com.bjgas.common.DirectionalViewPager.java Source code

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Here is the source code for com.bjgas.common.DirectionalViewPager.java

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/*
 * Copyright (C) 2011 The Android Open Source Project
 * Copyright (C) 2011 Jake Wharton
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.bjgas.common;

import android.annotation.SuppressLint;
import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

/**
 * Uses a combination of a PageTransformer and onTouchEvent to create the
 * illusion of a vertically scrolling ViewPager.
 * 
 * Requires API 11+
 * 
 */
@SuppressLint("NewApi")
public class DirectionalViewPager extends ViewPager {

    public DirectionalViewPager(Context context) {
        super(context);
        init();
    }

    public DirectionalViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        // The majority of the magic happens here
        setPageTransformer(true, new VerticalPageTransformer());
        // The easiest way to get rid of the overscroll drawing that happens on
        // the left and right
        setOverScrollMode(OVER_SCROLL_NEVER);
    }

    private class VerticalPageTransformer implements ViewPager.PageTransformer {

        @Override
        public void transformPage(View view, float position) {
            int pageWidth = view.getWidth();
            int pageHeight = view.getHeight();

            if (position < -1) { // [-Infinity,-1)
                // This page is way off-screen to the left.
                view.setAlpha(0);

            } else if (position <= 1) { // [-1,1]
                view.setAlpha(1);

                // Counteract the default slide transition
                view.setTranslationX(pageWidth * -position);

                // set Y position to swipe in from top
                float yPosition = position * pageHeight;
                view.setTranslationY(yPosition);

            } else { // (1,+Infinity]
                // This page is way off-screen to the right.
                view.setAlpha(0);
            }
        }
    }

    /**
     * Swaps the X and Y coordinates of your touch event
     */
    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        // swap the x and y coords of the touch event
        ev.setLocation(ev.getY(), ev.getX());

        return super.onTouchEvent(ev);
    }
}