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，会出现以下异常：
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$Worker.run(ThreadPoolExecutor.java:607)
at java.lang.Thread.run(Thread.java:761)
以下代码段描述了发生上述问题的位置：
camera.addCameraListener(object : CameraListener() {
override fun onPictureTaken(jpeg: ByteArray?) {
Toast.makeText(applicationContext, "Image Taken", Toast.LENGTH_SHORT).show()
doAsync() {
lateinit var result : Bitmap
CameraUtils.decodeBitmap(jpeg) {
val mat = Mat()
val bmp32 = it.copy(Bitmap.Config.ARGB_8888, true)
Utils.bitmapToMat(bmp32, mat)
val greyMat = Mat()
cvtColor(mat, greyMat, COLOR_BGRA2GRAY)
result = Bitmap.createBitmap(greyMat.cols(), greyMat.rows(), Bitmap.Config.ARGB_8888)
Utils.matToBitmap(greyMat, result)
}
uiThread {
val title = "${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异步上下文时使用 Toasts，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_width="match_parent"
android:layout_height="match_parent" >
<com.otaliastudios.cameraview.CameraView
android:id="@+id/camera"
android:keepScreenOn="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="@+id/take_photo"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Take Photo"
android:textAlignment="center"/>
</LinearLayout>