Show spinners only after 0.5 seconds

app/src/main/java/eu/faircode/email/ContentLoadingProgressBar.java

@@ -0,0 +1,35 @@
+package eu.faircode.email;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.widget.ProgressBar;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class ContentLoadingProgressBar extends ProgressBar {
+    public ContentLoadingProgressBar(@NonNull Context context) {
+        this(context, null);
+    }
+
+    public ContentLoadingProgressBar(@NonNull Context context, @Nullable AttributeSet attrs) {
+        super(context, attrs, 0);
+    }
+
+    @Override
+    public void setVisibility(int visibility) {
+        removeCallbacks(delayedShow);
+        if (visibility == VISIBLE) {
+            super.setVisibility(INVISIBLE);
+            postDelayed(delayedShow, 500);
+        } else
+            super.setVisibility(visibility);
+    }
+
+    private final Runnable delayedShow = new Runnable() {
+        @Override
+        public void run() {
+            ContentLoadingProgressBar.super.setVisibility(VISIBLE);
+        }
+    };
+}