use sdk 28 for real

requires dropping junit Assert and accessing an old Canvas method via reflection.

xwords4/android/app/build.gradle

@@ -36,7 +36,7 @@ android {
     buildToolsVersion '27.0.3'
     defaultConfig {
         minSdkVersion 14
-        targetSdkVersion 28
+        targetSdkVersion 28     // must match ../build.gradle
         versionCode VERSION_CODE_BASE
         versionName VERSION_NAME
     }

xwords4/android/app/src/main/java/org/eehouse/android/xw4/Assert.java

@@ -36,7 +36,7 @@ public class Assert {
         if (! val) {
             Log.e( TAG, "firing assert!" );
             DbgUtils.printStack( TAG );
-            junit.framework.Assert.fail();
+            assert false;
         }
     }
 

xwords4/android/app/src/main/java/org/eehouse/android/xw4/BoardCanvas.java

@@ -30,7 +30,9 @@ import android.graphics.Rect;
 import android.graphics.RectF;
 import android.graphics.drawable.BitmapDrawable;
 import android.graphics.drawable.Drawable;
+import android.os.Build;
 
+import java.lang.reflect.Method;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -574,6 +576,34 @@ public class BoardCanvas extends Canvas implements DrawCtx {
         }
     }
 
+    private static Method sSaveMethod;
+    private void saveImpl( Rect rect )
+    {
+        if ( Build.VERSION.SDK_INT >= 21 ) {
+            saveLayer( new RectF(rect), null );
+        } else {
+            if ( null == sSaveMethod ) {
+                try {
+                    Class<?> cls = Class.forName("android.graphics.Canvas");
+                    sSaveMethod = cls.getDeclaredMethod( "save", new Class[] {int.class} );
+                } catch ( NoSuchMethodException | ClassNotFoundException ex ) {
+                    Log.e( TAG, "%s", ex );
+                    Assert.fail();
+                }
+            }
+
+            final int CLIP_SAVE_FLAG = 0x02;
+            try {
+                sSaveMethod.invoke( this, CLIP_SAVE_FLAG );
+                Log.d( TAG, "saveImpl() worked" );
+            } catch ( java.lang.reflect.InvocationTargetException
+                      | IllegalAccessException ex ) {
+                Log.e( TAG, "%s", ex );
+                Assert.fail();
+            }
+        }
+    }
+
     private boolean drawTileImpl( Rect rect, String text, int val,
                                   int flags, boolean clearBack )
     {
@@ -583,7 +613,7 @@ public class BoardCanvas extends Canvas implements DrawCtx {
             boolean notEmpty = (flags & CELL_ISEMPTY) == 0;
             boolean isCursor = (flags & CELL_ISCURSOR) != 0;
 
-            save( Canvas.CLIP_SAVE_FLAG );
+            saveImpl( rect );
             rect.top += 1;
             clipRect( rect );
 

xwords4/android/build.gradle

@@ -32,7 +32,7 @@ subprojects {
     afterEvaluate {project ->
         if (project.hasProperty("android")) {
             android {
-                compileSdkVersion 26
+                compileSdkVersion 28 // must match app/build.gradle
             }
         }
     }