如何将Android相机运行时权限逻辑拆分至多个文件

我来帮你把相机权限的运行时逻辑拆分成更清晰的多个文件，这样代码结构更整洁，也方便后续复用。咱们可以按照「常量定义+扩展函数+权限助手类+业务Activity」的方式来拆分：

1. 权限常量统一管理：PermissionConstants.kt #

先把权限相关的常量单独抽出来，避免硬编码，方便后续维护：

package com.example.hasan.runtime.feature.constants

import android.Manifest

object PermissionConstants {
    const val PERMISSION_REQUEST_CAMERA = 0
    val CAMERA_PERMISSION = Manifest.permission.CAMERA
}

2. Context权限扩展函数：PermissionExtensions.kt #

把权限检查、请求、合理性提示这些通用逻辑封装成Context的扩展函数，让调用更简洁：

package com.example.hasan.runtime.feature.extensions

import android.content.Context
import android.content.pm.PackageManager
import android.support.v4.app.ActivityCompat
import android.support.v4.content.ContextCompat
import android.support.design.widget.Snackbar
import android.view.View

// 检查权限是否已授予
fun Context.isPermissionGranted(permission: String): Boolean {
    return ContextCompat.checkSelfPermission(this, permission) == PackageManager.PERMISSION_GRANTED
}

// 请求权限（需在Activity中调用）
fun Context.requestPermission(permission: String, requestCode: Int) {
    ActivityCompat.requestPermissions(this as android.app.Activity, arrayOf(permission), requestCode)
}

// 判断是否需要显示权限申请的合理性提示
fun Context.shouldShowPermissionRationale(permission: String): Boolean {
    return ActivityCompat.shouldShowRequestPermissionRationale(this as android.app.Activity, permission)
}

// View的Snackbar扩展函数
fun View.showSnackbar(
    messageResId: Int,
    duration: Int,
    actionResId: Int? = null,
    action: (() -> Unit)? = null
) {
    val snackbar = Snackbar.make(this, messageResId, duration)
    actionResId?.let {
        action?.let { act ->
            snackbar.setAction(it) { act() }
        }
    }
    snackbar.show()
}

3. 相机权限助手类：CameraPermissionHelper.kt #

把相机权限的具体请求逻辑、回调处理封装成单独的助手类，让Activity不用处理这些细节：

package com.example.hasan.runtime.feature.helpers

import android.app.Activity
import android.widget.Toast
import com.example.hasan.runtime.feature.constants.PermissionConstants
import com.example.hasan.runtime.feature.extensions.isPermissionGranted
import com.example.hasan.runtime.feature.extensions.requestPermission
import com.example.hasan.runtime.feature.extensions.shouldShowPermissionRationale
import com.example.hasan.runtime.feature.extensions.showSnackbar

class CameraPermissionHelper(private val activity: Activity, private val layout: android.view.View) {

    // 处理相机权限逻辑，传入权限通过后的回调
    fun handleCameraPermission(onPermissionGranted: () -> Unit) {
        when {
            activity.isPermissionGranted(PermissionConstants.CAMERA_PERMISSION) -> {
                layout.showSnackbar(
                    R.string.camera_permission_available,
                    Snackbar.LENGTH_INDEFINITE,
                    R.string.ok
                ) { onPermissionGranted() }
            }
            activity.shouldShowPermissionRationale(PermissionConstants.CAMERA_PERMISSION) -> {
                // 显示权限必要性的提示，引导用户授权
                layout.showSnackbar(
                    R.string.camera_permission_rationale,
                    Snackbar.LENGTH_INDEFINITE,
                    R.string.grant_permission
                ) {
                    activity.requestPermission(
                        PermissionConstants.CAMERA_PERMISSION,
                        PermissionConstants.PERMISSION_REQUEST_CAMERA
                    )
                }
            }
            else -> {
                // 首次请求权限
                activity.requestPermission(
                    PermissionConstants.CAMERA_PERMISSION,
                    PermissionConstants.PERMISSION_REQUEST_CAMERA
                )
            }
        }
    }

    // 处理权限请求的回调
    fun onRequestPermissionsResult(requestCode: Int, grantResults: IntArray): Boolean {
        if (requestCode == PermissionConstants.PERMISSION_REQUEST_CAMERA) {
            if (grantResults.isNotEmpty() && grantResults[0] == android.content.pm.PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(activity, "相机权限已授予", Toast.LENGTH_SHORT).show()
                return true
            } else {
                Toast.makeText(activity, "相机权限被拒绝，无法使用相机功能", Toast.LENGTH_SHORT).show()
                return false
            }
        }
        return false
    }
}

4. 简化后的MainActivity.kt #

现在MainActivity只需要专注业务逻辑，权限相关的事情交给助手类处理：

package com.example.hasan.runtime.feature

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.widget.Toast
import com.example.hasan.runtime.feature.constants.PermissionConstants
import com.example.hasan.runtime.feature.helpers.CameraPermissionHelper
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private lateinit var cameraPermissionHelper: CameraPermissionHelper

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        cameraPermissionHelper = CameraPermissionHelper(this, main_layout)

        btn_cam.setOnClickListener {
            showCamera()
        }
    }

    private fun showCamera() {
        cameraPermissionHelper.handleCameraPermission { startCamera() }
    }

    private fun startCamera() {
        // 这里可以替换成实际启动相机的逻辑
        Toast.makeText(this, "权限通过，准备启动相机", Toast.LENGTH_LONG).show()
    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (cameraPermissionHelper.onRequestPermissionsResult(requestCode, grantResults)) {
            // 如果权限被授予，直接启动相机
            startCamera()
        }
    }
}

这样拆分后，代码结构更清晰：

• 常量统一管理，避免硬编码错误
• 扩展函数可以在整个项目中复用
• 权限助手类封装了所有相机权限的逻辑，Activity只需要关注业务
• 后续如果要添加其他权限（比如存储），只需要新增对应的Helper类即可

内容的提问来源于stack exchange，提问作者Hasan A Yousef