Mediaplayer准备显示非法状态异常 [英] Mediaplayer prepare showing Illegal State Exception

问题描述

我正在尝试播放内部存储器中的音频文件. 我使用的代码是..

I am trying to play an audio file from the internal storage. The code I used is..

package com.abhi.firstapp.firstapp;
import android.content.Context;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import java.io.File;
import java.io.IOException;
import java.net.URI;

public class MainActivity extends AppCompatActivity {

     MediaPlayer mp;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
         setSupportActionBar(toolbar);



    File f= new File("/sdcard/a.mp3");
    if(f.exists())
    {

        Toast toast= Toast.makeText(this, "file exists", Toast.LENGTH_LONG);
        toast.show();
        Log.d("uri","1");
        Uri uri= Uri.fromFile(f);
        Log.d("uri", "2");

        mp= new MediaPlayer();
        mp.setAudioStreamType(AudioManager.STREAM_MUSIC);
        Log.d("uri", "3");

        try {
            mp.setDataSource("/sdcard/a.mp3");
        } catch (IOException e) {
            e.printStackTrace();
        }
        //mp.setDataSource(getBaseContext(), uri);
            Log.d("uri", "4");


        try {
            mp.prepare();
        } catch (IOException e) {
            e.printStackTrace();
            Log.d("uri", "IOException");
        }

        mp.start();


    }
    else {
        Toast toast1 = Toast.makeText(this, "file does not exist", Toast.LENGTH_LONG);
        toast1.show();
    }

    //MediaPlayer mp= MediaPlayer.create(getBaseContext(), uri);
    //mp.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.menu_main, 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();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

通过使用日志，我可以确定这段代码正在运行，直到mp.prepare(mediaplayer prepare).在这一步上，它给出了错误的非法状态异常

By using the log, I can determine that this code is running till the mp.prepare(mediaplayer prepare). And on this step, it gives the error Illegal State Exception

 Caused by: java.lang.IllegalStateException
   at android.media.MediaPlayer.prepare(Native Method)

请帮助！

推荐答案

您可能需要更改几件事.

There are a couple of things you might want to change.

首先:mp.prepare()将阻止您的主线程，这是被禁止的，并会导致Android关闭您的应用程序的异常.为了防止这种情况，设计了mp.prepareAsync.请改用该方法，并同时实现onPreparedListener和onErrorListener.

First: mp.prepare() will block your main thread, which is forbidden and will result in an exception where Android will close your app. To prevent this, mp.prepareAsync was designed. Use that method instead and implement both an onPreparedListener and an onErrorListener.

第二:在调用prepare()之前，您应该提供一个数据源.

Second: you should provide a datasource before you call prepare().

您可以通过以下方式进行此操作:

You could do this for example this way:

public class MainActivity extends AppCompatActivity implements MediaPlayer.OnPreparedListener, MediaPlayer.OnErrorListener {

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ...

        MediaPlayer mp = new MediaPlayer();
        mp.setAudioStreamType(AudioManager.STREAM_MUSIC);

        try { 
            mediaPlayer.setDataSource(streamURL);
        } catch (IOException e) {
            // Error, do something
        }

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

    ...

}

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