ViewPager实现应用的欢迎界面

在前一篇博客中介绍了Animation实现应用的欢迎界面，本篇博客介绍ViewPager实现应用的欢迎引导界面，并且实现继续向左滑动最后一张图片进入新的Activity的效果。

实现效果：



项目结构：



1.在activity_main.xml中添加ViewPager控件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="${relativePackage}.${activityClass}" >

<android.support.v4.view.ViewPager
android:id="@+id/id_viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</android.support.v4.view.ViewPager>

</RelativeLayout>

2.添加要显示的三张欢迎图片到drawable文件夹中



3.MainActivity

package com.example.viewpager1;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;

public class MainActivity extends Activity {

// 声明ViewPager控件
private ViewPager mViewPager;

// 声明图片的id
private int[] mImgIds = new int[] { R.drawable.a, R.drawable.b,
R.drawable.c };

// 定义存储ImageView的集合
private List<ImageView> mImages = new ArrayList<ImageView>();

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// 去除标题
requestWindowFeature(Window.FEATURE_NO_TITLE);

setContentView(R.layout.activity_main);

// 初始化ViewPager
mViewPager = (ViewPager) findViewById(R.id.id_viewpager);
// ========================为ViewPager添加切换动画效果开始========================
// 动画效果1 - DepthPageTransformer
// mViewPager.setPageTransformer(true, new DepthPageTransformer());
// 动画效果2 - ZoomOutPageTransformer
mViewPager.setPageTransformer(true, new ZoomOutPageTransformer());
// ========================为ViewPager添加切换动画效果结束========================

// 设置适配器
mViewPager.setAdapter(new PagerAdapter() {

@Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView imageView = new ImageView(MainActivity.this);
// 设置图片
imageView.setImageResource(mImgIds[position]);
imageView.setScaleType(ScaleType.CENTER_CROP);
container.addView(imageView);
mImages.add(imageView);
return imageView;
}

@Override
public void destroyItem(ViewGroup container, int position,
Object object) {
container.removeView(mImages.get(position));
}

@Override
public boolean isViewFromObject(View view, Object object) {
// TODO Auto-generated method stub
return view == object;
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return mImgIds.length;
}

});

// 绑定事件
mViewPager.setOnPageChangeListener(new OnPageChangeListener() {

@Override
public void onPageSelected(int arg0) {
// TODO Auto-generated method stub

}

@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
// 当滑动到最后一张图片打开新的activity
if (arg0 == mImgIds.length - 1) {
Intent intent = new Intent(MainActivity.this,
SecondActivity.class);
startActivity(intent);
finish();
}
}

@Override
public void onPageScrollStateChanged(int arg0) {
// TODO Auto-generated method stub

}
});

}
}

官方API: http://developer.android.com/training/animation/screen-slide.html

提供了两种ViewPager的切换动画



DepthPageTransformer.java

package com.example.viewpager1;

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

@SuppressLint("NewApi")
public class DepthPageTransformer implements ViewPager.PageTransformer {
private static final float MIN_SCALE = 0.75f;

@SuppressLint("NewApi")
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);
}
}
}

ZoomOutPageTransformer.java

package com.example.viewpager1;

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

@SuppressLint("NewApi")
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);
}
}
}

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