Android Criminal实例--（6）工具栏菜单项的使用

梦里梦外; 2022-05-18 07:25 129阅读 0赞

##### 菜单栏符号的选择 #####

Android studio中自带有很多菜单符号，选中drawable  
![这里写图片描述][70]  
![这里写图片描述][70 1]  
就可以随便选择需要的符号

##### 代码实现 #####

public class CrimeListFragment extends Fragment { 
    
        public static final String SUBTITLE = "subtitle";
        private RecyclerView mRecyclerView;
        private CrimeAdpater mCrimeAdpater;
    
    
        private boolean mSubtitleVisible;
    
    
        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
    
            //接受菜单选项回调
            setHasOptionsMenu(true);
        }
    
        @Nullable
        @Override
        public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
            View view=inflater.inflate(R.layout.crime_list_fragment,container,false);
    
            if(savedInstanceState!=null){
               mSubtitleVisible=savedInstanceState.getBoolean(SUBTITLE);
            }
    
            mRecyclerView=(RecyclerView)view.findViewById(R.id.crime_recycler);
            mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    
            updateUI();
            return view;
        }
    
        private class CrimeHolder extends RecyclerView.ViewHolder implements View.OnClickListener{ 
    
            private TextView list_title;
            private TextView list_date;
    
            Crime mCrime;
            public void bind(Crime crime){
                mCrime=crime;
                list_title.setText(crime.getTitle());
                list_date.setText(crime.getDate().toString());
            }
    
            public CrimeHolder(LayoutInflater inflater,ViewGroup parent){
                super(inflater.inflate(R.layout.crime_list_item,parent,false));
    
                list_title=(TextView)itemView.findViewById(R.id.list_title);
                list_date=(TextView)itemView.findViewById(R.id.list_date);
    
                itemView.setOnClickListener(this);
            }
    
    
    
            @Override
            public void onClick(View v) {
               // Toast.makeText(getActivity(), mCrime.getTitle()+"click!", Toast.LENGTH_SHORT).show();
               // Intent intent= new Intent(getActivity(),CrimeActivity.class);
               // Intent intent=CrimeActivity.newIntent(getActivity(),mCrime.getId());
                Intent intent= CrimePagerActivity.newIntent(getActivity(),mCrime.getId());
    
                startActivity(intent);
            }
        }
    
    
        private class CrimeAdpater extends RecyclerView.Adapter<CrimeHolder>{ 
    
            private List<Crime> mCrimes;
    
            public CrimeAdpater(List<Crime> crimes){
                mCrimes=crimes;
            }
    
            @Override
            public CrimeHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                LayoutInflater layoutInflater=LayoutInflater.from(getActivity());
                return new CrimeHolder(layoutInflater,parent);
            }
    
            @Override
            public void onBindViewHolder(CrimeHolder holder, int position) {
    
                Crime crime=mCrimes.get(position);
                holder.bind(crime);
            }
    
            @Override
            public int getItemCount() {
                return mCrimes.size();
            }
        }
    
        @Override
        public void onResume() {
            super.onResume();
            updateUI();
        }
    
        private void updateUI(){
    
            CrimeLab crimeLab=CrimeLab.getCrimeLab(getActivity());
            List<Crime> crimes=crimeLab.getCrimes();
    
    // mCrimeAdpater=new CrimeAdpater(crimes);
    // mRecyclerView.setAdapter(mCrimeAdpater);
            if(mCrimeAdpater==null){
                mCrimeAdpater=new CrimeAdpater(crimes);
                mRecyclerView.setAdapter(mCrimeAdpater);
            }else{
                mCrimeAdpater.notifyDataSetChanged();
            }
    
            updateSubtitle();
        }
    
    
    //创建菜单，传入菜单资源
        @Override
        public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
            super.onCreateOptionsMenu(menu, inflater);
            inflater.inflate(R.menu.fragment_crime_list,menu);
    
            MenuItem subtitleItem=menu.findItem(R.id.show_subtitle);
            if(mSubtitleVisible){
                subtitleItem.setTitle("show");
            }else{
                subtitleItem.setTitle("hide");
            }
        }
    
    
        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            switch (item.getItemId()){
                case R.id.new_crime:
                    Crime crime=new Crime();
                    CrimeLab.getCrimeLab(getActivity()).addCrime(crime);
                    Intent intent=CrimePagerActivity.newIntent(getActivity(),crime.getId());
                    startActivity(intent);
                    return true;
                case R.id.show_subtitle:
                    mSubtitleVisible=!mSubtitleVisible;
                    getActivity().invalidateOptionsMenu();
                    updateSubtitle();
                    return  true;
                    default:
                        return super.onOptionsItemSelected(item);
            }
        }
    
    //显示有多少条项目
        public void updateSubtitle(){
            CrimeLab crimeLab=CrimeLab.getCrimeLab(getActivity());
            int crimeCount=crimeLab.getCrimes().size();
            String subtitle=getString(R.string.subtitle_format,crimeCount);
    
            if(!mSubtitleVisible){
                subtitle=null;
            }
    
            AppCompatActivity activity=(AppCompatActivity)getActivity();
            activity.getSupportActionBar().setSubtitle(subtitle);
        }
    //屏幕旋转时数据丢失，通过bundle保存，再在onCreateView方法中获取
        @Override
        public void onSaveInstanceState(Bundle outState) {
            super.onSaveInstanceState(outState);
            outState.putBoolean(SUBTITLE,mSubtitleVisible);
        }
    }

##### 创建menu文件 #####

选中res

![这里写图片描述][70 2]

![这里写图片描述][70 3]  
最后自动会生成menu的文件夹及其xml文件

代码：

<?xml version="1.0" encoding="utf-8"?>
    <menu xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto">
    
        <item android:id="@+id/new_crime" android:icon="@drawable/ic_menu_add" android:title="@string/new_crime" app:showAsAction="ifRoom|withText"/>
    
        <item android:id="@+id/show_subtitle" android:title="@string/show_subtitle" app:showAsAction="ifRoom"/>
    </menu>

**app:showAsAction=”ifRoom|withText”**：  
意思是只要空间足够，菜单栏图标及文字描述都会显示在工具栏上，如果空间仅够显示图标，文字描述就不会显示，或是仅够显示文字描述，图标不会显示  
ifroom：让操作系统决定如何显示菜单栏

[70]: /images/20220518/0fb0aedb22b540b9b35c1fc4867aac6c.png
[70 1]: /images/20220518/48a2bab81cb44545902ad0626e1f7d4c.png
[70 2]: /images/20220518/e47d8e2e9fa14bd4bd1a2e73c8a5cee1.png
[70 3]: /images/20220518/7211c0c1843242d9973994a1cad49184.png