1. activity_main.xml
Add the LinearLayout of the horizontal layout in the LinearLayout of the vertical layout, and then add EditText product name, EditText amount, ImageView add button
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<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="Trade name"
android:inputType="textPersonName" />
<EditText
android:id="@+id/balaceET"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:hint="Amount of money"
android:inputType="number" />
<ImageView
android:onClick="add"
android:id="@+id/addIV"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:srcCompat="@android:drawable/ic_input_add" />
</LinearLayout>
<ListView
android:id="@+id/accountLV"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@id/addLL"/>
</LinearLayout>2. Create ListView Item layout
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:padding="10dp">
<TextView
android:id="@+id/idTV"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="13"
android:textColor="#000000"
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="#000000"
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="#000000"
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="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="2dp"
app:srcCompat="@android:drawable/arrow_up_float" />
<ImageView
android:id="@+id/downIV"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
app:srcCompat="@android:drawable/arrow_down_float" />
</LinearLayout>
<ImageView
android:id="@+id/deleteIV"
android:layout_width="25dp"
android:layout_height="25dp"
app:srcCompat="@android:drawable/ic_menu_delete" />
</LinearLayout>
Three textviews are added to display the id, commodity name, and amount of a piece of data in the database. Three imageviews are used to increase, decrease, and delete data.
3. Create a database, create a package named dao under the package, and define a MyHelper class under the package to inherit from SQLiteOpenHelper,
public class MyHelper extends SQLiteOpenHelper {
public MyHelper(Context context){
super(context, "itcast.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(30), balance INTEGER)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
System.out.println("onUpgrade");
}
}
4. Create the Account class,
It is convenient to store the data in a JavaBean object when operating the database. Therefore, it is necessary to build a bean package to store JavaBean classes, and then define a class Account under the package. The code is as follows:
package com.example.product.bean;
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 "[Serial number:" + id + "，Commodity name:" + name + "，Balance:" + balance + "]";
}
}
5. Create database operation logic class
Create an AccountDao class under dao to operate data. The code is as follows
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();
}
// Delete data by id
public int delete(long id){
SQLiteDatabase db = helper.getWritableDatabase();
int count = db.delete("account", "_id=?", new String[]{id+""});
db.close();
return count;
}
// Update data
public int update(Account account){
SQLiteDatabase db = helper.getWritableDatabase();
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;
}
//Query all data in reverse order
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;
}
}
The above code is the logical class AccountDao of the operation database class, which creates methods for adding, deleting, modifying and querying data.
6. MainActivity.java
package com.example.product;
import java.util.List;
import android.app.Activity;
import android.app.AlertDialog.Builder;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
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.example.product.bean.Account;
import com.example.product.dao.AccountDao;
public class MainActivity extends Activity {
// Data set to be adapted
private List<Account> list;
// Database addition, deletion, modification and query operation class
private AccountDao dao;
// Enter EditText for name
private EditText nameET;
// EditText of the input amount
private EditText balanceET;
// Adapter
private MyAdapter adapter;
// ListView
private ListView accountLV;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Initialize control
initView();
dao = new AccountDao(this);
// Query all data from database
list = dao.queryAll();
adapter = new MyAdapter();
accountLV.setAdapter(adapter);// Add adapter to ListView (automatically generate entries from data)
}
// Initialize control
private void initView() {
accountLV = (ListView) findViewById(R.id.accountLV);
nameET = (EditText) findViewById(R.id.nameET);
balanceET = (EditText) findViewById(R.id.balanceET);
// Add listener to listen for item click event
accountLV.setOnItemClickListener(new MyOnItemClickListener());
}
//activity_mian.xml corresponds to the method triggered by click event of ImageView
public void add(View v) {
String name = nameET.getText().toString().trim();
String balance = balanceET.getText().toString().trim();
//balance.equals("") is equal to 0
//Type conversion if balance is not an empty string
Account a = new Account(name, balance.equals("") ? 0
: Integer.parseInt(balance));
dao.insert(a); // insert database
list.add(a); // Insert set
adapter.notifyDataSetChanged(); // Refresh interface
// Select the last
accountLV.setSelection(accountLV.getCount() - 1);
nameET.setText("");
balanceET.setText("");
}
// Customize an adapter (tool for loading data into ListView)
private class MyAdapter extends BaseAdapter {
public int getCount() { // Get the total number of entries
return list.size();
}
public Object getItem(int position) { // Get objects by location
return list.get(position);
}
public long getItemId(int position) { // Get id based on location
return position;
}
// Get an item view
public View getView(int position, View convertView, ViewGroup parent) {
// Reuse convertView
View item = convertView != null ? convertView : View.inflate(
getApplicationContext(), R.layout.item, null);
// Get TextView in this view
TextView idTV = (TextView) item.findViewById(R.id.idTV);
TextView nameTV = (TextView) item.findViewById(R.id.nameTV);
TextView balanceTV = (TextView) item.findViewById(R.id.balanceTV);
// Get Account object based on current location
final Account a = list.get(position);
// Put the data in the Account object into TextView
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);
//Click event triggered method of up arrow
upIV.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
a.setBalance(a.getBalance() + 1); // Modified value
notifyDataSetChanged(); // Refresh interface
dao.update(a); // Update database
}
});
//The method to trigger the click event of the down arrow
downIV.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
a.setBalance(a.getBalance() - 1);
notifyDataSetChanged();
dao.update(a);
}
});
//How to delete the click event trigger of pictures
deleteIV.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
//Pop up a dialog box before deleting data
android.content.DialogInterface.OnClickListener listener =
new android.content.DialogInterface.
OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
list.remove(a); // Remove from collection
dao.delete(a.getId()); // Remove from database
notifyDataSetChanged();// Refresh interface
}
};
Builder builder = new Builder(MainActivity.this); // create a dialog box
builder.setTitle("Are you sure you want to delete?"); // Set title
// Set the text of the OK button and the listener
builder.setPositiveButton("Determine", listener);
builder.setNegativeButton("cancel", null); // Set cancel button
builder.show(); // display a dialog box
}
});
return item;
}
}
//Item click event of ListView
private class MyOnItemClickListener implements OnItemClickListener {
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// Get the data on the click location
Account a = (Account) parent.getItemAtPosition(position);
Toast.makeText(getApplicationContext(), a.toString(),
Toast.LENGTH_SHORT).show();
}
}
}