一、前文

Android系统默认支持2个摄像头，一个前置摄像头，一个后置摄像头
需要支持数量更多的摄像头，得修改Android Hal层的代码

在这里插入图片描述

二、CameraHal_Module.h

修改CAMERAS_SUPPORT_MAX

三、CameraHal_Module.cpp

修改camera_get_number_of_cameras()函数中变量camInfoTmp[]相关代码

四、编译&烧录Image

该部分的修改要生效的话，需要进行全编译

    ./build.sh
    ./build.sh mkimage
    ./build.sh mkupdate

五、App验证

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools">
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /> 
<uses-featureandroid:name="android.hardware.camera"android:required="false" />
<uses-featureandroid:name="android.hardware.camera.autofocus"android:required="false" />
<applicationandroid:allowBackup="true"
							android:dataExtractionRules="@xml/data_extraction_rules"
							android:fullBackupContent="@xml/backup_rules"
							android:icon="@mipmap/ic_launcher"
							android:label="@string/app_name"
							android:roundIcon="@mipmap/ic_launcher_round"
							android:supportsRtl="true"
							android:theme="@style/Theme.CameraApplication"tools:targetApi="31">
	<activityandroid:name=".MainActivity"
						android:exported="true">
						<intent-filter><action android:name="android.intent.action.MAIN" />
						<category android:name="android.intent.category.LAUNCHER" />
						</intent-filter><meta-dataandroid:name="android.app.lib_name"android:value="" />
	</activity>
</application>
</manifest>

MainActivity.java

package com.example.cameraapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.hardware.Camera;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
Camera camera1, camera2, camera3, camera4;
SurfaceHolder surfaceHolder1, surfaceHolder2, surfaceHolder3, surfaceHolder4;
SurfaceView surfaceView1, surfaceView2, surfaceView3, surfaceView4;
List<Camera> cameraList = new ArrayList<>();
List<SurfaceHolder> surfaceHolderList = new ArrayList<>();
List<SurfaceView> surfaceViewList = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    surfaceView1 = findViewById(R.id.camera_surface_view1);
    surfaceView2 = findViewById(R.id.camera_surface_view2);
    surfaceView3 = findViewById(R.id.camera_surface_view3);
    surfaceView4 = findViewById(R.id.camera_surface_view4);
    cameraList.add(camera1);
    cameraList.add(camera2);
    cameraList.add(camera3);
    cameraList.add(camera4);
    surfaceHolderList.add(surfaceHolder1);
    surfaceHolderList.add(surfaceHolder2);
    surfaceHolderList.add(surfaceHolder3);
    surfaceHolderList.add(surfaceHolder4);
    surfaceViewList.add(surfaceView1);
    surfaceViewList.add(surfaceView2);
    surfaceViewList.add(surfaceView3);
    surfaceViewList.add(surfaceView4);
    for(int i=0; i<cameraList.size(); i++){
        initCamera(i, cameraList.get(i), surfaceHolderList.get(i), surfaceViewList.get(i));
    }
    int number = Camera.getNumberOfCameras();//得到摄像头的个数
    Toast.makeText(MainActivity.this, "摄像头个数："+number, Toast.LENGTH_LONG).show();
}
private void initCamera(int number, Camera camera, SurfaceHolder surfaceHolder, SurfaceView surfaceView){
    try{
        camera = Camera.open(number);
        surfaceHolder = surfaceView.getHolder();
        surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        final Camera mCamera = camera;
        surfaceHolder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder surfaceHolder) {
                try {
                    if (mCamera!=null) {
                        mCamera.setPreviewDisplay(surfaceHolder);
                        mCamera.setDisplayOrientation(90);mCamera.startPreview();
                        }
                        } 
                        catch (Exception e) {
                            e.printStackTrace();
                            }
                            }
            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {

            }
            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
                releaseCamera(mCamera);
                }
        });
    }catch (Exception e){
        e.printStackTrace();
    }
}
/*** 释放相机资源*/
private void releaseCamera(Camera camera) {
    if (camera != null) {
        camera.setPreviewCallback(null);
        camera.stopPreview();
        camera.release();
        camera = null;
        }
}
/*** 释放相机资源*/
private void releaseAllCamera() {
    for(int i=0; i<cameraList.size(); i++){
        if (cameraList.get(i) != null) {
            cameraList.get(i).setPreviewCallback(null);
            cameraList.get(i).stopPreview();
            cameraList.get(i).release();
            cameraList.set(i, null);
        }
    }
}
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayoutxmlns: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"
android:orientation="vertical"
tools:context=".MainActivity">
<!--    <TextView-->
<!--        android:layout_gravity="center"-->
<!--        android:layout_margin="10dp"-->
<!--        android:layout_width="wrap_content"-->
<!--        android:layout_height="wrap_content"-->
<!--        android:text="摄像头个数："-->
<!--        app:layout_constraintBottom_toBottomOf="parent"-->
<!--        app:layout_constraintEnd_toEndOf="parent"-->
<!--        app:layout_constraintStart_toStartOf="parent"-->
<!--        app:layout_constraintTop_toTopOf="parent" />-->
<LinearLayoutandroid:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:layout_weight="1">
    <SurfaceViewandroid:id="@+id/camera_surface_view1"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"/>
    <SurfaceViewandroid:id="@+id/camera_surface_view2"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"/>
</LinearLayout>
<LinearLayoutandroid:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:layout_weight="1">
    <SurfaceViewandroid:id="@+id/camera_surface_view3"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"/>
    <SurfaceViewandroid:id="@+id/camera_surface_view4"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"/>
</LinearLayout>
</LinearLayout>