AndroidManifest.xml

<uses-feature android:name="android.hardware.camera" android:required="true" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Activity

import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.widget.Button;
import android.widget.ImageView;

import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.content.FileProvider;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    private ImageView imageView;
    private String currentPhotoPath;
    private ActivityResultLauncher<Uri> takePictureLauncher;

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

        imageView = findViewById(R.id.imageView);
        Button takePictureButton = findViewById(R.id.takePictureButton);

        takePictureLauncher = registerForActivityResult(new ActivityResultContracts.TakePicture(), result -> {
            if (result) {
                // 照片拍攝成功，顯示照片
                imageView.setImageURI(Uri.parse(currentPhotoPath));
            }
        });

        takePictureButton.setOnClickListener(v -> {
            // 啟動相機
            try {
                Uri photoUri = createImageFile();
                takePictureLauncher.launch(photoUri);
            } catch (IOException e) {
                e.printStackTrace();
            }
        });
    }

    private Uri createImageFile() throws IOException {
        // 使用時間戳生成文件名
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageFileName = "JPEG_" + timeStamp + "_";
        File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
        File image = File.createTempFile(
                imageFileName,  /* prefix */
                ".jpg",         /* suffix */
                storageDir      /* directory */
        );

        // Save a file: path for use with ACTION_VIEW intents
        currentPhotoPath = image.getAbsolutePath();
        return FileProvider.getUriForFile(this, "com.example.android.fileprovider", image);
    }
}

在 activity_main.xml 中加入 ImageView 和一個 Button:

<LinearLayout
    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:orientation="vertical"
    android:gravity="center"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:scaleType="centerCrop"
        app:srcCompat="@android:drawable/ic_menu_camera" />

    <Button
        android:id="@+id/takePictureButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="拍照" />
</LinearLayout>