Android开发学习--ViewPager使用入门

ViewPager已经有了滑动的功能

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/activity_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context="com.example.lemon.viewpagerdemo.MainActivity">

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

    </android.support.v4.view.ViewPager>
</LinearLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private ViewPager mViewPager;
    private int[] mImgIds = new int[] { R.drawable.a,
            R.drawable.b, R.drawable.c};
    private List<ImageView> mImageViews = new ArrayList<ImageView>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initData();
        mViewPager = (ViewPager) findViewById(R.id.main_viewpager);
        mViewPager.setAdapter(new PagerAdapter(){
            @Override
            public Object instantiateItem(ViewGroup container, int position)
            {

                container.addView(mImageViews.get(position));
                return mImageViews.get(position);
            }

            @Override
            public void destroyItem(ViewGroup container, int position,
                                    Object object)
            {

                container.removeView(mImageViews.get(position));
            }

            @Override
            public boolean isViewFromObject(View view, Object object)
            {
                return view == object;
            }

            @Override
            public int getCount()
            {
                return mImgIds.length;
            }
        });

//setPageTransformer(boolean reverseDrawingOrder, PageTransformer transformer)
//用于设置ViewPager切换时的动画效果
        mViewPager.setPageTransformer(true,new DepthPageTransformer());
    }

    private void initData() {
        for (int imgId : mImgIds)
        {
            ImageView imageView = new ImageView(getApplicationContext());
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setImageResource(imgId);
            mImageViews.add(imageView);
        }
    }
}

DepthPageTransformer.java

public class DepthPageTransformer implements ViewPager.PageTransformer{
    private static final float MIN_SCALE = 0.75f;
    @Override
    public void transformPage(View view, float position) {
        int pageWidth = view.getWidth();
        if(position<-1){ // [-Infinity,-1)
            view.setAlpha(0);
        }else if(position<=0){// [-1,0]
            view.setAlpha(1);
            view.setTranslationX(0);
            view.setScaleX(1);
            view.setScaleY(1);
        }else if(position<=1){// (0,1]
            view.setAlpha(1-position);
            view.setTranslationX(pageWidth*-position);
            float scaleFactor = MIN_SCALE+(1-MIN_SCALE)*(1-Math.abs(position));
            view.setScaleX(scaleFactor);
            view.setScaleY(scaleFactor);
        }else{//(1,+Infinity]
            view.setAlpha(0);
        }

    }
}