上
                    } else {
                        if (progress <= PROGRESS_BOTTOM) {
                            handleProgress(PROGRESS_START);
                        }
                        if (progress > PROGRESS_BOTTOM && progress <= PROGRESS_MIDDLE) {
                            handleProgress(PROGRESS_MIDDLE);
                        }
                        if (progress > PROGRESS_MIDDLE) {
                            mTouchStared = false;
                            handleProgress(PROGRESS_END);
                        }
                    }
                    return mTouchStared;
            }
        } else {
            if (event.getActionMasked() == MotionEvent.ACTION_CANCEL || event.getActionMasked() == MotionEvent.ACTION_UP) {
                mTouchStared = false;
                return super.onTouchEvent(event);
            }
        }
        return mTouchStared && super.onTouchEvent(event);

    }
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• bottom_scene.xml

1. 上拉超过顶部阀值 PROGRESS_TOP 之后标题出现在屏幕内，其余时候出现在屏幕外即可；
2. 初始状态这里把 scaleX 和 scaleY 设为0.9结束设为了1，仅仅是为了过渡好看，你可以不用设置随意修改即可
3. 背景色过渡，最开始透明，结束为白色背景。中间过渡关键帧95变纯白背景

结果和改进

• 设置允许中间状态后，之后进入下一步的过程，如图，过于生硬

• 改进方向

setProgress(pro);

private void handleProgress(float progress) {
        //如果需要设置的进度和当前进度相同不做处理
        if (progress == getProgress()){
            return;
        }
        //动画播放时间底值
        long time = 200;
        //进度间隔 >0 说明上拉 < 0说明下滑
        float interval = progress - getProgress();
        long startTime, endTime;
        if (interval > 0) {
            startTime = (long) (getProgress() * time);
            endTime = (long) (progress * time);
        } else {
            endTime = (long) (getProgress() * time);
            startTime = (long) (progress * time);
        }
        if (timeDisposable != null){
            timeDisposable.dispose();
        }
        //startTime 初始时间 endTime - startTime为次数 0为延迟时间 3为间隔 单位TimeUnit.MILLISECONDS 毫秒
        timeDisposable = Observable.intervalRange(startTime, endTime - startTime, 0, 3, TimeUnit.MILLISECONDS)
                .observeOn(Schedulers.io())
                .compose(((BaseActivity) getContext()).getProvider().bindToLifecycle())
                .observeOn(AndroidSchedulers.mainThread())
                .map(new Function<Long, Long>() {
                    @Override
                    public Long apply(Long aLong) throws Exception {
                        //下滑需要反向
                        if (interval < 0) {
                            long interStart = aLong - startTime;
                            return endTime - interStart;
                        }
                        return aLong;
                    }
                })
                .subscribe(new Consumer<Long>() {
                    @Override
                    public void accept(Long aLong) throws Exception {
                        float pro = (Float.valueOf(aLong) / time);
                        setProgress(pro);
                    }
                });
    }
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源码已放入sugar demo中，sugar是我会长期维护的一个库:arrow_down::arrow_down::arrow_down:

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License

Copyright 2019, wobiancao       
  
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at 
 
       http://www.apache.org/licenses/LICENSE-2.0 

   Unless required by applicable law or agreed to in writing, software
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   See the License for the specific language governing permissions and
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