Android笔记（四十一） Android中的数据存储——SQLite（三）select

SQLite 通过query实现查询，它通过一系列参数来定义查询条件。

各参数说明：

query()方法参数	对应sql部分	描述
table	from table_name	表名称
colums	select column1,column2	列名称数组
selection	where column = value	条件子句，相当于where
selectionArgs	-	条件语句的参数数组
groupBy	group by column	分组
having	having column = value	分组条件
orderBy	order by column,column	排序类
limit		分页查询的限制
Cursor		返回值，相当于结果集ResultSet

针对游标（Cursor）也提供了不少方法

方法名称	方法描述
getCount()	总记录条数
isFirst()	判断是否第一条记录
isLast()	判断是否最后一条记录
moveToFirst()	移动到第一条记录
moveToLast()	移动到最后一条记录
move(int offset)	移动到指定的记录
moveToNext()	移动到下一条记录
moveToPrevious()	移动到上一条记录
getColumnIndex(String columnName)	获得指定列索引的int类型值

下面我们通过例子来演示一下SQLite中的查询：

不带参数查询

MainActivity.java

package cn.lixyz.sqlite;

import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

private EditText name, age;
private Button insertButton, selectButton;

private SQLiteDatabase database;
private MySQLiteOpenHelper msop;

public String inputSex;

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

findView();

msop = new MySQLiteOpenHelper(this, "user.db", null, 1);
database = msop.getReadableDatabase();

}

private void findView() {
name = (EditText) findViewById(R.id.name);
age = (EditText) findViewById(R.id.age);
insertButton = (Button) findViewById(R.id.insertButton);
selectButton = (Button) findViewById(R.id.selectButton);
}

public void clickButton(View view) {
switch (view.getId()) {
case R.id.selectButton:
selectData();
break;

case R.id.insertButton:
insertData();
break;
}
}

private void insertData() {
String inputAge = age.getText().toString();
String inputName = name.getText().toString();
ContentValues cv = new ContentValues();
cv.put("name", inputName);
cv.put("age", inputAge);
database.insert("user", null, cv);
Toast.makeText(MainActivity.this, "插入成功", Toast.LENGTH_SHORT).show();
age.setText("");
name.setText("");

}

private void selectData() {
Cursor c = database.query("user", null, null, null, null, null, null);
if (c.moveToFirst()) {
do {
int id = c.getInt(c.getColumnIndex("id"));
String name = c.getString(c.getColumnIndex("name"));
String age = c.getString(c.getColumnIndex("age"));
Log.d("TTTT", "id=" + id + ",姓名=" + name + ",年龄=" + age);
} while (c.moveToNext());
}
c.close();

}

class MySQLiteOpenHelper extends SQLiteOpenHelper {

private static final String CREATE_USER = "create table user(id integer primary key autoincrement,name text,age text)";

private Context mContext;

public MySQLiteOpenHelper(Context context, String name, CursorFactory factory, int version) {
super(context, name, factory, version);
mContext = context;
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_USER);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub

}

}
}

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" >

<EditText
android:id="@+id/name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="输入姓名" />

<EditText
android:id="@+id/age"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="输入年龄" />

<Button
android:id="@+id/insertButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="clickButton"
android:text="点击插入" />

<Button
android:id="@+id/selectButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="clickButton"
android:text="点击查询" />

</LinearLayout>

　　先插入几条数据，然后点击查询按钮：

带参数查询

通过rawQuery实现的带参数查询

修改一下代码

MainActivity.java

package cn.lixyz.sqlite;

import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

private EditText name, age, paramter;
private Button insertButton, selectButton, paramterSelect;

private SQLiteDatabase database;
private MySQLiteOpenHelper msop;

public String inputSex;

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

findView();

msop = new MySQLiteOpenHelper(this, "user.db", null, 1);
database = msop.getReadableDatabase();

}

private void findView() {
name = (EditText) findViewById(R.id.name);
age = (EditText) findViewById(R.id.age);
insertButton = (Button) findViewById(R.id.insertButton);
selectButton = (Button) findViewById(R.id.selectButton);
paramter = (EditText) findViewById(R.id.paramter);
paramterSelect = (Button) findViewById(R.id.paramterSelect);
}

public void clickButton(View view) {
switch (view.getId()) {
case R.id.selectButton:
selectData();
break;

case R.id.insertButton:
insertData();
break;
case R.id.paramterSelect:
paramterSelect();
}
}

private void paramterSelect() {
String inputAge = paramter.getText().toString();
Cursor c = database.rawQuery("select * from user where age>?", new String[] { inputAge });
if (c.moveToFirst()) {
do {
int id = c.getInt(c.getColumnIndex("id"));
String name = c.getString(c.getColumnIndex("name"));
String age = c.getString(c.getColumnIndex("age"));
Log.d("TTTT", "id=" + id + ",name=" + name + ",age=" + age);
} while (c.moveToNext());
}
c.close();

}

private void insertData() {
String inputAge = age.getText().toString();
String inputName = name.getText().toString();
ContentValues cv = new ContentValues();
cv.put("name", inputName);
cv.put("age", inputAge);
database.insert("user", null, cv);
Toast.makeText(MainActivity.this, "插入成功", Toast.LENGTH_SHORT).show();
age.setText("");
name.setText("");

}

private void selectData() {
Cursor c = database.query("user", null, null, null, null, null, null);
if (c.moveToFirst()) {
do {
int id = c.getInt(c.getColumnIndex("id"));
String name = c.getString(c.getColumnIndex("name"));
String age = c.getString(c.getColumnIndex("age"));
Log.d("TTTT", "id=" + id + ",姓名=" + name + ",年龄=" + age);
} while (c.moveToNext());
}
c.close();

}

class MySQLiteOpenHelper extends SQLiteOpenHelper {

private static final String CREATE_USER = "create table user(id integer primary key autoincrement,name text,age text)";

private Context mContext;

public MySQLiteOpenHelper(Context context, String name, CursorFactory factory, int version) {
super(context, name, factory, version);
mContext = context;
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_USER);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub

}

}
}

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" >

<EditText
android:id="@+id/name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="输入姓名" />

<EditText
android:id="@+id/age"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="输入年龄" />

<Button
android:id="@+id/insertButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="clickButton"
android:text="点击插入" />

<Button
android:id="@+id/selectButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="clickButton"
android:text="点击查询" />

<TextView
android:id="@+id/text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="条件搜索" />

<EditText
android:id="@+id/paramter"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="您要搜多少岁以上的？" />

<Button
android:id="@+id/paramterSelect"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="clickButton"
android:text="点击搜索" />

</LinearLayout>

　　运行结果：