Question

你能告诉我或者给我一些我需要在这些代码中添加的代码来从我的数据库中检索图像。我是android编程的初学者，非常感谢任何帮助。

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XML文件。这些方面的东西：

<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。然后将列表视图中的任何字段设置为数据库中的相应数据，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
}

然后在您的活动中调用创建对象的实例，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();

我就是这样做的，这也是基于使用Parse数据库找到的信息：https://parse.com/tutorials/parse-query-adapter

这可能对您有所帮助，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列表视图创建自己的适配器。然后将listview适配器设置为该适配器。

如何从我的数据库中添加ListView中的图像？

1 个答案: