阅读 345

Android CameraX打开摄像头预览教程

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

目录

  • 前言

  • 引入依赖

  • 权限

  • 界面

  • 开启预览

  • 运行测试

  • 增加开关

  • 小结


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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
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

1
2
3
4
5
6
7
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"

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
```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

1
<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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
<?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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
// 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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
<?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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
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


伪原创工具 SEO网站优化  https://www.237it.com/ 


文章分类
代码人生
文章标签
android
camerax
摄像头
预览
教程
版权声明：本站是系统测试站点，无实际运营。本文内容由互联网用户自发贡献，该文观点仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌抄袭侵权/违法违规的内容， 请发送邮件至 XXXXXXo@163.com 举报，一经查实，本站将立刻删除。
相关推荐