【移动应用开发技术】android的ListView图文混搭

【移动应用开发技术】android的ListView图文混搭

main4.xml<?xml

version="1.0"

encoding="utf-8"?>

<LinearLayout

xmlns:android="/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent"

>

<ListView

android:id="@+id/listView4_1_1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

></ListView>

</LinearLayout>main4_item.xml<?xml

version="1.0"

encoding="utf-8"?>

<LinearLayout

xmlns:android="/apk/res/android"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal"

android:gravity="center"

>

<ImageView

android:id="@+id/p_w_picpathView4_1_1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:src="@drawable/ic_launcher"

/>

<TextView

android:id="@+id/textView4_1_1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="textView"

/>

</LinearLayout>MainActivity4package

com.example.listview;

import

java.util.ArrayList;

import

java.util.HashMap;

import

java.util.List;

import

java.util.Map;

import

android.R.anim;

import

android.R.drawable;

import

android.app.Activity;

import

android.os.Bundle;

import

android.widget.ListView;

import

android.widget.SimpleAdapter;

public

class

MainActivity4

extends

Activity{

private

ListView

listView;

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

//

TODO

Auto-generated

method

stub

super.onCreate(savedInstanceState);

setContentView(R.layout.main4);

listView=(ListView)

findViewById(R.id.listView4_1_1);

//一个列表项的内容

Map<String,

Object>

map=new

HashMap<String,

Object>();

map.put("p_w_picpath",

R.drawable.ic_launcher);

map.put("name",

"张三");

Map<String,

Object>

map2=new

HashMap<String,

Object>();

map2.put("p_w_picpath",

R.drawable.ic_launcher);

map2.put("name",

"王五");

List<Map<String,

Object>>

list=new

ArrayList<Map<String,Object>>();

list.add(map);

list.add(map2);

SimpleAdapter

simpleAdapter=new

SimpleAdapter(this,

list,

R.layout.main4_item,

new

String

[]

{"p_w_picpath","name"},

new

int

[]

{R.id.p_w_picpathView4_1_1,R.id.textView4_1_1});

listView.setAdapter(simpleAdapter);

}

}亦可以自定义Adaptermian5.xml<?xml

version="1.0"

encoding="utf-8"?>

<LinearLayout

xmlns:android="/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent"

>

<ListView

android:id="@+id/listView5_1_1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

></ListView>

</LinearLayout>main5_item.xml<?xml

version="1.0"

encoding="utf-8"?>

<LinearLayout

xmlns:android="/apk/res/android"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal"

android:gravity="center"

>

<ImageView

android:id="@+id/p_w_picpathView5_1_1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:src="@drawable/a"

/>

<TextView

android:id="@+id/textView5_1_1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="textView"

/>

</LinearLayout>MainActivity5package

com.example.listview;

import

android.app.Activity;

import

android.os.Bundle;

import

android.view.LayoutInflater;

import

android.view.View;

import

android.view.ViewGroup;

import

android.widget.BaseAdapter;

import

android.widget.ImageView;

import

android.widget.ListView;

import

android.widget.TextView;

public

class

MainActivity5

extends

Activity

{

private

ListView

listView;

//定义的数据

private

int

[]

p_w_picpaths={R.drawable.ic_launcher,R.drawable.ic_launcher};

private

String

[]

names={"xiaobai","xiaoming"};

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

//

TODO

Auto-generated

method

stub

super.onCreate(savedInstanceState);

setContentView(R.layout.main5);

listView=(ListView)

findViewById(R.id.listView5_1_1);

listView.setAdapter(new

MyAdapter());

}

//自定义适配器

class

MyAdapter

extends

BaseAdapter{

//获取列表项总数

@Override

public

int

getCount()

{

//

TODO

Auto-generated

method

stub

return

names.length;

}

//获取每一个列表项(根据下标获取)

@Override

public

Object

getItem(int

position)

{

//

TODO

Auto-generated

method

stub

return

names[position];

}

//获取每一个列表项的id

@Override

public

long

getItemId(int

position)

{

//

TODO

Auto-generated

method

stub

return

position;

}

//

@Override

public

View

getView(int

position,

View

convertView,

ViewGroup

parent)

{

//

TODO

Auto-generated

method

stub

//获取布局填充器

LayoutInflater

layoutInflater=getLayoutInflater();

//获取main5_item的布局模板

View

view=layoutInflater.inflate(R.layout.main5_item,

null);

//从得到的view查找相应view

ImageView

p_w_picpathView=(ImageView)

view.findViewById(R.id.p_w_picpathView5_1_1);

TextView

textView=(TextView)

view.findViewById(R.id.textView5_1_1);

p_w_picpathView.setImageResource(p_w_picpaths[position]);

textView.setText(names[position]);

return

view;

}

}

}这种方式会多次调用getView()方法优化方法main5.xml<?xml

version="1.0"

encoding="utf-8"?>

<LinearLayout

xmlns:android="/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent"

>

<ListView

android:id="@+id/listView5_1_1"

android:layout_width="match_parent"

android:layout_height="fill_parent"

></ListView>

</LinearLayout>

<!--

android:layout_height="wrap_content"

会导致在ListView中增加子组件时，多次重复调用getView方法

设置成

android:layout_height="fill_parent"

则每次增加新组建时调用一次

-->ListView设置成

android:layout_height="fill_parent"//屏幕一次显示7(假设)条记录，则调用7次getView方法，只负责在屏幕中显示的内容的创建，其他的在滑动显示时才创建

//因为ListView的高度设置为

android:layout_height="wrap_content"

//调用一次getView，绘制一次，增加子组件时会重新绘制(计算高度),所以会多次调用getView()方法

//增加一个组件，重新绘制ListView，

//每绘制一次ListView，每一个子组件都重新绘制(有几个子组件调用几次)

//ListView设置成

android:layout_height="fill_parent"

//只输出0,1,2,3,4,5一次

System.out.println("position:"+position);将activity中代码修改为： System.out.print("position:"+position);

System.out.println("

"+convertView);

//获取布局填充器

LayoutInflater

layoutInflater=getLayoutInflater();

//获取main5_item的布局模板,创建布局对象

//如果没有空闲的convertView，创建convertView，否则重复利用convertView

if(convertView==null){

convertView=layoutInflater.inflate(R.layout.main5_item,

null);

}convertView的使用，主要优化加载布局问题

增加优化二：内部类ViewHolder的使用。主要优化getView方法中每次回调用findviewByID()方法来获取一次控件的代码。新增加内部类ViewHolder,用于对控件的实力存储进行缓存。package

com.example.listview;

import

android.app.Activity;

import

android.os.Bundle;

import

android.view.LayoutInflater;

import

android.view.View;

import

android.view.ViewGroup;

import

android.widget.BaseAdapter;

import

android.widget.ImageView;

import

android.widget.ListView;

import

android.widget.TextView;

public

class

MainActivity5

extends

Activity

{

private

ListView

listView;

//定义的数据

private

int

[]

p_w_picpaths={R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher};

private

String

[]

names={"xiaobai","xiaoming","xiaobai","xiaoming","xiaobai","xiaoming","xiaobai","xiaoming","xiaobai","xiaoming","xiaobai","xiaoming"};

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

//

TODO

Auto-generated

method

stub

super.onCreate(savedInstanceState);

setContentView(R.layout.main5);

listView=(ListView)

findViewById(R.id.listView5_1_1);

listView.setAdapter(new

MyAdapter());

}

//自定义适配器

//ListView的优化：

//1.重复使用convertView对象

//2.使用viewHolder提高在容器中查找组件的效率

class

MyAdapter

extends

BaseAdapter{

//获取列表项总数

@Override

public

int

getCount()

{

//

TODO

Auto-generated

method

stub

return

names.length;

}

//获取每一个列表项(根据下标获取)

@Override

public

Object

getItem(int

position)

{

//

TODO

Auto-generated

method

stub

return

names[position];

}

//获取每一个列表项的id

@Override

public

long

getItemId(int

position)

{

//

TODO

Auto-generated

method

stub

return

position;

}

//

@Override

public

View

getView(int

position,

View

convertView,

ViewGroup

parent)

{

//

TODO

Auto-generated

method

stub

//屏幕一次显示7(假设)条记录，则调用7次getView方法，只负责在屏幕中显示的内容的创建，其他的在滑动显示时才创建

//因为ListView的高度设置为

android:layout_height="wrap_content"

//调用一次getView，绘制一次，增加子组件时会重新绘制(计算高度),所以会多次调用getView()方法

//增加一个组件，重新绘制ListView，

//每绘制一次ListView，每一个子组件都重新绘制(有几个子组件调用几次)

//ListView设置成

android:layout_height="fill_parent"

//只输出0,1,2,3,4,5一次

System.out.print("position:"+position);

System.out.println("

"+convertView);

//获取布局填充器

LayoutInflater

layoutInflater=getLayoutInflater();

//获取main5_item的布局模板,创建布局对象

//如果没有空闲的convertView，创建convertView，否则重复利用convertView

ViewHolder

viewHolder;

if(convertView==