《Android程式設計權威指南（第三版）》第八章挑戰練習Demo

第8章的直接就說RecyclerView，書本說的很詳細就不闡述了，這次代碼應該做注釋的我都做了，廢話少說，先發一張效果動态圖：

貼代碼，先是建立布局，其實就是加了一個按鈕：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="8dp">

    <TextView
        android:id="@+id/crime_title_police"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Crime Title"/>

    <TextView
        android:id="@+id/crime_date_police"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Crime Date"/>

    <Button
        android:id="@+id/connect_police"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Connect"
        android:textAllCaps="false"/>

</LinearLayout>
           

更改Crime類：

public class Crime {

    private UUID mId;
    private String mTitle;
    private Date mDate;
    private boolean mSolved;
    //是否聯系警察
    private boolean mRequiresPolice;

    public Crime() {
        mId = UUID.randomUUID();
        mDate = new Date();
    }
           

更改CrimeLab的構造方法：

private CrimeLab(Context context) {
        mCrimes = new ArrayList<>();
        for (int i = 0; i < 100; i++) {
            Crime crime = new Crime();
            crime.setTitle("Crime #" + i);
            crime.setSolved(i % 2 == 0);
            //定義item序号為3或7的倍數時就是聯系警察
            crime.setRequiresPolice(i % 3 == 0 || i % 7 == 0);
            mCrimes.add(crime);
        }
    }
           

最重要的的擴充卡代碼和Holader：

/**
     * 建立一個專門給警察Police的Holder，其實和CrimeHolder差不多
     */
    private class CrimePoliceHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        private TextView mTitleTextView;
        private TextView mDateTextView;
        private Button mConnect;
        private Crime mCrime;

        private CrimePoliceHolder(LayoutInflater inflater, ViewGroup parent) {
            super(inflater.inflate(R.layout.list_item_crime_police, parent, false));

            mTitleTextView = (TextView) itemView.findViewById(R.id.crime_title_police);
            mDateTextView = (TextView) itemView.findViewById(R.id.crime_date_police);
            mConnect = (Button) itemView.findViewById(R.id.connect_police);
            mConnect.setOnClickListener(this);
        }

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

        public void onClick(View view) {
            Toast.makeText(getActivity(), "已聯系警察", Toast.LENGTH_SHORT).show();
        }
    }

    private class CrimeAdapter extends RecyclerView.Adapter {
        private List<Crime> mCrimes;

        public CrimeAdapter(List<Crime> crimes) {
            mCrimes = crimes;
        }

        /**
         * 這裡最重要，擷取目前item是否需要聯系警察
         */
        @Override
        public int getItemViewType(int position) {
            int flag = 0;
            if (mCrimes.get(position).isRequiresPolice()){
                flag = 1;
            }
            return flag;
        }

        /**
         * getItemViewType的傳回值傳回到這裡的viewType裡面，通過判斷viewType的值判斷添加什麼布局
         */
        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
            if (viewType == 0) {
                return new CrimeHolder(layoutInflater, parent);
            } else {
                return new CrimePoliceHolder(layoutInflater, parent);
            }
        }

        /**
         * 這裡就是直接添加控件的标題，功能等
         */
        @Override
        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
            if (holder instanceof CrimeHolder) {
                Crime crime = mCrimes.get(position);
                ((CrimeHolder) holder).bind(crime);
            } else if (holder instanceof CrimePoliceHolder){
                Crime crime = mCrimes.get(position);
                ((CrimePoliceHolder) holder).bind(crime);
            }
        }

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

這次的挑戰練習主要是學會判斷recyclerview的item判斷，類似于recyclerview嵌套，關于recyclerview嵌套我有寫過相關的部落格，大家可以點選這裡檢視，本次挑戰練習的Demo代碼。