Util.java

package github.nisrulz.viewpager;

import android.os.Build;
import android.view.View;
import android.view.animation.AlphaAnimation;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author Nishant Srivastava
 */
public class Util {
    private static final AtomicInteger sNextGeneratedId = new AtomicInteger(1);

    /**
     * Generate a value suitable for use in setId(int)
     * This value will not collide with ID values generated at build time by aapt for R.id.
     *
     * @return a generated ID value
     */
    public static int generateViewId() {
        for (; ; ) {
            final int result = sNextGeneratedId.get();
            // aapt-generated IDs have the high byte nonzero; clamp to the range under that.
            int newValue = result + 1;
            if (newValue > 0x00FFFFFF) newValue = 1; // Roll over to 1, not 0.
            if (sNextGeneratedId.compareAndSet(result, newValue)) {
                return result;
            }
        }
    }

    /**
     * Support setAlpha method
     *
     * @param view the view
     * @param alpha the alpha value in float
     */

    static void setAlpha(View view, float alpha) {
        if (Build.VERSION.SDK_INT < 11) {
            final AlphaAnimation animation = new AlphaAnimation(alpha, alpha);
            animation.setDuration(0);
            animation.setFillAfter(true);
            view.startAnimation(animation);
        } else
            view.setAlpha(alpha);
    }
}