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Android CameraX打开摄像头预览教程

作者：AnRFDev

大家好，本篇文章主要讲的是Android CameraX打开摄像头预览教程，感兴趣的同学赶快来看一看吧，对你有帮助的话记得收藏一下

前言

目标很简单，用CameraX打开摄像头预览，实时显示在界面上。看看CameraX有没有Google说的那么好用。先按最简单的来，把预览显示出来。

引入依赖

模块gradle的一些配置，使用的Android SDK版本为31，启用了databinding

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

android {
    compileSdkVersion 31
    buildToolsVersion "31.0.0"
    defaultConfig {
        minSdkVersion 21
        targetSdkVersion 31
    }
    dataBinding {
        enabled = true
    }
}

引入CameraX依赖（CameraX 核心库是用camera2实现的），目前主要用1.1.0-alpha11版本

dependencies {
    implementation "androidx.camera:camera-core:1.1.0-alpha11"
    implementation "androidx.camera:camera-camera2:1.1.0-alpha11"
    implementation "androidx.camera:camera-lifecycle:1.1.0-alpha11"
    implementation "androidx.camera:camera-view:1.0.0-alpha31"
    implementation "androidx.camera:camera-extensions:1.0.0-alpha31"
}

使用1.0.2版本的CameraX核心库会报错，找不到getOrCreateInstance方法。

??? bug "NoSuchMethodError getOrCreateInstance"

```log
CrashHandler: In thread: Thread[main,5,main]
    UncaughtException detected: java.lang.NoSuchMethodError: No static method getOrCreateInstance(Landroid/content/Context;)Lcom/google/common/util/concurrent/ListenableFuture; in class Landroidx/camera/core/CameraX; or its super classes (declaration of 'androidx.camera.core.CameraX' appears in /data/app/com.rustfisher.tutorial2020-1/base.apk)
    at androidx.camera.lifecycle.ProcessCameraProvider.getInstance(ProcessCameraProvider.java:149)
    at com.rustfisher.tutorial2020.camera.SimplePreviewXAct.onCreate(SimplePreviewXAct.java:36)
    at android.app.Activity.performCreate(Activity.java:6161)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1112)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2507)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2640)
    at android.app.ActivityThread.access$800(ActivityThread.java:182)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1493)
    at android.os.Handler.dispatchMessage(Handler.java:111)
    at android.os.Looper.loop(Looper.java:194)
    at android.app.ActivityThread.main(ActivityThread.java:5682)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:963)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:758)
```

权限

需要动态申请android.permission.CAMERA权限

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

本文略过动态申请权限的地方

界面

CameraX为开发者贴心地准备了androidx.camera.view.PreviewView

把它放在一个FrameLayout里，如下的act_simple_preivew_x.layout

<?xml version="1.0" encoding="utf-8"?>
<layout>
    <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <androidx.camera.view.PreviewView
            android:id="@+id/previewView"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </FrameLayout>
</layout>

开启预览

在activity中开启相机预览

// SimplePreviewXAct.java
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.camera.core.Camera;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.core.content.ContextCompat;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.LifecycleOwner;

import com.google.common.util.concurrent.ListenableFuture;
// import com.rustfisher.tutorial2020.R;
// import com.rustfisher.tutorial2020.databinding.ActSimplePreivewXBinding;

import java.util.concurrent.ExecutionException;

public class SimplePreviewXAct extends AppCompatActivity {

    private ActSimplePreivewXBinding mBinding;
    private ListenableFuture<ProcessCameraProvider> cameraProviderFuture;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mBinding = DataBindingUtil.setContentView(this, R.layout.act_simple_preivew_x);
        cameraProviderFuture = ProcessCameraProvider.getInstance(this);
        cameraProviderFuture.addListener(() -> {
            try {
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
                bindPreview(cameraProvider);
            } catch (ExecutionException | InterruptedException e) {
                // 这里不用处理
            }
        }, ContextCompat.getMainExecutor(this));
    }

    void bindPreview(@NonNull ProcessCameraProvider cameraProvider) {
        Preview preview = new Preview.Builder().build();

        CameraSelector cameraSelector = new CameraSelector.Builder()
                .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                .build();

        preview.setSurfaceProvider(mBinding.previewView.getSurfaceProvider());

        Camera camera = cameraProvider.bindToLifecycle(this, cameraSelector, preview);
    }
}

注意我们这里使用的是androidx.appcompat.app.AppCompatActivity

为了获得ProcessCameraProvider，用ProcessCameraProvider.getInstance方法拿到一个cameraProviderFuture。
在cameraProviderFuture完成后取出ProcessCameraProvider（cameraProvider）。

要开启预览，通过Preview.Builder构建一个Preview。用CameraSelector来选择后置摄像头。
Preview的SurfaceProvider由layout中的androidx.camera.view.PreviewView提供。

cameraProvider.bindToLifecycle绑定上后，启动摄像头预览

运行测试

运行到手机上，打开这个Activity就可以看到摄像头预览。图像宽高比正常，没有拉伸现象。

荣耀 EMUI 3.1 Lite，Android 5.1 运行正常

Redmi 9A，MIUI 12.5.1稳定版，Android 10 运行正常

一加5，H2OS 10.0.3，Android 10 运行正常

增加开关

在layout里加2个按钮，控制相机开关

<?xml version="1.0" encoding="utf-8"?>
<layout>

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/colorPrimaryDark"
            android:gravity="center"
            android:orientation="horizontal"
            android:padding="4dp">

            <Button
                android:id="@+id/start"
                style="@style/NormalBtn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="打开" />

            <Button
                android:id="@+id/end"
                style="@style/NormalBtn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginStart="12dp"
                android:text="关闭" />
        </LinearLayout>

        <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/container"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <androidx.camera.view.PreviewView
                android:id="@+id/previewView"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />
        </FrameLayout>

    </LinearLayout>
</layout>

根layout换成LinearLayout

修改bindPreview方法，先检查传入的ProcessCameraProvider是否为空

private void bindPreview(ProcessCameraProvider cameraProvider) {
    if (cameraProvider == null) {
        Toast.makeText(getApplicationContext(), "没获取到相机", Toast.LENGTH_SHORT).show();
        return;
    }
    Preview preview = new Preview.Builder().build();

    CameraSelector cameraSelector = new CameraSelector.Builder()
            .requireLensFacing(CameraSelector.LENS_FACING_BACK)
            .build();

    preview.setSurfaceProvider(mBinding.previewView.getSurfaceProvider());

    Camera camera = cameraProvider.bindToLifecycle(this, cameraSelector, preview);
}

修改后的activity部分代码

import android.os.Bundle;
import android.widget.Toast;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.camera.core.Camera;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.core.content.ContextCompat;
import androidx.databinding.DataBindingUtil;

import com.google.common.util.concurrent.ListenableFuture;
// import com.rustfisher.tutorial2020.R;
// import com.rustfisher.tutorial2020.databinding.ActSimplePreivewXBinding;

import java.util.concurrent.ExecutionException;

public class SimplePreviewXAct extends AppCompatActivity {

    private ActSimplePreivewXBinding mBinding;
    private ListenableFuture<ProcessCameraProvider> mCameraProviderFuture;
    private ProcessCameraProvider mCameraProvider;
    private boolean mRunning = false;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mBinding = DataBindingUtil.setContentView(this, R.layout.act_simple_preivew_x);
        mCameraProviderFuture = ProcessCameraProvider.getInstance(this);
        mCameraProviderFuture.addListener(() -> {
            try {
                mCameraProvider = mCameraProviderFuture.get();
            } catch (ExecutionException | InterruptedException e) {
                // 这里不用处理
            }
        }, ContextCompat.getMainExecutor(this));
        mBinding.start.setOnClickListener(v -> {
            if (mCameraProvider != null && !mRunning) {
                bindPreview(mCameraProvider);
            }
        });
        mBinding.end.setOnClickListener(v -> {
            mCameraProvider.unbindAll();
            mRunning = false;
        });
    }

    private void bindPreview(ProcessCameraProvider cameraProvider) {
        if (cameraProvider == null) {
            Toast.makeText(getApplicationContext(), "没获取到相机", Toast.LENGTH_SHORT).show();
            return;
        }
        Preview preview = new Preview.Builder().build();

        CameraSelector cameraSelector = new CameraSelector.Builder()
                .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                .build();

        preview.setSurfaceProvider(mBinding.previewView.getSurfaceProvider());

        Camera camera = cameraProvider.bindToLifecycle(this, cameraSelector, preview);
        mRunning = true;
    }
}

拿到mCameraProvider后不要立刻绑定生命周期。

如果要开启预览，则调用bindPreview(mCameraProvider)。记录一下现在相机已经开启预览mRunning = true。

如果要停止预览，则解绑生命周期mCameraProvider.unbindAll()。这个方法需要在主线程调用。

运行起来后，可以用按钮来控制相机预览的开关。相比之前，PreviewView的高度变小了一点（让了点位置给按钮）。
但视频宽高比例正常，没有被拉伸。默认的配置下，还有自动对焦的功能。

小结

从简单的打开相机预览来看，CameraX简化了开发者的工作。提供了PreviewView，开发者不需要自定义SurfaceView或者TextureView。实时预览中，相机能够自动对焦。本文用的是1.1.0-alpha11，而CameraX还在发展之中。

到此这篇关于Android CameraX打开摄像头预览教程的文章就介绍到这了,更多相关Android CameraX摄像头预览内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！

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