Android 定制万能Adapter

Android 定制万能Adapter

• 不使用万能Adapter的开发流程
• • 开发步骤为：
  • • Animal.java
    • AnimalAdapter.java
    • MainActivity.java
• 使用万能Adapter
• • • ViewHolder
    • CommenAdapter

不使用万能Adapter的开发流程

例如需要添加一个ListView控件，在这个控件中存在图片和文本框布局

开发步骤为：

• 1、编写ListView中每一个子项的布局文件list_view_item.xml
• 2、编写一个实体类Animal.java
• 3、编写一个Adapter继承BaseAdapter
• 4、编写MainAcitivity.java

Animal.java

public class Animal {
    private String aName;
    private String aSpeak;
    private int aIcon;

    public Animal() {
    }

    public Animal(String aName, String aSpeak, int aIcon) {
        this.aName = aName;
        this.aSpeak = aSpeak;
        this.aIcon = aIcon;
    }

    public String getaName() {
        return aName;
    }

    public String getaSpeak() {
        return aSpeak;
    }

    public int getaIcon() {
        return aIcon;
    }

    public void setaName(String aName) {
        this.aName = aName;
    }

    public void setaSpeak(String aSpeak) {
        this.aSpeak = aSpeak;
    }

    public void setaIcon(int aIcon) {
        this.aIcon = aIcon;
    }
}

AnimalAdapter.java

public class AnimalAdapter extends BaseAdapter {

    private LinkedList<Animal> mData;
    private Context mContext;

    public AnimalAdapter(LinkedList<Animal> mData, Context mContext) {
        this.mData = mData;
        this.mContext = mContext;
    }

    @Override
    public int getCount() {
        return mData.size();
    }

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

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

    @Override
	public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder = null;
    if(convertView == null){
        convertView = LayoutInflater.from(mContext).
        inflate(R.layout.item_list_animal,parent,false);
        holder = new ViewHolder();
        holder.img_icon = (ImageView) convertView.findViewById(R.id.img_icon);
        holder.txt_aName = (TextView) convertView.findViewById(R.id.txt_aName);
        holder.txt_aSpeak = (TextView) convertView.findViewById(R.id.txt_aSpeak);
        convertView.setTag(holder);   //将Holder存储到convertView中
    }else{
        holder = (ViewHolder) convertView.getTag();
    }
    holder.img_icon.setBackgroundResource(mData.get(position).getaIcon());
    holder.txt_aName.setText(mData.get(position).getaName());
    holder.txt_aSpeak.setText(mData.get(position).getaSpeak());
    return convertView;
}

static class ViewHolder{
    ImageView img_icon;
    TextView txt_aName;
    TextView txt_aSpeak;
	}
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private List<Animal> mData = null;
    private Context mContext;
    private AnimalAdapter mAdapter = null;
    private ListView list_animal;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = MainActivity.this;
        list_animal = (ListView) findViewById(R.id.list_animal);
        mData = new LinkedList<Animal>();
        mData.add(new Animal("狗说", "你是狗么?", R.mipmap.ic_icon_dog));
        mData.add(new Animal("牛说", "你是牛么?", R.mipmap.ic_icon_cow));
        mData.add(new Animal("鸭说", "你是鸭么?", R.mipmap.ic_icon_duck));
        mData.add(new Animal("鱼说", "你是鱼么?", R.mipmap.ic_icon_fish));
        mData.add(new Animal("马说", "你是马么?", R.mipmap.ic_icon_horse));
        mAdapter = new AnimalAdapter((LinkedList<Animal>) mData, mContext);
        list_animal.setAdapter(mAdapter);
    }
}

---

这样就意味着如果项目需要20个ListView那么每个ListView需要重新编写实体类和各自的Adapter代码量巨大,因此可以将上述代码进行优化并提取，从而减少代码量。

使用万能Adapter

• 首先新建一个ViewHolder类对以下代码进行提取

 @Override
	public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder = null;
    if(convertView == null){
        convertView = LayoutInflater.from(mContext).
        inflate(R.layout.item_list_animal,parent,false);
        holder = new ViewHolder();
        holder.img_icon = (ImageView) convertView.findViewById(R.id.img_icon);
        holder.txt_aName = (TextView) convertView.findViewById(R.id.txt_aName);
        holder.txt_aSpeak = (TextView) convertView.findViewById(R.id.txt_aSpeak);
        convertView.setTag(holder);   //将Holder存储到convertView中
    }else{
        holder = (ViewHolder) convertView.getTag();
    }
    holder.img_icon.setBackgroundResource(mData.get(position).getaIcon());
    holder.txt_aName.setText(mData.get(position).getaName());
    holder.txt_aSpeak.setText(mData.get(position).getaSpeak());
    return convertView;
}

static class ViewHolder{
    ImageView img_icon;
    TextView txt_aName;
    TextView txt_aSpeak;
	}

从上面代码可以看出ViewHolder需要做两件事：

• 1、绑定控件
• 2、设置控件状态

ViewHolder

public class ViewHolder {
    private SparseArray<View> mViews;
    private int mPosition;
    private View mConvertView;

    public ViewHolder(Context context, ViewGroup parent,int layoutId,int position){
        this.mPosition = position;
        this.mViews = new SparseArray<View>();
        mConvertView = LayoutInflater.from(context).inflate(layoutId,parent,false);
        mConvertView.setTag(this);
    }

    public <T extends View> T getView(int viewId){
        View view = mViews.get(viewId);
        if (view == null){
            view = mConvertView.findViewById(viewId);
            mViews.put(viewId,view);
        }
        return (T)view;
    }

    public static ViewHolder get(Context context,View convertView,
                                 ViewGroup parent,int layoutId ,int position){
        if (convertView == null){
            return new ViewHolder(context,parent,layoutId,position);
        }else{
            ViewHolder holder = (ViewHolder) convertView.getTag();
            holder.mPosition = position;
            return holder;
        }
    }

    public View getmConvertView() {
        return mConvertView;
    }

    public ViewHolder setText(int viewId,String s){
        TextView textView = getView(viewId);
        textView.setText(s);
        return this;
    }
}

2、新建一个CommenAdapter对AnimalAdapter中其余的方法进行优化

CommenAdapter

public abstract class CommonAdapter<T> extends BaseAdapter {

    protected Context mContext;
    protected List<T> mDatas;
    protected LayoutInflater mInflater;
    protected int LayoutId;

    public CommonAdapter(Context context, List<T>datas,int layoutId){
        this.mContext = context;
        mInflater = LayoutInflater.from(context);
        this.mDatas =datas;
        this.LayoutId = layoutId;

    }


    @Override
    public int getCount() {
        return mDatas.size();
    }

    @Override
    public T getItem(int position) {
        return mDatas.get(position);
    }

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

    @Override
    public  View getView(int i, View view, ViewGroup viewGroup){
        ViewHolder holder = ViewHolder.get(mContext,view,viewGroup,LayoutId,i);
        convert(holder,getItem(i));
        return holder.getmConvertView();
    }

    public abstract void convert(ViewHolder holder,T t);
}