Android之自定義實現BaseAdapter（通用適配器三）

Android之自定義實現BaseAdapter（通用適配器三）

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，爲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，然後setXXX（）什麼的，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（關於ViewHodler類的代碼我就不再重複寫了，代碼在此：http://blog.csdn.net/qq_27630169/article/details/52200885），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，然後傳對應的數據，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<Student> 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());
    }
}

/**
* 優化後的MyAdapter
*/
public class MyAdapter extends MyBaseAdapter {
    public MyAdapter(List<Student> 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，我們這裏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;
    }

添加這兩個方法後，需要設置圖片就很輕鬆了，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<Student> 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<Student> {

    public MyAdapter(List<Student> 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<T> extends BaseAdapter {
    protected List<T> data;
    public MyBaseAdapter(List<T> 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<View> 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 extends View> 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;
    }
}