实现原理是这样的，每次在setData中都要查找控件，然后setXXX（）什么的，我们可以把这写实现放如到ViewHolder中去，在ViewHolder中写入一个链式的方法，来帮助我们来实现功能，链式方法如下：
public ViewHolder setText(int viewId, String data){ TextView tv = getView(viewId); tv.setText(data); return this; }
通过这个方法，我们可以很好的去设置对应的内容，只需要传一个需要设置控件的id，然后传对应的数据，就可以达到设置文字的效果了，下面再看看我们的MyAdapter.java中的代码
MyAdapter.java
/*** 之前MyAdapter*/public class MyAdapter extends MyBaseAdapter { public MyAdapter(List data) { super(data); } @Override public void setData(ViewHolder holder, Student t) { TextView tvName = holder.getView(R.id.mTv1); tvName.setText(t.getName()); TextView tvSex = holder.getView(R.id.mTv2); tvSex.setText(t.getSex()); }}/*** 优化后的MyAdapter*/public class MyAdapter extends MyBaseAdapter { public MyAdapter(List data) { super(data); } @Override public void setData(ViewHolder holder, Student t) { holder.setText(R.id.mTv1, t.getName()).setText(R.id.mTv2, t.getSex()); }}
ok，对比一下setData中的实现，我们这里只用一条代码就可以代替上面的实现了，这样是不是更方便呢，这样的话，我们的扩展就更加方便了，如果说，我们不仅仅只是设置文本内容，而是通过图片控件设置图片呢？很简单，我们只需要在ViewHolder中再添加我们要实现的方法即可，比如设置图片，我们可以添加如下代码：
public ViewHolder setImageResource(int viewId,int resId){ ImageView img = getView(viewId); img.setImageResource(resId); return this; } public ViewHolder setImageBitmap(int viewId, Bitmap bm){ ImageView img = getView(viewId); img.setImageBitmap(bm); return this; }
添加这两个方法后，需要设置图片就很轻松了，只需在setData中传递对应的参数即可
@Override public void setData(ViewHolder holder, Student t) { holder.setText(R.id.mTv1, t.getName()).setText(R.id.mTv2, t.getSex()); holder.setImageResource(R.id.img1,资源id).setImageBitmap(R.id.img2,bm); }
好了，一个通用的适配器就已经完成了，整体框架和代码都已经实现了，我将所有的代码都综合一下，写在下面，方便大家使用，分别是MainActivity.java（主界面类，负责传参设置ListView的数据）、MyAdapter.java(自定义的适配器)、MyBaseAdapter.java（通用的适配器类）、ViewHolder.java（通用的持有类对象）、以及实体类Student.java
MainActivity.java
public class MainActivity extends AppCompatActivity{ private List data; private ListView mList; MyAdapter adapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); getData(); mList = (ListView) findViewById(R.id.mList); adapter = new MyAdapter(data); mList.setAdapter(adapter); } private void getData() { data = new ArrayList<>(); Student stu = null; for (int i = 0; i < 20; i++) { stu = new Student(); stu.setName("姓名" + i); stu.setSex(i % 2 == 0 ? "男" : "女"); data.add(stu); } }}
MyAdapter.java
public class MyAdapter extends MyBaseAdapter { public MyAdapter(List data) { super(data); } @Override public void setData(ViewHolder holder, Student t) { holder.setText(R.id.mTv1, t.getName()).setText(R.id.mTv2, t.getSex()); }}
MyBaseAdapter.java
public abstract class MyBaseAdapter extends BaseAdapter { protected List data; public MyBaseAdapter(List data){ this.data = data; } @Override public int getCount() { return data == null ? 0 : data.size(); } @Override public Object getItem(int position) { return data.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder = ViewHolder.getHolder(convertView,parent,position, R.layout.list_item); setData(holder,data.get(position)); return holder.getConvertView(); } public abstract void setData(ViewHolder holder,T t);}
ViewHolder.java
public class ViewHolder { private int position; private SparseArray array; private View convertView; private Context context; private ViewHolder(ViewGroup parent, int position, int layout) { this.position = position; this.context = parent.getContext(); convertView = LayoutInflater.from(parent.getContext()).inflate(layout, null); convertView.setTag(this); array = new SparseArray<>(); } public static ViewHolder getHolder(View convertView, ViewGroup parent, int position, int layout) { if (convertView == null) { return new ViewHolder(parent, position, layout); } else { ViewHolder holder = (ViewHolder) convertView.getTag(); holder.position = position; return holder; } } public T getView(int viewId) { View view = array.get(viewId); if (view == null) { view = convertView.findViewById(viewId); array.put(viewId, view); } return (T) view; } public View getConvertView() { return convertView; } public ViewHolder setText(int viewId, String data) { TextView tv = getView(viewId); tv.setText(data); return this; } public ViewHolder setImageResource(int viewId, int resId) { ImageView img = getView(viewId); img.setImageResource(resId); return this; } public ViewHolder setImageBitmap(int viewId, Bitmap bm) { ImageView img = getView(viewId); img.setImageBitmap(bm); return this; }}
Student.java
public class Student { private String name; private String sex; public String getName() { return name; } public void setName(String name) { this.name = name; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; }}
