CameraX CameraView 中是否存在错误，因为它不起作用？

Question

我正在开发一个 android 应用程序，让用户可以录制视频。我使用 CameraX 和 CameraView 作为我的选择。该代码在 2 周前使用，但从本周开始，CameraView 一直只显示黑屏。有什么解决办法还是我做错了什么？

1) build.gradle(应用程序)

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.3"

    defaultConfig {
        applicationId "com.example.cameraxprototype4"
        minSdkVersion 28
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = JavaVersion.VERSION_1_8.toString()
    }
}

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.0'
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

    def camerax_version = "1.0.0-beta06"
    implementation "androidx.camera:camera-core:$camerax_version"
    implementation "androidx.camera:camera-camera2:$camerax_version"
    implementation "androidx.camera:camera-lifecycle:$camerax_version"
    implementation "androidx.camera:camera-view:1.0.0-alpha13"

}

2) 清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.cameraxprototype4">

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-permission android:name="android.permission.RECORD_AUDIO"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

3) 相机activity

package com.example.cameraxprototype4

import android.Manifest
import android.content.pm.PackageManager
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.Environment
import android.util.Log
import android.widget.Toast
import androidx.appcompat.app.AlertDialog
import androidx.camera.core.VideoCapture
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import kotlinx.android.synthetic.main.activity_main.*
import java.io.File

class MainActivity : AppCompatActivity() {

    val TAG = MainActivity::class.java.simpleName

    var isRecording: Boolean = false

    var CAMERA_PERMISSION = Manifest.permission.CAMERA
    var RECORD_AUDIO_PERMISSION = Manifest.permission.RECORD_AUDIO

    var RC_PERMISSION = 101

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val recordFiles = ContextCompat.getExternalFilesDirs(this, Environment.DIRECTORY_MOVIES)
        val storageDirectory = recordFiles[0]
        val videoRecordingFilePath = "${storageDirectory.absoluteFile}/${System.currentTimeMillis()}_video.mp4"

        preview.setOnClickListener {
            if (isRecording) {
                isRecording = false
                record.text = "Record Video"
                Toast.makeText(this, "Recording Stopped", Toast.LENGTH_SHORT).show()
                preview.stopRecording()
            } else {
                isRecording = true
                record.text = "Stop Recording"
                Toast.makeText(this, "Recording Started", Toast.LENGTH_SHORT).show()
                recordVideo(videoRecordingFilePath)
            }
        }
    }

    private fun startCameraSession() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            preview.bindToLifecycle(this)
        }
    }

    private fun recordVideo(videoRecordingFilePath: String) {
        preview.startRecording(File(videoRecordingFilePath), ContextCompat.getMainExecutor(this), object: VideoCapture.OnVideoSavedCallback {
            override fun onVideoSaved(file: File) {
                Toast.makeText(this@MainActivity, "Recording Saved", Toast.LENGTH_SHORT).show()
                Log.d(TAG, "onVideoSaved $videoRecordingFilePath")
            }

            override fun onError(videoCaptureError: Int, message: String, cause: Throwable?) {
                Toast.makeText(this@MainActivity, "Recording Failed", Toast.LENGTH_SHORT).show()
                Log.e(TAG, "onError $videoCaptureError $message")
            }
        })
    }

    private fun requestPermissions() {
        ActivityCompat.requestPermissions(this, arrayOf(CAMERA_PERMISSION, RECORD_AUDIO_PERMISSION), RC_PERMISSION)
    }

    private fun checkPermissions(): Boolean {
        return ((ActivityCompat.checkSelfPermission(this, CAMERA_PERMISSION)) == PackageManager.PERMISSION_GRANTED
                && (ActivityCompat.checkSelfPermission(this, CAMERA_PERMISSION)) == PackageManager.PERMISSION_GRANTED)
    }

    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        when(requestCode) {
            RC_PERMISSION -> {
                var allPermissionsGranted = false
                for (result in grantResults) {
                    if (result != PackageManager.PERMISSION_GRANTED) {
                        allPermissionsGranted = false
                        break
                    } else {
                        allPermissionsGranted = true
                    }
                }
                if (allPermissionsGranted) startCameraSession() else permissionsNotGranted()
            }
        }
    }

    private fun permissionsNotGranted() {
        AlertDialog.Builder(this).setTitle("Permissions required")
            .setMessage("These permissions are required to use this app. Please allow Camera and Audio permissions first")
            .setCancelable(false)
            .setPositiveButton("Grant") { dialog, which -> requestPermissions() }
            .show()
    }
}

4) 相机 XML 布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.camera.view.CameraView
        android:id="@+id/preview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:lensFacing="back"
        app:scaleType="fitCenter"
        app:pinchToZoomEnabled="true"
        app:captureMode="video"
        app:flash="off"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

    <Button
        android:id="@+id/record"
        android:layout_width="50dp"
        android:layout_height="50dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginBottom="20dp"/>



</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

onRequestPermissionsResult() 未在 onCreate() 之前调用，它是在您明确向用户请求权限并且他们授予或不授予权限（通过权限对话框）之后调用的。

调用 onCreate() 后，您必须明确检查是否已授予您需要的所有权限，如果是，则调用 preview.bindToLifecycle(this)，如果有 1 个或多个权限未授予如果未授予，您首先请求它们，然后一旦 onRequestPermissionsResult() 被调用，您再次检查是否授予权限，然后做出相应的反应。

所以逻辑应该是这样的：

override fun onCreate(savedInstanceState: Bundle?) {
    // ...
    if (checkPermissions()) {
        preview.bindToLifecycle(this)
    } else {
        requestPermissions()
    }
}

override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
    // ...
    if (requestCode == RC_PERMISSION) {
        if (checkPermissions()) {
            preview.bindToLifecycle(this)
        } else {
            // Handle the scenario where the user doesn't grant all the required permissions
        }
    }
}

此外，在您的清单文件中，您声明了 3 个权限（WRITE_EXTERNAL_STORAGE、CAMERA、RECORD_AUDIO），但是 requestPermissions() 缺少 WRITE_EXTERNAL_STORAGE 权限，而 checkPermissions() 只检查 CAMERA 权限。请务必请求并检查所有权限。

CameraX CameraView 中是否存在错误，因为它不起作用？

Is There a bug in CameraX CameraView because it doesn't work?

camera

android

kotlin

android-camerax