Android中Listview和RecycleView基本用法（優化寫法及多種條目展示效果）

介紹

在Android開發中Listview算是經常用的控件了，而對於他的升級產物RecycleView，就更加流行在我們的開發中，下面給出這兩控件的優化代碼的書寫方式，從而防止OOM，廢話不多說，下面的代碼：

對於ListView的Adapter裏實現方式如下：

class MyListViewAdapter extends BaseAdapter {

    private final Context context;
    private final ArrayList<ContactInfo> minfos;

    public MyListViewAdapter(Context context, ArrayList<ContactInfo> minfos) {
        this.context = context;
        this.minfos = minfos;
    }

    @Override
    public int getCount() {
        return minfos == null ? 0 : minfos.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view;
        ViewHolder holder;
        if (convertView==null) {
            convertView=View.inflate(context, R.layout.item, null);
            //當創建新的view 的時候  創建viewholder
            holder = new ViewHolder();
            //把viewholder 中view 賦值
            holder.tv_name=(TextView) convertView.findViewById(R.id.tv_name);
            holder.tv_phone=(TextView) convertView.findViewById(R.id.tv_phone);
            holder.tv_email=(TextView) convertView.findViewById(R.id.tv_email);
            //把viewholder 放到 convertView
            convertView.setTag(holder);
        }else{
            //複用的時候拿出 view 中viewholder
            holder=(ViewHolder) convertView.getTag();
        }
        //把findview 幹掉
        holder.tv_name.setText(minfos.get(position).getName());
        holder.tv_phone.setText(minfos.get(position).getPhone());
        holder.tv_email.setText(minfos.get(position).getEmail());

        return convertView;
    }
    private class ViewHolder{
        public TextView tv_name;
        public TextView tv_phone;
        public TextView tv_email;

    }
}

還有一種高度的抽取方式，代碼如下：

public abstract class CommAdapter<T> extends BaseAdapter {
    protected Context context;
    protected ArrayList<T> mData = null;

    public CommAdapter(ArrayList<T> mData, Context context) {
        this.mData = mData;
        this.context = context;
    }

    @Override
    public int getCount() {
        return mData == null ? 0 : mData.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    //讓子類具體實現
  /*  @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        return null;
    }*/
}

子類Adapter如下：

public class MyAdapter extends CommAdapter<ContactInfo>{

    public MyAdapter(ArrayList<ContactInfo> mData, Context context) {
        super(mData,context);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder=new ViewHolder(context,R.layout.item);
        TextView tv_email = holder.getView(R.id.tv_email);
        TextView tv_name = holder.getView(R.id.tv_name);
        TextView tv_phone = holder.getView(R.id.tv_phone);
        tv_email.setText(mData.get(position).getEmail());
        tv_name.setText(mData.get(position).getName());
        tv_phone.setText(mData.get(position).getPhone());
        return holder.getConvertView();
    }
}

ViewHolder代碼如下：

public class ViewHolder {
    SparseArray<View> mViews = null;
    private View mconvertView;
    public ViewHolder(Context context, int layoutID) {
        mViews = new SparseArray<>();
        mconvertView = View.inflate(context, layoutID, null);
        mconvertView.setTag(this);
    }
    public ViewHolder getViewHolder(Context context,View convertView,int layoutID){
        if (convertView==null) {
            return  new ViewHolder(context, layoutID);
        }
        return ((ViewHolder) mconvertView.getTag());
    }
    public View getConvertView() {
        return mconvertView;
    }
    public <T extends View> T getView(int viewId){
        View mView = mViews.get(viewId);
        if (mView==null){
            mView = mconvertView.findViewById(viewId);
            mViews.put(viewId,mView);
        }
        return (T)mView;
    }
}

對於RecycleView的Adapter裏實現方式如下：

class MyRecyclerViewAdapter extends RecyclerView.Adapter {
    private final Context context;
    private final ArrayList<ContactInfo> minfos;

    public MyRecyclerViewAdapter(Context context, ArrayList<ContactInfo> minfos) {
        this.context = context;
        this.minfos = minfos;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new MyRecyclerViewHolder(View.inflate(context, R.layout.item, null));
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        MyRecyclerViewHolder viewHolder = (MyRecyclerViewHolder) holder;
        viewHolder.bindData(minfos.get(position));
    }

    @Override
    public int getItemCount() {
        return minfos==null?0:minfos.size();
    }

    private class MyRecyclerViewHolder extends RecyclerView.ViewHolder {
        private final TextView tv_name;
        private final TextView tv_phone;
        private final TextView tv_email;

        public MyRecyclerViewHolder(View view) {
            super(view);
            tv_name=(TextView) view.findViewById(R.id.tv_name);
            tv_phone=(TextView) view.findViewById(R.id.tv_phone);
            tv_email=(TextView) view.findViewById(R.id.tv_email);
        }
        public void bindData(ContactInfo contactInfo){
            tv_email.setText(contactInfo.getEmail());
            tv_name.setText(contactInfo.getName());
            tv_phone.setText(contactInfo.getPhone());
        }

    }
}

注意在設置RecycleView的Adapter之前需要設置 setLayoutManager

• 有如下可設置的佈局管理

RecyclerView.LayoutManager吧，這是一個抽象類，好在系統提供了3個實現類：
LinearLayoutManager 線性管理器，支持橫向、縱向。 支持反轉
GridLayoutManager 網格佈局管理器 支持反轉
StaggeredGridLayoutManager 瀑布就式佈局管理器

那麼如何實現RecycleView 多種條目展示尼？下面介紹下：

1.創建不同的item佈局文件
2.爲每個類型的item創建數據bean類（主要是每一種條目對應的數據類型及其set get 方法）
3.創建通用的item數據bean類

public class RecycleViewItemData<T> {
    //用來裝載不同類型的item數據bean
    T t;
    //item數據bean的類型
    int dataType;
    public RecycleViewItemData () {
    }

    public RecycleViewItemData (T t, int dataType) {
        this.t = t;
        this.dataType = dataType;
    }

    public T getT () {
        return t;
    }

    public void setT (T t) {
        this.t = t;
    }

    public int getDataType () {
        return dataType;
    }

    public void setDataType (int dataType) {
        this.dataType = dataType;
    }
}

4.爲每個類型的item創建viewholder

public class EditViewHolder extends RecyclerView.ViewHolder {
       public TextView mTextView1;
       public TextView mTextView2;
       public EditText mEditText1;
       public EditText mEditText2;

       public EditViewHolder(View itemView) {
           super(itemView);
           mTextView1 = (TextView) itemView.findViewById(R.id.text1);
           mTextView2 = (TextView) itemView.findViewById(R.id.text2);
           mEditText1 = (EditText) itemView.findViewById(R.id.editText1);
           mEditText2 = (EditText) itemView.findViewById(R.id.editText2);
       }
   }

5.創建Adapter類

• 構造方法：一般用於接收數據集
• onCreateViewHolder: 創建ViewHolder，該方法會在RecyclerView需要展示一個item的時候回調。重寫該方法時，應該使ViewHolder加載item view的佈局。
• onBindeViewHolder: 該方法在RecyclerView在特定位置展示數據時候回調。把數據綁定、填充到相應的item view中。
• getItemCount :返回數據的數量。
• getItemViewType(int position) 注：需要時重寫,從這個方法中所返回的值會在onCreateViewHolder中用到。比如頭部，尾部，等等的特殊itemView（這裏說成ViewHolder比較好）都可以在這裏進行判斷。

public class Madapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private static final int TYPE_EDIT = 0;//編輯框
    private static final int TYPE_BUTTON = 1;//按鈕
    private static final int TYPE_SPINNER = 2;//下拉列表
    private ArrayList<RecycleViewItemData> dataList;//數據集合

    public Madapter(ArrayList<RecycleViewItemData> dataList) {
        this.dataList = dataList;
    }

    //用來創建ViewHolder
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        //如果viewType是編輯框類型,則創建EditViewHolder型viewholder
        if (viewType == TYPE_EDIT) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_creditcard_edit, parent, false);
            EditViewHolder viewHolder = new EditViewHolder(view);
            return viewHolder;
        }
        //如果viewType是按鈕類型,則創建ButtonViewHolder型viewholder
        if (viewType == TYPE_BUTTON) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_creditcard_button, parent, false);
            ButtonViewHolder viewHolder = new ButtonViewHolder(view);
            return viewHolder;
        }
        //如果viewType是下拉列表類型,則創建SpinnerHolder型viewholder
        if (viewType == TYPE_SPINNER) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_creditcard_spinner, parent, false);
            SpinnerHolder viewHolder = new SpinnerHolder(view);
            return viewHolder;
        }
        return null;
    }

    //用來綁定數據
    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        //如果holder是EditViewHolder的實例
        if (holder instanceof EditViewHolder) {
            //得到對應position的數據集
            EditItem mEditItem = (EditItem) dataList.get(position).getT();
            if (position == 0) {
                ((EditViewHolder) holder).mTextView1.setText("* Holder Name");
                ((EditViewHolder) holder).mTextView2.setText("* Card Number");
            } else if (position == 3) {
                ((EditViewHolder) holder).mTextView1.setText("          * Street ");
                ((EditViewHolder) holder).mTextView2.setText("           * City  ");
            } else if (position == 5) {
                ((EditViewHolder) holder).mTextView1.setText("                   Or ");
                ((EditViewHolder) holder).mTextView2.setText("           * Zipcode  ");
            }
            ((EditViewHolder) holder).mEditText1.setText(mEditItem.getText1());
            ((EditViewHolder) holder).mEditText2.setText(mEditItem.getText2());

        }
        //如果holder是ButtonViewHolder的實例
        if (holder instanceof ButtonViewHolder) {
            //從數據集合中取出該項
            ButtonItem mButtonItem = (ButtonItem) dataList.get(position).getT();
            //設置選中的按鈕
            switch (mButtonItem.getPosition()) {
                case 0:
                    ((ButtonViewHolder) holder).mRadioButton.setChecked(true);
                    break;
                case 1:
                    ((ButtonViewHolder) holder).mRadioButton2.setChecked(true);
                    break;
                case 2:
                    ((ButtonViewHolder) holder).mRadioButton3.setChecked(true);
                    break;
            }
        }
        //如果holder是SpinnerHolder的實例
        if (holder instanceof SpinnerHolder) {
        }
    }

    @Override
    public int getItemViewType(int position) {
        if (0 == dataList.get(position).getDataType()) {
            return TYPE_EDIT;// 編輯框
        } else if (1 == dataList.get(position).getDataType()) {
            return TYPE_BUTTON;// 按鈕
        } else if (2 == dataList.get(position).getDataType()) {
            return TYPE_SPINNER;//下拉列表
        } else {
            return 0;
        }
    }

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