1. 打开外部数据时，应该在AndroidManifest.xml文件中添加文件读写权限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/> package com.bwf.a11_sql_03; import android.app.Activity; import android.database.Cursor; import android.database.sqlite.SQLiteCantOpenDatabaseException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteException; import android.os.Bundle; import android.util.Log; public class MainActivity extends Activity { // 指定要打开数据库的全路径 String dbPath = "/storage/sdcard/DB/person.db"; Cursor cursor; String sql = ""; SQLiteDatabase db; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //openOrCreateDB(); //db_openDB(); //db_openOrCreateDb(); } /** * 使用SQLiteDatabase的openOrCreateDatabase方法打开或者创建数据库 * */ private void db_openOrCreateDb() { /** * @param String name 数据库的全路径 * @param CursorFactory factory 游标工厂 * */ db = SQLiteDatabase.openOrCreateDatabase(dbPath, null); hasTableToSelect(); } /** * 使用SQLiteDatabase的openDatabase方法打开数据库 * */ private void db_openDB() { try{ // 使用SQLiteDataBase的静态方法打开数据库， // 若数据库不存在则抛出异常SQLiteCantOpenDatabaseException /** * @param String name 数据库的全路径 * @param CursorFactory factory 游标工厂 * @param int mode 权限 * */ db = SQLiteDatabase.openDatabase(dbPath, null, MODE_PRIVATE); sql = "select * from person"; cursor = db.rawQuery(sql, null); showData(cursor); } catch(SQLiteCantOpenDatabaseException e){ // 处理异常 } } /** * 使用ContextWrapper中的openOrCreateDatabase方法打开或者创建数据库 * */ private void openOrCreateDB() { // 打开并使用外部数据库：ContextWrapper里边提供了方法，openOrCreateDatabase /** * @param String name 数据库的全路径 * @param int mode 权限 * @param CursorFactory factory 游标工厂 * */ db = openOrCreateDatabase(dbPath, MODE_PRIVATE, null); hasTableToSelect(); } /** * 直接查询或者建表插入数据后再查询 * */ private void hasTableToSelect() { try{ sql = "select * from person"; cursor = db.rawQuery(sql, null); } catch(SQLiteException s){ sql = "create table if not exists person(name varchar(10), age integer)"; db.execSQL(sql); sql = "insert into person values ('张三',22)"; db.execSQL(sql); sql = "insert into person values ('李三',21)"; db.execSQL(sql); sql = "select * from person"; cursor = db.rawQuery(sql, null); } showData(cursor); } /** * 取数据 * */ private void showData(Cursor cursor) { while(cursor.moveToNext()){ String name = cursor.getString(cursor.getColumnIndex("name")); int age = cursor.getInt(cursor.getColumnIndex("age")); Log.d("fanhy", "name:"+name+",age:"+age); } } } |
