Question

我正在尝试在Kotlin中编写我的应用程序代码，但是当我在EXTRA_NOTE打开EditNoteActivity时，我无法将null转换为非null类型并且app force停止。

任何帮助都得到高度赞赏

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：null无法强制转换为非null类型 com.midsizemango.databasekotlin.Note 在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2298）at 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） at java.lang.reflect.Method.invoke（Native Method）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）引起：kotlin.TypeCastException：null无法强制转换为非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） at java.lang.reflect.Method.invoke（Native Method）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）

Answer 1

在这一行：

note = intent.getSerializableExtra(EXTRA_NOTE) as Note

Note是non-null type，因此对它的强制转换会触发空检查。由于您之后手动将note与null进行比较，可能您的意思是safe cast operator，如果表达式不是右侧指定的类型，则会生成null侧：

note = intent.getSerializableExtra(EXTRA_NOTE) as? Note

kotlin.TypeCastException：null无法强制转换为非null类型com.midsizemango.databasekotlin.Note

1 个答案: