android :fragmentation使用中遇到的 NullPointerException
背景：fragmentation(单ACTIVITY+多个fragments)+brvah( recyclerView多级自定义菜单功能）
目的：实现 菜单栏的点击，fragment 显示相应的内容
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
mainActivity.xml
<?xml version="1.0" encoding="utf-8"?> <android.support.v4.widget.DrawerLayout android:id="@+id/drawer_layout" xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true" tools:openDrawer="start"> <FrameLayout android:id="@+id/fl_container" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".demo_flow.MainActivity"> </FrameLayout> <RelativeLayout android:id="@+id/menu_layout_left" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_gravity="left" android:background="@drawable/menu_bg" android:layout_marginRight="10dp" android:layout_marginTop="57dp" > <android.support.v7.widget.RecyclerView android:id="@+id/rv" android:layout_width="match_parent" android:layout_height="match_parent" /> </RelativeLayout> </android.support.v4.widget.DrawerLayout>
遇到的问题：
1、因为菜单点击显示 fragment
在菜单的adapter 中要实现对fragment的 控制，
我的实现方式： 回调函数
（1）菜单的adapter中的部分代码：
private SubClickListener subClickListener; public void setsubClickListener(SubClickListener topicClickListener) { this.subClickListener = topicClickListener; }
//接口，希望在mainActivity中实现 public interface SubClickListener { void OntopicClickListener(View v, int position); }
protected void convert(final BaseViewHolder holder, final MultiItemEntity item) {
switch (holder.getItemViewType()) { case TYPE_LEVEL_0: holder.setImageResource(R.id.iv_head, R.mipmap.head_img1); final Level0Item lv0 = (Level0Item) item; int subTitle = Integer.parseInt(lv0.subTitle.split("_")[0]); int itemID = Integer.parseInt(lv0.subTitle.split("_")[1]); switch (subTitle) { case 1: holder.setImageResource(R.id.iv_head,R.mipmap.head_img0); break; case 2: holder.setImageResource(R.id.iv_head,R.mipmap.head_img1); break; case 3: holder.setImageResource(R.id.iv_head,R.mipmap.head_img2); break; case 4: holder.setImageResource(R.id.iv_head,R.mipmap.head_img2); break; case 5: holder.setImageResource(R.id.iv_head,R.mipmap.head_img2); break; } //if(subTitle=="1") System.out.println("---------------------level--------------------"); //System.out.println("---------------------level-int-------------------"); String name = lv0.title; if(name.indexOf(".doc")>0) { holder.setTypeface(R.id.title, Typeface.SANS_SERIF); holder.setImageResource(R.id.iv_head,R.mipmap.head_img_1); } holder.setText(R.id.title, lv0.title) .setText(R.id.sub_title, lv0.subTitle) .setImageResource(R.id.iv, lv0.isExpanded() ? R.mipmap.arrow_b : R.mipmap.arrow_r); holder.itemView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { int pos = holder.getAdapterPosition(); if (subClickListener != null) { subClickListener.OntopicClickListener(v,pos); } if (lv0.isExpanded()) { collapse(pos); } else { expand(pos); } } }); break; //此处省略其他分支…… } }
（2）mainActivity.java
结构如下：
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); MySupportFragment fragment = findFragment(HomeFragment.class); if (fragment == null) { loadRootFragment(R.id.fl_container, HomeFragment.newInstance()); } initView(); }
final ISupportFragment topFragment = getTopFragment();
private void initView() { mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout); ActionBarDrawerToggle toggle = new ActionBarDrawerToggle( this, mDrawer, R.string.navigation_drawer_open, R.string.navigation_drawer_close); // mDrawer.setDrawerListener(toggle); toggle.syncState(); //added by ssqhan mRecyclerView = (RecyclerView)findViewById(R.id.rv); list=generateData(); adapter=new ExpandableItemAdapter(list); adapter.setsubClickListener(new ExpandableItemAdapter.SubClickListener() { @Override public void OntopicClickListener(View v, int position) { //实现菜单中adapter回调函数 TextView tv=(TextView)v.findViewById(R.id.title); final String wbs_name = (String) tv.getText(); boolean flag = (tv.getText().toString().indexOf(".doc")>0); if(flag) { mDrawer.closeDrawer(GravityCompat.START); mDrawer.postDelayed(new Runnable() { @Override public void run() { SartFragment(wbs_name); } }, 300); } } }); //adapter.get manager = new LinearLayoutManager(this); mRecyclerView.setAdapter(adapter); //important! setLayoutManager should be called after setAdapter mRecyclerView.setLayoutManager(manager); adapter.expandAll(); }
public void SartFragment(String tableName) { HomeFragment fragment=null; DiscoverFragment discoverFragment0=null; Bundle newBundle = new Bundle(); System.out.println("---------------discovery---------------"); switch (tableName) { case "避雷器实验报告.doc": fragment = findFragment(HomeFragment.class); newBundle.putString("from", "From:" + topFragment.getClass().getSimpleName()); fragment.putNewBundle(newBundle); start(fragment, SupportFragment.SINGLETASK); break; case "电缆头施工记录.doc": discoverFragment0 = findFragment(DiscoverFragment.class); if (discoverFragment0 == null) { popTo(HomeFragment.class, false, new Runnable() { @Override public void run() { start(DiscoverFragment.newInstance()); Bundle myBundle = new Bundle(); DiscoverFragment discoverFragment=null; if(topFragment==null) {
//这个地方，发现 topFragment 是空一直都是空 System.out.println("---------------------------------------"); System.out.println("----------topFragment is null----------"); System.out.println("---------------------------------------");
//loadRootFragment(R.id.fl_container, HomeFragment.newInstance()); } myBundle.putString("from", "From:" + topFragment.getClass().getSimpleName()); discoverFragment.putNewBundle(myBundle); start(discoverFragment, SupportFragment.SINGLETASK); } }); } else { newBundle.putString("from", "From:" + topFragment.getClass().getSimpleName()); discoverFragment0.putNewBundle(newBundle); start(discoverFragment0, SupportFragment.SINGLETASK); } break; } }
问题：如何解决，这个一直为空？？？
