fixed slow typing on the Language Selection screen, on the Delete Custom Words screen etc, caused by a main thread deadlock

app/src/main/java/io/github/sspanak/tt9/preferences/settings/SettingsStore.java

@@ -19,7 +19,7 @@ public class SettingsStore extends SettingsUI {
 	public final static int DICTIONARY_IMPORT_BATCH_SIZE = 5000; // words
 	public final static int DICTIONARY_IMPORT_PROGRESS_UPDATE_TIME = 250; // ms
 	public final static int INPUT_CONNECTION_ERRORS_MAX = 3;
-	public final static int INPUT_CONNECTION_OPERATIONS_TIMEOUT = 150; // ms
+	public final static int INPUT_CONNECTION_OPERATIONS_TIMEOUT = 100; // ms
 	public final static int RESIZE_THROTTLING_TIME = 60; // ms
 	public final static byte SLOW_QUERY_TIME = 50; // ms
 	public final static int SLOW_QUERY_TIMEOUT = 3000; // ms

app/src/main/java/io/github/sspanak/tt9/util/InputConnectionTools.java

@@ -3,26 +3,34 @@ package io.github.sspanak.tt9.util;
 import android.os.Build;
 import android.view.inputmethod.InputConnection;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 
 import io.github.sspanak.tt9.preferences.settings.SettingsStore;
 
 public class InputConnectionTools {
+	private static final String LOG_TAG = InputConnectionTools.class.getSimpleName();
+
 	@Nullable private final InputConnection connection;
-	private int connectionErrors;
+
-	private boolean isErrorReported;
+	@Nullable CompletableFuture<Boolean> future;
+	@NonNull ExecutorService executor = Executors.newSingleThreadExecutor();
+	private int connectionErrors = 0;
+	private boolean isErrorReported = false;
+
+	private CharSequence result;
 
 
 	public InputConnectionTools(@Nullable InputConnection connection) {
 		this.connection = connection;
-		connectionErrors = 0;
-		isErrorReported = false;
 	}
 
 
@@ -39,19 +47,20 @@ public class InputConnectionTools {
 	@Nullable
 	private CharSequence getTextNextToCursor(int i, int ii, boolean after) {
 		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
-			return getTextNextToCursorModern(i, ii, after);
+			getTextNextToCursorModern(i, ii, after);
 		} else {
-			return getTextNextToCursorClassic(i, ii, after);
+			getTextNextToCursorClassic(i, ii, after);
 		}
+
+		return result;
 	}
 
 
-	private CharSequence getTextNextToCursorClassic(int i, int ii, boolean after) {
+	private void getTextNextToCursorClassic(int i, int ii, boolean after) {
-		if (connection == null) {
+		result = null;
-			return null;
+		if (connection != null) {
+			result = after ? connection.getTextAfterCursor(i, ii) : connection.getTextBeforeCursor(i, ii);
 		}
-
-		return after ? connection.getTextAfterCursor(i, ii) : connection.getTextBeforeCursor(i, ii);
 	}
 
 
@@ -62,29 +71,54 @@ public class InputConnectionTools {
 	 * getTextBeforeCursor() that terminates the operations after a certain timeout. Just in case we
 	 * handle getTextAfterCursor() the same way.
 	 */
-	@Nullable
 	@RequiresApi(api = Build.VERSION_CODES.N)
-	private CharSequence getTextNextToCursorModern(int i, int ii, boolean after) {
+	private void getTextNextToCursorModern(int i, int ii, boolean after) {
-		CompletableFuture<CharSequence> future = CompletableFuture.supplyAsync(
+		// CompletableFuture is supported only in Android 24 and above, so we initialize it here.
-			() -> getTextNextToCursorClassic(i, ii, after)
+		future = new CompletableFuture<>();
-		);
+
+		// Start only the watchdog in a separate thread. If we start the main operation there too,
+		// it will causes a deadlock, because main would be waiting for the thread, which will be waiting
+		// for main to provide text.
+		executor.submit(this::awaitTextResult);
 
 		try {
-			return future.get(SettingsStore.INPUT_CONNECTION_OPERATIONS_TIMEOUT, TimeUnit.MILLISECONDS);
+			getTextNextToCursorClassic(i, ii, after);
+			future.complete(true);
+		} catch (Exception e) {
+			connectionErrors++;
+			logError("getStringBeforeCursor() failed " + connectionErrors + " times so far. Current error: " + e);
+		}
+	}
+
+
+	@RequiresApi(api = Build.VERSION_CODES.N)
+	private void awaitTextResult() {
+		if (future == null) {
+			logError("No future. Cannot call getStringBeforeCursor().");
+			return;
+		}
+
+		try {
+			if (!future.get(SettingsStore.INPUT_CONNECTION_OPERATIONS_TIMEOUT, TimeUnit.MILLISECONDS)) {
+				logError("Future is not true. InputConnection.getTextBeforeCursor() probably failed.");
+			}
 		} catch (TimeoutException e) {
 			connectionErrors++;
-			Logger.e(
+			logError(
-				getClass().getSimpleName(),
 				"getStringBeforeCursor() timed out after " + SettingsStore.INPUT_CONNECTION_OPERATIONS_TIMEOUT + "ms. " + connectionErrors + " errors so far."
 			);
-			return null;
 		} catch (InterruptedException | ExecutionException e) {
 			connectionErrors++;
-			Logger.e(getClass().getSimpleName(), "getStringBeforeCursor() failed " + connectionErrors + " times so far. Current error: " + e);
+			logError("getStringBeforeCursor() failed " + connectionErrors + " times so far. Current error: " + e);
-			return null;
 		}
 	}
 
+
+	private void logError(@NonNull String error) {
+		Logger.e(LOG_TAG, error);
+	}
+
+
 	public boolean shouldReportTimeout() {
 		if (!isErrorReported && connectionErrors > SettingsStore.INPUT_CONNECTION_ERRORS_MAX) {
 			isErrorReported = true;