kotlin.TypeCastException:不能将null强制转换为非null类型com.midsizemango.databasekotlin.

本文介绍了kotlin.TypeCastException:不能将null强制转换为非null类型com.midsizemango.databasekotlin.的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在尝试在Kotlin中编写我的应用程序代码，但是当我可能在EXTRA_NOTE中打开EditNoteActivity时，无法将null强制转换为非null类型，并且应用程序强制停止.

I am trying to code my app in Kotlin, but I am getting null cannot be casted to non-null type and app force stops when I open EditNoteActivity at EXTRA_NOTE probably.

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代码:

class EditNoteActivity : AppCompatActivity() { var note: Note? = null private val editNote: TextView? = null private val fabdrwble: Boolean? = null private val notesData: MutableList<Note>? = null private var databaseHelper: DatabaseHelper? = null private val save: Boolean? = null private var saveButton: FloatingActionButton? = null private val tint: ColorStateList? = null internal var mRowId: Long? = null internal var spinner: Spinner? = null internal var spinnertext: String? = null internal var fav: Int = 0 internal var mSharedFromIntentFilter = false internal var editTitle: EditText? = null internal var editContent: EditText? = null internal var inputlayoutTitle: TextInputLayout? = null internal var inputlayoutContent: TextInputLayout? = null override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_edit_note) var toolbar = findViewById(R.id.toolbar_edit) as Toolbar? setSupportActionBar(toolbar) if (supportActionBar != null) supportActionBar!!.setDisplayHomeAsUpEnabled(true) databaseHelper = DatabaseHelper(applicationContext) inputlayoutTitle = findViewById(R.id.inputlayoutTitle) as TextInputLayout? inputlayoutContent = findViewById(R.id.inputlayoutContent) as TextInputLayout? editTitle = findViewById(R.id.note_title) as EditText editContent = findViewById(R.id.note_content) as EditText? val bundle = intent.extras val s = bundle.getString("edit") if (s == "add") { window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE) } else if (s == "editv") { window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_HIDDEN) } note = intent.getSerializableExtra(EXTRA_NOTE) as Note if (note != null) { editTitle?.setText(note!!.getTitle()) editContent?.setText(note!!.getContent()) } else { note = Note() //note.setUpdatedAt(new Date()); } saveButton = findViewById(R.id.add_edit_button) as FloatingActionButton? saveButton!!.setOnClickListener { if (isNoteFormOk) { setNoteResult() finish() } else validateNoteForm() } var ll = findViewById(R.id.llmain) as LinearLayout? var ll1 = findViewById(R.id.ll1) as LinearLayout? /*if(note.getColor() == Color.TRANSPARENT){ selectedColor = preselect; }else { selectedColor = note.getColor(); } getWindow().addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS); systemBarTintManager = new SystemBarTintManager(this); systemBarTintManager.setStatusBarTintEnabled(true); ll.setBackgroundColor(selectedColor); ll1.setBackgroundColor(selectedColor); toolbar.setBackgroundColor(note.getColor()); systemBarTintManager.setStatusBarTintColor(selectedColor);*/ } override fun onResume() { super.onResume() } override fun onOptionsItemSelected(item: MenuItem): Boolean { when (item.itemId) { android.R.id.home -> { onBack() return true } /* case R.id.speech: try { displaySpeechRecognizer(); } catch (ActivityNotFoundException e) { Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("market.android/details?id=com.google.android.googlequicksearchbox")); startActivity(browserIntent); } return true;*/ else -> return super.onOptionsItemSelected(item) } } private fun displaySpeechRecognizer() { val intent = Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH) intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, RecognizerIntent.LANGUAGE_MODEL_FREE_FORM) startActivityForResult(intent, SPEECH_REQUEST_CODE) } override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent) { if (requestCode == SPEECH_REQUEST_CODE && resultCode == Activity.RESULT_OK) { val results = data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS) val spokenText = results[0] editContent?.setText(spokenText) } if (requestCode == RequestResultCode.REQUEST_CODE_ADD_NOTE) { if (resultCode == Activity.RESULT_OK) { addNote(data) } } } private val isNoteFormOk: Boolean get() { val title = editTitle?.text.toString() return !(title == null || title.trim { it <= ' ' }.length == 0) } private fun validateNoteForm() { var msg: String? = null if (isNullOrBlank(editTitle?.text.toString())) { msg = "Title Required" inputlayoutTitle?.error = "Title is Missing" } if (msg != null) { Toast.makeText(applicationContext, msg, Toast.LENGTH_LONG).show() } } private fun setNoteResult() { note!!.setTitle(editTitle?.text.toString().trim { it <= ' ' }) note!!.setContent(editContent?.text.toString().trim { it <= ' ' }) //note.setUpdatedAt(new Date()); val intent = Intent() intent.putExtra(EXTRA_NOTE, note) setResult(Activity.RESULT_OK, intent) //addNote(intent); Toast.makeText(this@EditNoteActivity, "Note Saved.", Toast.LENGTH_LONG).show() } private fun onBack() { if (isNoteFormOk) { if (editTitle?.text.toString() == note!!.getTitle() && editContent?.text.toString() == note!!.getContent()) { setResult(Activity.RESULT_CANCELED, Intent()) finish() } else { AlertDialog.Builder(this@EditNoteActivity) .setTitle("Save") .setMessage("Do You Want to Save Note") .setPositiveButton("SAVE") { dialog, which -> setNoteResult() finish() }.setNegativeButton("CANCEL") { dialog, which -> setResult(Activity.RESULT_CANCELED, Intent()) finish() }.show() } } else { setResult(Activity.RESULT_CANCELED, Intent()) finish() } } private fun addNote(data: Intent) { val note = data.getSerializableExtra(EXTRA_NOTE) as Note val noteId = databaseHelper!!.createNote(note) note.setId(noteId) } override fun onBackPressed() { onBack() val intentHome = Intent(this@EditNoteActivity, MainActivity::class.java) intentHome.flags = Intent.FLAG_ACTIVITY_CLEAR_TOP intentHome.putExtra(EXTRA_NOTE, note) setResult(Activity.RESULT_OK, intentHome) } companion object { private val EXTRA_NOTE = "EXTRA_NOTE" private val SPEECH_REQUEST_CODE = 0 fun isNullOrBlank(str: String?): Boolean { return str == null || str.trim { it <= ' ' }.length == 0 } } }

日志:

java.lang.RuntimeException:无法启动活动ComponentInfo { com.midsizemango.databasekotlin/com.midsizemango.databasekotlin.EditNoteActivity}: kotlin.TypeCastException:无法将null强制转换为非null类型 com.midsizemango.databasekotlin.Note 在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)处 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) 在android.app.ActivityThread.access $ 800(ActivityThread.java:144) 在 android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1278) 在android.os.Handler.dispatchMessage(Handler.java:102) 在android.os.Looper.loop(Looper.java:135) 在android.app.ActivityThread.main(ActivityThread.java:5221) 在java.lang.reflect.Method.invoke(本机方法) 在java.lang.reflect.Method.invoke(Method.java:372) 在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:899) 在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 原因:kotlin.TypeCastException:无法将null强制转换为非null 键入com.midsizemango.databasekotlin.Note 在 com.midsizemango.databasekotlin.EditNoteActivity.onCreate(EditNoteActivity.kt:82) 在android.app.Activity.performCreate(Activity.java:5933) 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251) 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) 在android.app.ActivityThread.access $ 800(ActivityThread.java:144) 在 android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1278) 在android.os.Handler.dispatchMessage(Handler.java:102) 在android.os.Looper.loop(Looper.java:135) 在android.app.ActivityThread.main(ActivityThread.java:5221) 在java.lang.reflect.Method.invoke(本机方法) 在java.lang.reflect.Method.invoke(Method.java:372) 在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:899) 在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

java.lang.RuntimeException: Unable to start activity ComponentInfo{ com.midsizemango.databasekotlin/com.midsizemango.databasekotlin.EditNoteActivity}: kotlin.TypeCastException: null cannot be cast to non-null type com.midsizemango.databasekotlin.Note at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Caused by: kotlin.TypeCastException: null cannot be cast to non-null type com.midsizemango.databasekotlin.Note at com.midsizemango.databasekotlin.EditNoteActivity.onCreate(EditNoteActivity.kt:82) at android.app.Activity.performCreate(Activity.java:5933) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)  at android.app.ActivityThread.access$800(ActivityThread.java:144)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:135)  at android.app.ActivityThread.main(ActivityThread.java:5221)  at java.lang.reflect.Method.invoke(Native Method)  at java.lang.reflect.Method.invoke(Method.java:372)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:694)

推荐答案

在这一行:

note = intent.getSerializableExtra(EXTRA_NOTE) as Note

Note是非null类型，因此对其进行强制转换会触发空检查.由于您之后要手动将note与null进行比较，因此您可能是说安全强制转换运算符，如果表达式不是右侧指定的类型，则产生null:

Note is a non-null type, so the cast to it triggers a null check. Since you're comparing note to null manually afterwards, probably you meant the safe cast operator, which yields null if the expression is not of the type specified in the right-hand side:

note = intent.getSerializableExtra(EXTRA_NOTE) as? Note