android仿多看阅读三屏滚动效果 -- 更改OnPageChangeListener

通过在滚动的时候动态的改变每一个item的padding值进行实现。

先看看效果吧：

 

 

 

以下是源代码。重点在MyOnPageChangeListener.java.

1、activity_viewpager.xml

<LinearLayout 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"android:orientation="vertical"android:background="#FF000000">    <android.support.v4.view.ViewPager     android:layout_width="fill_parent"     android:layout_height="wrap_content"     android:id="@+id/viewpager"     /></LinearLayout>

2、ViewPagerActivity.java

package com.example.duokan; import java.util.ArrayList; import android.app.Activity;import android.os.Bundle;import android.support.v4.view.ViewPager;import android.support.v4.view.ViewPager.LayoutParams;import android.view.Window;import android.widget.ImageView;import android.widget.ImageView.ScaleType;/*** ViewPagerActivity* @author xinye**/public class ViewPagerActivity extends Activity {    private ViewPager mViewPager = null;    private MyViewPagerAdapter mAdapter = null;    private MyOnPageChangeListener mListener = null;    private ArrayList<ImageView> mViewList = null;    private Integer[] mImageDrawableArray = {     R.drawable.p1, R.drawable.p2, R.drawable.p3, R.drawable.p4, R.drawable.p5 };     @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.activity_viewpager);        mViewPager = (ViewPager) findViewById(R.id.viewpager);         mViewList = new ArrayList<ImageView>();        LayoutParams params = new LayoutParams();        params.width = LayoutParams.FILL_PARENT;        params.height = LayoutParams.FILL_PARENT;         for (int i = 0; i < mImageDrawableArray.length; i++) {            ImageView imageView = new ImageView(ViewPagerActivity.this);            imageView.setImageResource(mImageDrawableArray[i]);            imageView.setScaleType(ScaleType.FIT_XY);            imageView.setLayoutParams(params);            this.mViewList.add(imageView);        }        mAdapter = new MyViewPagerAdapter(ViewPagerActivity.this, mViewList);        mViewPager.setAdapter(mAdapter);         mListener = new MyOnPageChangeListener(ViewPagerActivity.this,                mViewPager, mViewList);        mViewPager.setOnPageChangeListener(mListener);     } }

3、MyViewPagerAdapter.java

package com.example.duokan;  import java.util.ArrayList; import android.content.Context;import android.support.v4.view.PagerAdapter;import android.support.v4.view.ViewPager;import android.view.View;import android.widget.ImageView;/*** PagerAdapter* @author xinye**/public class MyViewPagerAdapter extends PagerAdapter {    private Context mContext;    private ArrayList<ImageView> mViewList = null;    public MyViewPagerAdapter(Context context,ArrayList<ImageView> list){        this.mContext = context;        this.mViewList = list;    }    @Override    public void destroyItem(View container, int position, Object object) {        ImageView view = mViewList.get(position);        ((ViewPager) container).removeView(view);//        view.setImageBitmap(null);    }     @Override    public Object instantiateItem(View container, int position) {        if(mViewList.get(position).getParent() == null){            ((ViewPager) container).addView(mViewList.get(position));                    }return mViewList.get(position);    }     @Override    public int getCount() {        return mViewList.size();    }     @Override    public boolean isViewFromObject(View view, Object object) {        return view == object;    } }

4、MyOnPageChangeListener.java

package com.example.duokan;  import java.util.ArrayList; import android.content.Context;import android.support.v4.view.ViewPager;import android.support.v4.view.ViewPager.OnPageChangeListener;import android.view.MotionEvent;import android.view.View;import android.view.View.OnTouchListener;import android.widget.ImageView;/**** @author xinye**/public class MyOnPageChangeListener implements OnPageChangeListener {    int offset = 0;    int downX = 0;        private Context mContext;    private ArrayList<ImageView> mViewList;    private ViewPager mViewPager;    public MyOnPageChangeListener(Context context,ViewPager viewPager,ArrayList<ImageView> list){        this.mContext = context;        this.mViewList = list;        mViewPager = viewPager;        mViewPager.setOnTouchListener(new OnTouchListener() {                        @Override            public boolean onTouch(View v, MotionEvent event) {                switch(event.getAction()){                case MotionEvent.ACTION_DOWN:                    downX = (int) event.getX();                    break;                case MotionEvent.ACTION_MOVE:                    offset = (int) (event.getX() - downX);                    break;                case MotionEvent.ACTION_UP:                    offset = 0;                    downX = 0;                    break;                }                return false;            }        });            }    @Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels){        int paddingNum = 200;    int paddingNext = (int)((paddingNum * (1 - positionOffset) / 2));    int paddingCurr = (int)((paddingNum * positionOffset / 2));    int width = mViewList.get(position).getWidth();    float scale = ((float)Math.abs(offset) / width);    if(positionOffset == 0){        paddingNext = (int)(paddingNum * (1 - scale) / 2);        paddingCurr = (int)(paddingNum * scale / 2);    }    if(position == 0){        if(offset > 0){            if(positionOffset == 0){                mViewList.get(position).setAlpha((int)(0xFF * (1 - scale)));                             }else{                mViewList.get(position).setAlpha((int)(0xFF * scale));                mViewList.get(position + 1).setAlpha((int)(0xFF * positionOffset));                            }                        mViewList.get(position).setPadding(paddingCurr,paddingCurr,-2 * paddingCurr,paddingCurr);            mViewList.get(position + 1).setPadding(paddingNext,paddingNext,paddingNext,paddingNext);        }else{            mViewList.get(position).setAlpha((int)(0xFF * (1 - scale)));            if(offset != 0){                mViewList.get(1).setAlpha((int)(0xFF * scale));                             }else{                mViewList.get(1).setAlpha(0xFF);            }                        mViewList.get(position).setPadding(paddingCurr,paddingCurr,paddingCurr,paddingCurr);            mViewList.get(position + 1).setPadding(paddingNext,paddingNext,paddingNext,paddingNext);        }    }else if(position == mViewList.size() - 1){        if(offset < 0){                mViewList.get(position).setAlpha((int)(0xFF * (1 - scale)));            mViewList.get(position).setPadding(paddingCurr,paddingCurr,paddingCurr,paddingCurr);            mViewList.get(position).setPadding(-2 * paddingCurr,paddingCurr,paddingCurr,paddingCurr);        }else{            mViewList.get(position - 1).setPadding(paddingNext,paddingNext,paddingNext,paddingNext);            mViewList.get(position).setPadding(paddingCurr,paddingCurr,paddingCurr,paddingCurr);        }    }else{        if(offset == 0 || positionOffset == 0){            mViewList.get(position + 1).setPadding(0,0,0,0);            mViewList.get(position - 1).setPadding(0,0,0,0);            mViewList.get(position).setPadding(0,0,0,0);                        mViewList.get(position + 1).setAlpha(0xFF);            mViewList.get(position - 1).setAlpha(0xFF);            mViewList.get(position).setAlpha(0xFF);            return ;        }        if(offset < 0){                mViewList.get(position).setAlpha((int)(0xFF * (1 - positionOffset)));                mViewList.get(position + 1).setAlpha((int)(0xFF * positionOffset));                mViewList.get(position - 1).setAlpha((int)(0xFF * positionOffset));                            mViewList.get(position + 1).setPadding(paddingNext,paddingNext,paddingNext,paddingNext);            mViewList.get(position - 1).setPadding(paddingNext,paddingNext,paddingNext,paddingNext);            mViewList.get(position).setPadding(paddingCurr,paddingCurr,paddingCurr,paddingCurr);        }else{                mViewList.get(position - 1).setAlpha((int)(0xFF * positionOffset));                mViewList.get(position + 1).setAlpha((int)(0xFF * positionOffset));                mViewList.get(position).setAlpha((int)(0xFF * (1 - positionOffset)));                            mViewList.get(position + 1).setPadding(paddingNext,paddingNext,paddingNext,paddingNext);            mViewList.get(position - 1).setPadding(paddingNext,paddingNext,paddingNext,paddingNext);            mViewList.get(position).setPadding(paddingCurr,paddingCurr,paddingCurr,paddingCurr);                     }    }//     mViewPager.invalidate();}     @Overridepublic void onPageSelected(int position){        mViewList.get(position).setAlpha(0xFF);        mViewList.get(position).setPadding(0, 0, 0, 0);              for(int i = 0;i < mViewList.size();i++){            mViewList.get(i).setPadding(0, 0, 0, 0);            mViewList.get(i).setAlpha(0xFF);        }}      @Overridepublic void onPageScrollStateChanged(int state){              if(state == ViewPager.SCROLL_STATE_IDLE){        for(int i = 0;i < mViewList.size();i++){            mViewList.get(i).setAlpha(0xFF);            mViewList.get(i).setPadding(0, 0, 0, 0);        }    }} }