kotlin.TypeCastException:不能将null强制转换为非null类型com.midsizemango.databasekotlin. [英] kotlin.TypeCastException: null cannot be cast to non-null type com.midsizemango.databasekotlin.Note

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("https://market.android.com/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

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