在上一篇中，我們說過，在setData中如果有很多控件的話，我們還是要在該方法中寫入很多代碼，為了降低開發的方便性，本次就在此基礎上再一次優化。實現原理是這樣的，每次在setData中都要查找控件，然后setXXX()什么的，我們可以把這寫實現放如到ViewHolder中去，在ViewHolder中寫入一個鏈式的方法，來幫助我們來實現功能(關于ViewHodler類的代碼我就不再重復寫了，代碼在此：Android之自定義實現BaseAdapter(通用適配器一) )，鏈式方法如下：
public ViewHolder setText(int viewId, String data){
TextView tv = getView(viewId);
tv.setText(data);
return this;
}
通過這個方法，我們可以很好的去設置對應的內容，只需要傳一個需要設置控件的id，然后傳對應的數據，就可以達到設置文字的效果了，下面再看看我們的MyAdapter.java中的代碼
MyAdapter.java
/**
* 上一篇中的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());
}
}
/**
* 優化后的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，對比一下setData中的實現，我們這里只用一條代碼就可以代替上面的實現了，這樣是不是更方便呢，這樣的話，我們的擴展就更加方便了，如果說，我們不僅僅只是設置文本內容，而是通過圖片控件設置圖片呢？很簡單，我們只需要在ViewHolder中再添加我們要實現的方法即可，比如設置圖片，我們可以添加如下代碼：
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;
}
添加這兩個方法后，需要設置圖片就很輕松了，只需在setData中傳遞對應的參數即可
@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,資源id).setImageBitmap(R.id.img2,bm);
}
好了，一個通用的適配器就已經完成了，整體框架和代碼都已經實現了，我將所有的代碼都綜合一下，寫在下面，方便大家使用，分別是MainActivity.java(主界面類，負責傳參設置ListView的數據)、MyAdapter.java(自定義的適配器)、MyBaseAdapter.java(通用的適配器類)、ViewHolder.java(通用的持有類對象)、以及實體類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;
}
}
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持腳本之家。
表單元素以及對各個表單元素的name、value屬性的理解)
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