[android] Raise minimum API level to 16

bramble-android/build.gradle

@@ -9,7 +9,7 @@ android {
 	buildToolsVersion '28.0.3'
 
 	defaultConfig {
-		minSdkVersion 14
+		minSdkVersion 16
 		targetSdkVersion 26
 		versionCode 10109
 		versionName "1.1.9"

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPluginFactory.java

 package org.briarproject.bramble.plugin.tor;
 
 import android.content.Context;
-import android.os.Build;
 
 import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.event.EventBus;
@@ -102,7 +101,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 			return null;
 		}
 		// Use position-independent executable for SDK >= 16
-		if (Build.VERSION.SDK_INT >= 16) architecture += "_pie";
+		architecture += "_pie";
 
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidSecureRandomProvider.java

@@ -23,6 +23,7 @@ import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static android.content.Context.WIFI_SERVICE;
+import static android.os.Build.VERSION.SDK_INT;
 import static android.provider.Settings.Secure.ANDROID_ID;
 
 @Immutable
@@ -74,8 +75,7 @@ class AndroidSecureRandomProvider extends UnixSecureRandomProvider {
 		// Silence strict mode
 		StrictMode.ThreadPolicy tp = StrictMode.allowThreadDiskWrites();
 		super.writeSeed();
-		if (Build.VERSION.SDK_INT >= 16 && Build.VERSION.SDK_INT <= 18)
-			applyOpenSslFix();
+		if (SDK_INT <= 18) applyOpenSslFix();
 		StrictMode.setThreadPolicy(tp);
 	}
 

briar-android/build.gradle

@@ -20,7 +20,7 @@ android {
 	buildToolsVersion '28.0.3'
 
 	defaultConfig {
-		minSdkVersion 15
+		minSdkVersion 16
 		targetSdkVersion 26
 		versionCode 10109
 		versionName "1.1.9"

briar-android/src/main/java/org/briarproject/briar/android/BackgroundMonitor.java

-package org.briarproject.briar.android;
-
-import android.app.Activity;
-import android.app.Application.ActivityLifecycleCallbacks;
-import android.os.Bundle;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.concurrent.atomic.AtomicInteger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.ThreadSafe;
-
-@ThreadSafe
-@NotNullByDefault
-class BackgroundMonitor implements ActivityLifecycleCallbacks {
-
-	private final AtomicInteger foregroundActivities = new AtomicInteger(0);
-
-	boolean isRunningInBackground() {
-		return foregroundActivities.get() == 0;
-	}
-
-	@Override
-	public void onActivityCreated(Activity a, @Nullable Bundle state) {
-	}
-
-	@Override
-	public void onActivityStarted(Activity a) {
-		foregroundActivities.incrementAndGet();
-	}
-
-	@Override
-	public void onActivityResumed(Activity a) {
-	}
-
-	@Override
-	public void onActivityPaused(Activity a) {
-	}
-
-	@Override
-	public void onActivityStopped(Activity a) {
-		foregroundActivities.decrementAndGet();
-	}
-
-	@Override
-	public void onActivitySaveInstanceState(Activity a,
-			@Nullable Bundle outState) {
-	}
-
-	@Override
-	public void onActivityDestroyed(Activity a) {
-	}
-}

briar-android/src/main/java/org/briarproject/briar/android/BriarApplicationImpl.java

@@ -34,7 +34,6 @@ import java.util.logging.LogRecord;
 import java.util.logging.Logger;
 
 import static android.app.ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND;
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
@@ -86,7 +85,6 @@ public class BriarApplicationImpl extends Application
 			getLogger(BriarApplicationImpl.class.getName());
 
 	private final CachingLogHandler logHandler = new CachingLogHandler();
-	private final BackgroundMonitor backgroundMonitor = new BackgroundMonitor();
 
 	private AndroidComponent applicationComponent;
 	private volatile SharedPreferences prefs;
@@ -127,9 +125,6 @@ public class BriarApplicationImpl extends Application
 
 		applicationComponent = createApplicationComponent();
 		EmojiManager.install(new GoogleEmojiProvider());
-
-		if (SDK_INT < 16)
-			registerActivityLifecycleCallbacks(backgroundMonitor);
 	}
 
 	protected AndroidComponent createApplicationComponent() {
@@ -191,12 +186,8 @@ public class BriarApplicationImpl extends Application
 
 	@Override
 	public boolean isRunningInBackground() {
-		if (SDK_INT >= 16) {
-			RunningAppProcessInfo info = new RunningAppProcessInfo();
-			ActivityManager.getMyMemoryState(info);
-			return (info.importance != IMPORTANCE_FOREGROUND);
-		} else {
-			return backgroundMonitor.isRunningInBackground();
-		}
+		RunningAppProcessInfo info = new RunningAppProcessInfo();
+		ActivityManager.getMyMemoryState(info);
+		return (info.importance != IMPORTANCE_FOREGROUND);
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/ScreenFilterMonitorImpl.java

@@ -150,7 +150,7 @@ class ScreenFilterMonitorImpl implements ScreenFilterMonitor, Service {
 		// Get permissions
 		String[] requestedPermissions = packageInfo.requestedPermissions;
 		if (requestedPermissions == null) return false;
-		if (SDK_INT >= 16 && SDK_INT < 23) {
+		if (SDK_INT < 23) {
 			// Check whether the permission has been requested and granted
 			int[] flags = packageInfo.requestedPermissionsFlags;
 			for (int i = 0; i < requestedPermissions.length; i++) {

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageActivity.java

@@ -142,11 +142,8 @@ public class ImageActivity extends BriarActivity
 		viewPager.setAdapter(pagerAdapter);
 		viewPager.setCurrentItem(position);
 
-		if (SDK_INT >= 16) {
-			viewModel.getOnImageClicked()
-					.observeEvent(this, this::onImageClicked);
-			window.getDecorView().setSystemUiVisibility(UI_FLAGS_DEFAULT);
-		}
+		viewModel.getOnImageClicked().observeEvent(this, this::onImageClicked);
+		window.getDecorView().setSystemUiVisibility(UI_FLAGS_DEFAULT);
 	}
 
 	@Override
@@ -265,7 +262,7 @@ public class ImageActivity extends BriarActivity
 	 * when the previous activity (with visible status bar) is shown.
 	 */
 	private void showStatusBarBeforeFinishing() {
-		if (SDK_INT >= 16 && appBarLayout.getVisibility() == GONE) {
+		if (appBarLayout.getVisibility() == GONE) {
 			View decorView = getWindow().getDecorView();
 			decorView.setSystemUiVisibility(UI_FLAGS_DEFAULT);
 		}

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/CameraView.java

@@ -340,7 +340,7 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 
 	@UiThread
 	private void setVideoStabilisation(Parameters params) {
-		if (SDK_INT >= 15 && params.isVideoStabilizationSupported()) {
+		if (params.isVideoStabilizationSupported()) {
 			params.setVideoStabilization(true);
 		}
 	}

briar-android/src/main/java/org/briarproject/briar/android/reporting/BriarReportPrimer.java

@@ -90,14 +90,9 @@ public class BriarReportPrimer implements ReportPrimer {
 			ActivityManager.MemoryInfo mem = new ActivityManager.MemoryInfo();
 			am.getMemoryInfo(mem);
 			String systemMemory;
-			if (Build.VERSION.SDK_INT >= 16) {
-				systemMemory = (mem.totalMem / 1024 / 1024) + " MiB total, "
-						+ (mem.availMem / 1024 / 1204) + " MiB free, "
-						+ (mem.threshold / 1024 / 1024) + " MiB threshold";
-			} else {
-				systemMemory = (mem.availMem / 1024 / 1204) + " MiB free, "
-						+ (mem.threshold / 1024 / 1024) + " MiB threshold";
-			}
+			systemMemory = (mem.totalMem / 1024 / 1024) + " MiB total, "
+					+ (mem.availMem / 1024 / 1204) + " MiB free, "
+					+ (mem.threshold / 1024 / 1024) + " MiB threshold";
 			customData.put("System memory", systemMemory);
 
 			// Virtual machine memory

briar-android/src/main/java/org/briarproject/briar/android/view/CompositeSendButton.java

@@ -13,7 +13,6 @@ import android.widget.ProgressBar;
 import org.briarproject.briar.R;
 
 import static android.content.Context.LAYOUT_INFLATER_SERVICE;
-import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Objects.requireNonNull;
 
 public class CompositeSendButton extends FrameLayout {
@@ -75,33 +74,24 @@ public class CompositeSendButton extends FrameLayout {
 		if (showImageButton) {
 			imageButton.setVisibility(VISIBLE);
 			sendButton.setEnabled(false);
-			if (SDK_INT <= 15) {
+			sendButton.clearAnimation();
+			sendButton.animate().alpha(0f).withEndAction(() -> {
 				sendButton.setVisibility(INVISIBLE);
 				imageButton.setEnabled(true);
-			} else {
-				sendButton.clearAnimation();
-				sendButton.animate().alpha(0f).withEndAction(() -> {
-					sendButton.setVisibility(INVISIBLE);
-					imageButton.setEnabled(true);
-				}).start();
-				imageButton.clearAnimation();
-				imageButton.animate().alpha(1f).start();
-			}
+			}).start();
+			imageButton.clearAnimation();
+			imageButton.animate().alpha(1f).start();
 		} else {
 			sendButton.setVisibility(VISIBLE);
 			// enable/disable buttons right away to allow fast sending
 			sendButton.setEnabled(sendEnabled);
 			imageButton.setEnabled(false);
-			if (SDK_INT <= 15) {
-				imageButton.setVisibility(INVISIBLE);
-			} else {
-				sendButton.clearAnimation();
-				sendButton.animate().alpha(1f).start();
-				imageButton.clearAnimation();
-				imageButton.animate().alpha(0f).withEndAction(() ->
-						imageButton.setVisibility(INVISIBLE)
-				).start();
-			}
+			sendButton.clearAnimation();
+			sendButton.animate().alpha(1f).start();
+			imageButton.clearAnimation();
+			imageButton.animate().alpha(0f).withEndAction(() ->
+					imageButton.setVisibility(INVISIBLE)
+			).start();
 		}
 	}