在我们开发的过程中可能会遇到类似需求，我们需要做一个左右滑动的tab导航，这个时候有些朋友可能会想到viewpager和fragment的结合来实现这个功能；
当然实现的方法不单单着一种。我们这个随笔讨论的是这种方式实现的效果、现在假如我们选中了服务这个列，服务列下有一个listview用来展示数据。然后滑动到第二个评价的fragment再到第三个商家fragment，或者是直接到最后一个fragment，然后再回来第一个fragment，我们会发现fragment刷新了一下。这里fragment重新create了，这个时候会发现listview的数据不对了。但我们并没有进行刷新操作！这个时候我们只需要重写ViewPager适配器的：
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
//super.destroyItem(container, position, object);
}然后把super.destroyItem(container, position, object);注释掉，让fragment一直存在着。这样你再次运行会发现刚刚那个问题已经解决了。
如：
/**
* ViewPager适配器
*
* @author xl
*/
class MyFragmentViewPager extends FragmentPagerAdapter {
public MyFragmentViewPager(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
return m_listFragment.get(position);
}
@Override
public int getCount() {
return m_listFragment.size();
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
//super.destroyItem(container, position, object);
}
}示例：
/**
* 主页
* Created by xl on 2019/10/9.
*/
public class HomeActivity extends FragmentActivity implements ViewPager.OnPageChangeListener, View.OnClickListener {
private final static String TAG = HomeActivity.class.getSimpleName();
private ViewPager m_viewPager;
private NavImageBtn[] m_navTabs = new NavImageBtn[4];
private List<Fragment> m_listFragment;
private MyFragmentViewPager m_viewPagerAdapter;
private MonitorFragment m_fragMonitor;
private MapFragment m_fragMap;
private FaultFragment m_fragFault;
private UserFragment m_fragUser;
private int m_iCurFragment = 0;
private String m_strVerName = "0.0.0"; // 例如1.0.3
private final int[] m_iArrTabResid = new int[]{
R.string.t_index_monitoring, R.string.t_list_map_monitor, R.string.t_index_breakdown, R.string.t_index_user
};
private final int[] m_iArrDefResid = new int[]{
R.drawable.index_monitor_p, R.drawable.tab_map, R.drawable.index_fault_p, R.drawable.index_info_p
};
private final int[] m_iArrSelResid = new int[]{
R.drawable.index_monitor, R.drawable.tab_map_p, R.drawable.index_fault, R.drawable.index_info
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
findView();
init();
}
private void findView() {
m_viewPager = (ViewPager) this.findViewById(R.id.viewpager);
m_navTabs[0] = (NavImageBtn) this.findViewById(R.id.tab1);
m_navTabs[1] = (NavImageBtn) this.findViewById(R.id.tab2);
m_navTabs[2] = (NavImageBtn) this.findViewById(R.id.tab3);
m_navTabs[3] = (NavImageBtn) this.findViewById(R.id.tab4);
}
private void init() {
// 将activity放入堆栈
AppManager.getAppManager().addActivity(this);
//初始化fragment集合
initFragmentList();
//初始化viewpager
m_viewPagerAdapter = new MyFragmentViewPager(getSupportFragmentManager());
m_viewPager.setAdapter(m_viewPagerAdapter);
m_viewPager.setOnPageChangeListener(this);
//初始化tab
initTab();
//默认显示第一页
setNavBtnStatus(0);
//判断当前是否是最新版本
getApkVersion();
}
/**
* 初始化fragment集合
*/
private void initFragmentList() {
m_listFragment = new ArrayList<>();
m_fragMonitor = new MonitorFragment();
m_fragMap = new MapFragment();
m_fragFault = new FaultFragment();
m_fragUser = new UserFragment();
m_listFragment.add(m_fragMonitor);
m_listFragment.add(m_fragMap);
m_listFragment.add(m_fragFault);
m_listFragment.add(m_fragUser);
}
@Override
public void onPageScrolled(int i, float v, int i1) {
}
@Override
public void onPageSelected(int position) {
setNavBtnStatus(position);
switch (position) {
case 0:
break;
case 1:
break;
case 2:
break;
case 3:
break;
}
}
@Override
public void onPageScrollStateChanged(int i) {
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.tab1:
m_viewPager.setCurrentItem(0, true);
break;
case R.id.tab2:
m_viewPager.setCurrentItem(1, true);
break;
case R.id.tab3:
m_viewPager.setCurrentItem(2, true);
break;
case R.id.tab4:
m_viewPager.setCurrentItem(3, true);
break;
}
}
/**
* ViewPager适配器
*
* @author xl
*/
class MyFragmentViewPager extends FragmentPagerAdapter {
public MyFragmentViewPager(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
return m_listFragment.get(position);
}
@Override
public int getCount() {
return m_listFragment.size();
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
//super.destroyItem(container, position, object);
}
}
/**
* 设置imgbtn
*
* @param position
*/
public void setNavBtnStatus(int position) {
switch (position) {
case 0:
m_navTabs[0].setClickStatus(true);
m_navTabs[1].setClickStatus(false);
m_navTabs[2].setClickStatus(false);
m_navTabs[3].setClickStatus(false);
break;
case 1:
m_navTabs[0].setClickStatus(false);
m_navTabs[1].setClickStatus(true);
m_navTabs[2].setClickStatus(false);
m_navTabs[3].setClickStatus(false);
break;
case 2:
m_navTabs[0].setClickStatus(false);
m_navTabs[1].setClickStatus(false);
m_navTabs[2].setClickStatus(true);
m_navTabs[3].setClickStatus(false);
break;
case 3:
m_navTabs[0].setClickStatus(false);
m_navTabs[1].setClickStatus(false);
m_navTabs[2].setClickStatus(false);
m_navTabs[3].setClickStatus(true);
break;
default:
break;
}
m_iCurFragment = position;
}
/**
* 初始化Tab
*/
private void initTab() {
for (int i = 0; i < m_navTabs.length; i++) {
m_navTabs[i].setText(m_iArrTabResid[i]);
m_navTabs[i].setImageSrc(m_iArrDefResid[i], m_iArrSelResid[i]);
m_navTabs[i].setOnTabClickListener(this);
}
}
@Override
public void onBackPressed() {
AppManager.getAppManager().AppExit(this);
}
/**
* 获取apk版本号
*/
public void getApkVersion() {
// 得到软件当前版本号
try {
PackageInfo info = getPackageManager().getPackageInfo(getPackageName(), 0);
m_strVerName = info.versionName; // 软件版本,例如"1.0.3"
} catch (PackageManager.NameNotFoundException e) {
e.printStackTrace(System.err);
}
HttpTask http = new HttpTask(HttpUrl.SOFT_VERSION, HttpPara.SOFT_VERSION, new OnFunHttpCallBack() {
@Override
public void OnStart() {
}
@Override
public void OnFinish(String url, String json) {
MyLogger.i(TAG, json);
try {
JSONObject result = new JSONObject(json);
if (url.equals(HttpUrl.SOFT_VERSION)) {
if (result.optString("msgCode").equals("0") && result.optString("data").compareTo(m_strVerName) > 0) {
updateTip(result.optString("data"));
}
}
} catch (Exception e) {
MyLogger.e(TAG, e.getMessage());
}
}
});
http.runGet();
}
/**
* 弹框提示更新
*
* @param version
*/
private void updateTip(final String version) {
DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (which == DialogInterface.BUTTON_POSITIVE) { // 确定按键的点击事件
softupdate(version);
} else if (which == DialogInterface.BUTTON_NEGATIVE) { // 取消按键的点击事件
}
}
};
// 创建提示信息对话框
int iconId = R.drawable.login_tip;
String title = getResources().getString(R.string.t_title_info);
String msg = getResources().getString(R.string.msg_update_tip_h) + version + getResources().getString(R.string.msg_update_tip_l);
CustomDialog.MessageBox(this, iconId, title, msg, listener, 2);
}
/**
* 下载apk
*
* @param version
*/
private void softupdate(String version) {
UpdateManager.getInstance().showDownloadDialog(this, version, HttpUrl.SOFT_UPDATE + "?" + HttpPara.SOFT_UPDATE);
}
/**
* 跳转到新的Activity
*
* @param aty
*/
public void enter(Class<? extends Activity> aty, Bundle bundle) {
Intent intent = new Intent(this, aty);
if (bundle != null) {
intent.putExtras(bundle);
}
startActivity(intent);
overridePendingTransition(R.anim.push_left_in, R.anim.push_left_out);
}
}完！！！
