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(0);
    }

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 < -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);
        }
    }
}