Android 是否在listview中显示来自sqlite的图像？

我在做一个小项目。我在assets文件夹中插入了.sqlite数据库文件，并在listview中获取信息。现在我必须用文本显示图像。我在xml文件中创建了imageview，然后在代码中添加了一些函数。但它不起作用。这是消息来源

MainActivity.java

    package com.example.arlequina.sqlitefromassetexample;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.widget.ListView;
import android.widget.Toast;
import com.example.arlequina.sqlitefromassetexample.adapter.ListProductAdapter;
import com.example.arlequina.sqlitefromassetexample.database.DatabaseHelper;
import com.example.arlequina.sqlitefromassetexample.model.Product;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.List;
/**
 * Created by ARLEQUINA on 2/10/2017.
 */
public class MainActivity extends Activity {
    private ListView lvProduct;
    private ListProductAdapter adapter;
    private List<Product> mProductList;
    private DatabaseHelper mDBHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        lvProduct = (ListView)findViewById(R.id.listview_product);
        mDBHelper = new DatabaseHelper(this);

        //Check exists database
        File database = getApplicationContext().getDatabasePath(DatabaseHelper.dbname);
        if(false == database.exists()){
            mDBHelper.getReadableDatabase();

            //Copy db
            if(copyDatabase(this)){
                Toast.makeText(this,"Copy database success", Toast.LENGTH_SHORT).show();
            }else{
                Toast.makeText(this, "Copy data error", Toast.LENGTH_SHORT).show();
                return;
            }
        }
        //Get product list in db when db exists
        mProductList = mDBHelper.getListProduct();
        //Init adapter
        adapter  = new ListProductAdapter(this,mProductList);
        //Set adapter for listview
        lvProduct.setAdapter(adapter);
    }
    private boolean copyDatabase(Context context){
        try{
            InputStream inputStream =  context.getAssets().open(DatabaseHelper.dbname);
            String outFileName = DatabaseHelper.dblocation + DatabaseHelper.dbname;
            OutputStream outputStream = new FileOutputStream(outFileName);
            byte[] buff = new byte[1024];
            int length = 0;
            while((length = inputStream.read(buff)) > 0){
                outputStream.write(buff, 0, length);
            }
            outputStream.flush();
            outputStream.close();
            Log.v("MainActivity", "DB copied");
            return true;
        } catch(Exception e){
            e.printStackTrace();
            return false;
        }
    }
}

DatabaseHelper.java

package com.example.arlequina.sqlitefromassetexample.database;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import com.example.arlequina.sqlitefromassetexample.model.Product;

import java.util.ArrayList;
import java.util.List;
import java.sql.Blob;

/**
 * Created by ARLEQUINA on 2/10/2017.
 */

public class DatabaseHelper extends SQLiteOpenHelper {
    public static final String dbname = "sample.db";
    public static final String dblocation = "/data/data/com.example.arlequina.sqlitefromassetexample/databases/";
    private Context mContext;
    private SQLiteDatabase mDatabase;

    public DatabaseHelper(Context context){
        super(context, dbname, null, 1);
        this.mContext = context;
    }
    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
    public void openDatabase(){
        String dbPath = mContext.getDatabasePath(dbname).getPath();
        if(mDatabase != null && mDatabase.isOpen()){
            return;
        }
        mDatabase = SQLiteDatabase.openDatabase(dbPath, null, SQLiteDatabase.OPEN_READWRITE);
    }
    public void closeDatabase(){
        if(mDatabase != null){
            mDatabase.close();
        }
    }
    public List<Product> getListProduct(){
        Product product = null;
        List<Product> productList = new ArrayList<>();
        openDatabase();
        Cursor cursor = mDatabase.rawQuery("SELECT * FROM Product", null);
        cursor.moveToFirst();
        while(!cursor.isAfterLast()){
            product = new Product(cursor.getInt(0), cursor.getString(1), cursor.getString(2),cursor.getString(3),cursor.getBlob(4));
            productList.add(product);
            cursor.moveToNext();
        }
        cursor.close();
        closeDatabase();
        return productList;
    }
}

---

cursor.getBlob（）返回字节[]数组，使用BitmapFactory.decodeByteArray（）方法将字节数组转换为图像。在Product.java中，将img类型从Blob更改为byte[]。以下是官方文档。

我认为将图像存储在DB中是个坏主意，而不是将图像保存在其他地方，并将该图像的相对路径与图像名称一起存储在SQLite存储中。

package com.example.arlequina.sqlitefromassetexample.database;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import com.example.arlequina.sqlitefromassetexample.model.Product;

import java.util.ArrayList;
import java.util.List;
import java.sql.Blob;

/**
 * Created by ARLEQUINA on 2/10/2017.
 */

public class DatabaseHelper extends SQLiteOpenHelper {
    public static final String dbname = "sample.db";
    public static final String dblocation = "/data/data/com.example.arlequina.sqlitefromassetexample/databases/";
    private Context mContext;
    private SQLiteDatabase mDatabase;

    public DatabaseHelper(Context context){
        super(context, dbname, null, 1);
        this.mContext = context;
    }
    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
    public void openDatabase(){
        String dbPath = mContext.getDatabasePath(dbname).getPath();
        if(mDatabase != null && mDatabase.isOpen()){
            return;
        }
        mDatabase = SQLiteDatabase.openDatabase(dbPath, null, SQLiteDatabase.OPEN_READWRITE);
    }
    public void closeDatabase(){
        if(mDatabase != null){
            mDatabase.close();
        }
    }
    public List<Product> getListProduct(){
        Product product = null;
        List<Product> productList = new ArrayList<>();
        openDatabase();
        Cursor cursor = mDatabase.rawQuery("SELECT * FROM Product", null);
        cursor.moveToFirst();
        while(!cursor.isAfterLast()){
            product = new Product(cursor.getInt(0), cursor.getString(1), cursor.getString(2),cursor.getString(3),cursor.getBlob(4));
            productList.add(product);
            cursor.moveToNext();
        }
        cursor.close();
        closeDatabase();
        return productList;
    }
}

package com.example.arlequina.sqlitefromassetexample.adapter;

import android.content.Context;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.arlequina.sqlitefromassetexample.R;
import com.example.arlequina.sqlitefromassetexample.model.Product;

import org.w3c.dom.Text;

import java.util.List;

/**
 * Created by ARLEQUINA on 2/10/2017.
 */

public class ListProductAdapter extends BaseAdapter{
    private Context mContext;
    private List<Product> mProductList;

    public ListProductAdapter(Context mContext, List<Product> mProductList){
        this.mContext = mContext;
        this.mProductList = mProductList;
    }

    @Override
    public int getCount() {
        return mProductList.size();
    }

    @Override
    public Object getItem(int position) {
        return mProductList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return mProductList.get(position).getId();
    }

    @RequiresApi(api = Build.VERSION_CODES.M)
    @Override
    public View getView(int position, View view, ViewGroup viewGroup) {
        View v = View.inflate(mContext, R.layout.item_listview, null);
        TextView tvName = (TextView)v.findViewById(R.id.tv_product_name);
        TextView tvPrice = (TextView)v.findViewById(R.id.tv_product_price);
        TextView tvDesc = (TextView)v.findViewById(R.id.tv_product_desc);
        ImageView tvImage = (ImageView)v.findViewById(R.id.tv_product_img);
        tvName.setText(mProductList.get(position).getName());
        tvPrice.setText(String.valueOf(mProductList.get(position).getPrice()) + " $");
        tvDesc.setText(mProductList.get(position).getDesc());
       // tvImage.setImageIcon(mProductList.get(position).getImage());
        return v;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ffffff"
    android:paddingBottom="5dp"
    android:paddingLeft="10dp"
    android:paddingRight="10dp"
    android:paddingTop="5dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/tv_product_name"
        android:text = "Name"
        android:textColor="#4bb6d6"
        android:textSize="20dp"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id = "@+id/tv_product_price"
        android:text="100$"
        android:textColor="#b30000"
        android:textSize="18dp"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id = "@+id/tv_product_desc"
        android:text="Description"
        android:textSize="16dp"
        android:textStyle="italic"/>
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id = "@+id/tv_product_img"
        android:layout_gravity="right"
        android:paddingRight="10dp"
        android:paddingBottom="10dp"/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#d1d1d1">

    <ListView
        android:id = "@+id/listview_product"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="10dp"
        android:divider="#d1d1d1"
        android:dividerHeight="10dp"></ListView>
</LinearLayout>

CREATE TABLE `Product` (
    `ID`    INTEGER PRIMARY KEY AUTOINCREMENT,
    `Name`  TEXT,
    `Price` TEXT,
    `Desc`  TEXT,
    `Image` BLOB
);