CardView shadow not rendered when converted to bitmap

问题

THE PROBLEM

I'm try to save a view group (which has a CardView as one of its childern) as a PNG file. To achieve this,

1. I inflate the view group and populate the views with required information
2. Load an image to an image view via Glide
3. Add a ViewTreeObserver.OnGlobalLayoutListener to the ViewTreeObserver of the image view and pass the entire (parent) view that is going to be shared to a method that converts the view to a bitmap when image view's bottom is greater than zero (image view's height attribute is set to wrap_content, thus its bottom will be zero until image is loaded).

By doing this, I'm able to convert the view to a bitmap, however, with one caveat: the CardView's show is not rendered on the bitmap.

FAILED ATTEMPTS

So far I've tried:

1. Switching between layerType attribute from "software" to "hardware".
2. Setting on and off cardUseCompatPadding attribute of the CardView.
3. Tried setting the image drawable without using Glide.
4. Tried without loading an image drawable at all.

THE CODE

Here are code snippets that might help you guys identify the problem:

The method used to convert a view to a bitmap

public static Bitmap getBitmapFromView(View view) {
    //Define a bitmap with the same size as the view
    Bitmap b = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);
    //Bind a canvas to it
    Canvas canvas = new Canvas(b);
    //Get the view's background
    Drawable bgDrawable = view.getBackground();
    if (bgDrawable != null)
        //has background drawable, then draw it on the canvas
        bgDrawable.draw(canvas);
    else
        //does not have background drawable, then draw white background on the canvas
        canvas.drawColor(Color.WHITE);
    // draw the view on the canvas
    view.draw(canvas);
    //return the bitmap
    return b;
}

XML layout file of the view that's being inflated and passed to the getBitmapFromView() above.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="16dp">

    <com.devspark.robototextview.widget.RobotoTextView
        android:id="@+id/title"
        style="@style/text_subhead"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top"
        android:layout_marginBottom="@dimen/lessons_horizontal_margin_narrow"
        android:layout_marginLeft="@dimen/lessons_horizontal_margin_narrow"
        android:layout_marginRight="@dimen/lessons_horizontal_margin_narrow"
        android:layout_marginTop="@dimen/lessons_horizontal_margin_narrow"
        android:gravity="left"
        app:typeface="roboto_medium" />

    <com.devspark.robototextview.widget.RobotoTextView
        android:id="@+id/text"
        style="@style/text_subhead"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="@dimen/lessons_horizontal_margin_narrow"
        android:layout_marginRight="@dimen/lessons_horizontal_margin_narrow"
        android:gravity="left"
        android:textColor="@color/text"
        app:typeface="roboto_regular" />

    <android.support.v7.widget.CardView
        android:id="@+id/image_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/lessons_horizontal_margin_narrow"
        app:cardCornerRadius="@dimen/lessons_image_card_corner_radius"
        app:cardElevation="3dp"
        app:cardPreventCornerOverlap="false"
        app:cardUseCompatPadding="true">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <com.makeramen.roundedimageview.RoundedImageView
                android:id="@+id/image"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:contentDescription="@null"
                app:riv_corner_radius_top_left="@dimen/lessons_image_card_corner_radius"
                app:riv_corner_radius_top_right="@dimen/lessons_image_card_corner_radius" />

            <com.devspark.robototextview.widget.RobotoTextView
                android:id="@+id/caption"
                style="@style/text_caption"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/lessons_image_card_caption_margin"
                android:gravity="left"
                app:typeface="roboto_condensed_regular" />

        </LinearLayout>

    </android.support.v7.widget.CardView>

    <!-- Some other views that aren't particularly interesting -->

</LinearLayout>

回答1:

just change cardview to view, and set

android:background="@android:drawable/dialog_holo_light_frame"

ofcause you need to deal the padding yourself

回答2:

I have a same problem. So after searching, I founded this. Hope this help https://medium.com/@ArmanSo/take-control-of-views-shadow-android-c6b35ba573e9

来源：https://stackoverflow.com/questions/32931652/cardview-shadow-not-rendered-when-converted-to-bitmap