无法在AppCompatActivity中解析findViewByID

我正在学习本教程:使用标签的Android Material Design

相关信息:

Android API等级21

依赖性被添加到graddle文件编译'com.android.support:appcompat-v7:23.0.1'并编译'com.android.support:design:23.0.1'}

无法解析方法"findViewById".我试着按照这个答案无法在Fragment中解析方法'findViewById(int)',但是这个AppCompatActivity使用OnCreateBundle代替OnCreateView,那么我无法获取View对象...

这段代码有什么问题？我错过了一些进口？

    package info.androidhive.materialtabs.activity;

import android.os.Bundle;
import android.support.design.widget.TabLayout;
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.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

import java.util.ArrayList;
import java.util.List;

import info.androidhive.materialtabs.R;
import info.androidhive.materialtabs.fragments.OneFragment;
import info.androidhive.materialtabs.fragments.ThreeFragment;
import info.androidhive.materialtabs.fragments.TwoFragment;

public class MainActivity extends AppCompatActivity {

    private Toolbar toolbar;
    private TabLayout tabLayout;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        viewPager = (ViewPager) findViewById(R.id.viewpager);
        setupViewPager(viewPager);

        tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(viewPager);
    }

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFragment(new OneFragment(), "ONE");
        adapter.addFragment(new TwoFragment(), "TWO");
        adapter.addFragment(new ThreeFragment(), "THREE");
        viewPager.setAdapter(adapter);
    }

    class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List mFragmentList = new ArrayList<>();
        private final List mFragmentTitleList = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        public void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }
}

这是Android Studio显示的"错误",但我在logevent窗口中获得了0个错误

您似乎遇到了Android Studio中的损坏缓存错误.

在使用自定义命名空间添加自定义视图时,这种情况发生了很多.如果您添加了任何自定义视图,则可能是您的问题.

要修复:文件>使高速缓存/重新启动无效

这应该重新索引所有内容并允许自动完成工作,同样,findViewById()应该工作.我查看了代码,没有看到任何错误.