相机崩溃时的返回按钮

Question

我一直在查看 Stackoverflow 上的各种解决方案，但似乎没有任何效果。我遇到一个问题，当用户启动相机然后按“后退”按钮取消相机时，应用程序崩溃。我认为下面的这段代码可以解决问题，但似乎不起作用。

else if (resultCode== Activity.RESULT_CANCELED) {
        startActivity(Intent(this, MainActivity::class.java))
        println("result cancelled")
        return
}

MainActivity.kt

import android.annotation.SuppressLint
import android.app.Activity
import android.app.AlertDialog
import android.content.Intent
import android.content.pm.ActivityInfo
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.media.MediaScannerConnection
import android.os.Bundle
import android.provider.MediaStore
import android.util.Log
import android.view.View
import android.widget.Button
import android.widget.ImageView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.core.graphics.drawable.RoundedBitmapDrawableFactory
import kotlinx.android.synthetic.main.activity_main.*
import java.io.ByteArrayOutputStream
import java.io.File
import java.io.FileOutputStream
import java.io.IOException
import java.util.*

class MainActivity : AppCompatActivity() {

    private var btn: Button? = null
    private var imageview: ImageView? = null
    private val GALLERY = 1
    private val CAMERA = 2

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

        requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT

        btn = findViewById<View>(R.id.btn) as Button
        imageview = findViewById<View>(R.id.iv) as ImageView

        val wallpaperDirectory = File(getExternalFilesDir(null).toString() + IMAGE_DIRECTORY)

        var listImages : Array<File>? = null
        listImages = wallpaperDirectory.listFiles()

        if(listImages != null && listImages.size!! > 0){

//            iv.setImageBitmap(BitmapFactory.decodeFile(listImages[0].absolutePath))
            val img2 = BitmapFactory.decodeFile(listImages[0].absolutePath)
            val round = RoundedBitmapDrawableFactory.create(resources, img2)
            round.isCircular = true
            iv.setImageDrawable(round)

        }
        else {
            val img = BitmapFactory.decodeResource(resources, R.mipmap.profile_image)
            val round = RoundedBitmapDrawableFactory.create(resources, img)
            round.isCircular = true
            iv.setImageDrawable(round)
            println("hit hit hit")

        }

        btn!!.setOnClickListener { showPictureDialog() }
    }

    private fun showPictureDialog() {
        val pictureDialog = AlertDialog.Builder(this)
        pictureDialog.setTitle("Select Action")
        val pictureDialogItems = arrayOf("Select Photo From Gallery", "Capture Photo From Camera")
        pictureDialog.setItems(pictureDialogItems
        ) { dialog, which ->
            when (which) {
                0 -> choosePhotoFromGallary()
                1 -> takePhotoFromCamera()
            }
        }
        pictureDialog.show()
    }

    fun choosePhotoFromGallary() {
        val galleryIntent = Intent(Intent.ACTION_PICK,
                MediaStore.Images.Media.EXTERNAL_CONTENT_URI)

        startActivityForResult(galleryIntent, GALLERY)
    }

    fun takePhotoFromCamera() {
        val intent = Intent(MediaStore.ACTION_IMAGE_CAPTURE)
        startActivityForResult(intent, CAMERA)
    }

    public override fun onActivityResult(requestCode:Int, resultCode:Int, data: Intent?) {

        super.onActivityResult(requestCode, resultCode, data)

        if (requestCode == GALLERY)
        {
            if (data != null)
            {
                val contentURI = data.data
                try
                {
                    val bitmap = MediaStore.Images.Media.getBitmap(this.contentResolver, contentURI)
                    val round = RoundedBitmapDrawableFactory.create(resources, bitmap)
                    round.isCircular = true

                    val path = saveImage(bitmap)
                    Toast.makeText(this@MainActivity, "Image Saved!", Toast.LENGTH_SHORT).show()
                    imageview!!.setImageDrawable(round)

                }
                catch (e: IOException) {
                    e.printStackTrace()
                    Toast.makeText(this@MainActivity, "Failed!", Toast.LENGTH_SHORT).show()
                }
            }
        }
        else if (requestCode == CAMERA)
        {
            val thumbnail = data!!.extras!!.get("data") as Bitmap
            val round = RoundedBitmapDrawableFactory.create(resources, thumbnail)
            round.isCircular = true
            imageview!!.setImageDrawable(round)
            saveImage(thumbnail)
            Toast.makeText(this@MainActivity, "Image Saved!", Toast.LENGTH_SHORT).show()

            }
        else if (resultCode== Activity.RESULT_CANCELED) {
            startActivity(Intent(this, MainActivity::class.java))

            println("result cancelled")


        }
    }

    fun saveImage(myBitmap: Bitmap):String {
        val bytes = ByteArrayOutputStream()
        myBitmap.compress(Bitmap.CompressFormat.JPEG, 90, bytes)
        val wallpaperDirectory = File(getExternalFilesDir(null).toString() + IMAGE_DIRECTORY)
        wallpaperDirectory.deleteRecursively()

        // have the object build the directory structure, if needed.
        Log.d("fee",wallpaperDirectory.toString())
        if (!wallpaperDirectory.exists())
        {

            wallpaperDirectory.mkdirs()
        }

        try
        {
            Log.d("heel",wallpaperDirectory.toString())
            val f = File(wallpaperDirectory, ((Calendar.getInstance()
                    .getTimeInMillis()).toString() + ".jpg"))
            f.createNewFile()
            val fo = FileOutputStream(f)
            fo.write(bytes.toByteArray())
            MediaScannerConnection.scanFile(this,
                    arrayOf(f.getPath()),
                    arrayOf("image/jpeg"), null)
            fo.close()
            Log.d("TAG", "File Saved::--->" + f.getAbsolutePath())

            return f.getAbsolutePath()
        }
        catch (e1: IOException) {
            e1.printStackTrace()
        }

        return ""
    }

    companion object {
        private val IMAGE_DIRECTORY = "/demonuts"

    }
}

acitivity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    android:exported="true"
    tools:context=".MainActivity">

    <!--        android:text="Select or Capture Image" -->
    <Button
        android:id="@+id/btn"
        android:layout_width="125dp"
        android:layout_height="125dp"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="40dp"
        android:width="2dp"
        android:background="#00000000" />

    <ImageView
        android:id="@+id/iv"
        android:layout_width="125dp"
        android:layout_height="125dp"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="-150dp"
        android:scaleType="fitXY"
        android:src="@mipmap/profile_image" />    
</LinearLayout>

错误日志：

java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=2, result=0, data=null} to activity {com.example.pickimagetakeexamples/com.example.pickimagetakeexamples.MainActivity}: kotlin.KotlinNullPointerException
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4998)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:5041)
        at android.app.ActivityThread.access$1600(ActivityThread.java:229)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1875)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:7325)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
     Caused by: kotlin.KotlinNullPointerException
        at com.example.pickimagetakeexamples.MainActivity.onActivityResult(MainActivity.kt:124)
        at android.app.Activity.dispatchActivityResult(Activity.java:7165)
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4994)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:5041) 
        at android.app.ActivityThread.access$1600(ActivityThread.java:229) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1875) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:148) 
        at android.app.ActivityThread.main(ActivityThread.java:7325) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 

Answer 1

根据您的日志，我可以说应用程序崩溃的原因是，您没有捕获图像并且您正在按下返回按钮，该按钮将 null 作为数据返回给您的 onActivityResult，您需要指定如果null 作为结果在您的 onActivityResult 中返回。只需添加默认参数或 if data==null 并处理这种情况。

Answer 2

你应该添加 if 条件。

相机打开，用户返回。使用 resultCode == Activity.RESULT_CANCELED 调用 onActivityResult()。同样，用户从相机拍照。使用 resultCode == Activity.RESULT_OK 调用 onActivityResult。

您在 if 条件中检查了 RequestCode，但没有检查 ResultCode。更改以下 if 条件：

if (Activity.RESULT_OK == resultCode && requestCode == GALLERY)
if (Activity.RESULT_OK == resultCode && requestCode == CAMERA)