Android:在媒体播放器活动中正确使用 PrepareAsync() [英] Android: correct usage of PrepareAsync() in media player activity

问题描述

我正在关注 this 教程，但使用 prepareAsync不清楚，我的代码不输出任何音频.我正在使用 prepareAsync() 因为我的 mp3 在线并且我不想在媒体播放器准备期间锁定活动.你能解释一下 prepareAsync 的基本用法吗?

I'm following this tutorial, but the usage of prepareAsync is not clear and my code does not output any audio. I'm using prepareAsync() because my mp3 is online and I don't want to lock the activity during media player preparing. Could you explain basic usage of prepareAsync?

package com.example.simplemediaplayer.app;

import android.media.AudioManager;
import android.media.MediaPlayer;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import java.io.IOException;


public class MediaPlayerActivity extends ActionBarActivity implements MediaPlayer.OnPreparedListener {

    private static final String TAG = "tag";

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

        String url = "http://www.brothershouse.narod.ru/music/pepe_link_-_guitar_vibe_113_club_mix.mp3"; // your URL here
        MediaPlayer myMediaPlayer = new MediaPlayer();
        myMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        try {
            myMediaPlayer.setDataSource(url);
            myMediaPlayer.prepareAsync(); // might take long! (for buffering, etc)

        } catch (IOException e) {
            Toast.makeText(this, "mp3 not found", Toast.LENGTH_SHORT).show();
            e.printStackTrace();
        }

    }

    /** Called when MediaPlayer is ready */
    @Override
    public void onPrepared(MediaPlayer player) {
        player.start();
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.media_player, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

推荐答案

解决方案是调用myMediaPlayer对象的setOnPreparedListener，等待prepareAsync()方法完成.

The solution is to call the setOnPreparedListener of myMediaPlayer object and wait until prepareAsync() method has finished.

package com.example.simplemediaplayer.app;

import android.media.AudioManager;
import android.media.MediaPlayer;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import java.io.IOException;


public class MediaPlayerActivity extends ActionBarActivity {

    private static final String TAG = "tag";

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

        String url = "http://www.brothershouse.narod.ru/music/pepe_link_-_guitar_vibe_113_club_mix.mp3"; // your URL here
        MediaPlayer myMediaPlayer = new MediaPlayer();
        myMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        try {
            myMediaPlayer.setDataSource(url);
            myMediaPlayer.prepareAsync(); // prepare async to not block main thread

        } catch (IOException e) {
            Toast.makeText(this, "mp3 not found", Toast.LENGTH_SHORT).show();
            e.printStackTrace();
        }

        //mp3 will be started after completion of preparing...
        myMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {

            @Override
            public void onPrepared(MediaPlayer player) {
                player.start();
            }

        });

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.media_player, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

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