Question

我试图在Android工作室制作MP3播放器，我已经在我的手机中加载了名为audioList的arraylist中的所有歌曲，但我不能制作recyclerView，有人能找到错误吗？

MainActivity.java

import android.Manifest;
import android.content.ComponentName;
import android.content.ContentResolver;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.os.IBinder;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.Toast;    
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    private MediaPlayerService player;
    private boolean serviceBound = false;
    private ArrayList<Audio> audioList;
    private RWAdapter adapt;
    RecyclerView recyclerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.M){
            requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, 0);
        }

        RecyclerView rv = (RecyclerView) findViewById(R.id.myRecyclerView);
        assert rv != null;
        rv.setLayoutManager(new LinearLayoutManager(this));;

        loadAudio();
        RWAdapter rwa = new RWAdapter(audioList);
        rv.setAdapter(rwa);

        playAudio(audioList.get(22).getData());

    }

    //ulozi sa instancia
    @Override
    protected void onSaveInstanceState(Bundle outState) {
        outState.putBoolean("ServiceState", serviceBound);
        super.onSaveInstanceState(outState);
    }

    //obnovi sa instancia tam kde bola naposledy ulozena
    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        serviceBound = savedInstanceState.getBoolean("ServiceState");
    }

    //znici instanciu
    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(serviceBound){
            unbindService(serviceConnection);
            player.stopSelf();
        }
    }

    //viaze tuto triedu s prehravacom, nastavi hodnotu serviceBound na true ked sa vytvori spojenie
    private ServiceConnection serviceConnection = new ServiceConnection(){
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            MediaPlayerService.LocalBinder binder = (MediaPlayerService.LocalBinder) service;
            player = binder.getService();
            serviceBound = true;

            Toast.makeText(MainActivity.this, "Service bound", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            serviceBound = false;
        }
    };

    //Metoda dava spravu,intnet druhej aktivite o spusteni hudby
    private void playAudio(String media){
        if(!serviceBound){
            Intent playerIntent = new Intent(this,MediaPlayerService.class);
            playerIntent.putExtra("media",media);
            startService(playerIntent);
            bindService(playerIntent, serviceConnection, Context.BIND_AUTO_CREATE);

        } else {    
        }
    }


    //nacita pesnicky z mobilu
    private void loadAudio() {
        ContentResolver contentResolver = getContentResolver();
        Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
        String selection = MediaStore.Audio.Media.IS_MUSIC + "!= 0";
        String sortOrder = MediaStore.Audio.Media.TITLE + " ASC";
        Cursor cursor = contentResolver.query(uri, null, selection, null, sortOrder);

        if(cursor != null && cursor.getCount() > 0) {
            audioList = new ArrayList<>();
            while (cursor.moveToNext()){
                String data = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));
                String title = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE));
                String album = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM));
                String artist = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST));
                audioList.add(new Audio(data, title, album, artist));
            }
        }
        cursor.close();
    }            
}

RecyclerViewAdapter

package com.example.rsabo.mp3player;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;    
import java.util.Collections;
import java.util.List;

/**
 * Created by RSabo on 15-Apr-17.
 */

public class RWAdapter extends RecyclerView.Adapter<RWAdapter.MyViewHolder>{
    private List<Audio> list;
    private Context context;

        public class MyViewHolder extends RecyclerView.ViewHolder {

            TextView title;
            ImageView play_pause;

            MyViewHolder(View itemView) {
                super(itemView);
                title = (TextView) itemView.findViewById(R.id.title);
                play_pause = (ImageView) itemView.findViewById(R.id.play_pause);

                itemView.setOnClickListener(new View.OnClickListener(){
                    @Override
                    public void onClick(View v) {
                        Audio currentAudio = list.get(getAdapterPosition());    
                    }
                });
            }
        }

    public RWAdapter(List<Audio> list) {
        this.list = list;
        this.context = context;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        //Inflate the layout, initialize the View Holder
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_songov, parent, false);
        return new MyViewHolder(v);   
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        //Use the provided View Holder on the onCreateViewHolder method to populate the current row on the RecyclerView
        holder.title.setText(list.get(position).getTitle());
    }

    @Override
    public int getItemCount() {
        //returns the number of elements the RecyclerView will display
        return list.size();
    }    
}

activity_main.xml中

<RelativeLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.rsabo.mp3player.MainActivity">

<include layout="@layout/list_songov" />

list_songov.xml

<?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.support.v7.widget.RecyclerView
    android:id="@+id/myRecyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

Answer 1

你没有调用函数loadAudio（），你应该在实例化你的适配器类时调用这个函数

Answer 2

基本上你的loadAudio()方法应该是AsyncTask（后台进程），你必须在加载时等待，所以在onPostExecute方法中使用AsyncTask并设置适配器，请参阅示例AsyncTask Android example或此https://developer.android.com/reference/android/os/AsyncTask.html < / p>

 //nacita pesnicky z mobilu
 private void loadAudio() {
    ContentResolver contentResolver = getContentResolver();
    Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    String selection = MediaStore.Audio.Media.IS_MUSIC + "!= 0";
    String sortOrder = MediaStore.Audio.Media.TITLE + " ASC";
    Cursor cursor = contentResolver.query(uri, null, selection, null, sortOrder);

    if(cursor != null && cursor.getCount() > 0) {
        audioList = new ArrayList<>();
        while (cursor.moveToNext()){
            String data = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));
            String title = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE));
            String album = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM));
            String artist = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST));
            audioList.add(new Audio(data, title, album, artist));
        }
    }
    cursor.close();
}

Answer 3

检查适配器中的以下代码。

@Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        //Inflate the layout, initialize the View Holder
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_songov, parent, false);
        return new MyViewHolder(v);   
    }

现在，在 list_songov.xml 布局文件中，没有TextView，ImageView for Title和play_pause。

请检查您是否在onCreateViewHolder（）中设置了正确的布局。

Recyclerview android不起作用

3 个答案: