Kotlin/Anko/OpenCV/CameraView 无法创建处理程序，因为线程尚未调用 Looper.prepare()

Posted 2023-04-17

【中文标题】Kotlin/Anko/OpenCV/CameraView 无法创建处理程序，因为线程尚未调用 Looper.prepare()

【英文标题】：Kotlin/Anko/OpenCV/CameraView can't create handler because thread hasn't called Looper.prepare()

【发布时间】：2019-03-14 03:44:32

【问题描述】：

所以，我目前正在尝试使用 OpenCV 将使用 CameraView 拍摄的照片转换为灰度。拍照后，我使用Anko 进行异步处理。处理完成后，我将图像写入 MediaStore。 Activity 有一个 CameraView 和一个 Button 来拍照。

但是，当我按下按钮时，出现以下异常：

java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
   at android.os.Handler.<init>(Handler.java:200)
   at android.os.Handler.<init>(Handler.java:114)
   at com.otaliastudios.cameraview.CameraUtils.decodeBitmap(CameraUtils.java:101)
   at com.otaliastudios.cameraview.CameraUtils.decodeBitmap(CameraUtils.java:83)
   at com.example.joao.waterprototype.MainActivity$onCreate$2$onPictureTaken$1.invoke(MainActivity.kt:55)
   at com.example.joao.waterprototype.MainActivity$onCreate$2$onPictureTaken$1.invoke(MainActivity.kt:46)
   at org.jetbrains.anko.AsyncKt$doAsync$1.invoke(Async.kt:143)
   at org.jetbrains.anko.AsyncKt$doAsync$1.invoke(Async.kt)
   at org.jetbrains.anko.AsyncKt$sam$java_util_concurrent_Callable$0.call(Async.kt)
   at java.util.concurrent.FutureTask.run(FutureTask.java:237)
   at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:272)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
   at java.lang.Thread.run(Thread.java:761)

上述问题发生的地方在下面的sn-p中有描述：

camera.addCameraListener(object : CameraListener() 

        override fun onPictureTaken(jpeg: ByteArray?) 

            Toast.makeText(applicationContext, "Image Taken", Toast.LENGTH_SHORT).show()

            doAsync() 

                lateinit var result : Bitmap
                CameraUtils.decodeBitmap(jpeg) 

                    val mat = Mat()
                    val bmp32 = it.copy(Bitmap.Config.ARGB_8888, true)
                    Utils.bitmapToMat(bmp32, mat)

                    val greyMat = Mat()
                    cvtColor(mat, greyMat, COLOR_BGRA2GRAY)

                    result = Bitmap.createBitmap(greyMat.cols(), greyMat.rows(), Bitmap.Config.ARGB_8888)
                    Utils.matToBitmap(greyMat, result)

                

                uiThread 

                    val title = "$UUID.randomUUID().jpg"
                    val savedImageURL = MediaStore.Images.Media.insertImage(
                            contentResolver,
                            result,
                            title,
                            "Image of $title"
                    )

                    val uri = Uri.parse(savedImageURL)
                    Toast.makeText(applicationContext, "Image Created at $uri.path", Toast.LENGTH_SHORT).show()

                
            
        

    )

这些异常的一个共同主题是在使用 Async 上下文时使用 Toast，但我已经仔细检查过它，并且我很小心不要在那里使用它们。事实上，在 decodeBitmap 调用中发生了上述错误。这很奇怪，因为 CameraView 文档坚持说该函数是在工作线程上调用的。你们中的任何人都可以向我解释发生了什么以及如何解决它吗？

为了更容易重现，这里是完整的 MainActivity.kt：

package com.example.joao.waterprototype

import android.graphics.Bitmap
import android.net.Uri
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.provider.MediaStore
import android.util.Log
import android.view.WindowManager
import android.widget.Toast
import com.otaliastudios.cameraview.CameraListener
import com.otaliastudios.cameraview.CameraUtils
import com.otaliastudios.cameraview.Gesture
import com.otaliastudios.cameraview.GestureAction
import kotlinx.android.synthetic.main.activity_main.*
import org.jetbrains.anko.doAsync
import org.jetbrains.anko.uiThread
import org.opencv.android.OpenCVLoader
import org.opencv.android.Utils
import org.opencv.core.Mat
import org.opencv.imgproc.Imgproc.COLOR_BGRA2GRAY
import org.opencv.imgproc.Imgproc.cvtColor
import java.util.*

class MainActivity : AppCompatActivity()


    override fun onCreate(savedInstanceState: Bundle?) 

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)
        window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
        camera.setLifecycleOwner(this)

        take_photo.setOnClickListener 
            camera.capturePicture()
        

        camera.mapGesture(Gesture.PINCH, GestureAction.ZOOM); // Pinch to zoom!
        camera.mapGesture(Gesture.TAP, GestureAction.FOCUS_WITH_MARKER); // Tap to focus!
        camera.mapGesture(Gesture.LONG_TAP, GestureAction.CAPTURE); // Long tap to shoot!

        camera.addCameraListener(object : CameraListener() 

            override fun onPictureTaken(jpeg: ByteArray?) 

                Toast.makeText(applicationContext, "Image Taken", Toast.LENGTH_SHORT).show()

                doAsync() 

                    lateinit var result : Bitmap
                    CameraUtils.decodeBitmap(jpeg) 

                        val mat = Mat()
                        val bmp32 = it.copy(Bitmap.Config.ARGB_8888, true)
                        Utils.bitmapToMat(bmp32, mat)

                        val greyMat = Mat()
                        cvtColor(mat, greyMat, COLOR_BGRA2GRAY)

                        result = Bitmap.createBitmap(greyMat.cols(), greyMat.rows(), Bitmap.Config.ARGB_8888)
                        Utils.matToBitmap(greyMat, result)

                    

                    uiThread 

                        val title = "$UUID.randomUUID().jpg"
                        val savedImageURL = MediaStore.Images.Media.insertImage(
                                contentResolver,
                                result,
                                title,
                                "Image of $title"
                        )

                        val uri = Uri.parse(savedImageURL)
                        Toast.makeText(applicationContext, "Image Created at $uri.path", Toast.LENGTH_SHORT).show()

                    
                
            

        )

    


    companion object 

        // Used to load the 'native-lib' library on application startup.
        init 

            if (!OpenCVLoader.initDebug()) 
                Log.e("OpenCV", "Cannot connect to OpenCV Manager")
             else 
                Log.e("OpenCV", "Connected Successfully")
            


        
    

这里是activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_
    android:layout_ >

    <com.otaliastudios.cameraview.CameraView
        android:id="@+id/camera"
        android:keepScreenOn="true"
        android:layout_
        android:layout_ />

    <Button
        android:id="@+id/take_photo"
        android:layout_
        android:layout_
        android:text="Take Photo"
        android:textAlignment="center"/>

</LinearLayout>

【参考方案1】：

我相信 decodeBitmmap 是从 UI 线程启动的假设，即使实际工作是在工作线程上完成的。这是有问题的代码......在调用者线程（第 101 行）上执行：

final Handler ui = new Handler();

关于类似问题有一点讨论here