微博随便看看

第一步，导入水果列表的代码。然后打开Fruit.java,添加变量：private String text;和private String time;分别的评论部分和显示时间的部分。添加Source-Generate Constructor using Fields,确定；再添加Getter、Setter方法。

第二步，这个时候系统会报错，打开MainActivity.java，修改initFruits()这个方法，Fruit apple = new Fruit("张小毛", R.drawable.p1,"好好学习天天向上！","4分钟前");下边的也类似。

第三步，打开FruitAdapter.java，修改 getView这个方法。添加TextView textView=(TextView)view.findViewById(R.id.textView);
TextView textView2=(TextView)view.findViewById(R.id.textView2);再添加textView.setText(fruit.getText());
textView2.setText(fruit.getTime());

第四步，自定义标题栏。

1.在res/value下建立mytitlebar.xml文件

<?xml version="1.0" encoding="utf-8"?>

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

    <style name="myTitleBg">

        <item name="android:background">#FF0000</item>

    </style>

    <style name="myTheme" parent="android:Theme">

        <item name="android:windowNoTitle">false</item>

        <item name="android:windowTitleSize">30dp</item>

        <item name="android:windowTitleBackgroundStyle">@style/myTitleBg</item>

    </style>

</resources>

2.修改AndroidManifest.xml文件

 android:theme="@style/myTheme"

下边是代码：

MainActivity.java

package com.example.ui_listview01;

import java.util.ArrayList;

import java.util.List;

import android.app.Activity;

import android.os.Bundle;

import android.view.Menu;

import android.view.View;

import android.widget.AdapterView;

import android.widget.Toast;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.ListView;

import com.example.ui_listview01.adpater.FruitAdapter;

import com.example.ui_listview01.model.Fruit;

public class MainActivity extends Activity {
private ListView lvFruits;
//1.准备好数据源
private List<Fruit> fruitList = new ArrayList<Fruit>();

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//1.准备好数据源
initFruits();

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

//2.创建Adapter

        FruitAdapter adapter=new FruitAdapter(this, R.layout.fruit_item,fruitList);

        

        //3.绑定AdapterView和Adapter之间的关联
lvFruits.setAdapter(adapter);
lvFruits.setOnItemClickListener(new OnItemClickListener() {

public void onItemClick(AdapterView<?> adapterView, View view, int position,
long id) {
   Fruit fruit=fruitList.get(position);
   Toast.makeText(MainActivity.this, fruit.getName(), Toast.LENGTH_SHORT).show();
}
});

}

private void initFruits() {
Fruit apple = new Fruit("张小毛", R.drawable.p1,"好好学习天天向上！","4分钟前");
fruitList.add(apple);
Fruit banana = new Fruit("郭小夏", R.drawable.p2,"今天风和日丽！","2分钟前");
fruitList.add(banana);
Fruit orange = new Fruit("李小春", R.drawable.p3,"今天心情很差。","5分钟前");
fruitList.add(orange);
Fruit watermelon = new Fruit("杨晓羞", R.drawable.p4,"你近来可好？","1小时前");
fruitList.add(watermelon);
Fruit pear = new Fruit("赵小冬", R.drawable.p5,"下雨了，睡觉！","2小时前");
fruitList.add(pear);
Fruit grape = new Fruit("夏小雨", R.drawable.p6,"我今天好悲催啊！","3.5小时前");
fruitList.add(grape);
Fruit pineapple = new Fruit(" 周小萌", R.drawable.p7,"三年不见，各自安好！","4小时前");
fruitList.add(pineapple);
Fruit strawberry = new Fruit("韩小晕", R.drawable.p8,"今晚想吃鸡公煲。","2天前");
fruitList.add(strawberry);
Fruit cherry = new Fruit("张一诺", R.drawable.p10,"青年，奋起。","2周前");
fruitList.add(cherry);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}

FruitAdapter.java

package com.example.ui_listview01.adpater;

import java.util.List;

import android.content.Context;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ArrayAdapter;

import android.widget.BaseAdapter;

import android.widget.ImageView;

import android.widget.TextView;

import com.example.ui_listview01.R;

import com.example.ui_listview01.model.Fruit;

//存在问题：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

public class FruitAdapter extends ArrayAdapter<Fruit> {
private int resourceId;
public FruitAdapter(Context context, int textViewResourceId,
List<Fruit> data) {
super(context, textViewResourceId, data);
resourceId=textViewResourceId;
}

// 这个方法在每个子项被滚动到屏幕内的时候会被调用
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Fruit fruit = getItem(position);
View view=LayoutInflater.from(getContext()).inflate(resourceId, null);
ImageView ivFruit=(ImageView) view.findViewById(R.id.ivFruit);
TextView tvFruit=(TextView) view.findViewById(R.id.tvFruit);
TextView textView=(TextView)view.findViewById(R.id.textView);
TextView textView2=(TextView)view.findViewById(R.id.textView2);
ivFruit.setImageResource(fruit.getImageId());
tvFruit.setText(fruit.getName());
textView.setText(fruit.getText());
textView2.setText(fruit.getTime());
return view;
}

}

FruitAdapterImprove1.java

package com.example.ui_listview01.adpater;

import android.content.Context;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ArrayAdapter;

import android.widget.ImageView;

import android.widget.TextView;

import com.example.ui_listview01.R;

import com.example.ui_listview01.model.Fruit;

//存在问题：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。

public class FruitAdapterImprove1 extends ArrayAdapter {

private int resourceId;

public FruitAdapterImprove1(Context context, int textViewResourceId) {
super(context, textViewResourceId);
resourceId = textViewResourceId;
}

// 这个方法在每个子项被滚动到屏幕内的时候会被调用
//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
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Fruit fruit = (Fruit) getItem(position);
View view=null;
if(convertView==null)
  view = LayoutInflater.from(getContext()).inflate(resourceId, null);
else
  view=convertView;
ImageView fruitImage = (ImageView) view.findViewById(R.id.ivFruit);
TextView fruitName = (TextView) view.findViewById(R.id.tvFruit);
fruitImage.setImageResource(fruit.getImageId());
fruitName.setText(fruit.getName());
return view;
}

}

FruitAdapterImprove2.java

package com.example.ui_listview01.adpater;

import android.content.Context;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ArrayAdapter;

import android.widget.ImageView;

import android.widget.TextView;

import com.example.ui_listview01.R;

import com.example.ui_listview01.model.Fruit;

//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。

public class FruitAdapterImprove2 extends ArrayAdapter {

private int resourceId;

public FruitAdapterImprove2(Context context, int textViewResourceId) {
super(context, textViewResourceId);
resourceId = textViewResourceId;
}

// 这个方法在每个子项被滚动到屏幕内的时候会被调用
// 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
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Fruit fruit = (Fruit) getItem(position);
View view = null;
ViewHolder viewHolder;
if (convertView == null) {
view = LayoutInflater.from(getContext()).inflate(resourceId, null);
viewHolder = new ViewHolder();
viewHolder.ivFruit = (ImageView) view.findViewById(R.id.ivFruit);
viewHolder.tvFruit = (TextView) view.findViewById(R.id.tvFruit);
view.setTag(viewHolder);
} else {
view = convertView;
viewHolder = (ViewHolder) convertView.getTag();
}
viewHolder.ivFruit.setImageResource(fruit.getImageId());
viewHolder.tvFruit.setText(fruit.getName());
return view;
}

class ViewHolder {

ImageView ivFruit;

TextView tvFruit;

}

}

Fruit.java

package com.example.ui_listview01.model;

public class Fruit {
private String name;
private int imageId;
private String text;
private String time;
public Fruit(String name, int imageId, String text, String time) {
super();
this.name = name;
this.imageId = imageId;
this.text = text;
this.time = time;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getImageId() {
return imageId;
}
public void setImageId(int imageId) {
this.imageId = imageId;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
public String getTime() {
return time;
}
public void setTime(String time) {
this.time = time;
}

}

fruit_item.xml

<?xml version="1.0" encoding="utf-8"?>

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

    android:layout_width="match_parent"

    android:layout_height="wrap_content"

    android:orientation="horizontal" >

    <ImageView

        android:id="@+id/ivFruit"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:src="@drawable/p1" />

    <TextView

        android:id="@+id/tvFruit"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_margin="10dp"

        android:layout_marginLeft="27dp"

        android:layout_toRightOf="@+id/ivFruit"

        android:text="Apple" />

    <TextView

        android:id="@+id/textView"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignLeft="@+id/tvFruit"

        android:layout_below="@+id/tvFruit"

        android:layout_marginLeft="21dp"

        android:text="今天真高兴" />

    <TextView

        android:id="@+id/textView2"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignBaseline="@+id/tvFruit"

        android:layout_alignBottom="@+id/tvFruit"

        android:layout_alignParentRight="true"

        android:layout_marginRight="16dp"

        android:text="TextView" />

< /RelativeLayout>

activity_main.xml

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

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

    android:id="@+id/LinearLayout1"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"

    tools:context=".MainActivity" >

    <ListView

        android:id="@+id/lvFruits"

        android:layout_width="match_parent"

        android:layout_height="wrap_content" >

    </ListView>

< /LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

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

    package="com.example.ui_listview01"

    android:versionCode="1"

    android:versionName="1.0" >

    

    <uses-sdk

        android:minSdkVersion="8"

        android:targetSdkVersion="17" />

    <application

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/myTheme" >

        <activity

            android:name="com.example.ui_listview01.MainActivity"

            android:label="@string/app_name" >

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

< /manifest>