Android: for scroll steps, use postOnAnimation when available

Using postOnAnimation in place of post noticably improves scroll
smoothness. Also avoid posting multiple runnables unnecessarily.

1 files changed, 42 insertions, 0 deletions

diff --git a/platform/android/src/com/artifex/mupdfdemo/Stepper.java b/platform/android/src/com/artifex/mupdfdemo/Stepper.java
new file mode 100644
index 00000000..d22240ef
--- /dev/null
+++ b/platform/android/src/com/artifex/mupdfdemo/Stepper.java
@@ -0,0 +1,42 @@
+package com.artifex.mupdfdemo;
+
+import android.annotation.SuppressLint;
+import android.os.Build;
+import android.view.View;
+
+public class Stepper {
+	protected final View mPoster;
+	protected final Runnable mTask;
+	protected boolean mPending;
+
+	public Stepper(View v, Runnable r) {
+		mPoster = v;
+		mTask = r;
+		mPending = false;
+	}
+
+	@SuppressLint("NewApi")
+	public void prod() {
+		if (!mPending) {
+			mPending = true;
+			if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
+				mPoster.postOnAnimation(new Runnable() {
+					@Override
+					public void run() {
+						mPending = false;
+						mTask.run();
+					}
+				});
+			} else {
+				mPoster.post(new Runnable() {
+					@Override
+					public void run() {
+						mPending = false;
+						mTask.run();
+					}
+				});
+
+			}
+		}
+	}
+}