我突然感覺不應該說那麼多，直接上程式碼和解釋就好了，畢竟根據需求搜尋的，說那麼多廢話也沒啥用處。

popwindow不想dialog那樣，彈出之後背景就會變暗，他的背景是不會變得，所以需要我們手動的去使他變暗。我們可以修改WindowManager的引數來是背景變暗，但是修改之後toolBar也會變暗，有些時間我們不希望toolBar變暗，就不能修改引數，我們可以通過新增一個View來來覆蓋介面達到變暗的效果。

首先寫一下修改WindowManager的引數來達到變暗的效果

 // 設定背景顏色變暗
        WindowManager.LayoutParams lp = getWindow().getAttributes
 
();
        lp.alpha = 0.7f;
        getWindow().setAttributes(lp);

然後我們可以監聽popWindow來取消變暗

 mPopupWindow.setOnDismissListener(new PopupWindow.OnDismissListener() {

            @Override
            public void onDismiss() {
                WindowManager.LayoutParams lp = getWindow().getAttributes();
                lp.alpha = 1
 
f;
                getWindow().setAttributes(lp);
            }
        });

以上是通過程式碼來達到變暗的效果。下面就講一下使用View覆蓋來達到效果。

這個是覆蓋的View

<View
        android:id="@+id/gray_layout"
        android:layout_below="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
 

        android:background="#66000000"
        android:visibility="gone" />

 //對黑色半透明背景做監聽，點選時開始退出動畫並將popupwindow dismiss掉
        mGrayLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (isPopWindowShowing) {
                    mPopupWindow.getContentView().startAnimation(AnimationUtil.createOutAnimation(MainActivity.this, fromYDelta));
                    mPopupWindow.getContentView().postDelayed(new Runnable() {
                        @Override
                        public void run() {
                            mPopupWindow.dismiss();
                        }
                    }, AnimationUtil.ANIMATION_OUT_TIME);
                }
            }
        });

下面是在你呼叫popWindow的地方的程式碼

if (isPopWindowShowing) {
            mPopupWindow.getContentView().startAnimation(AnimationUtil.createOutAnimation(MainActivity.this, fromYDelta));
            mPopupWindow.getContentView().postDelayed(new Runnable() {
                @Override
                public void run() {
                    mPopupWindow.dismiss();
                }
            }, AnimationUtil.ANIMATION_OUT_TIME);

        } else {
            showPopupWindow();
        }

顯示popWindow的方法

 private void showPopupWindow() {
        final View contentView = LayoutInflater.from(this).inflate(R.layout.selsectlist, null);
        TextView t1 = (TextView) contentView.findViewById(R.id.text1);
        mPopupWindow = new PopupWindow(contentView, LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
        mPopupWindow.setBackgroundDrawable(new BitmapDrawable());
        //將這兩個屬性設定為false，使點選popupwindow外面其他地方不會消失
        mPopupWindow.setOutsideTouchable(false);
        mPopupWindow.setFocusable(false);
        mGrayLayout.setVisibility(View.VISIBLE);
        //獲取popupwindow高度確定動畫開始位置
        int contentHeight = ViewUtils.getViewMeasuredHeight(contentView);
//        int contentHeight = contentView.getHeight();
        Log.i(TAG, "contentview height=" + contentHeight);

        fromYDelta = -contentHeight;
        Log.i(TAG, "fromYDelta=" + fromYDelta);
        mPopupWindow.showAsDropDown(toolbar, 0, 0);
        mPopupWindow.getContentView().startAnimation(AnimationUtil.createInAnimation(this, fromYDelta));
        mPopupWindow.setOnDismissListener(new PopupWindow.OnDismissListener() {
            @Override
            public void onDismiss() {
                isPopWindowShowing = false;
                mGrayLayout.setVisibility(View.GONE);
            }
        });
        isPopWindowShowing = true;
    }

給PopWindow新增動畫：

public class AnimationUtil {

    //動畫持續時間
    public final static int ANIMATION_IN_TIME=500;
    public final static int ANIMATION_OUT_TIME=500;

    public static Animation createInAnimation(Context context,int fromYDelta){
        AnimationSet set=new AnimationSet(context,null);
        set.setFillAfter(true);

        TranslateAnimation animation=new TranslateAnimation(0,0,fromYDelta,0);
        animation.setDuration(ANIMATION_IN_TIME);
        set.addAnimation(animation);

        AlphaAnimation alphaAnimation=new AlphaAnimation(0,1);
        alphaAnimation.setDuration(ANIMATION_IN_TIME);
        set.addAnimation(alphaAnimation);


        return set;
    }

    public static Animation createOutAnimation(Context context, int toYDelta){
        AnimationSet set=new AnimationSet(context,null);
        set.setFillAfter(true);

        TranslateAnimation animation=new TranslateAnimation(0,0,0,toYDelta);
        animation.setDuration(ANIMATION_OUT_TIME);
        set.addAnimation(animation);

        AlphaAnimation alphaAnimation=new AlphaAnimation(1,0);
        alphaAnimation.setDuration(ANIMATION_OUT_TIME);
        set.addAnimation(alphaAnimation);


        return set;
    }
}

測量PopWindow的寬高

public class ViewUtils {

    /**
     * 獲取控制元件的高度
     */
    public static int getViewMeasuredHeight(View view) {
        calculateViewMeasure(view);
        return view.getMeasuredHeight();
    }

    /**
     * 獲取控制元件的寬度
     */
    public static int getViewMeasuredWidth(View view) {
        calculateViewMeasure(view);
        return view.getMeasuredWidth();
    }

    /**
     * 測量控制元件的尺寸
     */
    private static void calculateViewMeasure(View view) {
        int w = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
        int h = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);

        view.measure(w, h);
    }
}