如何在 CameraX 预览视图上显示文本视图？

Question

我想在相机的预览视图中显示一个文本视图。它将在相机预览中显示为标签。它不应该影响图像。就像预览视图上的标签一样。我尝试使用框架布局，但文本视图在预览视图中消失了

这是我的布局

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    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"
    android:background="#000000"
    android:fitsSystemWindows="true"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/camera_capture_button"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:background="@drawable/ic_baseline_camera_24"
        android:elevation="2dp"
        android:layout_marginBottom="20dp"
        android:scaleType="fitCenter"
        android:layout_gravity="bottom|center"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.926" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="Hello"
        android:textSize="25dp" />
    <androidx.camera.view.PreviewView
        android:id="@+id/viewFinder"
        android:layout_width="379dp"
        android:layout_height="576dp"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="20dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent">


    </androidx.camera.view.PreviewView>

</FrameLayout> 

主要活动 这是主要逻辑->

package com.arpit.cameraxdemo

import android.Manifest
import android.content.pm.PackageManager
import android.os.Bundle
import android.util.Log
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.camera.core.CameraSelector
import androidx.camera.core.ImageCapture
import androidx.camera.core.Preview
import androidx.camera.lifecycle.ProcessCameraProvider
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import kotlinx.android.synthetic.main.activity_main.*
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors

class MainActivity : AppCompatActivity() {

    private var imageCapture: ImageCapture? = null
    private lateinit var cameraExecutor: ExecutorService

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        supportActionBar?.hide()

        if (allPermissionsGranted()) {
            startCamera()
        } else {
            ActivityCompat.requestPermissions(this, REQUIRED_PERMISSIONS, REQUEST_CODE_PERMISSIONS)
        }

        camera_capture_button.setOnClickListener {
            takePhoto()
        }
        cameraExecutor = Executors.newSingleThreadExecutor()
    }

    private fun takePhoto() {
    }

    private fun startCamera() {
        val cameraProviderFuture = ProcessCameraProvider.getInstance(this)

        cameraProviderFuture.addListener({
            val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()

            val preview = Preview.Builder()
                .build()
                .also {
                    it.setSurfaceProvider(viewFinder.surfaceProvider)
                }

            imageCapture = ImageCapture.Builder().build()
            val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

            try {
                cameraProvider.unbindAll()
                cameraProvider.bindToLifecycle(
                    this, cameraSelector, preview, imageCapture
                )

            } catch (exc: Exception) {
                Log.e(TAG, "Use case binding failed", exc)
            }

        }, ContextCompat.getMainExecutor(this))
    }

    private fun allPermissionsGranted() = REQUIRED_PERMISSIONS.all {
        ContextCompat.checkSelfPermission(baseContext, it) == PackageManager.PERMISSION_GRANTED
    }

    // checks the camera permission
    override fun onRequestPermissionsResult(
        requestCode: Int, permissions: Array<String>, grantResults:
        IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (requestCode == REQUEST_CODE_PERMISSIONS) {
            if (allPermissionsGranted()) {
                startCamera()
            } else {
                Toast.makeText(this, "Permissions not granted by the user.", Toast.LENGTH_SHORT).show()
                finish()
            }
        }
    }

    companion object {
        private const val TAG = "CameraXGFG"
        private const val REQUEST_CODE_PERMISSIONS = 20
        private val REQUIRED_PERMISSIONS = arrayOf(Manifest.permission.CAMERA)
    }

    override fun onDestroy() {
        super.onDestroy()
        cameraExecutor.shutdown()
    }
}

Answer 1

用RelativeLayout试试下面的代码

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
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" />
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:gravity="center"
    android:text="CameraX" />
<Button
    android:id="@+id/imageCaptureBtn"
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_margin="10dp"
    android:gravity="center"
    android:text="Click Image" />

</RelativeLayout>

Answer 2

感谢大家的帮助。我找到了我的问题的答案。其实我一直在寻找的是所谓的叠加

 viewFinder.overlay.add(tvText)

Answer 3

使用2dp元素“海拔”