Android中startActivityForResult已废弃，如何用registerForActivityResult实现Java版拍照功能

核心修改逻辑 #

• 移除原有手动维护的权限、拍照请求码常量，新API会自动管理请求标识
• 注册两个ActivityResultLauncher作为类成员变量，分别处理相机权限申请结果、拍照返回结果
• 替换原有废弃的权限申请、启动相机方法

完整修改后代码 #

package com.example.myapplication;

import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.Toast;

import com.google.android.material.snackbar.Snackbar;

public class MainActivity extends AppCompatActivity {

    private Button button;
    private ImageView image;
    private RelativeLayout parent;

    // 注册权限申请回调
    private final ActivityResultLauncher<String> permissionLauncher = registerForActivityResult(
            new ActivityResultContracts.RequestPermission(),
            isGranted -> {
                if (isGranted) {
                    // 权限通过，打开相机
                    openCamera();
                    Toast.makeText(this, "你已获得相机权限", Toast.LENGTH_SHORT).show();
                } else {
                    // 权限被拒绝
                    Toast.makeText(this, "相机权限被拒绝，无法拍照", Toast.LENGTH_SHORT).show();
                }
            }
    );

    // 注册拍照结果回调
    private final ActivityResultLauncher<Intent> takePhotoLauncher = registerForActivityResult(
            new ActivityResultContracts.StartActivityForResult(),
            result -> {
                if (result.getResultCode() == RESULT_OK && result.getData() != null) {
                    // 拿到拍照缩略图，设置到ImageView
                    Bitmap bitmap = (Bitmap) result.getData().getExtras().get("data");
                    image.setImageBitmap(bitmap);
                }
            }
    );

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

        button = findViewById(R.id.button);
        image = findViewById(R.id.image);
        parent = findViewById(R.id.parent);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                handlePermission();
            }
        });
    }

    private void handlePermission() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
            openCamera();
            Toast.makeText(this, "你有相机使用权限", Toast.LENGTH_SHORT).show();
        } else {
            if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA)) {
                showSnackBar();
            } else {
                // 直接调用权限launcher发起申请，替换原有requestPermissions方法
                permissionLauncher.launch(Manifest.permission.CAMERA);
            }
        }
    }

    private void showSnackBar() {
        Snackbar.make(parent, "需要相机权限才能完成拍照", Snackbar.LENGTH_INDEFINITE)
                .setAction("去授权", v -> permissionLauncher.launch(Manifest.permission.CAMERA))
                .show();
    }

    private void openCamera() {
        Intent intent =  new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        // 调用拍照launcher启动相机，替换原有startActivityForResult方法
        takePhotoLauncher.launch(intent);
    }
}

注意事项 #

• registerForActivityResult 必须在Activity的onStart生命周期前完成注册，因此需要定义为类成员变量，或者在onCreate方法中执行注册逻辑，不可以在点击事件等异步场景中注册
• 上述代码拿到的是相机返回的缩略图，如果需要获取高清原图，需要额外传入图片保存路径到拍照Intent中，对应调整Contract逻辑即可

内容的提问来源于stack exchange，提问作者Chris Ray