Android-Mediaplayer的下一个按钮不起作用

Question

I am working on a live streaming radio Android app...i have an array with 4 tracks, when i reach the end of the list suppose that the next button will represent " the last song" but it doesn't and crashes the app.

Here is the button code:

    counter=0;

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

    btn_next.setOnClickListener(new View.OnClickListener(){
         @Override
         public void onClick(View v) {
             if (counter < songurl.length) {
                 counter = counter + 1;
                 textview.setText(songurl[counter]);
                 try {
                     mediaPlayer.reset();
                 } catch (Exception ex) {
                     try {
                         mediaPlayer.setDataSource(songurl[counter]);
                     } catch (IOException e) {
                         e.printStackTrace();
                     }
                     try {
                         mediaPlayer.prepare();
                     } catch (IOException e) {
                         e.printStackTrace();
                     }
                     mediaPlayer.start();
                 }
             } else {

                 Toast.makeText(MainActivity.this, "last song", Toast.LENGTH_SHORT).show();
             }
         }
    });

One more question... in case I want to make it a closed loop when the app reaches the last song and I want to press next to start the list from the beginning how can I do it? Thanks.

Answer 1

You can simply add a modulo (%) operator in your code

counter = counter++ % songurl.length

no need to add an extra if else block

btn_next.setOnClickListener(new View.OnClickListener(){
    @Override
    public void onClick(View v) {
        counter = counter++ % songurl.length
        textview.setText(songurl[counter]);
        try {
            mediaPlayer.reset();
        } catch (Exception ex) {
            try {
                mediaPlayer.setDataSource(songurl[counter]);
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                mediaPlayer.prepare();
            } catch (IOException e) {
                e.printStackTrace();
            }
            mediaPlayer.start();
        }

    }
});

Answer 2

One problem you have is that you are incrementing the counter just after you check that it is within the bounds, which means your safety check is useless. Move counter = counter + 1; to the end of the if statement.

As far as making it loop continuously, you can change it to counter = (counter + 1) % songurl.length; at the end of the if statement body.

Beyond the scope of the question you asked, there are some problems with your usage of MediaPlayer . It doesn't make any sense to have so much key logic in a catch statement. That means you expect the exception to happen. You should re-think what you are doing there.

Answer 3

You see you called mediaPlayer.setDataSource(songurl[counter]) in the catch block. what if it will not have exception when you call mediaPlayer.reset()

try this:

try{
    mediaPlayer.reset();
    mediaPlayer.setDataSource();
    mediaPlayer.prepareAsync();--or mediaPlayer.prepare();
    (It depends on whether you load the url on the internet)
    mediaPlayer.start(); -- if you call mediaPlayer.prepareAsync() you should call mediaPlayer.start() at the OnPreparedListener;

 mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mediaPlayer) {
                mediaPlayer.start();
            }
        });
}

And if you still wondering, I suggest you to read something about MediaPlay's state.

PS If mediaPlayer is playing ,and you wanna let it play another one ,call mediaPlayer.stop() first;

Answer 4

To make the loop you should check in the onclicklistener that the if the counter is equal to the songurl.length which is i think the total number of song in the playlist.

int counter=0;

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

    btn_next.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {
            if (counter < songurl.length) {
                counter = counter + 1;
                textview.setText(songurl[counter]);
                try {
                    mediaPlayer.reset();
                } catch (Exception ex) {
                    try {
                        mediaPlayer.setDataSource(songurl[counter]);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    try {
                        mediaPlayer.prepare();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    mediaPlayer.start();
                }
            } else if(counter == songurl.length) {

                counter = 0;
               // Toast.makeText(MainActivity.this, "last song", Toast.LENGTH_SHORT).show();
                textview.setText(songurl[counter]);
                try {
                    mediaPlayer.reset();
                } catch (Exception ex) {
                    try {
                        mediaPlayer.setDataSource(songurl[counter]);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    try {
                        mediaPlayer.prepare();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    mediaPlayer.start();
                }
            }
        }
    });

in the elseif condition i have set the counter to 0. so that it will get in the loop.