【android】SimpleAdapter 使用浅析

目录

• 导读
• 操作环境
• 源码
• 实例

导读

SimpleAdapter 是一个将 map 数据与 xml 文件中定义的 view 对应起来简易适配器。其对 BaseAdapter 的封装一定程度上简化了开发人员的使用门槛。

操作环境

• 操作系统：win7-64bit 旗舰版
• android 版本：android-23
• 模拟器：海马玩模拟器 0.9.0 Beta

源码

所有的 magic 在源码面前都显得那么裸露。

• 构造方法：

public SimpleAdapter(Context context, List<? extends Map<String, ?>> data,            @LayoutRes int resource, String[] from, @IdRes int[] to)

• getView 方法：

    /**     * @see android.widget.Adapter#getView(int, View, ViewGroup)     */    public View getView(int position, View convertView, ViewGroup parent) {        return createViewFromResource(mInflater, position, convertView, parent, mResource);    }    private View createViewFromResource(LayoutInflater inflater, int position, View convertView,            ViewGroup parent, int resource) {        View v;        if (convertView == null) {            v = inflater.inflate(resource, parent, false);        } else {            v = convertView;        }        bindView(position, v);        return v;    }

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 ? "<unknown type>" : 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");                    }                }            }        }    }

简单说明：

• SimpleAdpter 会将 String[] from, @IdRes int[] to 的元素一一对应起来
• 若 getView 方法中的第二个参数 View convertView 为 null，则通过 inflater.inflate(resource, parent, false); 创建一个新的；若非空的话，则沿用之前的 convertView；
• 对于 xml 中的视图类型，目前仅支持：
  
  • Checkable 及其衍生类；如：CheckBoxes 等
  • TextView 及其衍生类；如：TextView，EditText 等
  • ImageView 及其衍生类；如：ImageView 等

实例

• test_item.xml：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent">    <!--红色背景-->    <TextView android:id="@+id/tv_content_1"        android:layout_width="match_parent"        android:layout_height="50dp"        android:background="#f00"        />    <!--绿色背景-->    <TextView android:id="@+id/tv_content_2"        android:layout_width="match_parent"        android:layout_height="50dp"        android:background="#0f0"        />    <!--蓝色背景-->    <TextView android:id="@+id/tv_content_3"        android:layout_width="match_parent"        android:layout_height="50dp"        android:background="#00f"        /></LinearLayout>

• test_simple_adapter.xml：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"     android:layout_width="match_parent"    android:layout_height="match_parent">    <ListView android:id="@+id/lv_test"        android:layout_width="match_parent"        android:layout_height="match_parent">    </ListView></LinearLayout>

• MainActivity.java：

public class MainActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.test_simple_adapter);        this.testSimpleAdapter();    }    // 测试 SimpleAdapter     void testSimpleAdapter(){        // 从 xml 中找到 listview 控件        ListView lv = (ListView)this.findViewById(R.id.lv_test);        // 设置 数据集        ArrayList<HashMap<String, String>> data = new ArrayList<>();        for(int i =0; i<2; i++) {            HashMap<String, String> map = new HashMap<>();            map.put("key1", "value1_item_" + i);            map.put("key2", "value2_item_" + i);            map.put("key3", "value3_item_" + i);            data.add(map);        }        // 设置数据集中的键 和 test_item.xml 中对应的控件ID        String[] from = new String[]{"key1", "key2", "key3"};        @IdRes int[] to = new int[]{R.id.tv_content_1, R.id.tv_content_2, R.id.tv_content_3};        // 实例化适配器        SimpleAdapter sa = new SimpleAdapter(this, data, R.layout.test_item, from, to);        // 设置 listview 的适配器        lv.setAdapter(sa);    }

• 效果图：