我一直在我的 Android 应用程序中使用 TextureView，它运行良好。就在最近，我在使用 Android API 25 (7.1.2) 的 Android 设备上测试了我的代码。相同的代码现在不起作用并引发错误，java.lang.UnsupportedOperationException: TextureView 不支持显示背景可绘制对象。

我知道 void setBackgroundDrawable(可绘制背景) 是 deprecated for a long time ，现在它必须已被删除。但我什至不是自己设置的。

我正在使用最新的 buildTools 和 SDK。所以，我想知道为什么没有更新 textureView 内部实现。

这是相关的堆栈跟踪:

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)

这是我如何使用我的(尚未定制的)自定义 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>

这是我的相关 AutoFitTextureView.java: 在此处输入代码

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);
        }
    }
}}

所以，如您所见，异常发生在 super() 方法中，这意味着我的自定义 TextureView 不对这个异常负责。这是内线电话。

这是我的 gradle 配置:

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'
}

知道为什么会发生这种情况吗？ Android API 25 的任何发行说明，其中讨论了此更改？

最佳答案

以下是 View 源代码的 fragment 安卓牛轧糖:

/**
 * Allow setForeground/setBackground to be called (and ignored) on a textureview,
 * without throwing
 */
static boolean sTextureViewIgnoresDrawableSetters = false;

在单参数构造函数中(从所有其他构造函数中调用):

        // Prior to N, TextureView would silently ignore calls to setBackground/setForeground.
        // On N+, we throw, but that breaks compatibility with apps that use these methods.
        sTextureViewIgnoresDrawableSetters = targetSdkVersion <= M;

在抛出异常的 View 构造函数中:

...
        switch (attr) {
            case com.android.internal.R.styleable.View_background:
                background = a.getDrawable(attr);
                break;
...
    if (background != null) {
        setBackground(background);  // <--- this is the problematic line, apparently "background" is not null here
    }

setBackground的实际定义:

/**
 * Set the background to a given Drawable, or remove the background. If the
 * background has padding, this View's padding is set to the background's
 * padding. However, when a background is removed, this View's padding isn't
 * touched. If setting the padding is desired, please use
 * {@link #setPadding(int, int, int, int)}.
 *
 * @param background The Drawable to use as the background, or null to remove the
 *        background
 */
public void setBackground(Drawable background) {
    //noinspection deprecation
    setBackgroundDrawable(background);
}

然后覆盖TextureView中的setBackgroundDrawable :

@Override
public void setBackgroundDrawable(Drawable background) {
    if (background != null && !sTextureViewIgnoresDrawableSetters) {
        throw new UnsupportedOperationException(
                "TextureView doesn't support displaying a background drawable");
    }
}

因此，您可以将以下所有内容拼凑起来: 1) 你有一个目标 SDK N (Nougat) - 从你的构建文件中很明显； 2) View 的构造函数确定非空背景(我暂时无法解释这部分)。

这就是成为一个实际问题所需要的一切。我没有看到您已设法在 xml 中定义可绘制对象，因此覆盖 setBackground 或 setBackgroundDrawable 似乎是解决我的问题的最明智的可能性。可能有另一种解决方法(或者“建议的用法”可能是一个更好的术语)，您可以设法强制构造函数中的 background 变量保持为空。

关于安卓牛轧糖 : TextureView doesn't support displaying a background drawable，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/43705434/