默认新建的 DialogFragment 是有边距的，想要充满整个屏幕，需要在onStart()里面加入下面代码：

 @Override
    public void onStart() {
        super.onStart();
        WindowManager.LayoutParams params = getDialog().getWindow().getAttributes();
        params.width = UIUtils.getScreenWidth(getContext());
        params.height = RelativeLayout.LayoutParams.MATCH_PARENT;
        params.gravity = Gravity.BOTTOM;
       //高度自己定义
        getDialog().getWindow().setLayout(RelativeLayout.LayoutParams.MATCH_PARENT, DensityUtil.dip2px(492));
    }

PS：而且记得在onCreat()里面设置dialog样式 setStyle()，要不然不起作用

@Override

    public void onCreate(@Nullable Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setStyle(DialogFragment.STYLE_NO_TITLE, R.style.fragment_dialog);

    }

fragment_dialog样式

<style name="fragment_dialog" parent="@style/Theme.AppCompat.Dialog">
        <item name="android:windowAnimationStyle">@style/ShareDialogAnimation</item>
        <item name="android:windowCloseOnTouchOutside">true</item> 
        <item name="android:windowFrame">@null</item>
        <item name="android:windowIsFloating">true</item>
        <item name="android:windowIsTranslucent">true</item>
        <item name="android:windowNoTitle">true</item>
        <item name="android:background">@android:color/transparent</item>
        <item name="android:windowBackground">@android:color/transparent</item>
    </style>