Android備考01 黑馬76期-day03 操作數據庫

 

 

數據庫創建以及原始方式操作數據庫

activity_main.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"
    tools:context=".MainActivity" >

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="click1"
        android:text="add" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="click2"
        android:text="delete" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="click3"
        android:text="update" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="click4"
        android:text="find" />

</LinearLayout>

MyOpenHelper.java

package com.example.sqlite2;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;


public class MyOpenHelper extends SQLiteOpenHelper {

	/**
	 * @param context 上下文
	 * @param name 數據庫的名字
	 * @param factory 創建cursor對象(就是遊標也即結果集)
	 * @param version 數據庫的版本
	 * 
	 */
	public MyOpenHelper(Context context) {
		super(context, "itheima.db", null, 3);
	}
	
	/**
	 * 數據庫第一創建時調用
	 * 特別適合做表格結構的初始化  
	 * 那麼可得此方法就是寫創建表的sql語句的
	 */
	@Override
	public void onCreate(SQLiteDatabase db) {
		//1. sqlite的id一般寫成 "_id"
		//2. 數據類型統一爲String 寫了和沒寫一樣 爲何和數據庫程序員融洽對接以及增加可讀性 企業還是要求規範寫
		db.execSQL("create table info(_id integer primary key autoincrement,name varchar(20))");
	}

	/**
	 * 數據庫版本升級時調用
	 * 適合於更新表結構
	 */
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		db.execSQL("alter table info add phone varchar(20)");
	}


}

MainActivity.java

package com.example.sqlite2;

import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {

    private MyOpenHelper helper;

	@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        helper = new MyOpenHelper(getApplicationContext());
        
        
        //打開或者創建數據庫 第一次創建
        //SQLiteDatabase writableDatabase = helper.getWritableDatabase();
        //打開或者創建數據庫 第一次創建 若磁盤滿 返回一個只讀的
//        SQLiteDatabase readableDatabase = helper.getReadableDatabase();
        
    }
    
    //點擊按鈕增加一條記錄
    public void click1(View v){
    	//[1]獲取數據庫對象
    	SQLiteDatabase db = helper.getWritableDatabase();
    	//[2]執行增加一條記錄的sql語句
    	db.execSQL("insert into info(name,phone) values(?,?);",new Object[]{"張三","14575651"});
    	//[3]數據庫用完關閉
    	db.close();
    }
    
    //刪除
    public void click2(View v){
    	SQLiteDatabase db = helper.getWritableDatabase();
    	db.execSQL("delete from info where name=?;", new Object[]{"張三"});
    	db.close();
    }
    
    //更新
    public void click3(View v){
    	SQLiteDatabase db = helper.getWritableDatabase();
    	db.execSQL("update info set phone=? where name=?;", new Object[]{"110120","張三"});
    	db.close();
    }
    
    //查詢
    public void click4(View v){
    	SQLiteDatabase db = helper.getReadableDatabase();
    	//獲取遊標  即結果集
    	Cursor cursor = db.rawQuery("select * from info;", null);
    	
    	if(cursor.getCount()<=0){
    		Toast.makeText(this, "數據庫空", 0).show();
    		return;
    	}
    	
    	StringBuffer ans=new StringBuffer();
    	//一行一行獲取數據
    	while(cursor.moveToNext()){
    		//編號重0開始  0是id不取
    		String name = cursor.getString(1);
    		String phone = cursor.getString(2);
    		ans.append("\nname:"+name+"   phone:"+phone);
    	}
    	Toast.makeText(this,ans, 0).show();
    	
    }
    
}

 

小結1

容易進行多表查詢

 

命令行訪問sqlite數據庫

adb shell
cd data/data
ls
cd com.example.sqlite2
ls
cd databases
ls
sqlite3 itheima.db
select * from info;

提示：sqlite3: not found
需要下載安裝sqlite3工具

★改變dos窗口的編碼（解決某些亂碼）

改爲gbk:  chcp 936

改爲u8: chcp 65001

 

 

使用api進行crud

有諸多好處，但寫起來特別複雜，不如直接寫sql語句

MainActivity.java

package com.example.sqlite2;

import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

import com.example.crud.R;

public class MainActivity extends Activity {

    private MyOpenHelper helper;

	@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        helper = new MyOpenHelper(getApplicationContext());
        
        
        //打開或者創建數據庫 第一次創建
        //SQLiteDatabase writableDatabase = helper.getWritableDatabase();
        //打開或者創建數據庫 第一次創建 若磁盤滿 返回一個只讀的
//        SQLiteDatabase readableDatabase = helper.getReadableDatabase();
        
    }
    
    //點擊按鈕增加一條記錄
    public void click1(View v){
    	//[1]獲取數據庫對象
    	SQLiteDatabase db = helper.getWritableDatabase();
    	//[2]執行增加一條記錄的sql語句
    	//db.execSQL("insert into info(name,phone) values(?,?);",new Object[]{"張三","14575651"});
    	/**
    	 * db.insert(table, nullColumnHack, values)
    	 * 
    	 * table:表名
    	 * values：ContentValues類內封裝一個map  key:列名   value:插入的值
    	 */
    	ContentValues values=new ContentValues();
    	values.put("name", "王五");
    	values.put("phone", "110");
    	//返回值爲插入新行的id
    	long insert = db.insert("info", null, values);//insert底層就在封裝sql語句
    	
    	//[3]數據庫用完關閉
    	db.close();
    	
    	if(insert>0){
    		Toast.makeText(getApplicationContext(), "添加成功!", 0).show();
    	}else{
    		Toast.makeText(getApplicationContext(), "添加失敗!", 0).show();
    	}
    	
    }
    
    //刪除
    public void click2(View v){
    	SQLiteDatabase db = helper.getWritableDatabase();
    	//db.execSQL("delete from info where name=?;", new Object[]{"張三"});
    	/**
    	 * db.delete(table, whereClause, whereArgs)
    	 * 
    	 * table:所刪表名
    	 * whereClause：刪除條件
    	 * whereArgs： 參數   注意是new String[]{}
    	 * 
    	 * 返回值：影響的行數
    	 */
    	int delete = db.delete("info", "name=?", new String[]{"王五"});
    	db.close();
    	
    	Toast.makeText(getApplicationContext(), "刪除了"+delete+"行！", 0).show();
    	
    }
    
    //更新
    public void click3(View v){
    	SQLiteDatabase db = helper.getWritableDatabase();
    	//db.execSQL("update info set phone=? where name=?;", new Object[]{"110120","張三"});
    	/**
    	 * db.update(table, values, whereClause, whereArgs)
    	 * 
    	 * table:表名
    	 * values：ContentValues  key:修改的列名   values:新的列值
    	 * whereClause:條件
    	 * whereArgs：參數
    	 * 返回值：更新了多少行
    	 */
    	
    	ContentValues values=new ContentValues();
    	values.put("phone", "114"); 
    	int update = db.update("info", values, "name=?", new String[]{"王五"});
    	db.close();
    	
    	Toast.makeText(getApplicationContext(), "更新了"+update+"行！", 0).show();
    	
    }
    
    //查詢
    public void click4(View v){
    	SQLiteDatabase db = helper.getReadableDatabase();
    	//獲取遊標  即結果集
    	//Cursor cursor = db.rawQuery("select * from info;", null);
    	/**
    	 * db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy)
    	 * 見名識義
    	 * columns：String[]  要查詢的列名   null代表查詢所有
    	 * selection: 查詢條件
    	 * selectionArgs: 查詢參數
    	 * groupBy：分組條件
    	 * having： 過濾條件
    	 * orderBy：排序條件
    	 * 
    	 * eg:db.query("info",new String[]{"phone"},"name=?",new String[]{"王五"},null,null,null);
    	 */
    	Cursor cursor = db.query("info",new String[]{"phone"},"name=?",
    							 new String[]{"王五"},null,null,null);
    	if(cursor.getCount()<=0){
    		Toast.makeText(this, "數據庫空", 0).show();
    		return;
    	}
    	
    	StringBuffer ans=new StringBuffer();
    	//一行一行獲取數據
    	while(cursor.moveToNext()){
    		//編號重0開始 注意此時只查詢一列 phone就是0
    		String phone = cursor.getString(0);
    		ans.append("\nphone:"+phone);
    	}
    	Toast.makeText(this,ans, 0).show();
    	
    }
    
}

 

 

 

Android事務模板（轉賬）

activity_main.xml

<RelativeLayout 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: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=".MainActivity" >

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

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginLeft="29dp"
        android:layout_marginTop="80dp"
        android:onClick="click"
        android:text="轉賬" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button1"
        android:layout_below="@+id/button1"
        android:layout_marginTop="125dp"
        android:onClick="click2"
        android:text="查詢" />

</RelativeLayout>

MyOpenHelper.java

package com.example.transaction;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class MyOpenHelper extends SQLiteOpenHelper {

	public MyOpenHelper(Context context) {
		super(context, "Account", null, 1);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		db.execSQL("create table info(_id integer primary key autoincrement,name varchar(20),phone varchar(20),account varchar(20))");
		db.execSQL("insert into info(name,phone,account) values('張三','110','3000')");
		db.execSQL("insert into info(name,phone,account) values('李四','120','3000')");
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
	}

}

MainActivity.java

package com.example.transaction;

import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {

	private SQLiteDatabase db;
	private SQLiteDatabase db2;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		MyOpenHelper myOpenHelper = new MyOpenHelper(getApplicationContext());
		db = myOpenHelper.getWritableDatabase();
		db2 = myOpenHelper.getReadableDatabase();

	}

	public void click(View v) {
		db.beginTransaction();//開啓事務
		try {
			db.execSQL("update info set account=account-100 where name=?",
					new String[] { "張三" });
			int i=1/0;
			db.execSQL("update info set account=account+100 where name=?",
					new String[] { "李四" });
			// 未發生異常會執行到此行，也就會幫你提交
			// 發生異常就不會執行到此行，自動回滾
			db.setTransactionSuccessful();
			Toast.makeText(getApplicationContext(), "轉賬成功!", 0).show();
		} catch (Exception e) {
			Toast.makeText(getApplicationContext(), "服務器忙，請稍後再試試~~", 0).show();
		} finally {
			db.endTransaction();//關閉事務
		}
	}

	//查詢所有
	public void click2(View v) {
		Cursor cursor = db2.rawQuery("select name,phone,account from info",
				null);
		StringBuffer sb = new StringBuffer();
		while (cursor.moveToNext()) {
			sb.append(cursor.getString(0) + "\t" + cursor.getString(1) + "\t"
					+ cursor.getString(2) + "\n");
		}
		Toast.makeText(getApplicationContext(), sb, 0).show();
	}
}

 

ListView控件入門

activity_main.xml裏寫一個文件，MainActivity.java裏用java代碼佈局顯示內容

activity_main.xml

<RelativeLayout 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: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=".MainActivity" >

   <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>

</RelativeLayout>

MainActivity.java

package com.example.listview;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        //[1]找到關心的控間
        ListView lv = (ListView) findViewById(R.id.lv);
        
        //[2]顯示數據 textview和其他普通控件有點區別 它的數據來源於數據適配器
        lv.setAdapter(new MyListAdapter());
        
    }
    
    /**
     * 初始化佈局代碼
     * @author Administrator
     *
     */
    //[3] 定義listview的數據適配器
    private class MyListAdapter extends BaseAdapter{
    	
    	//一共顯示多少條目
		@Override
		public int getCount() {
			return 100;
		}
		
		//返回指定position(重0開始)處的對象  用默認即可
		@Override
		public Object getItem(int position) {
			return null;
		}

		//返回position位置對應的id
		@Override
		public long getItemId(int position) {
			return 0;
		}
		
		/**
		 * 獲取一個view  用來顯示listview的數據 會作爲listview的一個條目出現
		 * 每條顯示多少
		 */
		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			TextView tv=new TextView(MainActivity.this);
			tv.setText("哈哈哈"+position);
			return tv;
		}
    }
}

 

ListView優化

佈局加滾動條

items採用複用技術，使得大大節省內存，也絕對不會內存溢出

activity_main.xml

<RelativeLayout 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: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=".MainActivity" >
	
    
   <ListView
        android:id="@+id/lv"
        android:fastScrollEnabled="true"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>

</RelativeLayout>

MainActivity.java

package com.example.listview;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        //[1]找到關心的控間
        ListView lv = (ListView) findViewById(R.id.lv);
        
        //[2]顯示數據 textview和其他普通控件有點區別 它的數據來源於數據適配器
        lv.setAdapter(new MyListAdapter());
        
    }
    
    /**
     * 初始化佈局代碼
     * @author Administrator
     *
     */
    //[3] 定義listview的數據適配器
    private class MyListAdapter extends BaseAdapter{
    	
    	//一共顯示多少條目
		@Override
		public int getCount() {
			return 1000;
		}
		
		//返回指定position(重0開始)處的對象  用默認即可
		@Override
		public Object getItem(int position) {
			return null;
		}

		//返回position位置對應的id
		@Override
		public long getItemId(int position) {
			return 0;
		}
		
		/**
		 * 獲取一個view  用來顯示listview的數據 會作爲listview的一個條目出現
		 * 每條顯示多少
		 */
		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
//			System.out.println("listview"+position);//說明界面上顯示一條才調用一次本方法
//			TextView tv=new TextView(MainActivity.this);//每次都new 內存不夠快速拖拽，前面的沒來得及釋放就會內存溢出
			
			TextView tv;
			//簡簡單單的判斷保證快速滑動也不會卡死  複用使得只用創建一屏能顯示的條目數個tv就行了
			if(convertView==null){
				tv=new TextView(MainActivity.this);
				System.out.println("創建view對象---"+position);
			}else{
				System.out.println("複用歷史緩存對象---"+position);
				tv=(TextView) convertView;
			}
			
			tv.setText("哈哈哈"+position);
			return tv;
		}
    }
}

 

 

奇怪現象

listview佈局中的android:layout_height="match_parent"   都寫match_parent  不要用wrap_content

都這麼寫：

<ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
         />

包裹內容就無法確定高度，也就無法準確計算出一屏一共需要new出多少個items就會多次嘗試最終new出很多多餘的item,效率會低點

 

 

listview練習複雜佈局

activity_main.xml

<RelativeLayout 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"
    tools:context=".MainActivity" >

    <ListView
        android:id="@+id/lv"
        android:fastScrollEnabled="true"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_marginTop="10dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >
	
    <ImageView
        android:id="@+id/iv_icon"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/pci" />
	<TextView 
	    android:id="@+id/iv_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@+id/iv_icon"
        android:singleLine="true"
        android:ellipsize="end"
        android:textColor="#000000"
        android:textSize="20sp"
        android:text="畢業生拒絕年薪300萬工作 選擇年薪200萬的華爲"
	    
	    />
	
	<TextView 
	    android:id="@+id/iv_messgae"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="5dp"
        android:layout_toRightOf="@+id/iv_icon"
        android:layout_below="@+id/iv_title"
        android:textColor="#999999"
        android:textSize="15sp"
        android:text="今天，剛畢業就年薪200萬”的話題衝上熱搜！他是誰？"
	    
	    />
	
    
</RelativeLayout>

MainActivity.java

package com.example.listviewLX;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        // [1]找到關心的控件
        ListView lv=(ListView) findViewById(R.id.lv);
        //[2]設置適配器佈局
        lv.setAdapter(new MyAdapter());
    }

    public class MyAdapter extends BaseAdapter{

		@Override
		public int getCount() {
			return 1000;
		}

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

		@Override
		public long getItemId(int position) {
			return 0;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			//[1]想辦法將自定義的佈局轉換爲一個view
			View view;
			if(convertView==null){
				/**
				 * View.inflate(context, resource, root)
				 * 
				 * 創建新的view對象 通過打氣筒inflate將一個xml佈局轉換爲一個view
				 * resource就是xml文件 通過R.layout找到
				 * root:ViewGroup類型 LinearLayout,reaLayout都繼承自ViewGroup，這種類型可以有自己的孩子
				 * 		root即用來指定默認的父親  此處只爲了轉換爲view,故用不到
				 */
				view = View.inflate(getApplicationContext(), R.layout.item, null);
			}else{
				//複用歷史緩存對象
				view=convertView;
			}
			return view;
		}
    	
    }
}

 

獲取打氣筒各種方法

3種方法，第一種最簡單，第三種最常用

// 獲取打氣筒方法一
view = View.inflate(getApplicationContext(), R.layout.item,null);

// 獲取打氣筒方法二
view = LayoutInflater.from(getApplicationContext()).inflate(R.layout.item, null);
				
//獲取打氣筒方法三
LayoutInflater layoutInflater=(LayoutInflater)getSystemService(LAYOUT_INFLATER_SERVICE);
view = layoutInflater.inflate(R.layout.item, null);

 

MainActivity.java

package com.example.listviewLX;

import android.os.Bundle;
import android.app.Activity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		// [1]找到關心的控件
		ListView lv = (ListView) findViewById(R.id.lv);
		// [2]設置適配器佈局
		lv.setAdapter(new MyAdapter());
	}

	public class MyAdapter extends BaseAdapter {

		@Override
		public int getCount() {
			return 1000;
		}

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

		@Override
		public long getItemId(int position) {
			return 0;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			// [1]想辦法將自定義的佈局轉換爲一個view
			View view;
			if (convertView == null) {
				/**
				 * View.inflate(context, resource, root)
				 * 
				 * 創建新的view對象 通過打氣筒inflate將一個xml佈局轉換爲一個view resource就是xml文件
				 * 通過R.layout找到 root:ViewGroup類型
				 * LinearLayout,reaLayout都繼承自ViewGroup，這種類型可以有自己的孩子
				 * root即用來指定默認的父親 此處只爲了轉換爲view,故用不到
				 */
				// 獲取打氣筒方法一
				// view = View.inflate(getApplicationContext(), R.layout.item,null);

				// 獲取打氣筒方法二
				//view = LayoutInflater.from(getApplicationContext()).inflate(R.layout.item, null);
				
				//獲取打氣筒方法三
				LayoutInflater layoutInflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
				view = layoutInflater.inflate(R.layout.item, null);

			} else {
				// 複用歷史緩存對象
				view = convertView;
			}
			return view;
		}

	}
}

 

每項顯示單一數據（textview）的listview適配器 arrayAdapter

activity_main.xml

<RelativeLayout 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: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=".MainActivity" >

    <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>

</RelativeLayout>

item.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="TextView" />

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="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/tv2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView" />

</LinearLayout>

MainActivity.java

package com.example.arrayadapter;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends Activity {

	String objects[]={"天河","紫英","夢璃","菱紗","天青","玄霄","夙玉"};
	
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        // [1]找到關心的控件
        ListView lv = (ListView) findViewById(R.id.lv);
        
        //顯式單一文本信息時不必要用basedaptor 用arrayadptor即可
        //[2]創建一個arrayAdapter   (注意此處的adapter的作用都只是專門顯式item到listview上)
        
        //方法1：注意自定義的R.layout.item只能是個textview  外面不能包什麼佈局
        //ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.item, objects);
        
        //方法2：自定義的R.layout.item2裏可以有佈局包裹了，但是一定要給定義的textview定義id 需要特別指定
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.item2, R.id.tv2, objects);
        
        //[3]設置數據適配器
        lv.setAdapter(adapter);
        
    }
}