Android之Adapter系列之SimpleAdapter类
SimpleAdapter继承了BaseAdapter，作为一个Adapter的简单实现，SimpleAdapter支持的控件也比较少：checkable控件（例如checkbox，radioButton)、TextView和ImageView。
源码部分
源码路径：framework\base\core\java\android\widget\SimpleAdapter.java
package android.widget;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.view.LayoutInflater;
import android.net.Uri;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* SimpleAdapter是一个将静态数据映射到在xml中定义的View上的简单的adapter。
* 开发者将数据保存在一个包含maps的ArrayList中。Arraylist中的每一项数据和view
* 中的每一个项对应。map中包含了view中每一行的数据。同样，开发者可以指定xml文件
* 来显示map中对应行的数据或者用map中的keys值来指定view。
*
* 数据的绑定发生在一下两种情况。
* 首先，如果{@link android.widget.SimpleAdapter.ViewBinder} 可见，
* {@link ViewBinder#setViewValue(android.view.View, Object, String)}被调用。
* 如果setViewValue返回true，那么则进行数据绑定。如果返回false，那么下面这些
* 情况将按顺序尝试执行
*
* - 如果View实现了Checkable(例如Checkbox)，那么返回值将是boolean类型
*
- TextView 返回值为String并且 {@link #setViewText(TextView, String)}将被调用
*
- ImageView 返回值为资源id或者string，并且{@link #setViewImage(ImageView, int)}
* 或者 {@link #setViewImage(ImageView, String)} 被调用
*
* 如果没有合适的binding返回，将会抛出 {@link IllegalStateException}异常
*/
public class SimpleAdapter extends BaseAdapter implements Filterable {
private int[] mTo;
private String[] mFrom;
private ViewBinder mViewBinder;
private List> mData;
private int mResource;
private int mDropDownResource;
private LayoutInflater mInflater;
private SimpleFilter mFilter;
private ArrayList> mUnfilteredData;
/**
* 构造函数
*
* @param context SimpleAdapter运行的上下文
* @param data 包含map的list列表。列表中给的每一项和view中的每一个item对应。Maps中则包含View
* 中每一行的所有数据，并且应该包含“from”中所有指定的项
* @param resource View中item的layout布局id，该view至少包含“to”中指定的项
*
* @param from 一个将要被添加到map中的列名列表，和map中的每一个item对应
* @param to 需要显示view的id和“from”参数对应。必须全是TextView。
*
*/
public SimpleAdapter(Context context, List> data,
int resource, String[] from, int[] to) {
mData = data;
mResource = mDropDownResource = resource;
mFrom = from;
mTo = to;
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
/**
* @see android.widget.Adapter#getCount()
*/
public int getCount() {
return mData.size();
}
/**
* @see android.widget.Adapter#getItem(int)
*/
public Object getItem(int position) {
return mData.get(position);
}
/**
* @see android.widget.Adapter#getItemId(int)
*/
public long getItemId(int position) {
return position;
}
/**
* getView直接调用createViewFromResource
*/
public View getView(int position, View convertView, ViewGroup parent) {
return createViewFromResource(position, convertView, parent, mResource);
}
/**
* greateViewFromResource进行了convertView的判断后，调用bindView来进行具体view的绑定
*/
private View createViewFromResource(int position, View convertView,
ViewGroup parent, int resource) {
View v;
if (convertView == null) {
v = mInflater.inflate(resource, parent, false);
} else {
v = convertView;
}
bindView(position, v);
return v;
}
/**
* 设置用来创建drop down 视图的布局id
* @param resource 定义了drop down 视图的资源文件
* @see #getDropDownView(int, android.view.View, android.view.ViewGroup)
*/
public void setDropDownViewResource(int resource) {
this.mDropDownResource = resource;
}
/**
* 同样调用createViewFromResource来生成对应的view
*/
@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
return createViewFromResource(position, convertView, parent, mDropDownResource);
}
/**
* bindview应该是SimpleAdapter中核心的方法其中position为需要获取的view的位置，view为convertView
*/
private void bindView(int position, View view) {
final Map dataSet = mData.get(position);
if (dataSet == null) {
return;
}
final ViewBinder binder = mViewBinder;
final String[] from = mFrom;
final int[] to = mTo;
final int count = to.length;
for (int i = 0; i < count; i++) {
final View v = view.findViewById(to[i]);
if (v != null) {
final Object data = dataSet.get(from[i]);
String text = data == null ? "" : data.toString();
if (text == null) {
text = "";
}
boolean bound = false;
if (binder != null) {
bound = binder.setViewValue(v, data, text);
}
if (!bound) {
if (v instanceof Checkable) {
if (data instanceof Boolean) {
((Checkable) v).setChecked((Boolean) data);
} else if (v instanceof TextView) {
// Note: keep the instanceof TextView check at the bottom of these
// ifs since a lot of views are TextViews (e.g. CheckBoxes).
setViewText((TextView) v, text);
} else {
throw new IllegalStateException(v.getClass().getName() +
" should be bound to a Boolean, not a " +
(data == null ? "" : data.getClass()));
}
} else if (v instanceof TextView) {
// Note: keep the instanceof TextView check at the bottom of these
// ifs since a lot of views are TextViews (e.g. CheckBoxes).
setViewText((TextView) v, text);
} else if (v instanceof ImageView) {
if (data instanceof Integer) {
setViewImage((ImageView) v, (Integer) data);
} else {
setViewImage((ImageView) v, text);
}
} else {
throw new IllegalStateException(v.getClass().getName() + " is not a " +
" view that can be bounds by this SimpleAdapter");
}
}
}
}
}
/**
* 返回一个ViewBinder
*/
public ViewBinder getViewBinder() {
return mViewBinder;
}
/**
* 设置ViewBinder
*/
public void setViewBinder(ViewBinder viewBinder) {
mViewBinder = viewBinder;
}
/**
* 该方法除被宾得View调用，用来给ImageView设置图片
* 如果ViewBinder不存在或者ViewBinder无法和ImageView绑定
*/
public void setViewImage(ImageView v, int value) {
v.setImageResource(value);
}
/**
* 该方法被bindView调用，用来给ImageView设置图片
* 如果ViewBinder不存在或者ViewBinder无法和ImageView绑定
*
* 默认情况下value被当作image资源，如果无法被当作image资源，那么将会被当作image uri
*/
public void setViewImage(ImageView v, String value) {
try {
v.setImageResource(Integer.parseInt(value));
} catch (NumberFormatException nfe) {
v.setImageURI(Uri.parse(value));
}
}
/**
* 该方法被bindView调用，用来给TextView色获知字符
* 如果ViewBinder不存在或者ViewBinder无法和TextView绑定
*/
public void setViewText(TextView v, String text) {
v.setText(text);
}
public Filter getFilter() {
if (mFilter == null) {
mFilter = new SimpleFilter();
}
return mFilter;
}
/**
* 这个内部静态接口被外部SimpleAdapter客户端用来修改views
* 开发者通过实现这个接口，来修改view，如果这些View不能直接被SIM所支持，
* 或者修改view绑定的方式
* @see SimpleAdapter#setViewImage(ImageView, int)
* @see SimpleAdapter#setViewImage(ImageView, String)
* @see SimpleAdapter#setViewText(TextView, String)
*/
public static interface ViewBinder {
/**
* 绑定指定的数据到指定的view上
* 如果binding被该方法处理，那么该方法必须返回true，如果返回false，那么SimpleAdapter
* 将会自己处理binding过程
* @param view the view to bind the data to
* @param data the data to bind to the view
* @param textRepresentation a safe String representation of the supplied data:
* it is either the result of data.toString() or an empty String but it
* is never null
*
* @return true if the data was bound to the view, false otherwise
*/
boolean setViewValue(View view, Object data, String textRepresentation);
}
/**
* 一个包含了某个前缀的数组过滤器，如果list中的每一项不包含该前缀，那么将会从该list中移除
*/
private class SimpleFilter extends Filter {
@Override
protected FilterResults performFiltering(CharSequence prefix) {
FilterResults results = new FilterResults();
if (mUnfilteredData == null) {
mUnfilteredData = new ArrayList>(mData);
}
if (prefix == null || prefix.length() == 0) {
ArrayList> list = mUnfilteredData;
results.values = list;
results.count = list.size();
} else {
String prefixString = prefix.toString().toLowerCase();
ArrayList> unfilteredValues = mUnfilteredData;
int count = unfilteredValues.size();
ArrayList> newValues = new ArrayList>(count);
for (int i = 0; i < count; i++) {
Map h = unfilteredValues.get(i);
if (h != null) {
int len = mTo.length;
for (int j=0; j>) results.values;
if (results.count > 0) {
notifyDataSetChanged();
} else {
notifyDataSetInvalidated();
}
}
}
}
事例部分
list_item.xml
SimpleAdapter中包含了一个Interface ViewBinder，这里分两种情况，分别介绍两个事例，第一个，不使用ViewBinder；第二个，使用ViewBinder
SimpleAdapterNoBinder.javapackage com.lj.simpleadaptertest;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class SimpleAdapterNoBinder extends Activity {
ListView mListView;
List> mData = new ArrayList>();
public static final String KEY_IMG = "imgage";
public static final String KEY_TITLE = "title";
public static final String KEY_SUMMARY = "summary";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_no_binder);
mListView = (ListView) findViewById(R.id.list_no_binder);
//定义一个mAdapter,设置自定义的layout布局，调用getData返回需要显示的数据
SimpleAdapter mAdapter = new SimpleAdapter(this, getData(),
R.layout.list_item, new String[] { KEY_IMG, KEY_TITLE,
KEY_SUMMARY, }, new int[] { R.id.image, R.id.title,
R.id.summary });
mListView.setAdapter(mAdapter);
}
//map中包含三部分数据，ImageView设置为默认的R.drawable.ic_launcher,两个TextView设置为随机的字符
private List> getData() {
List> list = new ArrayList>();
Map map;
for (int i = 0; i < 30; i++) {
map = new HashMap();
map.put(KEY_IMG, R.drawable.ic_launcher);
map.put(KEY_TITLE, getTitleText(8));
map.put(KEY_SUMMARY, getTitleText(10));
list.add(map);
}
return list;
}
private Object getTitleText(int length) {
String mString = "qwertyuiopasdfghjklzxcvbnm";
Random random = new Random();
StringBuffer sb = new StringBuffer();
for (int i = 0; i < length; i++) {
int number = random.nextInt(mString.length());
sb.append(mString.charAt(number));
}
return sb.toString();
}
} package com.lj.simpleadaptertest;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class SimpleAdapterWithBinder extends Activity {
ListView mListView;
List> mData = new ArrayList>();
public static final String KEY_IMG = "imgage";
public static final String KEY_TITLE = "title";
public static final String KEY_SUMMARY = "summary";
public static final String KEY_CHECK = "check";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_no_binder);
mListView = (ListView) findViewById(R.id.list_no_binder);
SimpleAdapter mAdapter = new SimpleAdapter(this, getData(),
R.layout.list_item, new String[] { KEY_IMG, KEY_TITLE,
KEY_SUMMARY, }, new int[] { R.id.image, R.id.title,
R.id.summary });
mAdapter.setViewBinder(new TestViewBinder());
mListView.setAdapter(mAdapter);
}
private List> getData() {
List> list = new ArrayList>();
Map map;
for (int i = 0; i < 30; i++) {
map = new HashMap();
map.put(KEY_IMG, R.drawable.ic_launcher);
map.put(KEY_TITLE, getTitleText(8));
map.put(KEY_SUMMARY, getTitleText(10));
map.put(KEY_CHECK, (i / 2 == 0 ? true : false));
list.add(map);
}
return list;
}
private Object getTitleText(int length) {
String mString = "qwertyuiopasdfghjklzxcvbnm";
Random random = new Random();
StringBuffer sb = new StringBuffer();
for (int i = 0; i < length; i++) {
int number = random.nextInt(mString.length());
sb.append(mString.charAt(number));
}
return sb.toString();
}
public Bitmap getBitmap(final String url) {
Log.e("lijian", "url = " + url);
Bitmap bmp = null;
try {
URL mUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection) mUrl.openConnection();
InputStream is = conn.getInputStream();
bmp = BitmapFactory.decodeStream(is);
} catch (Exception e) {
e.printStackTrace();
}
return bmp;
}
/**
* 实现ViewBinder接口
*
*/
class TestViewBinder implements SimpleAdapter.ViewBinder {
@Override
public boolean setViewValue(View view, Object data,
String textRepresentation) {
if ((view instanceof ImageView)) {
Log.e("lijian", "set internet image data " + data);
ImageView mImageView = (ImageView) view;
mImageView.setImageResource(R.drawable.error);
return true;
} else if (view instanceof TextView && view.getId() ==R.id.summary) {
TextView mTextView = (TextView) view;
mTextView.setText("你好");
return true;
}
return false;
}
}
} 效果图：
图 1
图二
事例总结
图片以和图片二分别代表不使用ViewBinder和使用ViewBinder的结果，每一个Item的图片和summary字符可以在ViewBinder实现的类中的setViewValue中修改。
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