写在前面

前几天有位同学在网站里提问说想要调用相机进行预览，于是今天我发这篇文章啦，那位同学看到之后请来认领哦~

官方文档

CameraX官方文档

添加访问相机权限

<!-- 拍照权限 -->
<uses-permission android:name="android.permission.CAMERA" />

添加依赖

在应用或模块的 build.gradle 文件中添加所需工件的依赖项：

    def cameraX_version = "1.0.0-beta11"
    // CameraX core library using camera2 implementation
    implementation "androidx.camera:camera-camera2:$cameraX_version"
    // CameraX Lifecycle Library
    implementation "androidx.camera:camera-lifecycle:$cameraX_version"
    // CameraX View class
    implementation "androidx.camera:camera-view:1.0.0-alpha10"

在布局中添加 PreviewView 视图

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".ui.activity.TakePhotoActivity">

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

</RelativeLayout>

在Activity中编写相应代码

在Activity中编写相应的代码（注：此处我对Activity进行了封装，同学们可以根据自己的代码习惯进行编写）

import android.annotation.SuppressLint;

import androidx.annotation.NonNull;
import androidx.camera.core.Camera;
import androidx.camera.core.CameraInfo;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.camera.view.PreviewView;
import androidx.core.content.ContextCompat;

import com.google.common.util.concurrent.ListenableFuture;

import java.util.concurrent.ExecutionException;

import butterknife.BindView;
import cn.cqautotest.cqviehelper.R;
import cn.cqautotest.cqviehelper.base.BaseActivity;

@SuppressLint("NonConstantResourceId")
public class TakePhotoActivity extends BaseActivity {

    @BindView(R.id.previewView)
    PreviewView previewView;

    @Override
    protected int getLayoutId() {
        return R.layout.activity_take_photo;
    }

    @Override
    protected void initView() {
        ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(this);
        cameraProviderFuture.addListener(() -> {
            try {
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
                bindPreview(cameraProvider);
            } catch (ExecutionException | InterruptedException e) {
                // No errors need to be handled for this Future.
                // This should never be reached.
                //译：对于此Future，无需处理任何错误。这永远都不会实现。
            }
        }, 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();
        
        Camera camera = cameraProvider.bindToLifecycle(this, cameraSelector, preview);
        
        CameraInfo cameraInfo = camera.getCameraInfo();
        preview.setSurfaceProvider(previewView.createSurfaceProvider(cameraInfo));
    }
}

相机预览效果

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