android仿多看閱讀三屏滾動效果 -- 更改OnPageChangeListener
阿新 • • 發佈：2018-12-31
通過在滾動的時候動態的改變每一個item的padding值進行實現。
先看看效果吧：
以下是原始碼。重點在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;
}
});
}
@Override
public 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();
}
@Override
public 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);
}
}
@Override
public 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);
}
}
}
}