使用webview外部佈局必須填滿或設定高度，所以佈局如下[二維碼原背景為無，chrome顯示為黑色，坑。。。]：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="horizontal">
    <WebView
        android:id
 
="@+id/web"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scrollbars="none"
        android:layout_gravity="center_horizontal"/>
</LinearLayout>

final View view = LayoutInflater.from(MainActivity.this).inflate(R.layout.qrcode,null);
final android.webkit
 
.WebView web = (android.webkit.WebView) view.findViewById(R.id.web);
web.getSettings().setUseWideViewPort(true);
web.getSettings().setLoadWithOverviewMode(true);
if(qrDialog == null){
     qrDialog = new AlertDialog.Builder(MainActivity.this)
                    .setView(view).create();
}
getProgressDialog().show
 
();
final android.view.WindowManager.LayoutParams p = qrDialog.getWindow().getAttributes();
final ViewGroup.LayoutParams params = web.getLayoutParams();

vto.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
    @Override
    public void onGlobalLayout() {
          if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                view.getViewTreeObserver().removeOnGlobalLayoutListener(this);
          }else
                view.getViewTreeObserver().removeGlobalOnLayoutListener(this);
                int height = view.getHeight();
                params.width = PictureUtil.dip2px(MainActivity.this,height);
                params.height = PictureUtil.dip2px(MainActivity.this,height);
                p.width = PictureUtil.dip2px(MainActivity.this,height)+70;
                qrDialog.getWindow().setAttributes(p);
                web.setLayoutParams(params);
          }
   });

web.setWebViewClient(new WebViewClient(){
     @Override
     public void onPageFinished(WebView view, String url) {
          super.onPageFinished(view, url);
          getProgressDialog().dismiss();
          qrDialog.show();
    }
});

 web.loadUrl("二維碼網址。。。");

比較坑的是，還是做不到長寬一致只能保證二維碼顯示是完整的，所以這裡加了一個數字，看起來稍微自然。
p.width = PictureUtil.dip2px(MainActivity.this,height)+70;