Question

我有一个RecyclerView，它显示了一个自定义布局，其中填充了两件事：

要显示的图片网址
图片的文字名称

我查询SQLite数据库，以从单击的歌手那里获得特定的歌曲。除了一件事情，我有这个工作。

我想使用图像的文本名称（2）作为查询中的变量，因为字符串设置为我要在搜索查询中使用的值。

我不知道如何访问此变量。

Artists.java

package com.apps.robloxmusic;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

import java.util.ArrayList;

public class Artists extends AppCompatActivity {

    private static final String TAG = "Artists";

    //Variables
    private ArrayList<String> mNames = new ArrayList<>();
    private ArrayList<String> mImagesUrls = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_artists);
        Log.d(TAG, "onCreate: started.");

        initImageBitmaps();

    }

    private void initImageBitmaps() {
        Log.d(TAG, "initImageBitmaps: preparing bitmaps.");

        mImagesUrls.add("https://cdn.blocktoro.com/wp-content/uploads/2019/07/bts-1097661412_1-e1562687430275-800x400.jpg");
        mNames.add("BTS");

        mImagesUrls.add("https://hdqwalls.com/download/post-malone-new-tattoo-2018-4k-lg-1920x1080.jpg");
        mNames.add("Post Malone");


        initRecyclerView();
    }

    private void initRecyclerView() {
        Log.d(TAG, "initRecyclerView: preparing recycler view.");

        RecyclerView recyclerView = findViewById(R.id.artistView);
        RecyclerViewAdapter adapter = new RecyclerViewAdapter(mNames, mImagesUrls, this);
        recyclerView.setAdapter(adapter);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));


    }
}

RecyclerViewAdapter.java

package com.apps.robloxmusic;

import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;
import android.widget.TextView;

import com.bumptech.glide.Glide;

import java.util.ArrayList;
import java.util.List;

import de.hdodenhof.circleimageview.CircleImageView;

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {

    private static final String TAG = "RecyclerViewAdapter";

    public ArrayList<String> mImagesNames = new ArrayList<>();
    private ArrayList<String> mImages = new ArrayList<>();
    private Context mContext;


    public RecyclerViewAdapter(ArrayList<String> mImagesNames, ArrayList<String> mImages, Context mContext) {
        this.mImagesNames = mImagesNames;
        this.mImages = mImages;
        this.mContext = mContext;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.layout_artistlist, viewGroup, false);
        ViewHolder holder = new ViewHolder(view);
        return holder;
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, final int position) {
        Log.d(TAG, "onBindViewerHolder: called.");

        Glide.with(mContext)
                .asBitmap()
                .load(mImages.get(position))
                .into(holder.artistImage);

        holder.artistName.setText(mImagesNames.get(position));

        holder.artistLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Log.d(TAG, "onClick: clicked on:" + mImagesNames.get(position));

                Intent intent = new Intent(mContext, BandView.class);
                intent.putExtra("image_url", mImages.get(position));
                //might not need this?
                intent.putExtra("image_name", mImagesNames.get(position));
                mContext.startActivity(intent);

            }
        });

    }

    @Override
    public int getItemCount() {
        return mImagesNames.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        CircleImageView artistImage;
        TextView artistName;
        RelativeLayout artistLayout;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            artistImage = itemView.findViewById(R.id.artistImage);
            artistName = itemView.findViewById(R.id.artistName);
            artistLayout = itemView.findViewById(R.id.artistLayout);
        }
    }

}

DatabaseAccess.java

私有字符串allArtistSongs是我想要设置文本变量的内容。 “防弹少年团”；只是一个占位符。

package com.apps.robloxmusic;

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

import java.util.ArrayList;
import java.util.List;

public class DatabaseAccess {
    private SQLiteOpenHelper openHelper;
    private SQLiteDatabase database;
    private static DatabaseAccess instance;

    private String allArtistSongs = "BTS";


    /**
     * Private constructor to avoid object creation from outside classes.
     *
     * @param context
     */
    private DatabaseAccess(Context context) {
        this.openHelper = new DatabaseOpenHelper(context);
    }

    /**
     * Return a singleton instance of DatabaseAccess.
     *
     * @param context the Context
     * @return the instance of DatabaseAccess
     */
    public static DatabaseAccess getInstance(Context context) {
        if (instance == null) {
            instance = new DatabaseAccess(context);
        }
        return instance;
    }

    /**
     * Open the database connection.
     */
    public void open() {
        this.database = openHelper.getWritableDatabase();
    }

    /**
     * Close the database connection.
     */
    public void close() {
        if (database != null) {
            this.database.close();
        }
    }

    /**
     * Read all songs from the database.
     *
     * @return a List of songs
     */
    public List<String> getSongs() {
        List<String> list = new ArrayList<>();
        Cursor cursor = database.rawQuery("SELECT * FROM [Music_Codes]", null);
        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            list.add(cursor.getString(0));
            cursor.moveToNext();
        }
        cursor.close();
        return list;
    }

    public List<String> getArtistSongs() {
        List<String> list = new ArrayList<>();
        Cursor cursor = database.rawQuery("SELECT * FROM [Music_Codes] WHERE Song LIKE ?", new String[] {"%"+ allArtistSongs+ "%"});
        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            list.add(cursor.getString(0));
            cursor.moveToNext();
        }
        cursor.close();
        return list;
    }


}

Answer 1

您需要在哪里调用getArtistSongs（）？我怀疑您需要在viewHolder上的clickListener启动的新活动中调用此方法。如果是这样，则可以将此字符串提供给意图（image_name ??）。然后，当新活动启动时，您可以从意图中获取字符串，并在getArtistSongs（）中使用它。

getArtistSongs（）需要具有用于查询的参数String，类似

    public List<String> getArtistSongs(String artist) {
        List<String> list = new ArrayList<>();
        Cursor cursor = database.rawQuery("SELECT * FROM [Music_Codes] WHERE Song LIKE ?", new String[] {"%"+ artist + "%"});
        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            list.add(cursor.getString(0));
            cursor.moveToNext();
        }
        cursor.close();
        return list;
    }

如何从另一个类访问String变量？

1 个答案: