使用界面的两个活动之间的通信未按预期工作
Communication between two activities using interface not working as expected
问题： 将数据从 activity2 发送到 activity1 使用接口导致 activity1 中的发送数据未分配，即使正在分配也是如此。因此，activity1 成员变量自动设置为 null。
设置详细信息： 单击 activity1 中的按钮，启动 activity2。现在用户可以在 activity2 中执行任何工作。但是一旦用户在 activity2 中执行工作，我的自定义界面就会将数据发送到 activity1。 Activity1 应该将该发送的值分配给它的成员变量，并且当用户导航回 activity1、[=64= activity1 的 ]onRestart() 方法必须使用新值更新用户界面。
点数设置：
1- 用户单击 ACTIVITY1
上的按钮
2- 按钮打开 ACTIVITY2
3- 用户执行触发我的接口发送数据的操作
4-接口在后台向ACTIVITY1发送数据（ACTIVITY2仍然可见)
5-发送数据通过接口
赋值给ACTIVITY1成员变量（boolean）
6- 用户返回按 ACTIVITY2 并导航回 ACTIVITY1
7-ONRESTART() of ACTIVITY1 被触发
8- ONRESTART() 检查布尔值是否为真，然后更新 UI
但是我的困惑开始了。 为什么赋值后布尔值还是null？ 为什么是ACTIVITY1的成员变量丢失赋值？
代码：
接口
override fun onReturnedToActivity(actionID: Int) {
when(actionID)
{
3 ->
{
newNoteCreated = true
}
}
}
ONRESTART()
override fun onRestart() {
super.onRestart()
if(newNoteCreated) //variable is null not true.
{
Toast.makeText(this,"TRUE",Toast.LENGTH_SHORT).show()
mDrawer!!.updateBadge(3, StringHolder(dbHandler.totalNotes().toString() ))
newNoteCreated = false
}
请教我这个问题。我一直在尝试在 SO 上找到它的解决方案，但还没有回答我的问题。我知道还有其他方法可以在活动之间发送数据，但我正在尝试特别使用接口。
引用自
https://developer.android.com/reference/android/app/Activity#ActivityLifecycle
"如果一个activity被另一个activity完全遮挡，它就会停止。它仍然保留所有状态和成员信息，但是，它不再对用户可见，因此它的 window 被隐藏，并且当其他地方需要内存时，它通常会被系统杀死。"
那为什么我的activity会丢失变量数据呢？
编辑
主要Activity(ACTIVITY1)
class MainActivity : AppCompatActivity(), ContextBarVisibilityListener, OnActionPerformedBadgeUpdater, ActivityReturningStateNotify {
private val dbHandler: PediaDatabase = PediaDatabase(this)
private var mDrawer: Drawer? = null
private var filePath: String? = null
private var backupFileName: String? = null
private var listBt: MenuItem? = null
private var gridBt: MenuItem? = null
private var frontAppName: TextView? = null
private var buttonStatePref: SharedPreferences? = null
private var speedDialView: SpeedDialView? = null
private var trashNotesCount: String? = null
private var archiveNotesCount: String? = null
private var onLayoutChange: LayoutChangeListener? = null
private var newNoteCreated: Boolean = false //THIS IS THE BOOL
private lateinit var mAdView: AdView
companion object
{
private const val LAYOUT_USER_PREF = "layout_preference"
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
onLayoutChange = NotesFrag()
if(savedInstanceState == null) //prevents reloading fragment
{
val transaction = supportFragmentManager.beginTransaction()
transaction.add(R.id.innerFrameLayout,NotesFrag()).commit()
}
trashNotesCount = dbHandler.trashedNotesCount().toString()
archiveNotesCount = dbHandler.archivedNoteCount().toString()
val drawerTrashBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(1).withName("Trash Bin")
.withIcon(R.drawable.delete_note_image)
.withBadge(trashNotesCount)
.withSelectedIcon(R.drawable.delete_drawer_selected)
val drawerArchiveBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(2).withName("Archive")
.withIcon(R.drawable.archive_note_img)
.withBadge(archiveNotesCount)
.withSelectedIcon(R.drawable.archive_drawer_selected)
val drawerNotesBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(3).withName("Notes")
.withIcon(R.drawable.notes_img)
.withBadge(dbHandler.totalNotes().toString())
.withSelectedIcon(R.drawable.notes_drawer_selected)
val drawerLockedNotesBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(4).withName("Locked Notes")
.withIcon(R.drawable.lock_button)
.withBadge("1")
.withSelectedIcon(R.drawable.locked_drawer_selected)
val drawerReminderNotesBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(5).withName("Reminder Notes")
.withIcon(R.drawable.reminder_notes)
.withBadge("1")
.withSelectedIcon(R.drawable.reminder_drawer_selected)
val drawerFavouriteNotesBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(6).withName("Favourite Notes")
.withIcon(R.drawable.rate_app_star_img)
.withBadge("1")
.withSelectedIcon(R.drawable.favourite_drawer_selected)
val drawerSettingsBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(7).withName("Settings")
.withIcon(R.drawable.settings_drawer)
mDrawer = DrawerBuilder().withActivity(this)
.withHeader(R.layout.navbar_header)
.addDrawerItems(drawerNotesBt,drawerArchiveBt,drawerTrashBt,
drawerLockedNotesBt,drawerReminderNotesBt,
drawerFavouriteNotesBt,DividerDrawerItem(), drawerSettingsBt)
.withOnDrawerItemClickListener(object: Drawer.OnDrawerItemClickListener{
override fun onItemClick(view: View?, position: Int, drawerItem: IDrawerItem<*, *>?): Boolean {
when(position)
{
1 ->
{
frontAppName!!.text = "Wonder Notes"
speedDialView!!.show() //show again because traversing to other fragments hides it
val transaction = supportFragmentManager.beginTransaction()
transaction.replace(R.id.innerFrameLayout, NotesFrag())
transaction.addToBackStack(null)
transaction.commit()
}
2 ->
{
speedDialView!!.hide()
supportFragmentManager.beginTransaction().replace(R.id.innerFrameLayout,ArchiveFragment()).commit()
}
3 ->
{
frontAppName!!.text = "Trash"
speedDialView!!.hide()
fabLayoutBehaviourSetter(false)
supportFragmentManager.beginTransaction().replace(R.id.innerFrameLayout, TrashFragment()).commit()
}
4 -> Log.d("locked notes","1")
5 -> Log.d("reminder","1")
6 -> Log.d("favourite","1")
}
return false // false closes drawer on click
}
}).build()
/*Below code handles swipe tabs adapter setting and displaying
* and implements fragments to viewpager programitically */
// mainActivityViewPagerID.adapter = ViewPagerAdapter(supportFragmentManager)
// attachNotesFrag()
//mainTabsID.setupWithViewPager(mainActivityViewPagerID)
//mainTabsID.setTabTextColors(Color.DKGRAY, Color.parseColor("white"))
val drawerOpener = findViewById<ImageButton>(R.id.drawerOpenImgBt)
val noteCounterAsBt = findViewById<TextView>(R.id.showNotesCountID)
drawerOpener.setOnClickListener { mDrawer!!.openDrawer() }
noteCounterAsBt.setOnClickListener { mDrawer!!.openDrawer() }
//navigationView.setNavigationItemSelectedListener(this)
val customToolbar: Toolbar = findViewById(R.id.toolbarID)
setSupportActionBar(customToolbar)
supportActionBar!!.setDisplayShowTitleEnabled(false) //set main title off
val toolbarTxtView = findViewById<TextView>(R.id.toolbar_title)
toolbarTxtView.visibility = View.GONE
checkForStoragePermission()
}//on create
override fun onContextBarVisibilityChange(isVisible: Boolean) { //custom interface
if(isVisible)
{
speedDialView!!.hide()
fabLayoutBehaviourSetter(false) //remove scrolling behaviour
}
else
{
speedDialView!!.show()
fabLayoutBehaviourSetter(true) //set scrolling behaviour
}
}
override fun onReturnedToActivity(actionID: Int) { ///it just recieves value from ACTIVITY2 and assign its value to ACTIVTY1`s "newNoteCreated" varaible
when(actionID)
{
3 ->
{
Log.d("INTERFACE","CALLED $actionID")
newNoteCreated = true
Log.d("INTERFACE","CALLED $newNoteCreated")
}
}
}
参考 ACTIVITY(ACTIVITY2)
我只包括接口将数据发送回 activity1 的部分，因为 activity2 的代码非常冗长，很可能会使读者感到困惑。
onActivityReturningStateNotify = MainActivity()
dbHandler!!.createNote(note)
//onActionPerformedBadgeUpdater!!.onActionPerformed(3)
onActivityReturningStateNotify!!.onReturnedToActivity(3)
接口
interface ActivityReturningStateNotify {
fun onReturnedToActivity(actionID: Int)
}
您的问题是您在 MainActivity 的新实例上调用 onReturnedToActivity()，而不是您开始的实例或您将 return 到达的实例。
有几种方法可以在活动之间共享数据，一种是使用startActivityForResult()。
我认为您的问题是 Activity1 将停止，因此您无法真正从 Activity2 向它发送数据。但是，您可以使用 startActivityForResult 和 return 结果启动 Activity2。
这是 documentation.
中的示例
正在启动 activity。
const val PICK_CONTACT_REQUEST = 1 // The request code
...
private fun pickContact() {
Intent(Intent.ACTION_PICK, Uri.parse("content://contacts")).also { pickContactIntent ->
pickContactIntent.type = Phone.CONTENT_TYPE // Show user only contacts w/ phone numbers
startActivityForResult(pickContactIntent, PICK_CONTACT_REQUEST)
}
}
正在获取 returned 数据。
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent) {
// Check which request we're responding to
if (requestCode == PICK_CONTACT_REQUEST) {
// Make sure the request was successful
if (resultCode == Activity.RESULT_OK) {
// The user picked a contact.
// The Intent's data Uri identifies which contact was selected.
// Do something with the contact here (bigger example below)
}
}
}
其他方案包括全局单例、使用 Intent 启动活动，或使用 SharedPreferences 在一个 activity 中写入数据，然后在另一个中读回。
如果您在 android share data between activities 上进行搜索，您会看到有多种选择可以实现这一目标。
通过接口将Activity1分配给Activity2是个坏主意，尝试在activity1中使用：startActivityForResult(intent, requestCode)在activity2中制作任何你想要的然后调用：onActivityResult(requestCode, resultCode, intent);并在activity1中覆盖功能： onActivityResult() 并从意图中获取布尔数据。
问题： 将数据从 activity2 发送到 activity1 使用接口导致 activity1 中的发送数据未分配，即使正在分配也是如此。因此，activity1 成员变量自动设置为 null。
设置详细信息： 单击 activity1 中的按钮，启动 activity2。现在用户可以在 activity2 中执行任何工作。但是一旦用户在 activity2 中执行工作，我的自定义界面就会将数据发送到 activity1。 Activity1 应该将该发送的值分配给它的成员变量，并且当用户导航回 activity1、[=64= activity1 的 ]onRestart() 方法必须使用新值更新用户界面。
点数设置：
1- 用户单击 ACTIVITY1
上的按钮2- 按钮打开 ACTIVITY2
3- 用户执行触发我的接口发送数据的操作
4-接口在后台向ACTIVITY1发送数据（ACTIVITY2仍然可见)
5-发送数据通过接口
赋值给ACTIVITY1成员变量（boolean）6- 用户返回按 ACTIVITY2 并导航回 ACTIVITY1
7-ONRESTART() of ACTIVITY1 被触发
8- ONRESTART() 检查布尔值是否为真，然后更新 UI
但是我的困惑开始了。 为什么赋值后布尔值还是null？ 为什么是ACTIVITY1的成员变量丢失赋值？
代码：
接口
override fun onReturnedToActivity(actionID: Int) {
when(actionID)
{
3 ->
{
newNoteCreated = true
}
}
}
ONRESTART()
override fun onRestart() {
super.onRestart()
if(newNoteCreated) //variable is null not true.
{
Toast.makeText(this,"TRUE",Toast.LENGTH_SHORT).show()
mDrawer!!.updateBadge(3, StringHolder(dbHandler.totalNotes().toString() ))
newNoteCreated = false
}
请教我这个问题。我一直在尝试在 SO 上找到它的解决方案，但还没有回答我的问题。我知道还有其他方法可以在活动之间发送数据，但我正在尝试特别使用接口。
引用自
https://developer.android.com/reference/android/app/Activity#ActivityLifecycle
"如果一个activity被另一个activity完全遮挡，它就会停止。它仍然保留所有状态和成员信息，但是，它不再对用户可见，因此它的 window 被隐藏，并且当其他地方需要内存时，它通常会被系统杀死。"
那为什么我的activity会丢失变量数据呢？
编辑
主要Activity(ACTIVITY1)
class MainActivity : AppCompatActivity(), ContextBarVisibilityListener, OnActionPerformedBadgeUpdater, ActivityReturningStateNotify {
private val dbHandler: PediaDatabase = PediaDatabase(this)
private var mDrawer: Drawer? = null
private var filePath: String? = null
private var backupFileName: String? = null
private var listBt: MenuItem? = null
private var gridBt: MenuItem? = null
private var frontAppName: TextView? = null
private var buttonStatePref: SharedPreferences? = null
private var speedDialView: SpeedDialView? = null
private var trashNotesCount: String? = null
private var archiveNotesCount: String? = null
private var onLayoutChange: LayoutChangeListener? = null
private var newNoteCreated: Boolean = false //THIS IS THE BOOL
private lateinit var mAdView: AdView
companion object
{
private const val LAYOUT_USER_PREF = "layout_preference"
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
onLayoutChange = NotesFrag()
if(savedInstanceState == null) //prevents reloading fragment
{
val transaction = supportFragmentManager.beginTransaction()
transaction.add(R.id.innerFrameLayout,NotesFrag()).commit()
}
trashNotesCount = dbHandler.trashedNotesCount().toString()
archiveNotesCount = dbHandler.archivedNoteCount().toString()
val drawerTrashBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(1).withName("Trash Bin")
.withIcon(R.drawable.delete_note_image)
.withBadge(trashNotesCount)
.withSelectedIcon(R.drawable.delete_drawer_selected)
val drawerArchiveBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(2).withName("Archive")
.withIcon(R.drawable.archive_note_img)
.withBadge(archiveNotesCount)
.withSelectedIcon(R.drawable.archive_drawer_selected)
val drawerNotesBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(3).withName("Notes")
.withIcon(R.drawable.notes_img)
.withBadge(dbHandler.totalNotes().toString())
.withSelectedIcon(R.drawable.notes_drawer_selected)
val drawerLockedNotesBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(4).withName("Locked Notes")
.withIcon(R.drawable.lock_button)
.withBadge("1")
.withSelectedIcon(R.drawable.locked_drawer_selected)
val drawerReminderNotesBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(5).withName("Reminder Notes")
.withIcon(R.drawable.reminder_notes)
.withBadge("1")
.withSelectedIcon(R.drawable.reminder_drawer_selected)
val drawerFavouriteNotesBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(6).withName("Favourite Notes")
.withIcon(R.drawable.rate_app_star_img)
.withBadge("1")
.withSelectedIcon(R.drawable.favourite_drawer_selected)
val drawerSettingsBt: PrimaryDrawerItem = PrimaryDrawerItem().withIdentifier(7).withName("Settings")
.withIcon(R.drawable.settings_drawer)
mDrawer = DrawerBuilder().withActivity(this)
.withHeader(R.layout.navbar_header)
.addDrawerItems(drawerNotesBt,drawerArchiveBt,drawerTrashBt,
drawerLockedNotesBt,drawerReminderNotesBt,
drawerFavouriteNotesBt,DividerDrawerItem(), drawerSettingsBt)
.withOnDrawerItemClickListener(object: Drawer.OnDrawerItemClickListener{
override fun onItemClick(view: View?, position: Int, drawerItem: IDrawerItem<*, *>?): Boolean {
when(position)
{
1 ->
{
frontAppName!!.text = "Wonder Notes"
speedDialView!!.show() //show again because traversing to other fragments hides it
val transaction = supportFragmentManager.beginTransaction()
transaction.replace(R.id.innerFrameLayout, NotesFrag())
transaction.addToBackStack(null)
transaction.commit()
}
2 ->
{
speedDialView!!.hide()
supportFragmentManager.beginTransaction().replace(R.id.innerFrameLayout,ArchiveFragment()).commit()
}
3 ->
{
frontAppName!!.text = "Trash"
speedDialView!!.hide()
fabLayoutBehaviourSetter(false)
supportFragmentManager.beginTransaction().replace(R.id.innerFrameLayout, TrashFragment()).commit()
}
4 -> Log.d("locked notes","1")
5 -> Log.d("reminder","1")
6 -> Log.d("favourite","1")
}
return false // false closes drawer on click
}
}).build()
/*Below code handles swipe tabs adapter setting and displaying
* and implements fragments to viewpager programitically */
// mainActivityViewPagerID.adapter = ViewPagerAdapter(supportFragmentManager)
// attachNotesFrag()
//mainTabsID.setupWithViewPager(mainActivityViewPagerID)
//mainTabsID.setTabTextColors(Color.DKGRAY, Color.parseColor("white"))
val drawerOpener = findViewById<ImageButton>(R.id.drawerOpenImgBt)
val noteCounterAsBt = findViewById<TextView>(R.id.showNotesCountID)
drawerOpener.setOnClickListener { mDrawer!!.openDrawer() }
noteCounterAsBt.setOnClickListener { mDrawer!!.openDrawer() }
//navigationView.setNavigationItemSelectedListener(this)
val customToolbar: Toolbar = findViewById(R.id.toolbarID)
setSupportActionBar(customToolbar)
supportActionBar!!.setDisplayShowTitleEnabled(false) //set main title off
val toolbarTxtView = findViewById<TextView>(R.id.toolbar_title)
toolbarTxtView.visibility = View.GONE
checkForStoragePermission()
}//on create
override fun onContextBarVisibilityChange(isVisible: Boolean) { //custom interface
if(isVisible)
{
speedDialView!!.hide()
fabLayoutBehaviourSetter(false) //remove scrolling behaviour
}
else
{
speedDialView!!.show()
fabLayoutBehaviourSetter(true) //set scrolling behaviour
}
}
override fun onReturnedToActivity(actionID: Int) { ///it just recieves value from ACTIVITY2 and assign its value to ACTIVTY1`s "newNoteCreated" varaible
when(actionID)
{
3 ->
{
Log.d("INTERFACE","CALLED $actionID")
newNoteCreated = true
Log.d("INTERFACE","CALLED $newNoteCreated")
}
}
}
参考 ACTIVITY(ACTIVITY2) 我只包括接口将数据发送回 activity1 的部分，因为 activity2 的代码非常冗长，很可能会使读者感到困惑。
onActivityReturningStateNotify = MainActivity()
dbHandler!!.createNote(note)
//onActionPerformedBadgeUpdater!!.onActionPerformed(3)
onActivityReturningStateNotify!!.onReturnedToActivity(3)
接口
interface ActivityReturningStateNotify {
fun onReturnedToActivity(actionID: Int)
}
您的问题是您在 MainActivity 的新实例上调用 onReturnedToActivity()，而不是您开始的实例或您将 return 到达的实例。
有几种方法可以在活动之间共享数据，一种是使用startActivityForResult()。
我认为您的问题是 Activity1 将停止，因此您无法真正从 Activity2 向它发送数据。但是，您可以使用 startActivityForResult 和 return 结果启动 Activity2。
这是 documentation.
正在启动 activity。
const val PICK_CONTACT_REQUEST = 1 // The request code
...
private fun pickContact() {
Intent(Intent.ACTION_PICK, Uri.parse("content://contacts")).also { pickContactIntent ->
pickContactIntent.type = Phone.CONTENT_TYPE // Show user only contacts w/ phone numbers
startActivityForResult(pickContactIntent, PICK_CONTACT_REQUEST)
}
}
正在获取 returned 数据。
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent) {
// Check which request we're responding to
if (requestCode == PICK_CONTACT_REQUEST) {
// Make sure the request was successful
if (resultCode == Activity.RESULT_OK) {
// The user picked a contact.
// The Intent's data Uri identifies which contact was selected.
// Do something with the contact here (bigger example below)
}
}
}
其他方案包括全局单例、使用 Intent 启动活动，或使用 SharedPreferences 在一个 activity 中写入数据，然后在另一个中读回。
如果您在 android share data between activities 上进行搜索，您会看到有多种选择可以实现这一目标。
通过接口将Activity1分配给Activity2是个坏主意，尝试在activity1中使用：startActivityForResult(intent, requestCode)在activity2中制作任何你想要的然后调用：onActivityResult(requestCode, resultCode, intent);并在activity1中覆盖功能： onActivityResult() 并从意图中获取布尔数据。