justdoit --ViewPager_Annotation

今天晚上电脑的转接口又出了问题，电脑一直联不了网；刚好手头的工作也告一段落了。好吧，择日不如撞日，今天就来写博客总结一下最近的学习经历吧。有些东西经常用却从未总结过，而有些东西是第一次接触，就通过一些列博客来做备忘吧!

一.android ViewPager滑动效果

首先，翻看developer文档，会发现常用的滑动效果有三种，分别是：default(默认效果)，ZoomOut，以及Depth。而之所以要将这些呢，是因为LZ个人认为，对用户提供可选择的空间，让他选择一种自己喜欢的切换方式，会比较好。或者说，一种动效用太久了，来换另一种尝试一下，总比一成不变要来的好很多。而至于ViewPager切换动效使用也很简单。只需要在你的ViewPager实例调用setPageTransformer(true,DepthPageTransformer.getInstance())即可，第二个参数为你传入的工具类的静态工厂产生的实例，而默认效果即使第二个参数值为null。因为这个比较简单，所以直接贴上代码。

package wenyue.justdoit.util;

import android.support.v4.view.ViewPager;
import android.view.View;

public class DepthPageTransformer implements ViewPager.PageTransformer {
private static float MIN_SCALE = 0.75f;

private static DepthPageTransformer depthPageTransformer = new DepthPageTransformer();

private DepthPageTransformer() {

}

public  static DepthPageTransformer getInstance() {

    return depthPageTransformer;

}

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

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

    } else if (position <= 0) { // [-1,0]
        // Use the default slide transition when moving to the left page
        view.setAlpha(1);
        view.setTranslationX(0);
        view.setScaleX(1);
        view.setScaleY(1);

    } else if (position <= 1) { // (0,1]
        // Fade the page out.
        view.setAlpha(1 - position);

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

        // Scale the page down (between MIN_SCALE and 1)
        float scaleFactor = MIN_SCALE
                + (1 - MIN_SCALE) * (1 - Math.abs(position));
        view.setScaleX(scaleFactor);
        view.setScaleY(scaleFactor);

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

接下来是ZoomOut效果的实现

package wenyue.justdoit.util;

import android.support.v4.view.ViewPager;
import android.view.View;

public class ZoomOutPageTransformer implements ViewPager.PageTransformer {
private static final float MIN_SCALE = 0.85f;
private static final float MIN_ALPHA = 0.5f;

  private static ZoomOutPageTransformer zoomOutPageTransformer = new     ZoomOutPageTransformer();

private ZoomOutPageTransformer() {

}

public  static ZoomOutPageTransformer getInstance() {

    return zoomOutPageTransformer;

}

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]
        // Modify the default slide transition to shrink the page as well
        float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
        float vertMargin = pageHeight * (1 - scaleFactor) / 2;
        float horzMargin = pageWidth * (1 - scaleFactor) / 2;
        if (position < 0) {
            view.setTranslationX(horzMargin - vertMargin / 2);
        } else {
            view.setTranslationX(-horzMargin + vertMargin / 2);
        }

        // Scale the page down (between MIN_SCALE and 1)
        view.setScaleX(scaleFactor);
        view.setScaleY(scaleFactor);

        // Fade the page relative to its size.
        view.setAlpha(MIN_ALPHA +
                (scaleFactor - MIN_SCALE) /
                (1 - MIN_SCALE) * (1 - MIN_ALPHA));

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

而一些具体的动效就可以通过在工具类里面设置相应的参数来实现。这里就不详细列举了。接下来，就来写一下关于自定义控件的一些事吧。好吧，我也是醉了，为了限制篇幅，重写一篇博客吧!