java - 如何从数据库添加图像到 ListView 中？

Question

你能告诉我或给我一些代码，我需要添加这些代码才能从我的数据库中检索图像。我是 Android 编程的初学者，任何帮助将不胜感激。

DBHelper类:

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;
import android.util.Log;

class DBHelper extends SQLiteOpenHelper {


private static final String DATABASE_PATH = "/data/data/com.example.imagelist/databases/";
private static final String DATABASE_NAME = "DbImage.db";
private static final int SCHEMA_VERSION = 1;
private static final String TABLE_NAME = "image";
private static final String COLUMN_ID = "_id";
private static final String COLUMN_IMAGE = "img";
private static final String COLUMN_NAME = "name";




public SQLiteDatabase dbSqlite;

private final Context myContext;

public DBHelper(Context context){
    super(context, DATABASE_NAME, null, SCHEMA_VERSION );
    this.myContext= context;

}

@Override
public void onCreate(SQLiteDatabase db) {

}

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

}

public void createDatabase() {

    createDB();

}

public void createDB(){

    boolean dbExist = DBExists();

    if(!dbExist){

        this.getReadableDatabase();

        copyDBFromResource();

    }

}



private boolean DBExists() {

    SQLiteDatabase db = null;

    try{
        String databasePath = DATABASE_PATH + DATABASE_NAME;
        db = SQLiteDatabase.openDatabase(databasePath, null, SQLiteDatabase.OPEN_READWRITE);
        db.setLocale(Locale.getDefault());
        db.setLockingEnabled(true);
        db.setVersion(1);

    } catch (SQLiteException e) {

        Log.e("SqlHelper", "database not found");
    }

    if (db != null){

        db.close();
    }

    return db != null ? true : false;

}



private void copyDBFromResource(){

    InputStream inputStream = null;
    OutputStream outStream = null;
    String dbFilePath =  DATABASE_PATH + DATABASE_NAME;

    try{

        inputStream = myContext.getAssets().open(DATABASE_NAME);

        outStream = new FileOutputStream(dbFilePath);

        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 database from resource file.");
    }

}


public void openDatabase () throws SQLException {

    String myPath = DATABASE_PATH + DATABASE_NAME;
    dbSqlite = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

}

@Override
public synchronized void close () {

    if (dbSqlite !=null){

        dbSqlite.close();
    }

    super.close();

}

public Cursor getCursor() {

    SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder ();

    queryBuilder.setTables(TABLE_NAME);

    String [] asColumnsToReturn = new String [] { COLUMN_ID, COLUMN_IMAGE, COLUMN_NAME};

    Cursor mCursor = queryBuilder.query(dbSqlite, asColumnsToReturn, null, null, null, null, "_id ASC");

    return mCursor;
}

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

}

主类:

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.CursorAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

public class Main extends Activity {


private DBHelper dblistHelper = null;
private Cursor ourCursor = null;
private recipeAdapter adapter = null;


@Override
protected void onCreate(Bundle savedInstanceState) {    
    try
    {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    ListView myListView = (ListView) findViewById(R.id.listView);

    dblistHelper = new DBHelper(this);

    dblistHelper.createDatabase();

    dblistHelper.openDatabase();

    ourCursor=dblistHelper.getCursor();

    startManagingCursor(ourCursor);

    adapter = new recipeAdapter(ourCursor);

    myListView.setAdapter(adapter);



    }
    catch (Exception e)
    {

        Log.e("ERROR", "ERROR IN CODE: " + e.toString());   

        e.printStackTrace();

    }


}




class recipeAdapter extends CursorAdapter {

    recipeAdapter(Cursor c){
        super(Main.this, c);
    }

    @Override
    public  void bindView (View row, Context ctxt, Cursor c)
    {
        Holder holder = (Holder)row.getTag();
        holder.populateFrom(c, dblistHelper);
    }
    @Override
    public  View newView(Context ctxt, Cursor c, ViewGroup parent)
    {
        LayoutInflater inflater = getLayoutInflater();
        View row=inflater.inflate(R.layout.row, parent, false);
        Holder holder = new Holder(row);
        row.setTag(holder);
        return(row);
    }


}

static class Holder {
    private TextView name=null;
    private ImageView image=null;

    Holder(View row){
        name=(TextView)row.findViewById(R.id.textView1);
        image=(ImageView)row.findViewById(R.id.imageView1);
    }

    void populateFrom(Cursor c, DBHelper r){
        name.setText(r.getName(c));
        image.setImageBitmap(bm);
    }
}
}

Answer 1

为 ListView 中的元素创建一个 XML 文件。沿着这些思路:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >


<TextView
    android:id="@+id/text1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/icon"
    android:layout_toRightOf="@id/icon"
    android:textColor="#FF0000" />

</RelativeLayout>

创建某种类型的适配器类，从数据库中提取内容。然后将 ListView 中的任何字段设置为数据库中的适当数据，如下所示:

public class CustomAdapter {
    public CustomAdapter(Context context){
        // connect to you database

    }


    public View getItemView(/*pass your db object*/, View v, ViewGroup parent){
        if (v == null) {
            v = View.inflate(getContext(), R.layout.row, null);
        }

        super.getItemView(object, v, parent);


        TextView textView = (TextView) v.findViewById(R.id.text1);
        textView.setText(/*dataObject.getdata*/);

        // Do this as much as necessary
    }
public void loadObject(){
   //Get all of your data, set each row in list view by calling getView
}

然后在您的 Activity 调用中创建对象的实例，获取 ListView 的实例，设置 ListView 的适配器并调用 loadobjects

private CustomAdapter customAdapter;
//...
customAdapter = new CustomAdapter(this);
ListView listView = (ListView) findViewById(R.id.main_list_view);
    listView.setAdapter(customAdapter);
    customAdapter.loadObjects();

这就是我所做的，这也是基于使用 Parse 数据库找到的信息:https://parse.com/tutorials/parse-query-adapter

这可能对您有帮助，因为它与 SQL 相关:http://www.mysamplecode.com/2012/07/android-listview-cursoradapter-sqlite.html

基本思想是为您设置数据的 ListView 创建您自己的适配器。然后将 ListView 适配器设置为该适配器。