android java编程 6.4.4 6.4.5
修改activity_main.xml文件<?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">
<Button
android:id="@+id/create_database"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="create database"/>
<Button
android:id="@+id/add_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Add data"/>
<Button
android:id="@+id/update_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Update data"/>
<Button
android:id="@+id/delete_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Delete data"/>
</LinearLayout>
修改mainactivity.java文件package com.example.xinwei.databasetest;
import android.content.ContentValues;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new MyDatabaseHelper(this,"BookStore.db",null,2);
Button createDatabase = (Button)findViewById(R.id.create_database);
createDatabase.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
dbHelper.getWritableDatabase();
}
});
addData();
updateData();
deleteData();
}
private void deleteData() {
Button deleteButton = (Button)findViewById(R.id.delete_data);
deleteButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.delete("book","pages>?",new String[]{"500"});
}
});
}
private void updateData() {
Button updateData = (Button)findViewById(R.id.update_data);
updateData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
SQLiteDatabase db=dbHelper.getWritableDatabase();
ContentValues values=new ContentValues();
values.put("price",10.99);
db.update("book",values,"name=?",new String[]{"The Da Vinci Code"});
}
});
}
private void addData() {
Button addData = (Button)findViewById(R.id.add_data);
addData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values=new ContentValues();
values.put("name","The Da Vinci Code");
values.put("author","Dan Brown");
values.put("pages",454);
values.put("price",16.96);
db.insert("book",null,values);
values.clear();
values.put("name","The Lost Temple");
values.put("author","Dan Brown");
values.put("pages",510);
values.put("price",19.95);
db.insert("book",null,values);
values.clear();
}
});
}
}
其中updateData()函数就是把达芬奇密码这本书的价格更新为10.99，deleteData()这个函数的作用是删除所有页数大于500的书。
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