Android Nougat: TextureView doesn't support displaying a background drawable

Question

I have been using a TextureView in my android app, and it was working fine. Just recently I tested my code on an Android device with Android API 25 (7.1.2). Same code now does not work and throws the error, java.lang.UnsupportedOperationException: TextureView doesn't support displaying a background drawable.

I know that void setBackgroundDrawable (Drawable background) had been deprecated for a long time, and now it must have been removed. But I am not even setting it by myself.

I am using latest buildTools and SDK. So, I wonder why hasn't the textureView internal implementation been updated.

Here is the relevant stack trace:

java.lang.UnsupportedOperationException: TextureView doesn't support displaying a background drawable
at android.view.TextureView.setBackgroundDrawable(TextureView.java:315)
at android.view.View.setBackground(View.java:18124)
at android.view.View.<init>(View.java:4573)
at android.view.View.<init>(View.java:4082)
at android.view.TextureView.<init>(TextureView.java:159)
at com.abdulwasaetariq.xyz.ui.customView.AutoFitTextureView.<init>(AutoFitTextureView.java:24)
at com.abdulwasaetariq.xyz.ui.customView.AutoFitTextureView.<init>(AutoFitTextureView.java:20)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
[...]
at java.lang.Thread.run(Thread.java:745)

Here is how i use my (not-yet customized) custom TextureView:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.abdulwasaetariq.xyz.ui.activity.MainActivity">

    <com.abdulwasaetariq.xyz.ui.customView.AutoFitTextureView
        android:id="@+id/texture"
        android:layout_width="1080px"
        android:layout_height="1080px"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true" />

</RelativeLayout>

Here is my relevant AutoFitTextureView.java: enter code here

public class AutoFitTextureView extends TextureView {

private int mRatioWidth = 0;
private int mRatioHeight = 0;

public AutoFitTextureView(Context context) {
    this(context, null);
}

public AutoFitTextureView(Context context, AttributeSet attrs) {
    this(context, attrs, 0); //(LINE#20)
}

public AutoFitTextureView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle); //(LINE#24)
}

public void setAspectRatio(int width, int height) {
    if (width < 0 || height < 0) {
        throw new IllegalArgumentException("Size cannot be negative.");
    }
    mRatioWidth = width;
    mRatioHeight = height;
    requestLayout();
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    int width = MeasureSpec.getSize(widthMeasureSpec);
    int height = MeasureSpec.getSize(heightMeasureSpec);
    if (0 == mRatioWidth || 0 == mRatioHeight) {
        setMeasuredDimension(width, height);
    } else {
        if (width < height * mRatioWidth / mRatioHeight) {
            setMeasuredDimension(width, width * mRatioHeight / mRatioWidth);
        } else {
            setMeasuredDimension(height * mRatioWidth / mRatioHeight, height);
        }
    }
}}

So, as you can see, the exceptions occur at the super() methods, which means that my custom TextureView is not responsible for this exception. It's an inside call.

Here is my gradle config:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion '25.0.2'
    defaultConfig {
        applicationId "com.abdulwasaetariq.xyz"
        minSdkVersion 21
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
        })
    compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha8'
    compile 'com.github.hotchemi:permissionsdispatcher:2.3.2'
    annotationProcessor 'com.github.hotchemi:permissionsdispatcher-processor:2.3.2'
}

Any ideas why this may be happening? Any release-notes of Android API 25, where this change is talked about?

Answer 1

If you look at the source for texture view for API 24 you will see the following:

/**
 * Subclasses of TextureView cannot do their own rendering
 * with the {@link Canvas} object.
 *
 * @param canvas The Canvas to which the View is rendered.
 */
@Override
public final void draw(Canvas canvas) {
    // NOTE: Maintain this carefully (see View#draw)
    mPrivateFlags = (mPrivateFlags & ~PFLAG_DIRTY_MASK) | PFLAG_DRAWN;

    /* Simplify drawing to guarantee the layer is the only thing drawn - so e.g. no background,
    scrolling, or fading edges. This guarantees all drawing is in the layer, so drawing
    properties (alpha, layer paint) affect all of the content of a TextureView. */

    if (canvas.isHardwareAccelerated()) {
        DisplayListCanvas displayListCanvas = (DisplayListCanvas) canvas;

        HardwareLayer layer = getHardwareLayer();
        if (layer != null) {
            applyUpdate();
            applyTransformMatrix();

            mLayer.setLayerPaint(mLayerPaint); // ensure layer paint is up to date
            displayListCanvas.drawHardwareLayer(layer);
        }
    }
}

The comment in the body of draw() gives the rationale for the change you have seen. This is the only documentation that I have found. Compare this to TextureView from API 23:

/**
 * Subclasses of TextureView cannot do their own rendering
 * with the {@link Canvas} object.
 *
 * @param canvas The Canvas to which the View is rendered.
 */
@Override
public final void draw(Canvas canvas) {
    // NOTE: Maintain this carefully (see View.java)
    mPrivateFlags = (mPrivateFlags & ~PFLAG_DIRTY_MASK) | PFLAG_DRAWN;

    applyUpdate();
    applyTransformMatrix();
}

API 24 also introduced overrides for the "set background" methods that are not overridden in API 23. Setting a background is now clearly discouraged and is just not allowed. If you are seeing the unsupported operation exception and you are not explicitly setting a background then it is probably sneaking in through your styles. Try setting android:background="@null" in your XML to force the background to be null to get around the error. You can also add the following code to your custom view to retain the functionality on those versions that support setting a background:

@Override
public void setBackgroundDrawable(Drawable background) {
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N && background != null) {
        setBackgroundDrawable(background);
    }
}

It is unclear how to replace the functionality that you have lost for API 24+ or if you even need it but just want to have the background tool in your arsenal.