refactor: hide backend Adapter handles

- static methods for backend adapters

vtm-android-gdx/src/org/oscim/android/canvas/AndroidGraphics.java

@@ -33,10 +33,9 @@ import android.graphics.drawable.BitmapDrawable;
 import android.graphics.drawable.Drawable;
 
 public final class AndroidGraphics extends CanvasAdapter {
-	public static final AndroidGraphics INSTANCE = new AndroidGraphics();
 
 	public static void init() {
-		g = INSTANCE;
+		CanvasAdapter.init(new AndroidGraphics());
 	}
 
 	//	public static android.graphics.Bitmap getAndroidBitmap(Bitmap bitmap) {
@@ -52,22 +51,22 @@ public final class AndroidGraphics extends CanvasAdapter {
 	}
 
 	@Override
-	public Bitmap decodeBitmap(InputStream inputStream) {
+	public Bitmap decodeBitmapImpl(InputStream inputStream) {
 		return new AndroidBitmap(inputStream);
 	}
 
 	@Override
-	public Paint getPaint() {
+	public Paint newPaintImpl() {
 		return new AndroidPaint();
 	}
 
 	@Override
-	public Bitmap getBitmap(int width, int height, int format) {
+	public Bitmap newBitmapImpl(int width, int height, int format) {
 		return new AndroidBitmap(width, height, format);
 	}
 
 	@Override
-	public Canvas getCanvas() {
+	public Canvas newCanvasImpl() {
 		return new AndroidCanvas();
 	}
 
@@ -100,7 +99,7 @@ public final class AndroidGraphics extends CanvasAdapter {
 	}
 
 	@Override
-	public Bitmap loadBitmapAsset(String fileName) {
+	public Bitmap loadBitmapAssetImpl(String fileName) {
 		try {
 			return createBitmap(fileName);
 		} catch (IOException e) {