android-RecyclerView.md

在fragment中使用RecyclerView

• 首先是添加依赖

• 然后在布局文件中创建出只有一个RecyclerView的fragment布局，用于给fragment设置布局（不是item的布局！）

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/crime_recycler_view">
</android.support.v7.widget.RecyclerView>

• 新建一个ViewHolder类，用来管理每个item的布局（在后面Adapter中也会用到）,主要是修改它的构造方法和内部变量,以便后面绑定数据

public class CrimeHolder extends RecyclerView.ViewHolder {
       private TextView mTitleTextView;
       private TextView mDateTextView;
       private CheckBox mSolvedCheckBox;
       private Crime mCrime;

       public CrimeHolder(View itemView) {
           super(itemView);
           mTitleTextView = (TextView) itemView.findViewById(R.id.list_item_crime_title_text_view);
           mDateTextView = (TextView) itemView.findViewById(R.id.list_item_crime_date_text_view);
           mSolvedCheckBox = (CheckBox) itemView.findViewById(R.id.list_item_crime_solved_check_box);
       }

       //注意这样可以加快速度，并且保持代码封装性
       public void bindCrime(Crime crime){
           mCrime = crime ;
           mTitleTextView.setText(mCrime.getTitle());
           mDateTextView.setText(mCrime.getDate()+"");
           mSolvedCheckBox.setChecked(mCrime.isSolved());
       }
   }

• 新建一个Adapter类，继承自RecyclerView.Adapter<一个ViewHolder对象>

• 类中有三个抽象方法需要实现

①onCreateViewHolder-----用来获取每个list的view，并用该view创建一个ViewHolder对象

@Override
       public CrimeHolder onCreateViewHolder(ViewGroup parent, int viewType) {
           LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
           View view = layoutInflater.inflate(android.R.layout.simple_list_item_1, parent, false);
           return new CrimeHolder(view);
       }

②onBindViewHolder----用来“绑定”数据，也就是填充数据

@Override
        public void onBindViewHolder(CrimeHolder holder, int position) {
            Crime crime = mCrimes.get(position);
            holder.mTitleTextView.setText(crime.getTitle());
        }

③getItemCount----用来得到List大小

@Override
       public int getItemCount() {
           return mCrimes.size();
       }

• 整体代码为

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());
            View view = layoutInflater.inflate(android.R.layout.simple_list_item_1, parent, false);
            return new CrimeHolder(view);
        }

        @Override
        public void onBindViewHolder(CrimeHolder holder, int position) {
            Crime crime = mCrimes.get(position);
             holder.bindCrime(crime);//这里直接调用holder中实现的方法，省时、简单
        }

        @Override
        public int getItemCount() {
            return mCrimes.size();
        }
    }

• Adapter类创建好后，需要在fragment中实例化它，并且将fragment中的RecyclerView与Adater绑定

private RecyclerView mCrimeRecyclerView;
    private CrimeAdapter mAdapter;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable 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;
    }

    private void updateUI(){
        CrimeLab crimeLab = CrimeLab.get(getActivity());   //得到List中的对象的实例化
        List<Crime>crimes = crimeLab.getCrimes();   //得到List
        mAdapter=new CrimeAdapter(crimes);  //实例化Adapter
        mCrimeRecyclerView.setAdapter(mAdapter); //将RecyclerView和Adapter绑定
    }