我有一個大約15MB的數據（太大，無法存儲在每個設備上）的SQLite數據庫。我正在構建一個應用程序來與這些數據進行交互。如何從應用程序的存儲位置訪問數據庫。我不是要求某人爲我做這件事，但我該怎麼去研究如何做到這一點。是否有一個android模塊在傳遞一個ip地址（或FTP服務器IP？）之後執行此操作？我在哪裏開始研究託管我的數據庫的最佳方式，然後將其鏈接到我的應用程序？這是如何完成的高層簡介？謝謝！從Android應用程序訪問外部數據庫
兩種方式
您可以將查詢發送到Web服務器和檢索結果（你需要接受查詢並通過HTTP發送結果Web服務器URL）。
您可以下載數據庫並將其放入應用程序數據庫目錄，然後您可以查詢此數據庫。
試試這個，
把你externalDB文件夾資產並打開此文件，並在數據庫中編寫，然後訪問它請看下面的例子中資產的文件夾我的externalDB文件。
main.xml中
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button android:id="@+id/button01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Copy Database">
</Button>
</LinearLayout>
DatabaseHelper.java
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DatabaseHelper extends SQLiteOpenHelper{
//The Android's default system path of your application database.
String DB_PATH =null;
private static String DB_NAME = "extenalDB";
private SQLiteDatabase myDataBase;
private final Context myContext;
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
*/
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
DB_PATH="/data/data/"+context.getPackageName()+"/"+"databases/";
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing - database already exist
}else{
//By calling this method and empty database will be created into the default system path
//of your application so we are gonna be able to overwrite that database with our database.
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
}
if(checkDB != null){
checkDB.close();
}
Log.v("check DB", ""+checkDB);
return checkDB != null ? true : false;
}
/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
// Log.v("read", "1"+myInput.read(buffer));
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException{
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
//return cursor
public Cursor query(String table,String[] columns, String selection,String[] selectionArgs,String groupBy,String having,String orderBy){
return myDataBase.query("EMP_TABLE", null, null, null, null, null, null);
}
}
Main.java
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class CopyDbActivity extends Activity {
/** Called when the activity is first created. */
Cursor c=null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
((Button)findViewById(R.id.button01)).setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
DatabaseHelper myDbHelper = new DatabaseHelper(CopyDbActivity.this);
try {
myDbHelper.createDataBase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
try {
myDbHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
Toast.makeText(CopyDbActivity.this, "Success", Toast.LENGTH_SHORT).show();
c=myDbHelper.query("EMP_TABLE", null, null, null, null,null, null);
if(c.moveToFirst())
{
do {
Toast.makeText(CopyDbActivity.this,
"_id: " + c.getString(0) + "\n" +
"E_NAME: " + c.getString(1) + "\n" +
"E_AGE: " + c.getString(2) + "\n" +
"E_DEPT: " + c.getString(3),
Toast.LENGTH_LONG).show();
} while (c.moveToNext());
}
}
});
}
}
竭誠爲您服務。
[網絡服務]（https://en.wikipedia.org/wiki/Web_service）已經存在了15年以上，是當今大多數主要網站和移動應用程序的基礎。 – CommonsWare