如何解决"NullPointerException: null不能转换为非空类型android.graphics.Bitmap"？
如何解决"NullPointerException: null不能转换为非空类型android.graphics.Bitmap"？
提问于 2020-11-16 22:41:29
我一直在尝试遵循本教程：https://developer.android.com/training/camera/photobasics
我使用了一个图像按钮，所以我打开相机并拍下照片，但是当我接受照片时，它就崩溃了：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.bujess, PID: 15270
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=null} to activity {com.example.bujess/com.example.bujess.WritingActivity}: java.lang.NullPointerException: null cannot be cast to non-null type android.graphics.Bitmap
at android.app.ActivityThread.deliverResults(ActivityThread.java:5097)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:5138)
at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2147)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:7814)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
Caused by: java.lang.NullPointerException: null cannot be cast to non-null type android.graphics.Bitmap
at com.example.bujess.WritingActivity.onActivityResult(WritingActivity.kt:61)
at android.app.Activity.dispatchActivityResult(Activity.java:8292)
at android.app.ActivityThread.deliverResults(ActivityThread.java:5090)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:5138)
at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2147)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:7814)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068) 最可疑的是“在com.example.bujess.WritingActivity.onActivityResult(WritingActivity.kt:61)".”但是，这些是我从指南onActivityResult复制的代码：
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
val imageBitmap = data?.extras?.get("data") as Bitmap
val imageView = findViewById<ImageView>(R.id.opGallNCam)
imageView?.setImageBitmap(imageBitmap)
galleryAddPic()
}
}第61行为："val imageBitmap = data?.extras?.get("data")作为位图“
opGallNCam是ImageButton的Id，我是Kotlin的新手。我提前感谢你
回答 2
Stack Overflow用户
回答已采纳
发布于 2020-11-16 22:56:27
java.lang.NullPointerException: null cannot be cast to non-null type android.graphics.Bitmap
问题是：data?.extras?.get("data")返回一个null值，您正在尝试将这个null转换为一个Bitmap
首先，data?.extras?.get("data")不会返回位图，但您可以首先使用data?.data获取Uri对象，然后将其转换为如下所示的Bitmap，将onActivityResult方法更改为：
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
if (requestCode == 10 && resultCode == RESULT_OK) {
val imageUri = data?.data as Uri
var imageBitmap: Bitmap
val bitmap = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
imageBitmap = ImageDecoder.decodeBitmap(ImageDecoder.createSource(contentResolver, imageUri))
} else {
imageBitmap = MediaStore.Images.Media.getBitmap(contentResolver, imageUri)
}
//............... rest of your codeStack Overflow用户
发布于 2020-11-17 05:20:48
为了避免抛出异常，可以使用安全的强制转换操作符作为？，它在失败时返回空。
val imageBitmap = data?.extras?.get("data") as? Bitmap看看这个，你会知道更多关于它的https://kotlinlang.org/docs/reference/typecasts.html#safe-nullable-cast-operator
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/64866779
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