MpPreview/Application/src/main/java/com/xypower/mppreview/MainActivity.java

package com.xypower.mppreview;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Switch;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ((Button)findViewById(R.id.channel1)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                takePhoto(1);
            }
        });
        ((Button)findViewById(R.id.channel2)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                takePhoto(2);
            }
        });
        ((Button)findViewById(R.id.channel3)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                takePhoto(3);
            }
        });
    }

    protected void takePhoto(int channel) {
        Switch hdrSwitch = (Switch) findViewById(R.id.hdr);
        takePhoto(channel, hdrSwitch.isChecked());
    }

    protected void takePhoto(int channel, boolean hdr) {
        int cameraId = channel - 1;
        if (channel == 1 && hdr) {
            cameraId = 1;
        }

        Intent intent = new Intent(MainActivity.this, CameraActivity.class);
        intent.putExtra("cameraId", cameraId);
        startActivity(intent);
    }
}