FragmentPagerAdapter刷新fragment最完美解决方案
先感谢kingjxl2006的博客文章《Android FragmentPagerAdapter数据刷新notifyDataSetChanged没效果研究》http://blog.sina.com.cn/s/blog_783ede03010173b4.html，没有他的抛砖引玉，就没有这篇博文。
kingjxl2006的办法是清除FragmentManager里面全部缓存的fragment。这很暴力我不赞同，全部清除会造成fragment重新加载，造成不必要的性能损失。
@Override
public Object instantiateItem(ViewGroup container,int position) {
//得到缓存的fragment
Fragment fragment = (Fragment)super.instantiateItem(container,
position);
//得到tag ❶
String fragmentTag = fragment.getTag();
if (fragmentsUpdateFlag[position %fragmentsUpdateFlag.length]) {
//如果这个fragment需要更新
FragmentTransaction ft =fm.beginTransaction();
//移除旧的fragment
ft.remove(fragment);
//换成新的fragment
fragment =fragments[position %fragments.length];
//添加新fragment时必须用前面获得的tag ❶
ft.add(container.getId(), fragment, fragmentTag);
ft.attach(fragment);
ft.commit();
//复位更新标志
fragmentsUpdateFlag[position %fragmentsUpdateFlag.length] =false;
}
return fragment;
}
代码注释得很清楚了，主要思路就是用新的fragment替换FragmentManager里缓存的旧的fragment，重点解释❶的地方，看kingjxl2006文章里的两条代码：
FragmentManager fm;
super(fm);
this.fm = fm;
}
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.Log;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.LinearLayout;
public class MainActivity extends FragmentActivity implements
FragmentEvent.OnEventListener {
ViewPager viewPager;
FragmentPagerAdapter adapter;
MainTab01 tab01 = new MainTab01();
MainTab02 tab02 = new MainTab02();
MainTab03 tab03 = new MainTab03();
MainTab04 tab04 = new MainTab04();
MainTab05 tab05 = new MainTab05();
Fragment[] fragments = { tab01, tab02, tab03, tab04 };
boolean[] fragmentsUpdateFlag = { false, false, false, false };
/**
* 底部四个按钮
*/
private LinearLayout tabBtnWeixin;
private LinearLayout tabBtnFrd;
private LinearLayout tabBtnAddress;
private LinearLayout tabBtnSettings;
Handler mainHandler = new Handler() {
/*
* （非 Javadoc）
*
* @see android.os.Handler#handleMessage(android.os.Message)
*/
@Override
public void handleMessage(Message msg) {
// TODO 自动生成的方法存根
super.handleMessage(msg);
switch (msg.what) {
case MSG.INTO_05:
fragments[3] = tab05;
fragmentsUpdateFlag[3] = true;
adapter.notifyDataSetChanged();
break;
default:
}
}
};
class MyFragmentPagerAdapter extends FragmentPagerAdapter {
FragmentManager fm;
MyFragmentPagerAdapter(FragmentManager fm) {
super(fm);
this.fm = fm;
}
@Override
public int getCount() {
return fragments.length;
}
@Override
public Fragment getItem(int position) {
Fragment fragment = fragments[position % fragments.length];
Log.i(Common.TAG, "getItem:position=" + position + ",fragment:"
+ fragment.getClass().getName() + ",fragment.tag="
+ fragment.getTag());
return fragments[position % fragments.length];
}
@Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
//得到缓存的fragment
Fragment fragment = (Fragment) super.instantiateItem(container,
position);
//得到tag，这点很重要
String fragmentTag = fragment.getTag();
if (fragmentsUpdateFlag[position % fragmentsUpdateFlag.length]) {
//如果这个fragment需要更新
FragmentTransaction ft = fm.beginTransaction();
//移除旧的fragment
ft.remove(fragment);
//换成新的fragment
fragment = fragments[position % fragments.length];
//添加新fragment时必须用前面获得的tag，这点很重要
ft.add(container.getId(), fragment, fragmentTag);
ft.attach(fragment);
ft.commit();
//复位更新标志
fragmentsUpdateFlag[position % fragmentsUpdateFlag.length] = false;
}
return fragment;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager) findViewById(R.id.id_viewpager);
tabBtnWeixin = (LinearLayout) findViewById(R.id.id_tab_bottom_weixin);
tabBtnFrd = (LinearLayout) findViewById(R.id.id_tab_bottom_friend);
tabBtnAddress = (LinearLayout) findViewById(R.id.id_tab_bottom_contact);
tabBtnSettings = (LinearLayout) findViewById(R.id.id_tab_bottom_setting);
adapter = new MyFragmentPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(adapter);
viewPager.setOnPageChangeListener(new OnPageChangeListener() {
private int currentIndex;
@Override
public void onPageSelected(int position) {
resetTabBtn();
switch (position) {
case 0:
((ImageButton) tabBtnWeixin
.findViewById(R.id.btn_tab_bottom_weixin))
.setImageResource(R.drawable.tab_weixin_pressed);
break;
case 1:
((ImageButton) tabBtnFrd
.findViewById(R.id.btn_tab_bottom_friend))
.setImageResource(R.drawable.tab_find_frd_pressed);
break;
case 2:
((ImageButton) tabBtnAddress
.findViewById(R.id.btn_tab_bottom_contact))
.setImageResource(R.drawable.tab_address_pressed);
break;
case 3:
((ImageButton) tabBtnSettings
.findViewById(R.id.btn_tab_bottom_setting))
.setImageResource(R.drawable.tab_settings_pressed);
break;
}
currentIndex = position;
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
@Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
protected void resetTabBtn() {
((ImageButton) tabBtnWeixin.findViewById(R.id.btn_tab_bottom_weixin))
.setImageResource(R.drawable.tab_weixin_normal);
((ImageButton) tabBtnFrd.findViewById(R.id.btn_tab_bottom_friend))
.setImageResource(R.drawable.tab_find_frd_normal);
((ImageButton) tabBtnAddress.findViewById(R.id.btn_tab_bottom_contact))
.setImageResource(R.drawable.tab_address_normal);
((ImageButton) tabBtnSettings.findViewById(R.id.btn_tab_bottom_setting))
.setImageResource(R.drawable.tab_settings_normal);
}
@Override
public void onEvent(int what, Bundle data, Object object) {
// TODO 自动生成的方法存根
mainHandler.sendEmptyMessage(what);
}
}