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作者:日月光华    发表时间:2024-05-02 11:56:56     消息  查看  搜索  好友  邮件  复制  引用

Android-商品展示案例
                  
1.创建程序

创建一个名为“商品展示”的应用程序,将包名修改为cn.edu.bzu。

2.用户交互界面

(1)“商品展示”程序对应的布局文件(activity_main.xml)
线性布局下包含一个水平显示的线性布局和一个ListView控件垂直显示;在水平显示的线性布局(LinearLayout)下建两个文本控件(EditText)“商品名称”、“金额”和一个显示图片控件。文本属性Android:inputType其中使用到了ImageView的属性Android:src来指定ImageView要显示的图片,但是只显示图片原图大小;如果使用Android:src属性,图片的大小会根据ImageView的大小进行拉伸。此外,ListView控件以列表的形式展示具体数据的内容,并且能够根据数据的长度自适应屏幕的显示。例:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_margin="8dp"
    tools:context="cn.edu.bzu.showproduct.MainActivity">
<LinearLayout
    android:id="@+id/addLL"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">
    <EditText
        android:id="@+id/nameET"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:hint="商品名称"
        android:inputType="textPersonName"/>
    <EditText
        android:id="@+id/balanceET"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:hint="金额"
        android:inputType="number"/>
    <ImageView
        android:onClick="add"
        android:layout_width="30dp"
        android:layout_height="32dp"
        android:src="@drawable/input" />
</LinearLayout>
    <ListView
        android:id="@+id/accoutLV"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/addLL">
    </ListView>
</LinearLayout>

(2)ListView Item 布局(item.xml)

用到了ListView布局,故要编写一个ListView itemd的布局。在res/layout目录下建一个item.xml文件,该文件有三个TextView文本控件,分别用于显示数据库中的某条数据的id、商品名称、金额和三个ImageView图片控件用于增加、减少金额,删除数据。例:


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="10dp">
    <TextView
        android:id="@+id/idTV"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="1"
        android:textColor="@color/colorAccent"
        android:textSize="20sp"/>
    <TextView
        android:id="@+id/nameTV"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:text="PQ"
        android:textColor="@color/colorAccent"
        android:textSize="20sp"/>
    <TextView
        android:id="@+id/balanceTV"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:text="12345"
        android:textColor="@color/colorAccent"
        android:textSize="20sp"/>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <ImageView
            android:id="@+id/upIV"
            android:layout_width="18dp"
            android:layout_height="18dp"
            android:layout_marginBottom="2dp"
            android:src="@drawable/up"/>
        <ImageView
            android:id="@+id/downIV"
            android:layout_width="18dp"
            android:layout_height="18dp"
            android:src="@drawable/down"/>
    </LinearLayout>
    <ImageView
        android:id="@+id/deleteIV"
        android:layout_width="28dp"
        android:layout_height="40dp"
        android:src="@drawable/delete"/>
</LinearLayout>

3.创建数据库

数据库操作,在cn.itcast.product的包下创建一个名为dao 的包并在其下定义一个MyHelp类继承自SQLiteOpenHelper,代码如下:


public class MyHelper extends SQLiteOpenHelper {
    public MyHelper(Context context){
        super(context,"itcast.db",null,2);
    }
    public void onCreate(SQLiteDatabase db){
        System.out.println("onCreate");
        db.execSQL("CREATE TABLE account(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),BALANCE INTEGER)");
    }
    public  void  onUpgrade(SQLiteDatabase db,int oldVersion,int newViersion){
        System.out.println("onUpgrade");
    }
}

4.Account类

该类主要是创建JavaBean对象,用来存放操作数据库时的数据。在cn.itcast.product创建一个bean包存放JavaBean类,然后在cn.itcast.product.bean包下定义一个类Accout,代码如下:


package cn.edu.bzu.showproduct.bean;

/**
* Created by Administrator on 2017/5/4.
*/


public class Account {
    private Long id;
    private String name;
    private Integer balance;


    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getBalance() {
        return balance;
    }

    public void setBalance(Integer balance) {
        this.balance = balance;
    }
    public Account(Long id,String name,Integer balance){
        super();
        this.id=id;
        this.name=name;
        this.balance=balance;
    }
    public Account(String name,Integer balance){
        super();
        this.name=name;
        this.balance=balance;
    }
    public Account(){
        super();
    }
    public String toString(){
        return "[序号:"+id+",商品名称:"+name+",余额:"+balance+"]";
    }
}

5.创建数据操作逻辑类

在cn.itcast.product.dao包下建AccountDao类用于对数据进行增、删、改、查操作方法。
insert()方法中调用了db.insert()方法,这个方法第二个参数如果传入null,是无法插入一条空数据的,如果想插入一条空数据,第二个参数必须写一个列名,用来拼接SQL语句。
代码如下:


package cn.edu.bzu.showproduct.dao;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

import java.util.ArrayList;
import java.util.List;

import cn.edu.bzu.showproduct.bean.Account;

/**
* Created by Administrator on 2017/5/4.
*/


public class AccountDao {
    private MyHelper helper;

    public AccountDao(Context context) {
        helper = new MyHelper(context);
    }

    public void insert(Account account) {
        SQLiteDatabase db = helper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("name", account.getName());
        values.put("balance", account.getBalance());
        long id = db.insert("account", null, values);
        account.setId(id);
        db.close();
    }

    public int delete(long id) {
        SQLiteDatabase db = helper.getWritableDatabase();
        int count = db.delete("account", "_id=?", new String[]{id + ""});
        db.close();
        return count;
    }
    public int update(Account account){
        SQLiteDatabase db=helper.getWritableDatabase();
        ContentValues valuse=new ContentValues();
        valuse.put("name",account.getName());
        valuse.put("balance",account.getBalance());
        int count=db.update("account",valuse,"_id=?",new String[]{account.getId()+""});
        db.close();
        return count;
    }
    public List<Account> queryAll(){
        SQLiteDatabase db=helper.getReadableDatabase();
        Cursor c=db.query("account",null,null,null,null,null,"balance DESC");
        List<Account>list=new ArrayList<Account>();
        while (c.moveToNext()){
            long id=c.getLong(c.getColumnIndex("_id"));
            String name=c.getString(1);
            int balance=c.getInt(2);
            list.add(new Account(id,name,balance));
        }
        c.close();
        db.close();
        return list;
    }

}

6.编写界面交互代码

数据库的操作完成之后需要界面与数据库进行交互,用于实现将数据库中的数据以ListView的形式展示在界面上,代码如下:


package cn.edu.bzu.showproduct;

import android.content.DialogInterface;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.appindexing.Thing;
import com.google.android.gms.common.api.GoogleApiClient;

import org.w3c.dom.Text;

import java.util.List;

import cn.edu.bzu.showproduct.R;
import cn.edu.bzu.showproduct.bean.Account;
import cn.edu.bzu.showproduct.dao.AccountDao;
import cn.edu.bzu.showproduct.dao.MyHelper;

public class MainActivity extends AppCompatActivity {

    private List<Account> list;
    private AccountDao dao;
    private EditText nameET;
    private EditText balanceET;
    private MyAdapter adapter;
    private ListView accountLV;
    /**
     * ATTENTION: This was auto-generated to implement the App Indexing API.
     * See https://g.co/AppIndexing/AndroidStudio for more information.
     */

    private GoogleApiClient client;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        dao = new AccountDao(this);
        list = dao.queryAll();
        adapter = new MyAdapter();
        accountLV.setAdapter(adapter);
        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
    }

    private void initView() {
        accountLV = (ListView) findViewById(R.id.accoutLV);
        nameET = (EditText) findViewById(R.id.nameET);
        balanceET = (EditText) findViewById(R.id.balanceET);
        accountLV.setOnItemClickListener((AdapterView.OnItemClickListener) new MyOnItemClickListener());
    }

    public void add(View v) {
        String name = nameET.getText().toString().trim();
        String balance = balanceET.getText().toString().trim();
        Account a = new Account(name, balance.equals("") ? 0 : Integer.parseInt(balance));
        dao.insert(a);
        list.add(a);
        adapter.notifyDataSetChanged();
        accountLV.setSelection(accountLV.getCount() - 1);
        nameET.setText("");
        balanceET.setText("");
    }

    /**
     * ATTENTION: This was auto-generated to implement the App Indexing API.
     * See https://g.co/AppIndexing/AndroidStudio for more information.
     */

    public Action getIndexApiAction() {
        Thing object = new Thing.Builder()
                .setName("Main Page") // TODO: Define a title for the content shown.
                // TODO: Make sure this auto-generated URL is correct.
                .setUrl(Uri.parse("http://[ENTER-YOUR-URL-HERE]"))
                .build();
        return new Action.Builder(Action.TYPE_VIEW)
                .setObject(object)
                .setActionStatus(Action.STATUS_TYPE_COMPLETED)
                .build();
    }

    @Override
    public void onStart() {
        super.onStart();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client.connect();
        AppIndex.AppIndexApi.start(client, getIndexApiAction());
    }

    @Override
    public void onStop() {
        super.onStop();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        AppIndex.AppIndexApi.end(client, getIndexApiAction());
        client.disconnect();
    }

    private class MyAdapter extends BaseAdapter {
        public int getCount() {
            return list.size();
        }

        public Object getItem(int position) {
            return list.get(position);
        }

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

        public View getView(int position, View convertView, ViewGroup parent) {
            View item = convertView != null ? convertView : View.inflate(getApplicationContext(), R.layout.item, null);
            TextView idTV = (TextView) item.findViewById(R.id.idTV);
            TextView nameTV = (TextView) item.findViewById(R.id.nameTV);
            TextView balanceTV = (TextView) item.findViewById(R.id.balanceTV);
            final Account a = list.get(position);
            idTV.setText(a.getId() + "");
            nameTV.setText(a.getName());
            balanceTV.setText(a.getBalance());
            ImageView upIV = (ImageView) item.findViewById(R.id.upIV);
            ImageView downIV = (ImageView) item.findViewById(R.id.downIV);
            ImageView deleteIV = (ImageView) item.findViewById(R.id.deleteIV);
            upIV.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    a.setBalance(a.getBalance() + 1);
                    notifyDataSetChanged();
                    dao.update(a);
                }
            });
            downIV.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    a.setBalance(a.getBalance() - 1);
                    notifyDataSetChanged();
                    dao.update(a);
                }
            });
            deleteIV.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            list.remove(a);
                            dao.delete(a.getId());
                            notifyDataSetChanged();
                        }
                    };
                    Builder builder = new Builder(MainActivity.this);
                    builder.setTitle("确定要删除吗?");
                    builder.setPositiveButton("确定", listener);
                    builder.setNegativeButton("取消", null);
                    builder.show();
                }
            });
            return item;
        }
    }

    private class MyOnItemClickListener implements DialogInterface.OnClickListener {
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Account a = (Account) parent.getItemAtPosition(position);
            Toast.makeText(getApplicationContext(), a.toString(), Toast.LENGTH_SHORT).show();
        }
    }
}

7.运行程序

(1)“商品展示”界面;

点击在新窗口中浏览原图
CTRL+鼠标滚轮放大或缩小

点击在新窗口中浏览原图
CTRL+鼠标滚轮放大或缩小

(2)在提示“商品名称”和“金额”上的文本框中输入姓名和金额后单击“添加”按钮,添加数据至数据库并显示适配器到ListView中;
(3)单击条目的向上按钮,对应的金额将会增加,单击向下按钮,金额会减少;
(4)单击删除按钮,会弹出一个对话框,单击对话框的确认按钮就将第二条数据删除了;
(5)单击条目会弹出一个Toast,要实现该功能需要给ListView的item设置条目点击监听事件。
————————————————
版权声明:本文为CSDN博主「huilang_ai」的原创文章,遵循 CC 4.0 BY-SA 版权协议,转载请附上原文出处链接及本声明。
原文链接:https://blog.csdn.net/huilang_ai/article/details/71158485



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