Android学习-第26天

今天的任务为实现层级式导航以及可选菜单项：

CrimeLab.java:

package com.bignerdranch.android.criminallntent;

import android.content.Context;

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

public class CrimeLab {
    private static CrimeLab sCrimeLab;
    private List<Crime> mCrimes;

    public static CrimeLab get(Context context){
        if(sCrimeLab==null){
            sCrimeLab=new CrimeLab(context);
        }
        return sCrimeLab;
    }
    private CrimeLab(Context context){
        mCrimes=new ArrayList<>();
    }

    public void addCrime(Crime c){
        mCrimes.add(c);
    }

    public List<Crime> getCrimes(){
        return mCrimes;
    }
    public Crime getCrime(UUID id){
        for(Crime crime : mCrimes){
            if(crime.getId().equals(id)){
                return crime;
            }
        }
        return null;
    }
}

CrimeListFragment.java

package com.bignerdranch.android.criminallntent;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;

import java.util.List;

public class CrimeListFragment extends Fragment {
    private RecyclerView mCrimeRecyclerView;
    private CrimeAdapter mAdapter;

    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_crime_list, container, false);

        mCrimeRecyclerView = (RecyclerView) view.findViewById(R.id.crime_recycler_view);
        mCrimeRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

        updateUI();

        return view;
    }

    @Override
    public void onResume(){
        super.onResume();
        updateUI();
    }

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater){
        super.onCreateOptionsMenu(menu,inflater);
        inflater.inflate(R.menu.fragment_cime_list,menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item){
        switch (item.getItemId()){
            case R.id.new_crime:
            Crime crime=new Crime();
            CrimeLab.get(getActivity()).addCrime(crime);
            Intent intent=CrimePagerActivity.newIntnet(getActivity(),crime.getId());
            startActivity(intent);
            return true;
            case R.id.show_subtitle:
                updateSubtitle();
                return true;
            default:
                return  super.onOptionsItemSelected(item);
        }
    }

    private void updateSubtitle(){
        CrimeLab crimeLab=CrimeLab.get(getActivity());
        int crimeCount=crimeLab.getCrimes().size();
        String subtitle=getString(R.string.subtitle_format,crimeCount);

        AppCompatActivity activity=(AppCompatActivity) getActivity();
        activity.getSupportActionBar().setSubtitle(subtitle);
    }

    private void updateUI() {
        CrimeLab crimeLab=CrimeLab.get(getActivity());
        List<Crime> crimes=crimeLab.getCrimes();

        if(mAdapter==null) {
            mAdapter = new CrimeAdapter(crimes);
            mCrimeRecyclerView.setAdapter(mAdapter);
        }else{
            mAdapter.notifyDataSetChanged();
        }
    }

    private class CrimeHolder extends RecyclerView.ViewHolder implements View.OnClickListener{

        private TextView mTitleTextView;
        private TextView mDateTextView;
        private Crime mCrime;

        public CrimeHolder(LayoutInflater inflater,ViewGroup parent) {
            super(inflater.inflate(R.layout.list_item_crime,parent,false));
            itemView.setOnClickListener(this);

            mTitleTextView=(TextView)itemView.findViewById(R.id.crime_title);
            mDateTextView=(TextView)itemView.findViewById(R.id.crime_date);
        }

        public void bind(Crime crime){
            mCrime=crime;
            mTitleTextView.setText(mCrime.getTitle());
            mDateTextView.setText((mCrime.getDate().toString()));
        }

        @Override
        public void onClick(View view) {
            //Intent intent=new Intent(getActivity(),CrimeActivity.class);
            //Intent intent=CrimeActivity.newIntent(getActivity(),mCrime.getId());
            Intent intent=CrimePagerActivity.newIntnet(getActivity(),mCrime.getId());
            startActivity(intent);
        }
    }

    private class CrimeAdapter extends RecyclerView.Adapter<CrimeHolder>{
        private List<Crime> mCrimes;
        public CrimeAdapter(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();
        }
    }
}

fragment_crime_list.xml:

<?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>

截图如下：