我正在尝试运行以下链接在Kotlin中重写的应用程序： https://www.androidhive.info/RxJava/android-rxjava-networking-with-retrofit-gson-notes-app/
该示例最初是用Java编写的代码库。运行应用程序时出现以下错误。
2018-11-16 12:12:38.173 11843-11843/com.touchsides.rxjavanetworking E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.touchsides.rxjavanetworking, PID: 11843
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.touchsides.rxjavanetworking/com.touchsides.rxjavanetworking.view.MainActivity}: java.lang.InstantiationException: java.lang.Class<com.touchsides.rxjavanetworking.view.MainActivity> cannot be instantiated
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2843)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.InstantiationException: java.lang.Class<com.touchsides.rxjavanetworking.view.MainActivity> cannot be instantiated
at java.lang.Class.newInstance(Native Method)
at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:69)
at android.support.v4.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:43)
at android.app.Instrumentation.newActivity(Instrumentation.java:1215)
MainActivity代码如下：
abstract class MainActivity : AppCompatActivity()
{
lateinit var apiService: ApiService
var disposable = CompositeDisposable()
lateinit var mAdapter: NotesAdapter
var noteList = ArrayList<Note>()
companion object
{
val TAG = MainActivity::class.java.simpleName;
}
@BindView(R.id.coordinator_layout) var coordinatorLayout: CoordinatorLayout? = null
@BindView(R.id.recycler_view) var recyclerView: RecyclerView? = null
@BindView(R.id.txt_empty_notes_view) var noNotesView: TextView? = null
override fun onCreate(savedInstanceState: Bundle?)
{
super.onCreate(savedInstanceState)
getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
val toolbar = findViewById<Toolbar>(R.id.toolbar)
toolbar.setTitle(getString(R.string.activity_title_home))
setSupportActionBar(toolbar)
fab.setOnClickListener { view ->
showNoteDialog(false, null, -1);
}
}
override fun onCreateOptionsMenu(menu: Menu): Boolean
{
// Inflate the menu; this adds items to the action bar if it is present.
menuInflater.inflate(R.menu.menu_main, menu)
return true
}
override fun onOptionsItemSelected(item: MenuItem): Boolean
{
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
return when (item.itemId)
{
R.id.action_settings -> true
else -> super.onOptionsItemSelected(item)
}
}
/**
* Registering new user
* sending unique id as device identification
* https://developer.android.com/training/articles/user-data-ids.html
*/
private fun registerUser()
{
// unique id to identify the device
val uniqueId = UUID.randomUUID().toString()
disposable.add(apiService.register(uniqueId).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribeWith(
object : DisposableSingleObserver<User>()
{
override fun onSuccess(user: User)
{
// Storing user API Key in preferences
user.apiKey?.let { PrefUtils.storeApiKey(applicationContext, it) }
Toast.makeText(applicationContext,
"Device is registered successfully! ApiKey: " + PrefUtils.getApiKey(applicationContext),
Toast.LENGTH_LONG).show()
}
override fun onError(e: Throwable)
{
Log.e(TAG, "onError: " + e.message)
showError(e)
}
}))
}
/**
* Creating new note
*/
private fun createNote(note: String)
{
disposable.add(apiService.createNote(note).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribeWith(
object : DisposableSingleObserver<Note>()
{
override fun onSuccess(note: Note)
{
if (!TextUtils.isEmpty(note.error))
{
Toast.makeText(applicationContext, note.error, Toast.LENGTH_LONG).show()
return
}
Log.d(TAG, "new note created: " + note.id + ", " + note.note + ", " + note.timestamp)
// Add new item and notify adapter
noteList.add(0, note)
mAdapter.notifyItemInserted(0)
toggleEmptyNotes()
}
override fun onError(e: Throwable)
{
Log.e(TAG, "onError: " + e.message)
showError(e)
}
}))
}
/**
* Updating a note
*/
private fun updateNote(noteId: Int, note: String, position: Int)
{
disposable.add(apiService.updateNote(noteId,
note).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribeWith(object :
DisposableCompletableObserver()
{
override fun onComplete()
{
Log.d(TAG, "Note updated!")
val n = noteList.get(position)
n.note = (note)
// Update item and notify adapter
noteList.set(position, n)
mAdapter.notifyItemChanged(position)
}
override fun onError(e: Throwable)
{
Log.e(TAG, "onError: " + e.message)
showError(e)
}
}))
}
/**
* Deleting a note
*/
private fun deleteNote(noteId: Int, position: Int)
{
Log.e(TAG, "deleteNote: $noteId, $position")
disposable.add(apiService.deleteNote(noteId).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribeWith(
object : DisposableCompletableObserver()
{
override fun onComplete()
{
Log.d(TAG, "Note deleted! $noteId")
// Remove and notify adapter about item deletion
noteList.removeAt(position)
mAdapter.notifyItemRemoved(position)
Toast.makeText(this@MainActivity, "Note deleted!", Toast.LENGTH_SHORT).show()
toggleEmptyNotes()
}
override fun onError(e: Throwable)
{
Log.e(TAG, "onError: " + e.message)
showError(e)
}
}))
}
/**
* Shows alert dialog with EditText options to enter / edit
* a note.
* when shouldUpdate=true, it automatically displays old note and changes the
* button text to UPDATE
*/
private fun showNoteDialog(shouldUpdate: Boolean, note: Note?, position: Int)
{
val layoutInflaterAndroid = LayoutInflater.from(applicationContext)
val view = layoutInflaterAndroid.inflate(R.layout.note_dialog, null)
val alertDialogBuilderUserInput = AlertDialog.Builder(this@MainActivity)
alertDialogBuilderUserInput.setView(view)
val inputNote = view.findViewById<EditText>(R.id.note)
val dialogTitle = view.findViewById<TextView>(R.id.dialog_title)
dialogTitle.setText(if (!shouldUpdate) getString(R.string.lbl_new_note_title) else getString(R.string.lbl_edit_note_title))
if (shouldUpdate && note != null)
{
inputNote.setText(note.note)
}
alertDialogBuilderUserInput.setCancelable(false).setPositiveButton(if (shouldUpdate) "update" else "save",
DialogInterface.OnClickListener { dialogBox, id -> })
.setNegativeButton("cancel", DialogInterface.OnClickListener { dialogBox, id -> dialogBox.cancel() })
val alertDialog = alertDialogBuilderUserInput.create()
alertDialog.show()
alertDialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(View.OnClickListener {
// Show toast message when no text is entered
if (TextUtils.isEmpty(inputNote.text.toString()))
{
Toast.makeText(this@MainActivity, "Enter note!", Toast.LENGTH_SHORT).show()
return@OnClickListener
} else
{
alertDialog.dismiss()
}
// check if user updating note
if (shouldUpdate && note != null)
{
// update note by it's id
updateNote(note.id, inputNote.text.toString(), position)
} else
{
// create new note
createNote(inputNote.text.toString())
}
})
}
/**
* Opens dialog with Edit - Delete options
* Edit - 0
* Delete - 0
*/
private fun showActionsDialog(position: Int)
{
val colors = arrayOf<CharSequence>("Edit", "Delete")
val builder = AlertDialog.Builder(this)
builder.setTitle("Choose option")
builder.setItems(colors) { dialog, which ->
if (which == 0)
{
showNoteDialog(true, noteList.get(position), position)
} else
{
deleteNote(noteList.get(position).id, position)
}
}
builder.show()
}
private fun toggleEmptyNotes()
{
if (noteList.size > 0)
{
noNotesView?.setVisibility(View.GONE)
} else
{
noNotesView?.setVisibility(View.VISIBLE)
}
}
/**
* Showing a Snackbar with error message
* The error body will be in json format
* {"error": "Error message!"}
*/
fun showError(e: Throwable)
{
var message = ""
try
{
if (e is IOException)
{
message = "No internet connection!"
}
else (e is HttpException)
{
var error = e as HttpException
var errorBody = error.response().errorBody().toString()
val jObj = JSONObject(errorBody)
message = jObj.getString("error")
}
}
catch (e1: IOException)
{
e1.printStackTrace()
}
catch (e1: JSONException)
{
e1.printStackTrace()
}
catch (e1: Exception)
{
e1.printStackTrace()
}
if (TextUtils.isEmpty(message))
{
message = "Unknown error occurred! Check LogCat.";
}
val snackbar = coordinatorLayout?.let { Snackbar.make(it, message, Snackbar.LENGTH_LONG) }
val sbView = snackbar?.getView()
val textView = sbView?.findViewById<TextView>(android.support.design.R.id.snackbar_text)
textView?.setTextColor(Color.YELLOW)
snackbar?.show()
}
fun whiteNotificationBar(view: View)
{
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
{
var flags = view.getSystemUiVisibility();
flags = View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR;
view.setSystemUiVisibility(flags);
getWindow().setStatusBarColor(Color.WHITE);
}
}
override fun onDestroy()
{
super.onDestroy()
disposable.dispose()
}
}
答案 0 :(得分：0)
我发现了问题所在。似乎通过使用code complete选项，它最终使MainActivity类抽象了
abstract class MainActivity : AppCompatActivity()
{
/// code base
}
代替
class MainActivity : AppCompatActivity()
{
// code base
}