Fix NoSuchMethod exception for HelperSHA256 on API Level prior to P

app/build.gradle

@@ -128,6 +128,8 @@ dependencies {
     annotationProcessor 'com.github.bumptech.glide:compiler:4.11.0'
 
     testImplementation 'junit:junit:4.12'
+    androidTestImplementation 'androidx.test:runner:1.3.0'
+    androidTestImplementation 'androidx.test:rules:1.3.0'
     androidTestImplementation 'androidx.test.ext:junit:1.1.2'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
 

app/src/androidTest/java/io/lbry/browser/utils/HelperTest.java

@@ -0,0 +1,15 @@
+package io.lbry.browser.utils;
+
+import androidx.test.filters.SmallTest;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+@SmallTest
+public class HelperTest {
+    @Test
+    public void SHA256() {
+        assertEquals("de9edb2044d012f04553e49b04d54cbec8e8a46a40ad5a19bc5dcce1da00ecfd", Helper.SHA256(String.valueOf(12345678912345L)));
+    }
+}

app/src/main/java/io/lbry/browser/utils/Helper.java

@@ -795,7 +795,11 @@ public final class Helper {
         try {
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
             byte[] hash = digest.digest(value.getBytes(StandardCharsets.UTF_8));
-            return Hex.encodeHexString(hash, true);
+
+            if (Build.VERSION.SDK_INT > Build.VERSION_CODES.O_MR1)
+                return Hex.encodeHexString(hash, true);
+            else
+                return new String(Hex.encodeHex(hash)).toLowerCase();
         } catch (NoSuchAlgorithmException ex) {
             return null;
         }