SQLite数据库应用之商品展示

一、设计主界面

使用系统自带的图片作为drawable使用的图片

主布局：activity_main

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:padding="10dp">
<TextView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/idTV"
android:layout_weight="1"
android:text="13"
android:textColor="#000000"
android:textSize="20sp" />
<TextView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/nameTV"
android:layout_weight="2"
android:text="PQ"
android:singleLine="true"
android:textColor="#000000"
android:textSize="20sp" />
<TextView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/balanceTV"
android:layout_weight="2"
android:text="12345"
android:singleLine="true"
android:textColor="#000000"
android:textSize="20sp" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/upIV"
android:layout_marginBottom="2dp"
android:src="@android:drawable/arrow_up_float"/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/downIV"
android:layout_marginBottom="2dp"
android:src="@android:drawable/arrow_down_float"/>
</LinearLayout>
<ImageView
android:layout_width="25dp"
android:layout_height="25dp"
android:id="@+id/deleteIV"
android:src="@android:drawable/ic_menu_delete"/>
</LinearLayout>

二、创建ListView Item布局

创建了三个TextView和三个ImageView

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:padding="10dp">
<TextView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/idTV"
android:layout_weight="1"
android:text="13"
android:textColor="#000000"
android:textSize="20sp" />
<TextView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/nameTV"
android:layout_weight="2"
android:text="PQ"
android:singleLine="true"
android:textColor="#000000"
android:textSize="20sp" />
<TextView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/balanceTV"
android:layout_weight="2"
android:text="12345"
android:singleLine="true"
android:textColor="#000000"
android:textSize="20sp" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/upIV"
android:layout_marginBottom="2dp"
android:src="@android:drawable/arrow_up_float"/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/downIV"
android:layout_marginBottom="2dp"
android:src="@android:drawable/arrow_down_float"/>
</LinearLayout>
<ImageView
android:layout_width="25dp"
android:layout_height="25dp"
android:id="@+id/deleteIV"
android:src="@android:drawable/ic_menu_delete"/>
</Linea
ee54
rLayout>

在系统包下创建一个名为dao的包 定义一个MyHelper类继承SQLiteOpenHelper

代码如下:

public class MyHelper extends SQLiteOpenHelper {
public MyHelper(Context context) {
super(context,"18Lab10.db", null, 2);
}
@Override
public void onCreate(SQLiteDatabase db) {
System.out.println("onCreate");
db.execSQL("CREATE TABLE account(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),balance INTEGER)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
System.out.println("onUpgrade");
}
}

在操作数据库时将数据存放在一个对象中操作会更方便，因此需要创建一个bean包来存放Javabean类然后再定义一个类Account

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();
}

@Override
public String toString() {
return "[序号：" + id +
", 商品名称'" + name + '\'' +
", 余额：" + balance +
']';
}
}

五、创建数据操作逻辑类

在dao包下创建一个AccountDao类用于操作数据

public class AccountDao {
private MyHelper helper;
SQLiteDatabase db=helper.getWritableDatabase();

public AccountDao(Context context) {
helper=new MyHelper(context);
}
public void insert(Account account){
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){
int count=db.delete("account","_id=?",new String[] {id+""});
db.close();
return count;
}
public int update(Account account){
ContentValues values=new ContentValues();
values.put("name",account.getName());
values.put("balance",account.getBalance());
int count=db.update("account",values,"_id=?",new String[] {account.getId()+""});
db.close();
return count;
}

public List<Account> queryAll(){
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;
}
}

六、编写界面交互代码（main_activity）

public class MainActivity extends AppCompatActivity {
private List<Account> list;
private AccountDao dao;
private EditText nameET;
private EditText balanceET;
private MyAdapter adapter;
private ListView accountLV;

@Override
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);
}

private void initView() {
accountLV = (ListView) findViewById(R.id.accountLV);
nameET = (EditText) findViewById(R.id.nameET);
balanceET = (EditText) findViewById(R.id.balanceET);
accountLV.setOnItemClickListener(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("");
}

public 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;
}

@Override
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();
}
};
AlertDialog.Builder builder=new AlertDialog.Builder(MainActivity.this);
builder.setTitle("确定要删除吗？");
builder.setNegativeButton("取消",null);
builder.setPositiveButton("确定",listener);
builder.show();
}
});
return item;
}
}

private class MyOnItemClickListener implements AdapterView.OnItemClickListener {
@Override
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();
}
}
}

构造出我们需要的对话框，然 后调用show方法显示出来，

在onCreate方法中调用，只需传入this即 可。