实战演练——音乐播放器
修改例3-2，加入进度条（SeekBar）功能和退出（Quit）功能。修改后的音乐播放器界面如图所示。功能如下：
（1）播放/暂停、停止、退出功能；
（2）进度条显示播放进度，拖动进度条可改变播放进度。
提示：进度条（SeekBar）功能的实现。
SeekBar的功能包括显示歌曲播放进度，以及拖动SeekBar至任意位置来改变播放进度，由于Android已经封装好了这些函数，所以直接调用就行，具体实现如下：
添加成员变量：SeekBar seekBar; MediaPlayer mediaPlayer; boolean isSeekBarChanging;
然后在onCreate()方法中加入进度条（SeekBar）的功能。
seekBar = (SeekBar) findViewById(R.id.seekBar);
mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mp) {
seekBar.setMax(mp.getDuration());
int m=mp.getDuration()/1000/60; //分
int s=mp.getDuration()/1000%60; //秒
txt2.setText("0"+m+":"+s);
}
});
seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
isSeekBarChanging = true;
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
isSeekBarChanging = false;
mediaPlayer.seekTo(seekBar.getProgress());
}
});
最后加入以下功能：媒体播放器处于播放状态时，使用一个Timer定时器对象实时获取音乐的播放进度，并刷新SeekBar的状态。
Timer timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
if (!isSeekBarChanging){
seekBar.setProgress(mediaPlayer.getCurrentPosition());
}
}
},0,1000);
操作示范如下
MusicActivity 参考代码如下:
package com.example.chap03;
import androidx.appcompat.app.AppCompatActivity;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.TextView;
import java.util.Timer;
import java.util.TimerTask;
public class MusicActivity extends AppCompatActivity {
private TextView txt2;
private SeekBar seekbar;
private Button play,exit,stop;
private MediaPlayer mediaPlayer;
private boolean isSeekBarChanging;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.demo);
txt2 = (TextView)findViewById(R.id.txt2);
seekbar=(SeekBar)findViewById(R.id.seekbar);
play=(Button)findViewById(R.id.play);
stop=(Button)findViewById(R.id.stop);
exit=(Button)findViewById(R.id.exit);
mediaPlayer = MediaPlayer.create(this,R.raw.abc);
mediaPlayer.setOnPreparedListener(new Medprepared());
seekbar.setOnSeekBarChangeListener(new SeekBarChange());
play.setOnClickListener(new mPlay());
stop.setOnClickListener(new mStop());
exit.setOnClickListener(new mExit());
}
//媒体播放器的同步监听 OnPreparedListener
class Medprepared implements MediaPlayer.OnPreparedListener{
@Override
public void onPrepared(MediaPlayer mp) {
seekbar.setMax(mp.getDuration());
int m = mp.getDuration()/1000/60;
int s = mp.getDuration()/1000%60;
txt2.setText("0"+m+":"+s);
}
}
//进度条监听 OnSeekBarChangeListener
class SeekBarChange implements SeekBar.OnSeekBarChangeListener{
@Override
public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
isSeekBarChanging = true;
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
isSeekBarChanging = false;
mediaPlayer.seekTo(seekBar.getProgress());
}
}
class mPlay implements View.OnClickListener {
@Override
public void onClick(View view) {
if (!mediaPlayer.isPlaying()) {
mediaPlayer.start();
play.setText("pause");
Timer timer= new Timer();
TimerTask task= new TimerTask(){
@Override
public void run() {
seekbar.setProgress(mediaPlayer.getCurrentPosition());
}
};
timer.schedule(task,0,1000);
} else {
mediaPlayer.pause();
play.setText("play");
}
}
}
class mStop implements View.OnClickListener{
@Override
public void onClick(View view) {
mediaPlayer.stop();
mediaPlayer = MediaPlayer.create(MusicActivity.this,R.raw.abc);
play.setText("play");
}
}
class mExit implements View.OnClickListener{
@Override
public void onClick(View view) {
mediaPlayer.release();
MusicActivity.this.finish();
}
}
}
