默认DialogFragment距离屏幕的两边有一定的间距，所以宽度填充满需要手动设置。
1, 在start设置它的宽度

override fun onStart() {
        super.onStart()
        val dialog = dialog
        dialog!!.setCancelable(false)
        dialog.setCanceledOnTouchOutside(false)
        if (dialog != null) {
            //java 
            //DisplayMetrics dm =new DisplayMetrics();
            val dm = DisplayMetrics()
            activity!!.windowManager.defaultDisplay.getMetrics(dm)
            dialog.window!!.setLayout(dm.widthPixels * 1, ViewGroup.LayoutParams.WRAP_CONTENT)
            //dialog.window!!.setLayout( ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT)
        }
    }

2,必须注意，单这么设置还不行，必须设置它的style,否则不起作用。

public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setStyle(DialogFragment.STYLE_NO_TITLE, R.style.MyDialog);
    }

style name="MyDialog" parent="@style/Theme.AppCompat.Dialog">
        <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/black</item>
        <item name="android:windowBackground">@android:color/transparent</item>
    </style>

//TODO 设置dialog位置 
    private void initData(View view) {
        Dialog dialog = getDialog();
        Window window = dialog.getWindow();
        window.setGravity(Gravity.CENTER);
        window.setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
    }