FragmentManager replace() 似乎在 RecyclerView 中复制卡片
FragmentManager replace() appears to duplicate cards in RecyclerView
我刚开始在堆栈溢出中发帖和 android 编程,所以请原谅我犯的任何错误。
在我的主 activity 中,我有一个导航抽屉,其中使用了 onNavigationDrawerItemSelected 函数,显示的是其中的代码:
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
Fragment myFragment = null;
switch(position)
{
case 0:
myFragment = new HomeFragment();
break;
case 1:
//myFragment = new TestFragment();
break;
case 2:
// TODO: Add more
break;
}
if(myFragment!=null)
{
getFragmentManager().beginTransaction()
.replace(R.id.nav_contentframe, myFragment)
.commit();
}
}
应该注意的是,当我尝试 select 调用 HomeFragment 的按钮时,应用程序反而添加到卡片上,而不是替换它。下面的代码是HomeFragment.java
package tk.easthigh.witsmobile;
import android.app.FragmentManager;
import android.content.Context;
import android.os.Bundle;
import android.app.Fragment;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
public class HomeFragment extends Fragment {
SimpleRecyclerAdapter adapter;
public HomeFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.fragment_home, container, false);
RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.home_recyclerview);
final Context context = getActivity().getApplicationContext();
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(context));
recyclerView.setItemAnimator(new DefaultItemAnimator());
if (adapter == null) {
adapter = new SimpleRecyclerAdapter(context);
recyclerView.setAdapter(adapter);
}
adapter.SetOnItemClickListener(new SimpleRecyclerAdapter.OnItemClickListener() {
@Override
public void onItemClick(View view, int position) {
switch (position) {
case 0:
Toast.makeText(getActivity().getBaseContext(), "Hi!", Toast.LENGTH_SHORT).show();
break;
case 1:
break;
case 2:
break;
default:
Toast.makeText(getActivity().getBaseContext(), "Undefined Click!", Toast.LENGTH_SHORT).show();
}
}
});
// Inflate the layout for this fragment
return view;
}
}
对 SimpleAdapter 的引用是位于此 github 的代码。
这里是 activity_main.xml,其中包含 id 为 "nav_contentframe":
的 FrameLayout
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/nav_drawer"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<include layout="@layout/toolbar" />
<FrameLayout
android:id="@+id/nav_contentframe"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="?attr/actionBarSize"
android:background="@android:color/background_light">
</FrameLayout>
</RelativeLayout>
<android.support.design.widget.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="@layout/drawer_header"
app:menu="@menu/drawer" />
这里是fragment_home.xml:
<FrameLayout 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" tools:context="tk.easthigh.witsmobile.HomeFragment">
<android.support.v7.widget.RecyclerView
android:id="@+id/home_recyclerview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false" />
我能够确定从 FragmentManager 调用 replace 方法似乎会添加 HomeFragment 的 RecyclerView 中所有卡片的副本。
例如,RecyclerView 有 4 张卡片。然而,按下导航抽屉上应该替换内容的按钮,反而复制了卡片,最终产品留下了 8 张卡片。再次按下它会产生 12 张牌,依此类推。当然,这不是预期的情况,但在 google 几个小时后,并尝试调试,我无法找出问题所在。
正如我在评论中所述,SimpleRecyclerAdapter
引用了两个静态列表:
public static List<String> homeActivitiesList = new ArrayList<String>();
public static List<String> homeActivitiesSubList = new ArrayList<String>();
这些将用于 SimpleRecyclerAdapter
的每个引用。最重要的是,每次创建 SimpleRecyclerAdapter
对象时都会填充它们,这显然发生在这里。
我不知道开发者为什么选择这样做。如果是出于效率原因,那么在 SimpleRecyclerAdapter
的构造函数中,您需要进行检查以防止在创建列表后填充它们。像这样:
public static List<String> homeActivitiesList = null;
public static List<String> homeActivitiesSubList = null;
Context context;
OnItemClickListener clickListener;
public SimpleRecyclerAdapter(Context context) {
isHomeList = true;
this.context = context;
setHomeActivitiesList(context);
}
public void setHomeActivitiesList(Context context) {
if (homeActivitiesList == null) {
homeActivitiesList = new ArrayList<String>();
homeActivitiesSubList = new ArrayList<String();
String[] listArray = context.getResources().getStringArray(R.array.home_activities);
String[] subTitleArray = context.getResources().getStringArray(R.array.home_activities_subtitle);
for (int i = 0; i < listArray.length; ++i) {
homeActivitiesList.add(listArray[i]);
homeActivitiesSubList.add(subTitleArray[i]);
}
}
}
另一件事是确保您不会在每次替换时都创建新的片段。因此,在您的 Main Activity 中,您可以保留对 HomeFragment 的引用,并使用它而不是像这样创建一个新的:
HomeFragment mHomeFragment = null
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
Fragment myFragment = null;
switch(position)
{
case 0:
if (mHomeFragment == null) {
mHomeFragment = new HomeFragment();
}
myFragment = mHomeFragment;
break;
case 1:
//myFragment = new TestFragment();
break;
case 2:
// TODO: Add more
break;
}
if(myFragment!=null)
{
getFragmentManager().beginTransaction()
.replace(R.id.nav_contentframe, myFragment)
.commit();
}
}
这样就可以保证只要MainActivity在内存中,最后一个HomeFragment的内容就一直在内存中。
我刚开始在堆栈溢出中发帖和 android 编程,所以请原谅我犯的任何错误。
在我的主 activity 中,我有一个导航抽屉,其中使用了 onNavigationDrawerItemSelected 函数,显示的是其中的代码:
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
Fragment myFragment = null;
switch(position)
{
case 0:
myFragment = new HomeFragment();
break;
case 1:
//myFragment = new TestFragment();
break;
case 2:
// TODO: Add more
break;
}
if(myFragment!=null)
{
getFragmentManager().beginTransaction()
.replace(R.id.nav_contentframe, myFragment)
.commit();
}
}
应该注意的是,当我尝试 select 调用 HomeFragment 的按钮时,应用程序反而添加到卡片上,而不是替换它。下面的代码是HomeFragment.java
package tk.easthigh.witsmobile;
import android.app.FragmentManager;
import android.content.Context;
import android.os.Bundle;
import android.app.Fragment;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
public class HomeFragment extends Fragment {
SimpleRecyclerAdapter adapter;
public HomeFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.fragment_home, container, false);
RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.home_recyclerview);
final Context context = getActivity().getApplicationContext();
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(context));
recyclerView.setItemAnimator(new DefaultItemAnimator());
if (adapter == null) {
adapter = new SimpleRecyclerAdapter(context);
recyclerView.setAdapter(adapter);
}
adapter.SetOnItemClickListener(new SimpleRecyclerAdapter.OnItemClickListener() {
@Override
public void onItemClick(View view, int position) {
switch (position) {
case 0:
Toast.makeText(getActivity().getBaseContext(), "Hi!", Toast.LENGTH_SHORT).show();
break;
case 1:
break;
case 2:
break;
default:
Toast.makeText(getActivity().getBaseContext(), "Undefined Click!", Toast.LENGTH_SHORT).show();
}
}
});
// Inflate the layout for this fragment
return view;
}
}
对 SimpleAdapter 的引用是位于此 github 的代码。 这里是 activity_main.xml,其中包含 id 为 "nav_contentframe":
的 FrameLayout<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/nav_drawer"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<include layout="@layout/toolbar" />
<FrameLayout
android:id="@+id/nav_contentframe"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="?attr/actionBarSize"
android:background="@android:color/background_light">
</FrameLayout>
</RelativeLayout>
<android.support.design.widget.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="@layout/drawer_header"
app:menu="@menu/drawer" />
这里是fragment_home.xml:
<FrameLayout 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" tools:context="tk.easthigh.witsmobile.HomeFragment">
<android.support.v7.widget.RecyclerView
android:id="@+id/home_recyclerview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false" />
我能够确定从 FragmentManager 调用 replace 方法似乎会添加 HomeFragment 的 RecyclerView 中所有卡片的副本。
例如,RecyclerView 有 4 张卡片。然而,按下导航抽屉上应该替换内容的按钮,反而复制了卡片,最终产品留下了 8 张卡片。再次按下它会产生 12 张牌,依此类推。当然,这不是预期的情况,但在 google 几个小时后,并尝试调试,我无法找出问题所在。
正如我在评论中所述,SimpleRecyclerAdapter
引用了两个静态列表:
public static List<String> homeActivitiesList = new ArrayList<String>();
public static List<String> homeActivitiesSubList = new ArrayList<String>();
这些将用于 SimpleRecyclerAdapter
的每个引用。最重要的是,每次创建 SimpleRecyclerAdapter
对象时都会填充它们,这显然发生在这里。
我不知道开发者为什么选择这样做。如果是出于效率原因,那么在 SimpleRecyclerAdapter
的构造函数中,您需要进行检查以防止在创建列表后填充它们。像这样:
public static List<String> homeActivitiesList = null;
public static List<String> homeActivitiesSubList = null;
Context context;
OnItemClickListener clickListener;
public SimpleRecyclerAdapter(Context context) {
isHomeList = true;
this.context = context;
setHomeActivitiesList(context);
}
public void setHomeActivitiesList(Context context) {
if (homeActivitiesList == null) {
homeActivitiesList = new ArrayList<String>();
homeActivitiesSubList = new ArrayList<String();
String[] listArray = context.getResources().getStringArray(R.array.home_activities);
String[] subTitleArray = context.getResources().getStringArray(R.array.home_activities_subtitle);
for (int i = 0; i < listArray.length; ++i) {
homeActivitiesList.add(listArray[i]);
homeActivitiesSubList.add(subTitleArray[i]);
}
}
}
另一件事是确保您不会在每次替换时都创建新的片段。因此,在您的 Main Activity 中,您可以保留对 HomeFragment 的引用,并使用它而不是像这样创建一个新的:
HomeFragment mHomeFragment = null
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
Fragment myFragment = null;
switch(position)
{
case 0:
if (mHomeFragment == null) {
mHomeFragment = new HomeFragment();
}
myFragment = mHomeFragment;
break;
case 1:
//myFragment = new TestFragment();
break;
case 2:
// TODO: Add more
break;
}
if(myFragment!=null)
{
getFragmentManager().beginTransaction()
.replace(R.id.nav_contentframe, myFragment)
.commit();
}
}
这样就可以保证只要MainActivity在内存中,最后一个HomeFragment的内容就一直在内存中。