1

我第一次在 Android 中使用 sqlite 数据库，我在 Sqlite 中创建了我的数据库并将其复制到 android“资产”，我想通过“单击”“按钮”从数据库中获取数据，我有一个表包含4 个字段“ID、位置、纬度、经度”，但我无法从中获取任何数据。在我的 xml 中，我为插入数据“纬度”和“经度”制作了两个“编辑文本”，然后使用“搜索”按钮从数据库中获取数据位置。但我无法获得任何数据。我是安卓新手，请帮帮我

在这里我发布我的代码

数据库适配器

package com.joel.databases;

import java.io.IOException;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;

import android.content.Context;
import android.content.res.AssetManager;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

public class DBAdapter {

private static String DB_PATH = "/data/data/com.tracking/databases/";
private static String DB_NAME = "tracking.sqlite";
private SQLiteDatabase db; 
//private final Context myContext;
private DBAdapter DBHelper;
private final Context context;

public DBAdapter(Context ctx) 
{
    this.context = ctx;
    DBHelper = new DBAdapter(context);
    //super(context, DB_NAME, null, 1);
    //this.myContext = context;
}

public void createDataBase() throws IOException {
    boolean dbExist = checkDataBase();
    if (!dbExist) {
        /*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 file.");
        }
      }
     } 

private void getReadableDatabase() {
    // TODO Auto-generated method stub

}

public 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();
    }
    return checkDB != null ? true : false;
    }

private void copyDataBase() throws IOException{
    InputStream myinput =               
     context.getApplicationContext().getAssets().open(DB_NAME);
    OutputStream myoutput = new FileOutputStream("/data/data/com.tracking 
     /databases/"+ context.getApplicationContext().getPackageName() +"/databases
     /tracking.sqlite");
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myinput.read(buffer)) > 0) {
        myoutput.write(buffer, 0, length);
    }

    myoutput.flush();
    myoutput.close();
    myinput.close();


  }

  public void openDataBase() throws SQLException{
      //Open the database
      String myPath = DB_PATH + DB_NAME;
      db = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    }


    public synchronized void close() {
    if(db != null) db.close();
    db.close();
}

public void onCreate(SQLiteDatabase db) {}

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}
    }

这是我的database.java

   package com.joel.databases;

   //import com.google.android.maps.MapView;
   import com.joel.databases.R;
   import android.app.Activity;
   import android.os.Bundle;
   import java.io.IOException;
   import android.app.Dialog;
   import android.app.ListActivity;
    import android.app.ProgressDialog;
    import android.content.Intent;
    import android.os.AsyncTask;
   import android.os.Bundle;
   import android.view.View;
   import android.widget.AdapterView;
   import android.widget.ArrayAdapter;
   import android.widget.Button;
   import android.widget.ListView;
   import android.widget.Toast;
   import android.widget.AdapterView.OnItemClickListener;
   import android.database.Cursor;

    public class databases extends Activity {
    /** Called when the activity is first created. */
private Button cari;
private databases this_class = this;



    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    DBAdapter db = new DBAdapter(this); 
    db.openDataBase();

    cari = (Button) findViewById(R.id.cari);
     // cari.setOnClickListener(new Button.OnClickListener(){
    //public void onClick(View v){
    InitDatabase();
    }



     public void InitDatabase() {
     AsyncTask<String, Void, String> InitDB = new AsyncTask<String, Void, String>() {
        Dialog progress = null;
        String msg;
        DBAdapter db_adapter;

        @Override
        protected void onPreExecute() {
            db_adapter = new DBAdapter(this_class);
            if (!db_adapter.checkDataBase())
            progress = ProgressDialog.show(this_class, "", "Installing 
         Database.\nPlease wait.");
            super.onPreExecute();
        }

        @Override
        protected String doInBackground(String... params) {
            try {
                db_adapter.createDataBase();
                msg = "Database successfully installed.";
            } catch (IOException ioe) {
                msg = "Database installation failed.";
            }
            return msg;
         }

          @Override
         protected void onPostExecute(String result) {
            super.onPostExecute(result);
            if (progress!=null) {
                progress.dismiss();
                Toast.makeText(getApplicationContext(), result, 
          Toast.LENGTH_SHORT).show();
             }
          }
         };
        InitDB.execute(new String());
         } 

         }
4

3 回答 3

1

利用

 OutputStream myoutput = new FileOutputStream(DB_PATH + DB_NAME);

代替

 OutputStream myoutput = new FileOutputStream("/data/data/com.tracking 
     /databases/"+ context.getApplicationContext().getPackageName() +"/databases
     /tracking.sqlite");
于 2012-05-09T20:50:55.147 回答
0

看看这个链接

http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/

它解释了如何在您的 Android 应用程序中使用和访问一个独立的、预加载的数据库。

于 2012-05-09T21:30:19.067 回答
0

显然，你想要达到的目标远远超出了你的水平——我诚实且不受欢迎的建议是：花一些时间在一些更简单的平台上编写简单的东西。这样，您就可以继续前进，而无需一直寻求人们的帮助。独自前进是唯一能让你学习的东西。

然后学习一些 Java（只是基础知识，但包括语言和它周围的部分，比如命名约定）。

然后回到安卓。突然间，所有的教程和 api 文档都开始对你有意义了。

于 2012-05-28T22:01:41.340 回答