CameraX小試牛刀，實現二維碼掃描

時間 2019-11-08

標籤 camerax 小試牛刀實現二維掃描简体版

原文原文鏈接

在今年的Google I/O大會上，Google新推出了CameraX支持包，按照官方的說法, 這個包的做用是php

help you make camera app development easierandroid

google在幾年前推出了Camera2 API用於取代Camera1，大部分開發者仍是喜歡使用Camera1的api，一是由於api太難用，二是要兼容5.0以前的s設備，此次推出的CameraX支持包不只消除各類使用上的障礙，還與大受好評的archecture component 包的Lifecycle結合，自動管理相機的生命週期，開發者不在須要去關心何時打開相機，何時釋放相機。甚至聯繫各個手機廠商提供統一的api調用使用美顏等接口。git

關於cameraX的介紹本文不在贅述，將使用cameraX實現一個小功能：使用最少的代碼實現二維碼解碼，在這個demo中將會使用到CameraX中三大功能中的兩個：github

preview
analysis

建立app

建立app，聲明相機權限api

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" package="github.hotstu.camerax.qrcodec">

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

    <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" tools:ignore="GoogleAppIndexingWarning">
        <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>
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添加相關依賴app

implementation 'com.tbruyelle.rxpermissions2:rxpermissions:0.9.5'
    def camerax_version = "1.0.0-alpha02"
    implementation "androidx.camera:camera-core:${camerax_version}"
    // If you want to use Camera2 extensions.
    implementation "androidx.camera:camera-camera2:${camerax_version}"
    implementation 'com.google.zxing:core:3.3.2'
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注意，這裏有個坑，由於camerax尚未發佈正式版，而它依賴的androidx.core:core:1.1.0-rc1中AppcompatActivity竟然不是LifeCycleOwner,，然而camerax依賴LifeCycleOwner才能管理生命週期，因此要祭出在support liabary時代解決依賴衝突的黃金代碼:ide

subprojects {
    configurations.all {
        resolutionStrategy {
            force "androidx.core:core:1.0.2"
        }
    }
}
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編寫代碼實現攝像頭預覽

val previewConfig = PreviewConfig.Builder().apply {
            setTargetAspectRatio(Rational(1, 1))
            setTargetResolution(Size(640, 640))
        }.build()
        val preview = Preview(previewConfig)
       preview.setOnPreviewOutputUpdateListener {
            textureView.surfaceTexture = it.surfaceTexture
        }
        CameraX.bindToLifecycle(this@MainActivity, preview)
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編寫代碼實現數據分析回調

數據分析能夠指定回調的線程oop

val analysisConfig = ImageAnalysisConfig.Builder().apply {
            setImageReaderMode(ImageAnalysis.ImageReaderMode.ACQUIRE_LATEST_IMAGE)
            val analyzerThread = HandlerThread("BarcodeAnalyzer").apply { start() }
            setCallbackHandler(Handler(analyzerThread.looper))
        }.build()

        val analysis = ImageAnalysis(analysisConfig)
        analysis.analyzer = QRcodeAnalyzer()

        CameraX.bindToLifecycle(this@MainActivity, analysis)
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同時綁定預覽和分析，而且搞定權限申請

class MainActivity : AppCompatActivity() {

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

        val previewConfig = PreviewConfig.Builder().apply {
            setTargetAspectRatio(Rational(1, 1))
            setTargetResolution(Size(640, 640))
        }.build()

        val analysisConfig = ImageAnalysisConfig.Builder().apply {
            setImageReaderMode(ImageAnalysis.ImageReaderMode.ACQUIRE_LATEST_IMAGE)
            val analyzerThread = HandlerThread("BarcodeAnalyzer").apply { start() }
            setCallbackHandler(Handler(analyzerThread.looper))
        }.build()

        val rxPermissions = RxPermissions(this)
        val preview = Preview(previewConfig)
        val analysis = ImageAnalysis(analysisConfig)

        preview.setOnPreviewOutputUpdateListener {
            textureView.surfaceTexture = it.surfaceTexture
        }

        analysis.analyzer = QRcodeAnalyzer()
        rxPermissions.request(android.Manifest.permission.CAMERA)
                .subscribe {
                    CameraX.bindToLifecycle(this@MainActivity,
                            preview,
                            analysis)
                }
    }
}
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實現QRcodeAnalyzer

作二維碼解碼，不少開發者是直接在zxing-Android 項目基礎上刪刪改改，其實不建議這樣作，應爲那個項目是從Android早期版本開始的，一些東西都爲了支持老版本系統而作出了妥協，不少代碼都顯得老舊並且不優雅，查看源碼你會發現它調用攝像頭的方法是很是複雜的。這裏咱們只是用xzing核心庫com.google.zxing:coreui

class QRcodeAnalyzer : ImageAnalysis.Analyzer {
    private val reader: MultiFormatReader = MultiFormatReader()

    init {
        val map = mapOf<DecodeHintType, Collection<BarcodeFormat>>(
            Pair(DecodeHintType.POSSIBLE_FORMATS, arrayListOf(BarcodeFormat.QR_CODE))
        )
        reader.setHints(map)
    }

    override fun analyze(image: ImageProxy, rotationDegrees: Int) {
        if (ImageFormat.YUV_420_888 != image.format) {
            Log.e("BarcodeAnalyzer", "expect YUV_420_888, now = ${image.format}")
            return
        }
        val buffer = image.planes[0].buffer
        val data = ByteArray(buffer.remaining())
        val height = image.height
        val width = image.width
        buffer.get(data)
        //TODO 調整crop的矩形區域，目前是全屏（全屏有更好的識別體驗，可是在部分手機上可能OOM）
        val source = PlanarYUVLuminanceSource(data, width, height, 0, 0, width, height, false)

        val bitmap = BinaryBitmap(HybridBinarizer(source))

        try {
            val result = reader.decode(bitmap)
            Log.e("BarcodeAnalyzer", "resolved!!! = $result")
        } catch (e: Exception) {
            Log.d("BarcodeAnalyzer", "Error decoding barcode")
        }

    }
}
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