文章目录
-
- Android SQLite数据库
-
-
- 布局文件
- 主界面代码
- 找到当前应用的文件目录和数据库文件
- 电脑和模拟器共享的文件目录
- 使用SQLiteOpenHelper
-
- 定义一个StudentOpenHelper
- 布局文件
- 增删查改学生
- 定义ContentProvider
Android SQLite数据库
布局文件
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:orientation="vertical">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="创建/打开数据库"
android:id="@+id/btn_1"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="创建数据表"
android:id="@+id/btn_2"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="插入数据"
android:id="@+id/btn_3"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="查询数据"
android:id="@+id/btn_4"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删除数据"
android:id="@+id/btn_5"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="更新数据"
android:id="@+id/btn_6"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="查询结果"
android:id="@+id/tv_result"/>
LinearLayout>
主界面代码
package com.example.demo;
import androidx.appcompat.app.AppCompatActivity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import java.io.File;
public class MainActivity extends AppCompatActivity {
private Button btn1;
private Button btn2;
private Button btn3;
private Button btn4;
private Button btn5;
private Button btn6;
private TextView tv_result;
private SQLiteDatabase sqLiteDatabase;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn1 = findViewById(R.id.btn_1);
btn1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String dbFilePath = getFilesDir().getAbsolutePath() + File.separator + "stu.db";
sqLiteDatabase =
SQLiteDatabase.openOrCreateDatabase(dbFilePath, null);
}
});
btn2 = findViewById(R.id.btn_2);
btn2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String sql = "create table if not exists student (stuno varchar, name varchar, age int)";
sqLiteDatabase.execSQL(sql);
}
});
btn3 = findViewById(R.id.btn_3);
btn3.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ContentValues contentValues = new ContentValues();
contentValues.put("stuno","2019555");
contentValues.put("name", "黄心怡");
contentValues.put("age", 19);
sqLiteDatabase.insert("student", null,contentValues);
}
});
tv_result = findViewById(R.id.tv_result);
btn4 = findViewById(R.id.btn_4);
btn4.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Cursor cursor = sqLiteDatabase.query("student",null,null,null,
null,null,null);
StringBuffer stringBuffer = new StringBuffer();
for(cursor.moveToFirst(); !cursor.isAfterLast();cursor.moveToNext()){
String stuno = cursor.getString(0);
String name = cursor.getString(1);
int age = cursor.getInt(2);
stringBuffer.append(stuno).append(" ").append(name).append(" ").append(age).append("\n");
}
tv_result.setText(stringBuffer);
}
});
btn5 = findViewById(R.id.btn_5);
btn5.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String[] args = {
"黄心怡"};
sqLiteDatabase.delete("student", "name=?", args);
}
});
btn6 = findViewById(R.id.btn_6);
btn6.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ContentValues contentValues = new ContentValues();
contentValues.put("name","李佩珊");
contentValues.put("age", 18);
sqLiteDatabase.update("student", contentValues, "stuno='2019555'", null);
}
});
}
}
找到当前应用的文件目录和数据库文件
电脑和模拟器共享的文件目录
使用SQLiteOpenHelper
定义一个StudentOpenHelper
package com.example.demo;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import androidx.annotation.Nullable;
public class StudentOpenHelper extends SQLiteOpenHelper {
public StudentOpenHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.e("StudentOpenHelper", "onCreate");
String sql = "create table student (id varchar, name varchar, age int, address varchar)";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if(oldVersion == 1 && newVersion == 2){
String sql = "alter table student add address varchar";
db.execSQL(sql);
}
}
}
布局文件
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:orientation="vertical">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="添加学生"
android:id="@+id/btn_add"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="查询学生"
android:id="@+id/btn_query"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删除学生"
android:id="@+id/btn_delete"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="更新学生"
android:id="@+id/btn_update"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/tv_query"
android:text="查询结果"/>
LinearLayout>
增删查改学生
package com.example.demo;
import androidx.appcompat.app.AppCompatActivity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private Button btn_add;
private Button btn_query;
private Button btn_delete;
private Button btn_update;
private TextView tv_query;
private StudentOpenHelper studentOpenHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
studentOpenHelper = new StudentOpenHelper(MainActivity.this,
"stu.db", null, 2);
tv_query = findViewById(R.id.tv_query);
btn_add = findViewById(R.id.btn_add);
btn_add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
addUseContentProvider();
}
});
btn_query = findViewById(R.id.btn_query);
btn_query.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
queryUseContentProvider();
}
});
btn_delete = findViewById(R.id.btn_delete);
btn_delete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase writableDatabase = studentOpenHelper.getWritableDatabase();
String where = "name = '蓝宁宁'";
int rows = writableDatabase.delete("student", where, null);
Toast.makeText(MainActivity.this, "删除了" + rows + "行", Toast.LENGTH_SHORT).show();
}
});
btn_update = findViewById(R.id.btn_update);
btn_update.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase writableDatabase = studentOpenHelper.getWritableDatabase();
String where = "name = '李碧珊'";
ContentValues contentValues = new ContentValues();
contentValues.put("age", 20);
int rows = writableDatabase.update("student", contentValues, where, null);
Toast.makeText(MainActivity.this, "更新了" + rows + "行", Toast.LENGTH_SHORT).show();
}
});
}
private void addUseContentProvider() {
ContentValues contentValues = new ContentValues();
contentValues.put("id", 1004);
contentValues.put("name", "李四");
contentValues.put("age", 19);
contentValues.put("address", "天源路789");
getContentResolver().insert(StudentProvider.URI_STUDENT, contentValues);
}
private void addUseOpenHelper() {
SQLiteDatabase writableDatabase = studentOpenHelper.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("id", 1003);
contentValues.put("name", "许泽森");
contentValues.put("age", 19);
contentValues.put("address", "天源路789");
writableDatabase.insert("student", null, contentValues);
}
private void queryUseContentProvider() {
Cursor cursor = getContentResolver().query(StudentProvider.URI_STUDENT, null,
null, null, null);
StringBuffer stringBuffer = new StringBuffer();
for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {
String id = cursor.getString(0);
String name = cursor.getString(1);
int age = cursor.getInt(2);
String address = cursor.getString(3);
stringBuffer.append("学号").append(id).append(" 姓名").append(name).append(" 年龄").append(age).append(" 地址").append(address).append("\n");
tv_query.setText(stringBuffer.toString());
}
}
private void queryUseOpenHelper() {
SQLiteDatabase readableDatabase = studentOpenHelper.getReadableDatabase();
Cursor cursor = readableDatabase.query("student", null, null, null, null, null, null);
StringBuffer stringBuffer = new StringBuffer();
for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {
String id = cursor.getString(0);
String name = cursor.getString(1);
int age = cursor.getInt(2);
String address = cursor.getString(3);
stringBuffer.append("学号").append(id).append(" 姓名").append(name).append(" 年龄").append(age).append(" 地址").append(address).append("\n");
tv_query.setText(stringBuffer.toString());
}
}
}
定义ContentProvider
package com.example.demo;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
public class StudentProvider extends ContentProvider {
private StudentOpenHelper studentOpenHelper;
public static Uri URI_STUDENT = Uri.parse("content://com.example.demo/student");
Uri URI_SCORE = Uri.parse("content://com.example.demo/score");
static UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
static {
uriMatcher.addURI("com.example.demo","student", 1);
uriMatcher.addURI("com.example.demo","score", 2);
}
@Override
public boolean onCreate() {
studentOpenHelper = new StudentOpenHelper(getContext(),"stu.db"
, null, 2);
return false;
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
SQLiteDatabase readableDatabase = studentOpenHelper.getReadableDatabase();
int match = uriMatcher.match(uri);
if(match == 1){
return readableDatabase.query("student", projection, selection, selectionArgs, null ,null, sortOrder );
}
return null;
}
@Nullable
@Override
public String getType(@NonNull Uri uri) {
return null;
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
SQLiteDatabase writableDatabase = studentOpenHelper.getWritableDatabase();
if(uriMatcher.match(uri) == 1){
writableDatabase.insert("student", null, values);
writableDatabase.close();
}
return null;
}
@Override
public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
return 0;
}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
return 0;
}
}
