android ListView 动态切换Item布局

需求是这样的，在列表中，第一个列表项显示一种布局，其他的列表项显示另一种布局，所以需要在列表中根据条件进行判断，动态切换布局

方法就是在定义BaseAdapter的时候，重写两个方法：

@Override
public int getViewTypeCount() {
return number;
}

@Override
public int getItemViewType(int position) {
return type;
}

getItemViewType用来返回第position个Item是何种类型，getViewTypeCount返回不同布局的总数。

关于ListView的运行效率的提高，摘抄《第一行代码》书中的一段进行说明

3.5.3 提升 ListView 的运行效率

之所以说 ListView 这个控件很难用，就是因为它有很多的细节可以优化，其中运行效率

就是很重要的一点。 目前我们 ListView的运行效率是很低的， 因为在 FruitAdapter的 getView()

方法中每次都将布局重新加载了一遍，当 ListView 快速滚动的时候这就会成为性能的瓶颈。

仔细观察，getView()方法中还有一个 convertView 参数，这个参数用于将之前加载好的

布局进行缓存，以便之后可以进行重用。修改 FruitAdapter 中的代码，如下所示：

public class FruitAdapter extends ArrayAdapter {

……

@Override

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

Fruit fruit = getItem(position);

View view;

if (convertView == null) {

view = LayoutInflater.from(getContext()).inflate(resourceId, null);

} else {

view = convertView;

}

ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);

TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);

fruitImage.setImageResource(fruit.getImageId());

fruitName.setText(fruit.getName());

return view;

}

}

可以看到，现在我们在 getView()方法中进行了判断，如果 convertView 为空，则使用

LayoutInflater 去加载布局，如果不为空则直接对 convertView 进行重用。这样就大大提高了

ListView 的运行效率，在快速滚动的时候也可以表现出更好的性能。

不过， 目前我们的这份代码还是可以继续优化的， 虽然现在已经不会再重复去加载布局，

但是每次在 getView()方法中还是会调用 View的 findViewById()方法来获取一次控件的实例。

我们可以借助一个 ViewHolder 来对这部分性能进行优化，修改 FruitAdapter 中的代码，如下

所示：

public class FruitAdapter extends ArrayAdapter {

……

@Override

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

Fruit fruit = getItem(position);

View view;

ViewHolder viewHolder;

if (convertView == null) {

view = LayoutInflater.from(getContext()).inflate(resourceId, null);

viewHolder = new ViewHolder();

viewHolder.fruitImage = (ImageView) view.findViewById

(R.id.fruit_image);

viewHolder.fruitName = (TextView) view.findViewById

(R.id.fruit_name);

view.setTag(viewHolder); // 将ViewHolder存储在View中

} else {

view = convertView;

viewHolder = (ViewHolder) view.getTag(); // 重新获取ViewHolder

}

viewHolder.fruitImage.setImageResource(fruit.getImageId());

viewHolder.fruitName.setText(fruit.getName());

return view;

}

class ViewHolder {

ImageView fruitImage;

TextView fruitName;

}

}

我们新增了一个内部类 ViewHolder，用于对控件的实例进行缓存。当 convertView 为空

的时候， 创建一个 ViewHolder 对象， 并将控件的实例都存放在 ViewHolder 里， 然后调用 View

的 setTag()方法，将 ViewHolder 对象存储在 View 中。当 convertView 不为空的时候则调用

View 的 getTag()方法， 把 ViewHolder 重新取出。 这样所有控件的实例都缓存在了 ViewHolder

里，就没有必要每次都通过 findViewById()方法来获取控件实例了。

两个布局my_order_top_item.xml，my_order_item.xml

my_order_top_item.xml

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

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:background="@drawable/rect_white"
android:orientation="vertical">

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@mipmap/button_green"
android:gravity="center"
android:orientation="horizontal">

<TextView
android:id="@+id/id_textOrderTime"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_weight="1"
android:drawableLeft="@mipmap/order_time1"
android:drawablePadding="10dp"
android:textColor="#ffffff"
android:textSize="14sp" />

<ImageView
android:id="@+id/id_imageOrderNavi"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:src="@mipmap/order_navi" />
</LinearLayout>

<TextView
android:id="@+id/id_textOrderCharge"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:drawableLeft="@mipmap/order_charge"
android:drawablePadding="10dp"
android:textColor="#555555"
android:textSize="14sp" />

<TextView
android:id="@+id/id_textOrderAddress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:drawableLeft="@mipmap/order_point"
android:drawablePadding="10dp"
android:textColor="#555555"
android:textSize="14sp" />

<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="#a2a2a2" />

<TextView
android:id="@+id/id_orderTime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:textColor="#a2a2a2"
android:textSize="16sp" />

<TextView
android:id="@+id/id_orderAddress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="5dp"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:textColor="#a2a2a2"
android:textSize="16sp" />
</LinearLayout>
</LinearLayout>

my_order_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">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_margin="10dp"
android:background="@drawable/rect_white">

<TextView
android:id="@+id/id_textOrderCharge"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:textSize="14sp"
android:textColor="#555555"
android:drawableLeft="@mipmap/order_charge"
android:drawablePadding="10dp"/>
<TextView
android:id="@+id/id_textOrderAddress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginBottom="10dp"
android:textSize="14sp"
android:textColor="#555555"
android:drawableLeft="@mipmap/order_point"
android:drawablePadding="10dp"/>
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="#a2a2a2"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:id="@+id/id_orderTime"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="16sp"
android:textColor="#a2a2a2"
android:layout_margin="5dp"/>
<TextView
android:id="@+id/id_orderState"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="16sp"
android:textColor="#a2a2a2"
android:layout_margin="5dp"/>
</LinearLayout>

</LinearLayout>
</LinearLayout>

Adapter:

private class MyOrderAdapter extends BaseAdapter {
Context mContext;
LayoutInflater inflater;
final int TYPE_1 = 0;
final int TYPE_2 = 1;

//各个布局的控件资源
class ViewHolder1 {

TextView textOrderTime;

ImageView imageOrderNavi;
TextView textOrderCharge;
TextView textOrderAddress;
TextView orderTime;
TextView orderAddress;

}

class ViewHolder2 {
TextView textOrderCharge;
TextView textOrderAddress;
TextView orderTime;
TextView orderState;

}

public MyOrderAdapter(Context context) {
mContext = context;
inflater = LayoutInflater.from(mContext);
}

@Override
public int getCount() {
return 10;
}

@Override
public Object getItem(int position) {
return position;
}

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

@Override
public int getViewTypeCount() {
return 2;
}

@Override
public int getItemViewType(int position) {
if (position == 0) {
return TYPE_1;
} else {
return TYPE_2;
}
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
int type = getItemViewType(position);
ViewHolder1 viewHolder1 = null;
ViewHolder2 viewHolder2 = null;
if (convertView == null) {
if (type == TYPE_1) {
convertView = LayoutInflater.from(MyOrderActivity.this).inflate(R.layout.my_order_top_item, null);
viewHolder1 = new ViewHolder1();
viewHolder1 .textOrderTime = (TextView) convertView.findViewById(R.id.id_textOrderTime);

viewHolder1.imageOrderNavi = (ImageView) convertView.findViewById(R.id.id_imageOrderNavi);
viewHolder1.textOrderCharge = (TextView) convertView.findViewById(R.id.id_textOrderCharge);
viewHolder1.textOrderAddress = (TextView) convertView.findViewById(R.id.id_textOrderAddress);
viewHolder1.orderTime = (TextView) convertView.findViewById(R.id.id_orderTime);
viewHolder1.orderAddress = (TextView) convertView.findViewById(R.id.id_orderAddress);
convertView.setTag(viewHolder1);
} else if (type == TYPE_2) {
viewHolder2 = new ViewHolder2();
convertView = LayoutInflater.from(MyOrderActivity.this).inflate(R.layout.my_order_item, null);
viewHolder2.textOrderCharge = (TextView) convertView.findViewById(R.id.id_textOrderCharge);
viewHolder2.textOrderAddress = (TextView) convertView.findViewById(R.id.id_textOrderAddress);
viewHolder2.orderTime = (TextView) convertView.findViewById(R.id.id_orderTime);
viewHolder2.orderState = (TextView) convertView.findViewById(R.id.id_orderState);
convertView.setTag(viewHolder2);
}
} else {
if (type == TYPE_1) {
viewHolder1 = (ViewHolder1) convertView.getTag();
} else if (type == TYPE_2) {
viewHolder2 = (ViewHolder2) convertView.getTag();
}
}

if (type == TYPE_1) {
viewHolder1.textOrderCharge.setText("电桩号 101668");
viewHolder1.textOrderAddress.setText("充电点 无锡工业设计大厦");
viewHolder1.orderTime.setText("预约时间 2016-1-11");
viewHolder1.orderAddress.setText("充电位置 无锡工业设计大厦");

}
if (type == TYPE_2) {
viewHolder2.textOrderCharge.setText("电桩号 101668");
viewHolder2.textOrderAddress.setText("充电点 无锡工业设计大厦");
viewHolder2.orderTime.setText("预约时间 2016-1-11");
viewHolder2.orderState.setText("已完成");

}
return convertView;
}

}

列表我使用的是PullToRefreshListView，用于上拉下拉刷新，并且设置了列表为空进行显示的TextView

mPullRefreshListView = (PullToRefreshListView) findViewById(R.id.id_orderListView);
mPullRefreshListView.setMode(PullToRefreshBase.Mode.BOTH);
TextView textView = new TextView(MyOrderActivity.this);
textView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT));
textView.setText("没有查询到相应数据");
textView.setGravity(Gravity.CENTER_HORIZONTAL | Gravity.CENTER_VERTICAL);
textView.setVisibility(View.GONE);
((ViewGroup) mPullRefreshListView.getParent()).addView(textView);
mPullRefreshListView.setEmptyView(textView);

final ILoadingLayout startLabels = mPullRefreshListView
.getLoadingLayoutProxy(true, false);
startLabels.setPullLabel("下拉刷新...");// 刚下拉时，显示的提示
startLabels.setRefreshingLabel("正在载入...");// 刷新时
startLabels.setReleaseLabel("放开刷新...");// 下来达到一定距离时，显示的提示

ILoadingLayout endLabels = mPullRefreshListView.getLoadingLayoutProxy(
false, true);
endLabels.setPullLabel("上拉刷新...");// 刚下拉时，显示的提示
endLabels.setRefreshingLabel("正在载入...");// 刷新时
endLabels.setReleaseLabel("放开刷新...");// 下来达到一定距离时，显示的提示

mPullRefreshListView.setOnRefreshListener(new PullToRefreshBase.OnRefreshListener2<ListView>() {
@Override
public void onPullDownToRefresh(PullToRefreshBase<ListView> refreshView) {
String label = DateUtils.formatDateTime(MyOrderActivity.this, System.currentTimeMillis(),
DateUtils.FORMAT_SHOW_TIME | DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_ABBREV_ALL);

// Update the LastUpdatedLabel
refreshView.getLoadingLayoutProxy().setLastUpdatedLabel(label);

// Do work to refresh the list here.
// new GetDataTask().execute();
new getDataThread().start();
}

@Override
public void onPullUpToRefresh(PullToRefreshBase<ListView> refreshView) {
String label = DateUtils.formatDateTime(MyOrderActivity.this, System.currentTimeMillis(),
DateUtils.FORMAT_SHOW_TIME | DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_ABBREV_ALL);

// Update the LastUpdatedLabel
refreshView.getLoadingLayoutProxy().setLastUpdatedLabel(label);

// Do work to refresh the list here.
// new GetDataTask().execute();
new getDataThread().start();
}
});

/*
如果ListView中的单个Item的view中存在checkbox，button等view，会导致ListView.setOnItemClickListener无效，
事件会被子View捕获到，ListView无法捕获处理该事件.
解决方法：
在checkbox、button对应的view处加android:
focusable = "false"
android:
clickable = "false" android:
focusableInTouchMode = "false"
其中focusable是关键
*/

ListView actualListView = mPullRefreshListView.getRefreshableView();
actualListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

}
});

myOrderAdapter = new MyOrderAdapter(MyOrderActivity.this);
actualListView.setAdapter(myOrderAdapter);

}

loadUiHandler myHandler = new loadUiHandler();

private class getDataThread extends Thread {
@Override
public void run() {
super.run();
try {
Thread.sleep(2000);

} catch (InterruptedException e) {
e.printStackTrace();
}

Message message = new Message();
message.what = 0;
myHandler.sendMessage(message);
}
}

private class loadUiHandler extends Handler {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);

myOrderAdapter.notifyDataSetChanged();

// Call onRefreshComplete when the list has been refreshed.
mPullRefreshListView.onRefreshComplete();
}
}

参考

Android杂谈–ListView之BaseAdapter的使用

Android类库–与Adapter相关的类