我一直在研究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，当用户启动摄像头，然后按“后退”按钮取消摄像头时，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)
根据您的日志，我可以说，使应用程序崩溃的原因是，您没有捕获图像，而是按下了后退按钮，该按钮会将null作为数据返回到onActivityResult，因此您需要指定为null时该怎么做结果返回到您的onActivityResult中。只需添加默认参数，或者如果data == null即可处理这种情况。
如果有条件，您应该添加。