Android项目实战（三）：实现第一次进入软件的引导页

最近做的APP接近尾声了，就是些优化工作了，

我们都知道现在的APP都会有引导页，就是安装之后第一次打开才显示的引导页面（介绍这个软件的几张可以切换的图）

自己做了一下，结合之前学过的

慕课网_ViewPager切换动画（3.0版本以上有效果）

思路很简单，APP的主界面还是作为主Activity，只要新添加一个类来判断是不是第一次打开APP

设主activity 名字为：MainActivity.java   判断是不是第一次打开APP且实现引导页面的类 LoginActivity ，另外还需要一个类 这是安卓开发_慕课网_ViewPager切换动画（3.0版本以上有效果）中用到的 ZoomOutPageTransformer.java

1.在主activity中,在一开始 先跳转到LoginActivity类中

  protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         requestWindowFeature(Window.FEATURE_NO_TITLE);
         setContentView(R.layout.activity_main);
         startActivity(new Intent(MainActivity.this, LoginActivity.class)); //跳转到LoginActivity类中
       //初始化
         init();
         initEvent();
         //默认显示第一个功能的界面(微信界面)
         setSelect();
     }

2.在LoginActivity类中判断是不是第一次打开，如果是，则显示ViewPager切换动画效果

如果不是，则执行finish();语句，直接结束这个Activity  自然的就回到了主Activity中了

LoginActivity代码

 package com.example.qunxiong;

 import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.List;

 import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.content.SharedPreferences.Editor;
 import android.os.Bundle;
 import android.support.v4.view.PagerAdapter;
 import android.support.v4.view.ViewPager;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.ImageView;
 import android.widget.ImageView.ScaleType;

 public class LoginActivity extends Activity {
     private ViewPager mviewpager; //控件
     private int[] mImgIds = new int[]{R.drawable.bg_rank_shenqi_0,R.drawable.bg_rank_shenqi_1,R.drawable.bg_rank_shenqi_10};//初始化图片
     private List<ImageView> mImages = new ArrayList<ImageView>();
     private Button jump;
      private SharedPreferences preferences;
       private Editor editor;
       private OutputStream os;
       @Override
       protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        preferences = getSharedPreferences("phone", Context.MODE_PRIVATE);
        jump = (Button) findViewById(R.id.jump);
        jump.setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {
                 // TODO Auto-generated method stub
                 finish();
             }
         });
        //判断是不是首次登录，
        if (preferences.getBoolean("firststart", true)) {
         editor = preferences.edit();
         //将登录标志位设置为false，下次登录时不在显示首次登录界面
         editor.putBoolean("firststart", false);
         editor.commit();
         mviewpager = (ViewPager) findViewById(R.id.id_viewpager);
         //为ViewPage切换添加动画效果(3.0以上版本才可以有效果)
         mviewpager.setPageTransformer(true, new ZoomOutPageTransformer());

         mviewpager.setAdapter(new PagerAdapter() {

             @Override
             public Object instantiateItem(View container, int position) {
                 ImageView imageview = new ImageView(LoginActivity.this);
                 imageview.setImageResource(mImgIds[position]);
                 imageview.setScaleType(ScaleType.CENTER_CROP); //设置图片不变形
                 ((ViewGroup) container).addView(imageview);
                 mImages.add(imageview);
                 return imageview;
             };
             @Override
             public void destroyItem(View container, int position, Object object) {
                 // TODO Auto-generated method stub

                 ((ViewPager) container).removeView(mImages.get(position));
             }
             public boolean isViewFromObject(View view, Object object) {
                 // TODO Auto-generated method stub
                 return view == object;
             }

             @Override
             public int getCount() {                   //返回图片个数
                 // TODO Auto-generated method stub
                 return mImgIds.length;
             }
         });
        }
        else
        {
            finish();
        }

       }
 }
       

切换动画效果代码

ZoomOutPageTransformer.java

 package com.example.qunxiong;

 import android.annotation.SuppressLint;
 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;

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

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

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

             // 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) /
                     ( - MIN_SCALE) * ( - MIN_ALPHA));

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