极客观点
项目管理
HarmonyOS
做了一个demo就是下面是菜单，上面的toobar在调试过称出现空指针，
03-18 07:35:50.567 1908-1908/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.fiz.bottomtabbar, PID: 1908
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.fiz.bottomtabbar/com.example.fiz.bottomtabbar.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.Toolbar.setTitle(java.lang.CharSequence)' 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.Toolbar.setTitle(java.lang.CharSequence)' on a null object reference
at com.example.fiz.bottomtabbar.MainActivity.onCreate(MainActivity.java:31)
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) 想问问怎么修改代码，新手不会了？这***
package com.example.fiz.bottomtabbar;
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;
public class MainActivity extends AppCompatActivity {
private ViewPager mPager;
private ArrayList<Fragment> fragmentsList;
private LinearLayout ll_top;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
toolbar.setTitle("demo");
setSupportActionBar(toolbar);
setContentView(R.layout.activity_main);// initView();
}
private void initView() {
ll_top = (LinearLayout) findViewById(R.id.ll_top);
mPager = (ViewPager) findViewById(R.id.vPager);
fragmentsList = new ArrayList<Fragment>();
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("1234");
fragmentsList.add(activityfragment);/**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);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public class MyFragmentPagerAdapter extends FragmentPagerAdapter {
private ArrayList<Fragment> fragmentsList;
public MyFragmentPagerAdapter(FragmentManager fm) {
super(fm);
}
public MyFragmentPagerAdapter(FragmentManager fm,
ArrayList<Fragment> 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);
}
}
}
android
java
换下顺序：