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Android CameraX 打开摄像头预览功能

发布时间：2026-01-11

点击量：
目录
  • 引入依赖
  • 权限
  • 界面
  • 开启预览
    • 运行测试
  • 增加开关
    • 小结

      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.tutorial2025-1/base.apk)
    at androidx.camera.lifecycle.ProcessCameraProvider.getInstance(ProcessCameraProvider.java:149)
    at com.rustfisher.tutorial2025.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.tutorial2025.R;
// import com.rustfisher.tutorial2025.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.tutorial2025.R;
// import com.rustfisher.tutorial2025.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。

      参考

      camerax实现预览 - developer.android.com

      https://developer.android.com/jetpack/androidx/releases/camera

      NoSuchMethodError - stackoverflow

      原文链接CameraX 打开摄像头预览

      标签：# 不需要  # 构建一个  # 稳定版  # 为空  # 就可以  # 机上  # 最简单  # 好用  # 报错  # 自定义  # 很简单  # 把它  # 可以用  # 找不到  # Android CameraX 摄像头预览  # 还在  # 放在  # 自动对焦  # 里加  # 绑定  # 的是  # Android进阶CameraX与Camera2使用比对详解  # Android自定义相机Camera实现手动对焦的方法示例  # Android CameraX打开摄像头预览教程  # Android Camera2开启自动曝光功能  # Android Camera+SurfaceView自动聚焦防止变形拉伸  # Android CameraX 预览  

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