如何正确使用registerForActivityResult？获取"LifecycleOwners必须在启动前调用注册表“

Question

我使用registerForActivityResult就像这样：

package com.example.livedata

import android.Manifest
import android.app.Activity
import android.app.AlertDialog
import android.app.Dialog
import android.content.ActivityNotFoundException
import android.content.Intent
import android.graphics.Bitmap
import android.net.Uri
import android.os.Bundle
import android.provider.Settings
import android.view.View
import android.widget.Toast
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity
import com.example.livedata.databinding.ActivityAddBinding
import com.example.livedata.databinding.DialogCustomImageSelectionBinding


class AddActivity : AppCompatActivity(), View.OnClickListener {
    private lateinit var binding: ActivityAddBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityAddBinding.inflate(layoutInflater)
        setContentView(binding.root)
        setupActionBar()

        binding.photoAdd.setOnClickListener(this)
    }

    private fun setupActionBar() {
        setSupportActionBar(binding.toolbar)
        supportActionBar?.setDisplayHomeAsUpEnabled(true)
        binding.toolbar.setNavigationOnClickListener { onBackPressed() }
    }

    override fun onClick(v: View?) {
        if (v != null) {
            when (v.id) {
                R.id.photo_add -> {
                    imageDialog()
                    return
                }
            }
        }
    }

    private fun imageDialog() {
        val dialog = Dialog(this)
        val dialogBinding: DialogCustomImageSelectionBinding =
            DialogCustomImageSelectionBinding.inflate(layoutInflater)
        dialog.setContentView(dialogBinding.root)
        dialog.show()

        dialogBinding.impCamera.setOnClickListener {
            registerForActivityResult(ActivityResultContracts.TakePicturePreview()) {
                if (it != null) {
                    Toast.makeText(this@AddActivity, "TakePicturePreview", Toast.LENGTH_SHORT).show()
                }
            }.launch(null).apply { arrayOf(
                Manifest.permission.READ_EXTERNAL_STORAGE,
                Manifest.permission.WRITE_EXTERNAL_STORAGE,
                Manifest.permission.CAMERA) }
            dialog.dismiss()
        }

    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == 1 && resultCode == Activity.RESULT_OK) {
            data?.let {
                val bp = data.getParcelableExtra<Bitmap>("data")
                binding.imageView.setImageBitmap(bp)

            }
        }
    }

    private fun showPermissions() {
        AlertDialog.Builder(this).setMessage("Applay Permissions!")
            .setPositiveButton("Go to Settings") { _, _ ->
                try {
                    val intel = Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS)
                    val uri = Uri.fromParts("package", packageName, null)
                    intel.data = uri
                    startActivity(intel)
                } catch (e: ActivityNotFoundException) {
                    e.printStackTrace()
                }
            }.setNegativeButton("Cancel") { dialog, _ ->
                dialog.dismiss()
            }.show()
    }
}

但是它不能工作并在这里抛出一个异常：

2021-07-16 15:38:50.472 29885-29885/com.example.livedata E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.livedata, PID: 29885
    java.lang.IllegalStateException: LifecycleOwner com.example.livedata.AddActivity@9fc53b9 is attempting to register while current state is RESUMED. LifecycleOwners must call register before they are STARTED.
        at androidx.activity.result.ActivityResultRegistry.register(ActivityResultRegistry.java:123)
        at androidx.activity.ComponentActivity.registerForActivityResult(ComponentActivity.java:659)
        at androidx.activity.ComponentActivity.registerForActivityResult(ComponentActivity.java:668)
        at com.example.livedata.AddActivity.imageDialog$lambda-3(AddActivity.kt:68)
        at com.example.livedata.AddActivity.lambda$N7K_EbTML-ycmUwpA7-i8b_L-Sw(Unknown Source:0)
        at com.example.livedata.-$$Lambda$AddActivity$N7K_EbTML-ycmUwpA7-i8b_L-Sw.onClick(Unknown Source:4)
        at android.view.View.performClick(View.java:7281)
        at android.view.View.performClickInternal(View.java:7255)
        at android.view.View.access$3600(View.java:828)
        at android.view.View$PerformClick.run(View.java:27925)
        at android.os.Handler.handleCallback(Handler.java:900)
        at android.os.Handler.dispatchMessage(Handler.java:103)
        at android.os.Looper.loop(Looper.java:219)
        at android.app.ActivityThread.main(ActivityThread.java:8393)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1055)
2021-07-16 15:38:50.539 1689-2062/? E/InputDispatcher: channel 'ba7a009 com.example.livedata/com.example.livedata.AddActivity (server)' ~ Channel is unrecoverably broken and will be disposed!

如何使用registerForActivityResult而不是过时的方法来完成此任务？所有的帮助都非常感谢。

Answer 1

下面的代码代替了startActivityForResult的弃用，这个方法给出结果本身并返回一个值。

val resultLauncher = registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
    when (result.resultCode) {
        Activity.RESULT_OK -> {
            // logic
        }
        else -> {
            // logic
        }
    }
}

Answer 2

您正在尝试调用单击侦听器中的registerForActivityResult。这是行不通的，因为在结果交付之前，您的Activity可能会被销毁并重新创建。重新创建的Activity不会被注册来接收结果，因为它只在您单击按钮时注册，并且该按钮只在原始Activity中单击。

要解决此问题，您需要无条件地调用registerForActivityResult并将结果存储在一个变量中：

class MyActivity : AppCompatActivity() {
    private val activityLauncher = registerForActivityResult(...

这样，重新创建的Activity将被注册以接收结果。然后使用该activityLauncher变量从单击listener按钮启动它。

有关详细信息，请参阅official guide。