Android中万能的适配器的详细讲解

Android中万能的适配器的详细讲解
在Android开发中，适配器的用处是非常大的，尤其是效率优化方面。除了使用ViewHolder复用View之外，如果存在很多的ListView或者是一个ListView中存在很多的View组件，那对代码的阅读不是很好的。考虑到优化以及共通方面，我封装了ViewHolder类以及将Adapter类封装成共通的了，将对以后的开发带来很大的方便。

(1).ViewHolder类的封装如下：ViewHolder类：

package com.chengdong.su.baseadapter.util;

import android.content.Context;
import android.util.Log;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

/**
 * the common object of the ViewHolder
 * 
 * @author scd
 * 
 */
public class ViewHolder {
    /** the object of the TAG */
    private String TAG = getClass().getSimpleName();
    /** the object of the view */
    private SparseArray<View> mViews;
    /** the object of the position */
    private int mPosition;
    /** the object of the converview */
    private View mConvertView;

    /***
     * 构造方法
     * 
     * @param context
     * @param parent
     * @param layoutId
     * @param position
     */
    public ViewHolder(Context context, ViewGroup parent, int layoutId,int position) {
      super();
      this.mPosition = position;
      this.mViews = new SparseArray<View>();
      mConvertView = LayoutInflater.from(context).inflate(layoutId, parent,
                false);
        mConvertView.setTag(this);

    }

    /**
     * get the object of the ViewHolder
     * 
     * @param context
     * @param convertView
     * @param parent
     * @param layoutId
     * @param position
     * @return
     */
    public static ViewHolder getViewHolder(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();
            // 修改位置变化
            holder.mPosition = position;
            Log.d("getViewHolder", "getViewHolder：position:--->" + position);
            return holder;
        }
    }

    /**
     * find the view by the viewId
     * 
     * @param viewId
     * @return
     */
    @SuppressWarnings("unchecked")
    public <T extends View> T findView(int viewId) {
        View view = mViews.get(viewId);
        if (view == null) {
            view = mConvertView.findViewById(viewId);
            // 添加View对象
            mViews.put(viewId, view);

        }
        return (T) view;
    }

    /**
     * get the object of the convertView
     * 
     * @return
     */
    public View getConvertView() {
        return mConvertView;
    }

    public int getPosition() {
        return mPosition;
    }

    /**
     * 为TextView设置值
     * 
     * @param viewId
     * @param text
     * @return
     */
    public ViewHolder setText(int viewId, String text) {
        TextView textView = findView(viewId);
        textView.setText(text);
        return this;
    }

    /**
     * 为ImageView设置值
     * 
     * @param viewId
     * @param resId
     * @return
     */
    public ViewHolder setImageResource(int viewId, int resId) {
        ImageView view = findView(viewId);
        view.setImageResource(resId);
        return this;
    }

    // TODO 待写View设置的辅助的方法

}

(2).CommonAdapter共通类的实现如下：

package com.chengdong.su.baseadapter.util;

import java.util.List;

import android.R.integer;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

import com.chengdong.su.baseadapter.R;

public abstract class CommonAdapter<T> extends BaseAdapter {
    /** 上下文 */
    protected Context mContext;
    /** 数据源 */
    protected List<T> mData;
    private int mLayoutId;

    public CommonAdapter(Context mContext, int layoutId) {
        super();
        this.mContext = mContext;
        this.mLayoutId = layoutId;
    }

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

    @Override
    public T getItem(int position) {
        return (T) (mData == null ? 0 : mData.get(position));
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder holder = ViewHolder.getViewHolder(mContext, convertView,
                parent, mLayoutId, position);
        convert(holder, getItem(position));
        return holder.getConvertView();

    }

    /*** 设置数据 */
    public abstract void setData(List<T> data);

    /*** 实现给View赋数据的方法 */
    public abstract void convert(ViewHolder holder, T item);
}

(3).MyAdapter类的实现：

package com.chengdong.su.baseadapter.adapter;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.view.View;
import android.widget.CheckBox;

import com.chengdong.su.baseadapter.R;
import com.chengdong.su.baseadapter.bean.Bean;
import com.chengdong.su.baseadapter.util.CommonAdapter;
import com.chengdong.su.baseadapter.util.ViewHolder;

/**
 * 通用的ViewHolder
 * 
 * @author scd
 * 
 */
public class MyAdapter extends CommonAdapter<Bean> {
    private List<Integer> mList = new ArrayList<Integer>();

    public MyAdapter(Context mContext) {
        super(mContext, R.layout.item_listview);
    }

    @Override
    public void setData(List<Bean> data) {
        mData = data;

    }

    @Override
    public void convert(final ViewHolder holder, Bean item) {
        // 链式编程
        holder.setText(R.id.tv_title, item.getTitle())
                .setText(R.id.tv_desc, item.getDesc())
                .setText(R.id.tv_time, item.getTime())
                .setText(R.id.tv_phone, item.getPhone());

        // checkBox复用导致内容错乱的解决方法
        final CheckBox checkBox = holder.findView(R.id.cb_select);
        // // 默认状态下都不选中
        checkBox.setChecked(false);
        if (mList.contains(holder.getPosition())) {
            checkBox.setChecked(true);
        }
        checkBox.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                if (checkBox.isChecked()) {
                    mList.add((Integer) holder.getPosition());

                } else {
                    mList.remove((Integer) holder.getPosition());
                }

            }
        });

    }

}

(4)MainActivity类的实现如下：

package com.chengdong.su.baseadapter;

import java.util.ArrayList;
import java.util.List;

import com.chengdong.su.baseadapter.adapter.MyAdapter;
import com.chengdong.su.baseadapter.bean.Bean;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

public class MainActivity extends Activity {
    private ListView mListView;
    private MyAdapter mAdapter;
    private List<Bean> mData;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();

    }

    private void initView() {
        mListView = (ListView) findViewById(R.id.lv_show);
        mAdapter = new MyAdapter(MainActivity.this);
        initData();
        mAdapter.setData(mData);
        mListView.setAdapter(mAdapter);

    }

    private void initData() {
        mData = new ArrayList<Bean>();
        Bean bean = new Bean("1", "2", "3", "4");
        for (int i = 0; i < 11; i++) {

            mData.add(bean);
        }

    }

}

(5).activity_main类的实现如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/lv_show"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

(6).item_listview类的实现：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:descendantFocusability="blocksDescendants"
    android:orientation="vertical"
    android:padding="8dp" >

    <CheckBox
        android:id="@+id/cb_select"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:focusable="false" />

    <TextView
        android:id="@+id/tv_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@id/cb_select"
        android:maxLines="1"
        android:text="标题" />

    <TextView
        android:id="@+id/tv_desc"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/tv_title"
        android:layout_marginTop="8dp"
        android:maxLines="1"
        android:text="描述" />


    <TextView
        android:id="@+id/tv_time"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/tv_desc"
        android:layout_marginTop="8dp"
        android:text="时间" />

    <TextView
        android:id="@+id/tv_phone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_below="@id/tv_desc"
        android:layout_marginTop="8dp"
        android:text="电话" />


</RelativeLayout>

说明：
android:descendantFocusability="blocksDescendants"
android:focusable="false"
是当存在checkbox或者其他控件存在导致item抢占焦点的解决方案：解决item不能被选中点击。
// checkBox复用导致内容错乱的解决方法如下：

 final CheckBox checkBox = holder.findView(R.id.cb_select);
        // // 默认状态下都不选中
        checkBox.setChecked(false);
        if (mList.contains(holder.getPosition())) {
            checkBox.setChecked(true);
        }
        checkBox.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                if (checkBox.isChecked()) {
                    mList.add((Integer) holder.getPosition());

                } else {
                    mList.remove((Integer) holder.getPosition());
                }

            }
        });