Android 实现相机（CameraX）预览_apk 动态获取相机权限怎么设置

CameraX 是一个 Jetpack 库，旨在帮助您更轻松地开发相机应用。 对于新应用，我们建议从 CameraX 开始。它提供一致且易于使用的 API，适用于绝大多数 Android 设备，并向后兼容 Android 5.0（API 级别 21）。

CameraX 支持大多数常见的相机用例：

• 预览：在屏幕上查看图片。
• 图片分析：无缝访问缓冲区中的图片以便在算法中使用，例如将其传递到机器学习套件。
• 图片拍摄：保存图片。
• 视频拍摄：保存视频和音频。

这篇文章讲的是 – 实现预览

在向应用添加预览时，请使用 PreviewView，这是一种可以剪裁、缩放和旋转以确保正确显示的 View。
当相机处于活动状态时，图片预览会流式传输到 PreviewView 中的 Surface。

效果图

配置：

• 注意：CameraX 支持的最小SDK版本是21
  
• 一、添加权限

1、清单文件中加入相机权限

<uses-permission android:name="android.permission.CAMERA" />
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2、动态获取相机权限

  if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_DENIED) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                requestPermissions(new String[]{Manifest.permission.CAMERA}, 11);
            }
        } else {
            //启动相机 
        }
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• 二、在build.gradle中 添加CameraX依赖

    implementation "androidx.camera:camera-core:1.1.0-alpha10"
// CameraX Camera2 extensions[可选]拓展库可实现人像、HDR、夜间和美颜、滤镜但依赖于OEM
    implementation "androidx.camera:camera-camera2:1.1.0-alpha10"
// CameraX Lifecycle library[可选]避免手动在生命周期释放和销毁数据
    implementation "androidx.camera:camera-lifecycle:1.1.0-alpha10"
// CameraX View class[可选]最佳实践，最好用里面的PreviewView，它会自行判断用SurfaceView还是TextureView来实现
    implementation 'androidx.camera:camera-view:1.0.0-alpha23'
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使用 PreviewView案例步骤：

1、（可选）配置 CameraXConfig.Provider。
2、 将 PreviewView 添加到布局。
3、 请求 ProcessCameraProvider。
4、 在创建 View 时，请检查 ProcessCameraProvider。
5、 选择相机并绑定生命周期和用例。

• 将 PreviewView 添加到布局

<?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=".MainActivity">
    <FrameLayout
        android:layout_centerInParent="true"
        android:layout_width="500dp"
        android:layout_height="500dp">
        <androidx.camera.view.PreviewView
            android:id="@+id/previewView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            />
    </FrameLayout>
</RelativeLayout>
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• 步骤3、4、5、的处理

package com.example.myapplication;

import androidx.annotation.NonNull;
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.camera.view.PreviewView;
import androidx.core.content.ContextCompat;
import androidx.lifecycle.LifecycleOwner;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.concurrent.ExecutionException;


public class MainActivity extends AppCompatActivity {
    
    private ListenableFuture<ProcessCameraProvider> cameraProviderFuture;
    private PreviewView previewView;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        previewView=findViewById(R.id.previewView);//初始化
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_DENIED) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                requestPermissions(new String[]{Manifest.permission.CAMERA}, 11);
            }
        } else {
            //启动相机
            startCamera();
        }
    }

    private void startCamera() {
        // 请求 CameraProvider
        cameraProviderFuture = ProcessCameraProvider.getInstance(this);
        //检查 CameraProvider 可用性，验证它能否在视图创建后成功初始化
        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.
            }
        }, ContextCompat.getMainExecutor(this));
    }
    //选择相机并绑定生命周期和用例
    private void bindPreview(@NonNull ProcessCameraProvider cameraProvider) {
        Preview preview = new Preview.Builder()
                .build();

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

        preview.setSurfaceProvider(previewView.getSurfaceProvider());

        Camera camera = cameraProvider.bindToLifecycle((LifecycleOwner)this, cameraSelector, preview);
    }
}
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• 到bindPreview这一步，相机预览已经显示，请查验

如果是前后翻转

• 解绑每个组件

cameraProvider.unbindAll();

• 布局如下：

<?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=".MainActivity">
    <Button
        android:onClick="btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="前置摄像头"
        />
    <Button
        android:onClick="btn2"
        android:layout_alignParentRight="true"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="后置摄像头"
        />
    <FrameLayout
        android:layout_centerInParent="true"
        android:layout_width="500dp"
        android:layout_height="500dp">
        <androidx.camera.view.PreviewView
            android:id="@+id/previewView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            />
    </FrameLayout>
</RelativeLayout>

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• 代码详情如下：

public class MainActivity extends AppCompatActivity {

    private ListenableFuture<ProcessCameraProvider> cameraProviderFuture;
    private PreviewView previewView;
    private ProcessCameraProvider cameraProvider;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        previewView=findViewById(R.id.previewView);//初始化
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_DENIED) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                requestPermissions(new String[]{Manifest.permission.CAMERA}, 11);
            }
        } else {
            //启动相机
            startCamera(CameraSelector.LENS_FACING_BACK);
        }
    }


    private void startCamera(int state) {
        // 请求 CameraProvider
        cameraProviderFuture = ProcessCameraProvider.getInstance(this);
        //检查 CameraProvider 可用性，验证它能否在视图创建后成功初始化
        cameraProviderFuture.addListener(() -> {
            try {
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
                bindPreview(cameraProvider,state);
            } catch (ExecutionException | InterruptedException e) {
                // No errors need to be handled for this Future.
                // This should never be reached.
            }
        }, ContextCompat.getMainExecutor(this));
    }
    //选择相机并绑定生命周期和用例
    private void bindPreview(@NonNull ProcessCameraProvider cp,int state) {
        this.cameraProvider=cp;
        Preview preview = new Preview.Builder()
                .build();

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

        preview.setSurfaceProvider(previewView.getSurfaceProvider());
        cameraProvider.unbindAll();//解绑组件
        cameraProvider.bindToLifecycle((LifecycleOwner) this, cameraSelector, preview);
    }

    //点击翻转到前置
    public void btn1(View view) {
        //启动相机
        bindPreview(cameraProvider,CameraSelector.LENS_FACING_FRONT);
    }
    //点击翻转到后置
    public void btn2(View view) {
        //启动相机
        bindPreview(cameraProvider,CameraSelector.LENS_FACING_BACK);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode==11){//获取权限后，开启摄像头
            //启动相机
            startCamera(CameraSelector.LENS_FACING_BACK);
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        cameraProvider.unbindAll();
    }
}
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