如何在预加载的数据库中填充 ListView

Posted 2023-04-19

【中文标题】如何在预加载的数据库中填充 ListView

【英文标题】：How to populate ListView in a Preloaded Database

【发布时间】：2015-01-04 11:21:19

【问题描述】：

我正在尝试使用预加载的数据库创建列表视图，应用程序正在运行但数据未显示。请帮助我。我使用 Sqlite 的数据库浏览器。或者有人可以给我一个例子吗？

这是我的 DataListView.java

package com.example.thetrial;
import java.util.ArrayList;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;  
import android.database.sqlite.SQLiteException;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CursorAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class DataListView extends Activity 
private DBHelper dbDBHelper = null;
private Cursor ourCursor = null;
private DBAdapter adapter = null;

@Override
public void onCreate(Bundle savedInstanceState) 
    // TODO Auto-generated method stub
    try
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    ListView myListView = (ListView)findViewById(R.id.myListView);
dbDBHelper = new DBHelper(this);
dbDBHelper.createDataBase();
dbDBHelper.openDataBase();
ourCursor = dbDBHelper.getCursor();
startManagingCursor(ourCursor);
adapter = new DBAdapter(ourCursor);
myListView.setAdapter(adapter);
catch (Exception e)

    Log.e("Error", "Error in code: " + e.toString());
    e.printStackTrace();


class DBAdapter extends CursorAdapter
    DBAdapter(Cursor c)
        super(DataListView.this,c,0);
    

    @Override
    public void bindView(View view, Context context, Cursor cursor) 
        // TODO Auto-generated method stub
        DBHolder holder = (DBHolder)view.getTag();
        holder.populateFrom(cursor, dbDBHelper);
    

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) 
        // TODO Auto-generated method stub
        LayoutInflater inflater = getLayoutInflater();
        View view=inflater.inflate(R.layout.row, parent, false);
        DBHolder holder = new DBHolder(view);
        view.setTag(holder);
        return(view);
    


static class DBHolder 
    private TextView name = null;
    DBHolder (View view)
        name = (TextView)view.findViewById(R.id.text);

    
    void populateFrom(Cursor c, DBHelper r)
    name.setText(r.getName(c)); 
    
    

DBHelper.java

package com.example.thetrial;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Locale;
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.database.sqlite.SQLiteQueryBuilder;

public class DBHelper extends SQLiteOpenHelper

public SQLiteDatabase DB;
private static String DB_Path = "/data/data/com.example.thetrial/databases/";
private static String DB_Name = "trialakoagain.db";
public  static final String TABLE_Name = "linux_comm";
public static final String Column_Id = "_id";
public static final String Column_Comm = "comm";
public static final String Column_Desc = "desc";
private final Context myContext;


public DBHelper(Context context) 
    super(context, DB_Name, null, 1);
    this.myContext = context;
   

 public void createDataBase()

        boolean dbExist = checkDataBase();
        if(!dbExist)
            this.getReadableDatabase();
            copyDataBase();
         
 
        /*
        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");

            
        

    */
 private boolean checkDataBase() 
        // TODO Auto-generated method stub
     SQLiteDatabase checkDB = null;

        try
            String myPath = DB_Path + DB_Name;
            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
            checkDB.setLocale(Locale.getDefault());
            //checkDB.setLockingEnabled(true);
            checkDB.setVersion(1);

        catch(SQLiteException e)

            //database does't exist yet.

        

        if(checkDB != null)

            checkDB.close();

        

        return checkDB != null ? true : false;
     

private void copyDataBase()  
InputStream inputStream = null;
OutputStream outStream = null;
String outFileName = DB_Path + DB_Name;
try
    inputStream = myContext.getAssets().open(DB_Name);
    outStream = new FileOutputStream(outFileName);
    byte[] buffer = new byte[1024];
    int length;
    while ((length = inputStream.read(buffer)) > 0)
        outStream.write(buffer,0,length);
    
    outStream.flush();
    outStream.close();
    inputStream.close();
catch (IOException e)
    throw new Error("Problem copying db to resource!");



public void openDataBase() throws SQLException

        //Open the database
        String myPath = DB_Path + DB_Name;
        DB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

    

    @Override
    public synchronized void close() 

            if(DB != null)
                DB.close();

            super.close();

    

    @Override
    public void onCreate(SQLiteDatabase db) 

    

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 

    

        // Add your public helper methods to access and get content from the database.
       // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
       // to you to create adapters for your views.

    public Cursor getCursor()
        SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
        queryBuilder.setTables (TABLE_Name);
        String [] asColumnToReturn = new String [] Column_Id,Column_Comm,Column_Desc;

        Cursor mCursor = queryBuilder.query(DB, asColumnToReturn, null, null, null, null, null);
        return mCursor;

    
    public String getName(Cursor c)
        return(c.getString(2));
    

Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.thetrial"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="14"
    android:targetSdkVersion="21" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".DataListView"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

我不确定这些是否正确我只是看了一个教程，它从未说过 main.xml 和 row.xml 的需求是什么

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_
android:layout_
>
<ListView
android:id="@+id/myListView"
android:layout_
android:layout_ >
</ListView>

行.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_
android:layout_
android:orientation="vertical" >

<TextView
    android:id="@+id/text"
    android:layout_
    android:layout_
    />

【参考方案1】：

我认为问题的发生是因为您忘记将数据库中的项目添加到您的适配器：

adapter = new DBAdapter(ourCursor);
myListView.setAdapter(adapter);
//add your adapter data here
adapter.notifyDataSetChanged(); //dont forget to refresh your list

【讨论】：

我是 Java 新手，不知道如何添加适配器。你能告诉我怎么做吗？谢谢。