Android编程入门-第13天

这周由于忙着嵌入式开发，没时间学Android，今天抽空学习了一下RecyclerView部分。

① RecyclerView封装了viewholder的回收复用，编写Adapter面向的是ViewHolder，复用的逻辑被封装，写起来更加简单。

② 提供了一种插拔式的体验，高度的解耦，异常的灵活，针对一个Item的显示RecyclerView专门抽取出了相应的类，来控制Item的显示，使其的扩展性非常强。

以下是部分练习代码（不包含以前未改动的部分）：

CrimeFragment.java

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;

import static android.widget.CompoundButton.*;

public class CrimeFragment extends Fragment {

    private Crime mCrime;
    private EditText mTitleField;
    private Button mDateButton;
    private CheckBox mSolvedCheckbox;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mCrime = new Crime();
    }

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

        mTitleField = (EditText) v.findViewById(R.id.crime_title);
        mTitleField.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                mCrime.setTitle(s.toString());
            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });

        mDateButton = (Button) v.findViewById(R.id.crime_date);
        mDateButton.setText(mCrime.getDate().toString());
        mDateButton.setEnabled(false);

        mSolvedCheckbox = (CheckBox) v.findViewById(R.id.crime_solved);
        mSolvedCheckbox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, 
                    boolean isChecked) {
                mCrime.setSolved(isChecked);
            }
        });

        return v;
    }
}

CrimeListFragment.java

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

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

    @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;
    }

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

        mAdapter = new CrimeAdapter(crimes);
        mCrimeRecyclerView.setAdapter(mAdapter);
    }

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

        private Crime mCrime;

        private TextView mTitleTextView;
        private TextView mDateTextView;

        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) {
            Toast.makeText(getActivity(),
                    mCrime.getTitle() + " clicked!", Toast.LENGTH_SHORT)
                    .show();
        }
    }

    private class CrimeAdapter extends RecyclerView.Adapter {

        private List mCrimes;

        public CrimeAdapter(List 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();
        }
    }
}