android播放本地音乐程序

在android中播放音乐我们一般使用MediaPlayer类来实现。新建一个PlayAudio项目：

activity_main.xml中的代码如下：

布局文件中放了三个按钮，依次用于播放、暂停和停止音乐。

AndroidManifest.xml中的代码如下：

因为要读取sd卡中的音频文件，所以要申请WRITE_EXTERNAL_STORAGE权限

MainActivity中的代码如下：

package com.tangliang.playaudio;

import android.Manifest;
import android.content.pm.PackageManager;
import android.media.MediaPlayer;
import android.os.Environment;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.io.File;

public class MainActivity extends AppCompatActivity {

    private MediaPlayer mediaPlayer = new MediaPlayer();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button play = (Button) findViewById(R.id.play);
        Button pause = (Button) findViewById(R.id.pause);
        Button stop = (Button) findViewById(R.id.stop);
        play.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(!mediaPlayer.isPlaying()){
                    mediaPlayer.start();
                }
            }
        });
        pause.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(mediaPlayer.isPlaying()){
                    mediaPlayer.pause();
                }
            }
        });
        stop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(mediaPlayer.isPlaying()){
                    mediaPlayer.reset();
                    initMediaPlayer();
                }
            }
        });
        if(ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) !=
                PackageManager.PERMISSION_GRANTED){
            ActivityCompat.requestPermissions(MainActivity.this, new String[] {Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
        }
        else{
            initMediaPlayer();
        }
    }

    private void initMediaPlayer(){
        try{
            File file = new File(Environment.getExternalStorageDirectory(), "ringtone.mp3");
            mediaPlayer.setDataSource(file.getPath());
            mediaPlayer.prepare();
        }
        catch (Exception e){
            e.printStackTrace();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode){
            case 1:
            if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                initMediaPlayer();
            }
            else{
                Toast.makeText(this, "拒绝权限将无法使用程序", Toast.LENGTH_SHORT).show();
                finish();
            }
            break;
            default:
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(mediaPlayer != null){
            mediaPlayer.stop();
            mediaPlayer.release();
        }
    }
}