常用控件：03_004 ScrollView嵌套ListView实现和其替代方法

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#1 需求

在项目中我们会遇到这样的需求：多种类型的数据集（各个类型的数据集的长度不确定）放到一个可滚动的View中展示

#2 效果图

#3 方法一：ScrollView嵌套ListView

1.原理：多个ListView解决多种不确定长度数据集的显示，而ScrollView解决整体显示滑动的效果；但ListView加载数据后，会发现显示不全，这时候要重新根据其item来设置其高度从而显示全部

2.代码：

（1）xml视图：activity_main.xml、adapter_item1.xml、adapter_item2.xml

activity_main.xml：

adapter_item1.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="40dp"
android:orientation="vertical" >

<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="item1" />

<TextView
android:layout_gravity="center_horizontal"
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />

</LinearLayout>

adapter_item2.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="70dp"
android:orientation="vertical" >

<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:text="item2" />

<ImageView
android:layout_gravity="center_horizontal"
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_launcher" />

</LinearLayout>

（2）数据Bean：BeanItem1、BeanItem2:

public class BeanItem1 {}

public class BeanItem2 {}

(3) MyAdapter1、MyAdapter2：

public class MyAdapter1 extends BaseAdapter {

private Context mContext;

private List<BeanItem1> mList;

public MyAdapter1(Context context,List<BeanItem1> list){

mContext = context;

mList = list;

}

@Override

public int getCount() {

return mList.size();

}

@Override

public Object getItem(int position) {

return mList.get(position);

}

@Override

public long getItemId(int position) {

return position;

}

@Override

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

return View.inflate(mContext, R.layout.adapter_item1, null);

}

public class MyAdapter2 extends BaseAdapter {

private Context mContext;

private List<BeanItem2> mList;

public MyAdapter2(Context context,List<BeanItem2> list){

mContext = context;

mList = list;

}

@Override

public int getCount() {

return mList.size();

}

@Override

public Object getItem(int position) {

return mList.get(position);

}

@Override

public long getItemId(int position) {

return position;

}

@Override

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

return View.inflate(mContext, R.layout.adapter_item2, null);

}

（4）MainActivity

public class MainActivity extends Activity implements OnClickListener {

private ListView listview1,listview2;

private TextView tv_add1,tv_add2,tv_solve;

private Context context;

private List<BeanItem1> mList1;

private List<BeanItem2> mList2;

private MyAdapter1 mAdapter1;

private MyAdapter2 mAdapter2;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

context = this;

mList1 = new ArrayList<BeanItem1>();

mList2 = new ArrayList<BeanItem2>();

listview1 = (ListView) findViewById(R.id.listview1);

listview2 = (ListView) findViewById(R.id.listview2);

tv_add1 = (TextView) findViewById(R.id.tv_add1);

tv_add2 = (TextView) findViewById(R.id.tv_add2);

tv_solve = (TextView) findViewById(R.id.tv_solve);

tv_add1.setOnClickListener(this);

tv_add2.setOnClickListener(this);

tv_solve.setOnClickListener(this);

initData();

mAdapter1 = new MyAdapter1(context, mList1);

listview1.setAdapter(mAdapter1);

UtilsView.setListViewHeightBasedOnChildren(listview1);

mAdapter2 = new MyAdapter2(context, mList2);

listview2.setAdapter(mAdapter2);

UtilsView.setListViewHeightBasedOnChildren(listview2);

}

private void initData() {

for (int i = 0; i < 6; i++) {

BeanItem1 item1 = new BeanItem1();

mList1.add(item1);

}

for (int i = 0; i < 5; i++) {

BeanItem2 item2 = new BeanItem2();

mList2.add(item2);

}

/**

* 当动态添加listview2的item时，listview2 会随着

@Override

public void onClick(View v) {

switch (v.getId()) {

case R.id.tv_add1:

BeanItem1 item1 = new BeanItem1();

mList1.add(item1);

mAdapter1.notifyDataSetChanged();

UtilsView.setListViewHeightBasedOnChildren(listview1);

break;

case R.id.tv_add2:

BeanItem2 item2 = new BeanItem2();

mList2.add(item2);

mAdapter2.notifyDataSetChanged();

UtilsView.setListViewHeightBasedOnChildren(listview2);

break;

case R.id.tv_solve:

/**

* ScrollView嵌套listView是非常影响效率的，xml通常会提示

* 解决方法：LinerLayout动态添加View

MainActivity.this.startActivity(new Intent(MainActivity.this, SolveActivity.class));

break;

}

（4）UtilsView工具类

public class UtilsView {

public static void setListViewHeightBasedOnChildren(ListView listView){

if(listView == null) return;

ListAdapter listAdapter = listView.getAdapter();

if (listAdapter == null) {

return;

}

int totalHeight = 0;

for (int i = 0; i < listAdapter.getCount(); i++) {

View listItem = listAdapter.getView(i, null, listView);

listItem.measure(0, 0);

totalHeight += listItem.getMeasuredHeight();

}

ViewGroup.LayoutParams params = listView.getLayoutParams();

params.height = totalHeight + (listView.getDividerHeight() * (listAdapter.getCount() - 1));

listView.setLayoutParams(params);

}

5. 问题：不建议使用scrollView嵌套ListView，影响效率，底内存的手机容易报OOM，xml也会提出警告：

The vertically scrolling ScrollView should not contain another vertically scrolling widget (ListView)

#4 方法二：json数据结果改变

可以用一个ListView加载不同类型的item，当这要求后台个的json是单层的，将不同类型数据的条目都集成到一个Object上，只是字段不一样，让后再定义一个字段进行标记，加载不同item，不过要改变数据结构，server麻烦一下或者前段获取到数据后，重新组拼。优点是显示时比较简单，数据类型少时，实现容易，加载速度也快；缺点是重新组拼数据有可能比较麻烦，而且视图本来就是为了进行显示，不能本末倒置因为视图而去改变数据结果，在更复杂的业务逻辑中你会发现这样会很麻烦。

#5 方法三：多个LinerLayout动态添加

1. 原理：用ScrollView加LinerLayout实现，一个Linerlayout表示一种类型的数据，通过遍历数据集动态添加View，这里要注意的是当添加View时，用代码new出来，或用xml引入，要不停的new或inflat，如果只inflate一次，可能报异常如下：

java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.

2. 代码：

（1）xml：

activity_resolve.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

android:paddingBottom="@dimen/activity_vertical_margin"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

tools:context="com.bpj.listview.MainActivity" >

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginTop="15dp"

android:text="ScrollView中Linerlayout动态添加Item" />

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginTop="10dp"

android:orientation="horizontal" >

<TextView

android:id="@+id/tv_add1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="添加Item1" />

<TextView

android:id="@+id/tv_add2"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginLeft="30dp"

android:text="添加Item2" />

</LinearLayout>

<ScrollView

android:id="@+id/scrollview"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:layout_marginTop="15dp" >

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="vertical" >

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginTop="10dp"

android:text="标题一" />

<LinearLayout

android:id="@+id/ll_1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginTop="10dp"

android:orientation="vertical" />

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginTop="10dp"

android:text="标题二" />

<LinearLayout

android:id="@+id/ll_2"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="vertical" />

</LinearLayout>

</ScrollView>

</LinearLayout>

adapter_item1.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="40dp"

android:orientation="vertical" >

<TextView

android:id="@+id/textView1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="item1" />

<TextView

android:layout_gravity="center_horizontal"

android:id="@+id/textView2"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="TextView" />

</LinearLayout>

adapter_item2.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="70dp"

android:orientation="vertical" >

<TextView

android:id="@+id/textView1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginLeft="5dp"

android:text="item2" />

<ImageView

android:layout_gravity="center_horizontal"

android:id="@+id/imageView1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:src="@drawable/ic_launcher" />

</LinearLayout>

（2）Bean

public class BeanItem1 {}

public class BeanItem2 {}

（3）Activity：

public class SolveActivity extends Activity implements OnClickListener{

private LinearLayout ll_1,ll_2;

private TextView tv_add1,tv_add2;

private List<BeanItem1> mList1;

private List<BeanItem2> mList2;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_resolve);

ll_1 = (LinearLayout) findViewById(R.id.ll_1);

ll_2 = (LinearLayout) findViewById(R.id.ll_2);

tv_add1 = (TextView) findViewById(R.id.tv_add1);

tv_add2 = (TextView) findViewById(R.id.tv_add2);

tv_add1.setOnClickListener(this);

tv_add2.setOnClickListener(this);

initData();

setAdapter();

}

private void setAdapter() {

MySimpleAdapter adapter1 = new MySimpleAdapter(this, mList1);

adapter1.setView(ll_1);

MySimpleAdapter adapter2 = new MySimpleAdapter(this, mList2);

adapter2.setView(ll_2);

}

private void initData() {

mList1 = new ArrayList<BeanItem1>();

mList2 = new ArrayList<BeanItem2>();

for (int i = 0; i < 6; i++) {

BeanItem1 item1 = new BeanItem1();

mList1.add(item1);

}

for (int i = 0; i < 5; i++) {

BeanItem2 item2 = new BeanItem2();

mList2.add(item2);

}

public void onClick(View v) {

switch (v.getId()) {

case R.id.tv_add1:

View view = View.inflate(SolveActivity.this, R.layout.adapter_item1, null);

ll_1.addView(view);

break;

case R.id.tv_add2:

View view2 = View.inflate(SolveActivity.this, R.layout.adapter_item2, null);

ll_2.addView(view2);

break;

}

（4）Adapter：

public class MySimpleAdapter {

private Context mContext;

private List<?> mList;

public MySimpleAdapter(Context context,List<?> list){

mContext = context;

mList = list;

}

public void setView(LinearLayout ll){

View covertView;

for (int i = 0; i < mList.size(); i++) {

covertView = View.inflate(mContext, R.layout.adapter_item1, null);

ll.addView(covertView);

}

优点：不需要嵌套，Linerlayout也写可以写成动态添加到ScrollView中去，Adapter中的View可以是xml也可以直接new出来

缺点：每次都new或inflate，影响效率，可以像ListView的Adapter一样维持一个集合从而复用，具体参照BaseAdapter的源码

Demo下载地址：http://download.csdn.net/detail/baopengjian/

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