高仿网易严选底部弹出菜单

在网易严选的看东西的时候在商品详情页里看到他的底部弹出菜单，本能反应是想用DottomSheetDialog或者PopupWindow来实现，可是发现实现不了他那种效果，于是就自己模仿一个像严选这样的底部弹出菜单。

不管是DottomSheetDialog或者PopupWindow他们的阴影背景都是全部覆盖的，这就造成除了菜单内容的View之外其他都是阴影的，而严选不是这样的。唠叨到此，首先展示效果图如下：

是不是还可以呢，由于代码量不多却注释详细，所以先贴出代码再一一详说:

BottomPopupWindowView类：
“`

public class BottomPopupWindowView extends LinearLayout{

private AnimatorListener animatorListener;
//底部内容的View
private FrameLayout base_view;
//内容的View
private FrameLayout content_view;
//背景的View
private RelativeLayout popup_bg;
//xml加载的View
private View bottomPopouView;
//外部加载的内容View
private View contentView;
//外部加载的底部内容View
private View baseView;
//手势的最小值
private float minVelocity=0;
//加载一次的判断值
private boolean mDrawable=true;

public void setAnimatorListener(AnimatorListener animatorListener) {
    this.animatorListener = animatorListener;
}

public void setBaseView(View baseView){
    this.baseView=baseView;
}

public void setContextView(View view){
    this.contentView=view;
}

public void setContentView(int id){
    this.contentView=LayoutInflater.from(getContext()).inflate(id,null);
}

public BottomPopupWindowView(Context context) {
    this(context,null);
}

public BottomPopupWindowView(Context context, @Nullable AttributeSet attrs) {
    this(context,attrs,0);
}

public BottomPopupWindowView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    //初始化各种数值
    minVelocity=ViewConfiguration.get(getContext()).getScaledTouchSlop();
    bottomPopouView= LayoutInflater.from(getContext()).inflate(R.layout.layout_bottom_popup,null);
    base_view=(FrameLayout)bottomPopouView.findViewById(R.id.bottom_view);
    content_view=(FrameLayout)bottomPopouView.findViewById(R.id.content_view);
    popup_bg=(RelativeLayout)bottomPopouView.findViewById(R.id.popup_bg);
    //把整个View都加载在LinearLayout里以显示出来
    addView(bottomPopouView);
    //背景颜色监听
    popup_bg.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            disMissPopupView();
        }
    });

    //屏蔽内容区域点击事件
    content_view.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View view){}
    });

    //屏蔽底部内容区域点击事件
    base_view.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View view){}
    });

    //内容区域判断是否向下，手势向下就关闭弹框
    content_view.setOnTouchListener(new OnTouchListener() {
        @Override
        public boolean onTouch(View view, MotionEvent motionEvent) {
            float y1=0,y2=0;
            if(motionEvent.getAction() == MotionEvent.ACTION_DOWN) {
                y1 = motionEvent.getY();
            }
            if(motionEvent.getAction() == MotionEvent.ACTION_UP){
                y2 = motionEvent.getY();
                if((y2-y1)>minVelocity){
                    disMissPopupView();
                }
            }
            return false;
        }
    });

}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if(mDrawable&&baseView!=null){
        //刚开始加载底部内容区域，只需一次就行，多次报错
        base_view.addView(baseView);
        mDrawable=false;
    }
}

public void showPopouView(){
    if(contentView!=null){
        //开始动画数据
        startAnimation();
        //开启背景颜色的渐变动画
        popup_bg.setVisibility(View.VISIBLE);
        popup_bg.setAnimation(AnimationUtils.loadAnimation(getContext(), R.anim.bp_bottom_bg_in));
        //把这个区域全部显示出来
        ((BottomPopupWindowView)this).setLayoutParams(new RelativeLayout.LayoutParams(
                RelativeLayout.LayoutParams.MATCH_PARENT,RelativeLayout.LayoutParams.MATCH_PARENT));
        //假如内容区域
        content_view.addView(contentView,0);
        content_view.setVisibility(View.VISIBLE);
        //开启内容区域动画
        content_view.setAnimation(AnimationUtils.loadAnimation(getContext(),R.anim.bp_bottom_view_in));
    }
}

public void disMissPopupView(){
    //开始关闭动画数据
    endAnimation();
    //开启内容区域动画
    content_view.setVisibility(View.GONE);
    Animation animation=AnimationUtils.loadAnimation(getContext(),R.anim.bp_bottom_view_out);
    animation.setAnimationListener(new Animation.AnimationListener() {
        @Override
        public void onAnimationStart(Animation animation) {}
        @Override
        public void onAnimationRepeat(Animation animation) {}
        @Override
        public void onAnimationEnd(Animation animation) {
            //等内容区域动画结束后，清楚所有View
            content_view.removeAllViews();
            //开启背景颜色的渐变动画
            popup_bg.setVisibility(View.GONE);
            popup_bg.setAnimation(AnimationUtils.loadAnimation(getContext(), R.anim.bp_bottom_bg_out));
            //把整个控件的大小恢复到底部View区域的大小
            RelativeLayout.LayoutParams layoutParams=new RelativeLayout.LayoutParams(
                    RelativeLayout.LayoutParams.MATCH_PARENT,getViewHeight((BottomPopupWindowView)BottomPopupWindowView.this));
            layoutParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM,-1);
            ((BottomPopupWindowView)BottomPopupWindowView.this).setLayoutParams(layoutParams);
        }
    });
    //开始动画
    content_view.setAnimation(animation);
}

//获取View的高度
public int getViewHeight(View view){
    int width =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
    int height =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
    view.measure(width,height);
    return view.getMeasuredHeight();
}

//开始动画数据变化
public void startAnimation(){
    ValueAnimator valueAnimator = ValueAnimator.ofInt(0,40);
    valueAnimator.setDuration(250);
    valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator valueAnimator) {
            if(animatorListener!=null){
                animatorListener.startValue((int) valueAnimator.getAnimatedValue());
            }
        }
    });
    valueAnimator.start();
}

//结束动画数值变化
public void endAnimation() {
    ValueAnimator valueAnimator = ValueAnimator.ofInt(40,0);
    valueAnimator.setDuration(250);
    valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator valueAnimator) {
            if(animatorListener!=null){
                animatorListener.endValue((int) valueAnimator.getAnimatedValue());
            }
        }
    });
    valueAnimator.start();
}

}

对应的加载的xml布局是：
layout_bottom_popou.xml如下：

1.在BottomPopupWindowView是继承LinearLayout，而layout_bottom_popou.xml是这整个BottomPopupWindowView里的骨架，然后在BottomPopupWindowView初始化的时候通过addView()来加载整个骨架布局。在onDraw()里只需加载一次baseView就可以了，不然后重复加载导致报错。这样就初始化成功了，刚开始只会加载baseView的界面，就相当于严选最下面的购物车立即购买等界面。
![baseView.png](http://upload-images.jianshu.io/upload_images/925576-b6d39da3e30437a3.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

2.当调用showPopouView()时显示菜单的。startAnimation()方法只是为了产生动画的数据。```
popup_bg.setVisibility(View.VISIBLE);
popup_bg.setAnimation(AnimationUtils.loadAnimation(getContext(), R.anim.bp_bottom_bg_in)); ```只是为了开启背景渐变的动画没什么说的。最重要的是显示菜单实现是把BottomPopupWindowView的大小扩展到全屏，所以设置```((BottomPopupWindowView)this).setLayoutParams(new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT,RelativeLayout.LayoutParams.MATCH_PARENT)); ```,然后把弹出菜单的View即contentView装进content_view即可，然后开启弹出动画就实现了。

3.最后是disMissPopupView()方法关闭弹窗。endAnimation()方法只是为了产生动画的数据。再启动内容域View即content_View的退出动画，在动画结束后用```content_view.removeAllViews(); ```
起初菜单内容，再像上面一样开启背景颜色渐变动画，最后只需使BottomPopupWindowView恢复原来的baseView的大小及可以了，具体如下:```  RelativeLayout.LayoutParams layoutParams=new RelativeLayout.LayoutParams(
                        RelativeLayout.LayoutParams.MATCH_PARENT,getViewHeight((BottomPopupWindowView)BottomPopupWindowView.this));
                layoutParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM,-1);
                ((BottomPopupWindowView)BottomPopupWindowView.this).setLayoutParams(layoutParams); ```。这就是核心的代码功能了，代码量不多具体细节看上面的源码。


有人或许会问返回动画的数据有什么用，很简单就是为了实现严选菜单框出来时整个上面详情的缩放。具体看如下demo,首先给出界面xml,如下:

这就是上面效果图的界面布局，没什么可以说的，再看事例代码如下：

public class MainActivity extends AppCompatActivity implements View.OnClickListener, AnimatorListener {

private BottomPopupWindowView bottomPopupWindowView;
private View contentView;
private View bottomView;
private LinearLayout mainView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mainView=(LinearLayout)findViewById(R.id.main_view);

    bottomView=LayoutInflater.from(this).inflate(R.layout.layout_bottom_view,null);
    (bottomView.findViewById(R.id.promptly_buy)).setOnClickListener(this);
    (findViewById(R.id.guige)).setOnClickListener(this);
    bottomPopupWindowView=(BottomPopupWindowView)findViewById(R.id.bottom_popup);
    bottomPopupWindowView.setOnClickListener(this);
    bottomPopupWindowView.setBaseView(bottomView);
    contentView=LayoutInflater.from(this).inflate(R.layout.layout_content_view,null);
    bottomPopupWindowView.setContextView(contentView);
    (contentView.findViewById(R.id.ic_cancel)).setOnClickListener(this);
    bottomPopupWindowView.setAnimatorListener(this);
}

@Override
public void onClick(View view) {
    switch(view.getId()){
        case R.id.promptly_buy:
        case R.id.ic_cancel:
            bottomPopupWindowView.disMissPopupView();
            break;
        case R.id.guige:
            bottomPopupWindowView.showPopouView();
            break;
    }
}

@Override
public void startValue(int value) {
    setMargins (mainView,value-10,value,value-10,value);
}

@Override
public void endValue(int value) {
    setMargins (mainView,value,value,value,value);
}

public static void setMargins (View v, int l, int t, int r, int b) {
    if (v.getLayoutParams() instanceof ViewGroup.MarginLayoutParams) {
        ViewGroup.MarginLayoutParams p = (ViewGroup.MarginLayoutParams) v.getLayoutParams();
        p.setMargins(l, t, r, b);
        v.requestLayout();
    }
}

}


其中设置内容菜单的View
BottomPopupWindowView.setContextView(bottomView);
设置没有显示菜单时候显示的View(注:bottomView的高度要和BottomPopupWindowView的高度一样，具体看demo)
BottomPopupWindowView.setBaseView(bottomView);“`而回调的
public void startValue(int value)和public void endValue(int value)设置动画监听放回的数据，以便根据数据实现动画，严选的弹出和显示商品详情动画很简单就是不断设设置View的间距就可以了。

最后附上demo和源码链接https://github.com/jack921/BottomPopupWindowDemo