Replace RxJava3 code with coroutines (#4290)

This pull request removes the remaining RxJava code and replaces it with
coroutine-equivalent implementations.

- Remove all duplicate methods in `MastodonApi`:
- Methods returning a RxJava `Single` have been replaced by suspending
methods returning a `NetworkResult` in order to be consistent with the
new code.
- _sync_/_async_ method variants are replaced with the _async_ version
only (suspending method), and `runBlocking{}` is used to make the async
variant synchronous.
- Create a custom coroutine-based implementation of `Single` for usage
in Java code where launching a coroutine is not possible. This class can
be deleted after remaining Java code has been converted to Kotlin.
- `NotificationsFragment.java` can subscribe to `EventHub` events by
calling the new lifecycle-aware `EventHub.subscribe()` method. This
allows using the `SharedFlow` as single source of truth for all events.
- Rx Autodispose is replaced by `lifecycleScope.launch()` which will
automatically cancel the coroutine when the Fragment view/Activity is
destroyed.
- Background work is launched in the existing injectable
`externalScope`, since using `GlobalScope` is discouraged.
`externalScope` has been changed to be a `@Singleton` and to use the
main dispatcher by default.
- Transform `ShareShortcutHelper` to an injectable utility class so it
can use the application `Context` and `externalScope` as provided
dependencies to launch a background coroutine.
- Implement a custom Glide extension method
`RequestBuilder.submitAsync()` to do the same thing as
`RequestBuilder.submit().get()` in a non-blocking way. This way there is
no need to switch to a background dispatcher and block a background
thread, and cancellation is supported out-of-the-box.
- An utility method `Fragment.updateRelativeTimePeriodically()` has been
added to remove duplicate logic in `TimelineFragment` and
`NotificationsFragment`, and the logic is now implemented using a simple
coroutine instead of `Observable.interval()`. Note that the periodic
update now happens between onStart and onStop instead of between
onResume and onPause, since the Fragment is not interactive but is still
visible in the started state.
- Rewrite `BottomSheetActivityTest` using coroutines tests.
- Remove all RxJava library dependencies.

app/src/main/java/com/keylesspalace/tusky/ViewMediaActivity.kt

@@ -42,13 +42,10 @@ import androidx.core.app.ShareCompat
 import androidx.core.content.FileProvider
 import androidx.core.content.IntentCompat
 import androidx.fragment.app.FragmentActivity
-import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.lifecycleScope
 import androidx.viewpager2.adapter.FragmentStateAdapter
 import androidx.viewpager2.widget.ViewPager2
-import autodispose2.androidx.lifecycle.AndroidLifecycleScopeProvider
-import autodispose2.autoDispose
 import com.bumptech.glide.Glide
-import com.bumptech.glide.request.FutureTarget
 import com.keylesspalace.tusky.BuildConfig.APPLICATION_ID
 import com.keylesspalace.tusky.components.viewthread.ViewThreadActivity
 import com.keylesspalace.tusky.databinding.ActivityViewMediaBinding
@@ -59,19 +56,18 @@ import com.keylesspalace.tusky.pager.ImagePagerAdapter
 import com.keylesspalace.tusky.pager.SingleImagePagerAdapter
 import com.keylesspalace.tusky.util.getTemporaryMediaFilename
 import com.keylesspalace.tusky.util.startActivityWithSlideInAnimation
+import com.keylesspalace.tusky.util.submitAsync
 import com.keylesspalace.tusky.util.viewBinding
 import com.keylesspalace.tusky.viewdata.AttachmentViewData
 import dagger.android.DispatchingAndroidInjector
 import dagger.android.HasAndroidInjector
-import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers
-import io.reactivex.rxjava3.core.Single
-import io.reactivex.rxjava3.schedulers.Schedulers
 import java.io.File
-import java.io.FileNotFoundException
 import java.io.FileOutputStream
 import java.io.IOException
 import java.util.Locale
 import javax.inject.Inject
+import kotlinx.coroutines.CancellationException
+import kotlinx.coroutines.launch
 
 typealias ToolbarVisibilityListener = (isVisible: Boolean) -> Unit
 
@@ -310,46 +306,37 @@ class ViewMediaActivity :
         isCreating = true
         binding.progressBarShare.visibility = View.VISIBLE
         invalidateOptionsMenu()
-        val file = File(directory, getTemporaryMediaFilename("png"))
-        val futureTask: FutureTarget<Bitmap> =
-            Glide.with(applicationContext).asBitmap().load(Uri.parse(url)).submit()
-        Single.fromCallable {
-            val bitmap = futureTask.get()
-            try {
-                val stream = FileOutputStream(file)
-                bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream)
-                stream.close()
-                return@fromCallable true
-            } catch (fnfe: FileNotFoundException) {
-                Log.e(TAG, "Error writing temporary media.")
-            } catch (ioe: IOException) {
-                Log.e(TAG, "Error writing temporary media.")
-            }
-            return@fromCallable false
-        }
-            .subscribeOn(Schedulers.io())
-            .observeOn(AndroidSchedulers.mainThread())
-            .doOnDispose {
-                futureTask.cancel(true)
-            }
-            .autoDispose(AndroidLifecycleScopeProvider.from(this, Lifecycle.Event.ON_DESTROY))
-            .subscribe(
-                { result ->
-                    Log.d(TAG, "Download image result: $result")
-                    isCreating = false
-                    invalidateOptionsMenu()
-                    binding.progressBarShare.visibility = View.GONE
-                    if (result) {
-                        shareFile(file, "image/png")
+
+        lifecycleScope.launch {
+            val file = File(directory, getTemporaryMediaFilename("png"))
+            val result = try {
+                val bitmap =
+                    Glide.with(applicationContext).asBitmap().load(Uri.parse(url)).submitAsync()
+                try {
+                    FileOutputStream(file).use { stream ->
+                        bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream)
                     }
-                },
-                { error ->
-                    isCreating = false
-                    invalidateOptionsMenu()
-                    binding.progressBarShare.visibility = View.GONE
-                    Log.e(TAG, "Failed to download image", error)
+                    true
+                } catch (ioe: IOException) {
+                    // FileNotFoundException is covered by IOException
+                    Log.e(TAG, "Error writing temporary media.")
+                    false
+                }.also { result -> Log.d(TAG, "Download image result: $result") }
+            } catch (error: Throwable) {
+                if (error is CancellationException) {
+                    throw error
                 }
-            )
+                Log.e(TAG, "Failed to download image", error)
+                false
+            }
+
+            isCreating = false
+            invalidateOptionsMenu()
+            binding.progressBarShare.visibility = View.GONE
+            if (result) {
+                shareFile(file, "image/png")
+            }
+        }
     }
 
     private fun shareMediaFile(directory: File, url: String) {