想在首页使用RecyclerView来显示数据,因为使用了fragment所以我想在返回首页这一部分是填充数据,但是一直报错,这个控件不是太熟悉可以看看代码哪里有问题
package com.example.fiz.myapplication; import android.graphics.Color; import android.os.Bundle; import android.support.design.widget.FloatingActionButton; import android.support.design.widget.Snackbar; import android.support.v4.app.Fragment; import android.support.v4.view.ViewPager; import android.support.v7.app.AppCompatActivity; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.support.v7.widget.RecyclerView.ViewHolder; import android.support.v7.widget.Toolbar; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.widget.LinearLayout; import android.graphics.Color; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import java.util.ArrayList; import android.support.v7.app.ActionBarActivity; import android.support.v7.app.ActionBar; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentManager; import android.support.v4.app.FragmentPagerAdapter; import android.support.v4.view.ViewPager; import android.view.Menu; import android.view.MenuItem; import android.widget.LinearLayout; import android.support.v7.widget.Toolbar; import android.widget.TextView; import java.util.ArrayList; import java.util.List; public class MainActivity extends AppCompatActivity { private ViewPager mPager; private ArrayListfragmentsList; private LinearLayout ll_top; //首页组件定义 private RecyclerView mRecyclerView; private List mDatas; private HomeAdapter mAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); toolbar.setTitle("demo"); toolbar.setSubtitle("1234"); toolbar.setLogo(R.drawable.ic_launcher); setSupportActionBar(toolbar); initView(); } private void initView() { ll_top = (LinearLayout) findViewById(R.id.ll_top); mPager = (ViewPager) findViewById(R.id.vPager); fragmentsList = new ArrayList (); //首页个recelerView添加数据 // initData(); // mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view); // mRecyclerView.setLayoutManager(new LinearLayoutManager(this)); // mRecyclerView.setAdapter(mAdapter = new HomeAdapter()); // Fragment activityfragment = TestFragment.newInstance("界面一"); Fragment groupFragment = TestFragment.newInstance("界面2"); Fragment friendsFragment = TestFragment.newInstance("界面3"); Fragment chatFragment = TestFragment.newInstance("界面4"); Fragment about = About.about("1234"); Fragment homepage = HomePage.homePage("首页"); fragmentsList.add(homepage);/**首页**/ fragmentsList.add(groupFragment); fragmentsList.add(friendsFragment); fragmentsList.add(chatFragment); mPager.setAdapter(new MyFragmentPagerAdapter( getSupportFragmentManager(), fragmentsList)); mPager.setCurrentItem(0); BottomTabBar navigationBar = new BottomTabBar(this); ll_top.setBackgroundColor(Color.parseColor("#F8F8FF")); navigationBar.attachToParent(ll_top, new String[]{"首页", "消息", "发现", "我"}, mPager); } protected void initData() { mDatas = new ArrayList (); for (int i = 'A'; i < 'z'; i++) { mDatas.add("this is a demo---" + (char) i); } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.menu_main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); //noinspection SimplifiableIfStatement if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } public class MyFragmentPagerAdapter extends FragmentPagerAdapter { private ArrayList fragmentsList; public MyFragmentPagerAdapter(FragmentManager fm) { super(fm); } public MyFragmentPagerAdapter(FragmentManager fm, ArrayList fragments) { super(fm); this.fragmentsList = fragments; } @Override public int getCount() { return fragmentsList.size(); } @Override public Fragment getItem(int arg0) { return fragmentsList.get(arg0); } @Override public int getItemPosition(Object object) { return super.getItemPosition(object); } } class HomeAdapter extends RecyclerView.Adapter { @Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { MyViewHolder holder = new MyViewHolder(LayoutInflater.from( MainActivity.this).inflate(R.layout.item_home, parent, false)); return holder; } @Override public void onBindViewHolder(MyViewHolder holder, int position) { holder.tv.setText(mDatas.get(position)); } @Override public int getItemCount() { return mDatas.size(); } class MyViewHolder extends ViewHolder { TextView tv; public MyViewHolder(View view) { super(view); tv = (TextView) view.findViewById(R.id.id_num); } } } }
@SuppressLint("ValidFragment") public class HomePage extends Fragment { private String textString; //首页组件 public HomePage(String textString) { this.textString = textString; } public static HomePage homePage(String textString) { HomePage myabout = new HomePage(textString); return myabout; } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View view = inflater.inflate(R.layout.home_page, container, false); return view; } }
03-19 23:41:20.809 3818-3818/? E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.fiz.myapplication, PID: 3818 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.fiz.myapplication/com.example.fiz.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference at com.example.fiz.myapplication.MainActivity.initView(MainActivity.java:77) at com.example.fiz.myapplication.MainActivity.onCreate(MainActivity.java:64) at android.app.Activity.performCreate(Activity.java:6237) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
ava.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference at com.example.fiz.myapplication.MainActivity.initView(MainActivity.java:77)
我觉得你需要看懂是哪里错误分析log。这里的错误信息写的很清楚MainActivity.java的77行有一个空指针错误
这句不能注释啊
// mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
我有个RecyclerView使用的Demo,可以看看