本文主要介绍如何利用ViewPager实现Gallery的画廊效果,即一屏显示多个Fragment。具体代码可见ViewPager MultiFragment@Google Code,示例APK地址TrineaAndroidDemo.apk(其中的ViewPager Multi Fragment Demo)。
在使用Gallery的时候大家会发现有几个问题(1). 无法控制每次滑动只滑动一页, (2). Gallery默认第一个item居中,无法修改它与Gallery的左间距。ViewPager可以方便的解决上面两个问题,但默认却无法在屏幕上显示 多个Fragment。
下面介绍如何利用ViewPager及android:clipChildren属性解决这个问题。
1、定义xml
Java
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:layerType="software" >
<android.support.v4.view.ViewPager
android:id="@+id/view_pager"
android:layout_width="250dp"
android:layout_height="450dp"
android:layout_gravity="center"
android:clipChildren="false" />
</RelativeLayout>
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<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:layerType="software" >
<android.support.v4.view.ViewPager
android:id="@+id/view_pager"
android:layout_width="250dp"
android:layout_height="450dp"
android:layout_gravity="center"
android:clipChildren="false" />
</RelativeLayout>
发现上面的RelativeLayout(可以用其它layout替换)和ViewPager的android:clipChildren都设置为了false。
android:clipChildren表示是否限制子View在其范围内,在animations动画以及本文的情况下可以发挥很大的作用。默认为true。
2、Java部分
这里我们主要完成
(1). ViewPager设置
需要setOnPageChangeListener,在onPageScrolled(int position, float positionOffset, int positionOffsetPixels)函数中不断刷新layout。
还可以
Java
viewPager.setOffscreenPageLimit(TOTAL_COUNT);
viewPager.setPageMargin(getResources().getDimensionPixelSize(R.dimen.page_margin));
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viewPager.setOffscreenPageLimit(TOTAL_COUNT);
viewPager.setPageMargin(getResources().getDimensionPixelSize(R.dimen.page_margin));
setOffscreenPageLimit表示设置缓存,这样左右拖动即可看见后面的Fragment。setPageMargin表示设置Fragment之间的间距
(2). FrameLayout设置
需要setOnTouchListener函数中将滑动滑动事件传递给viewPager,否则只有viewPager中间的view可以滑动,设置后整个viewPager都可以滑动。
具体代码如下:
Java部分实现
Java
package com.trinea.android.demo;
import android.app.ActionBar;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RelativeLayout;
/**
* ViewPager实现画廊效果
*
* @author Trinea 2013-04-03
*/
public class ViewPagerMulTiFragmentDemo extends FragmentActivity {
private static intTOTAL_COUNT = 3;
private RelativeLayout viewPagerContainer;
private ViewPagerviewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_pager_multi_fragment_demo);
viewPager = (ViewPager)findViewById(R.id.view_pager);
viewPagerContainer = (RelativeLayout)findViewById(R.id.pager_layout);
viewPager.setAdapter(new MyPagerAdapter());
// to cache all page, or we will see the right item delayed
viewPager.setOffscreenPageLimit(TOTAL_COUNT);
viewPager.setPageMargin(getResources().getDimensionPixelSize(R.dimen.page_margin));
MyOnPageChangeListener myOnPageChangeListener = new MyOnPageChangeListener();
viewPager.setOnPageChangeListener(myOnPageChangeListener);
viewPagerContainer.setOnTouchListener(new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
// dispatch the events to the ViewPager, to solve the problem that we can swipe only the middle view.
return viewPager.dispatchTouchEvent(event);
}
});
}
/**
* this is a example fragment, just a imageview, u can replace it with your needs
*
* @author Trinea 2013-04-03
*/
class MyPagerAdapter extends PagerAdapter {
@Override
public int getCount() {
return TOTAL_COUNT;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return (view == object);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView imageView = new ImageView(ViewPagerMulTiFragmentDemo.this);
imageView.setImageResource(R.drawable.image1 + position);
((ViewPager)container).addView(imageView, position);
return imageView;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager)container).removeView((ImageView)object);
}
}
public class MyOnPageChangeListener implements OnPageChangeListener {
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
// to refresh frameLayout
if (viewPagerContainer != null) {
viewPagerContainer.invalidate();
}
}
@Override
public void onPageScrollStateChanged(int arg0) {
}
}
}
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package com.trinea.android.demo;
import android.app.ActionBar;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RelativeLayout;
/**
* ViewPager实现画廊效果
*
* @author Trinea 2013-04-03
*/
public class ViewPagerMulTiFragmentDemo extends FragmentActivity {
private static intTOTAL_COUNT = 3;
private RelativeLayout viewPagerContainer;
private ViewPagerviewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_pager_multi_fragment_demo);
viewPager = (ViewPager)findViewById(R.id.view_pager);
viewPagerContainer = (RelativeLayout)findViewById(R.id.pager_layout);
viewPager.setAdapter(new MyPagerAdapter());
// to cache all page, or we will see the right item delayed
viewPager.setOffscreenPageLimit(TOTAL_COUNT);
viewPager.setPageMargin(getResources().getDimensionPixelSize(R.dimen.page_margin));
MyOnPageChangeListener myOnPageChangeListener = new MyOnPageChangeListener();
viewPager.setOnPageChangeListener(myOnPageChangeListener);
viewPagerContainer.setOnTouchListener(new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
// dispatch the events to the ViewPager, to solve the problem that we can swipe only the middle view.
return viewPager.dispatchTouchEvent(event);
}
});
}
/**
* this is a example fragment, just a imageview, u can replace it with your needs
*
* @author Trinea 2013-04-03
*/
class MyPagerAdapter extends PagerAdapter {
@Override
public int getCount() {
return TOTAL_COUNT;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return (view == object);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView imageView = new ImageView(ViewPagerMulTiFragmentDemo.this);
imageView.setImageResource(R.drawable.image1 + position);
((ViewPager)container).addView(imageView, position);
return imageView;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager)container).removeView((ImageView)object);
}
}
public class MyOnPageChangeListener implements OnPageChangeListener {
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
// to refresh frameLayout
if (viewPagerContainer != null) {
viewPagerContainer.invalidate();
}
}
@Override
public void onPageScrollStateChanged(int arg0) {
}
}
}
效果图如下:
可能运行后出现viewpager的部分Fragment无法看见或是突然消失的问题,请确保RelativeLayout和ViewPager的 android:clipChildren都设置为了false并且 viewPager.setOffscreenPageLimit(TOTAL_COUNT);其中TOTAL_COUNT大于0. 当然子Fragment本身不能是match_parent的。viewpager设置了paddingTop也会导致无法实现画廊而只是显示一屏。