与 Handler 相关的多个编译错误

Question

复制源代码后有一些错误无法解决。谁能知道我该怎么办？

以下是错误：

• 无法解析“处理程序”中的方法“sendMessage”
• 类“从处理程序派生的匿名类”必须声明为抽象或在“处理程序”中实现抽象方法“publish(LogRecord)”

MusicPlayer.java

package com.example.serenityapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Message;
import android.view.View;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.logging.Handler;

public class MusicPlayer extends AppCompatActivity {

ImageView play, prev, next, imageView;
TextView songTitle;
SeekBar mSeekBarTime, mSeekBarVol;
static MediaPlayer mMediaPlayer;
private Runnable runnable;
private AudioManager mAudioManager;
int currentIndex = 0;

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

    mAudioManager = (AudioManager) getSystemService(AUDIO_SERVICE);

    // initializing views

    play = findViewById(R.id.play);
    prev = findViewById(R.id.prev);
    next = findViewById(R.id.next);
    songTitle = findViewById(R.id.songTitle);
    imageView = findViewById(R.id.imageView);
    mSeekBarTime = findViewById(R.id.seekBarTime);
    mSeekBarVol = findViewById(R.id.seekBarVol);

    // creating an ArrayList to store our songs

    final ArrayList<Integer> songs = new ArrayList<>();

    songs.add(0, R.raw.sound1);
    songs.add(1, R.raw.sound2);
    songs.add(2, R.raw.sound3);
    songs.add(3, R.raw.sound4);
    songs.add(4, R.raw.sound5);


    // intializing mediaplayer

    mMediaPlayer = MediaPlayer.create(getApplicationContext(), songs.get(currentIndex));



    // seekbar volume

    int maxV = mAudioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
    int curV = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
    mSeekBarVol.setMax(maxV);
    mSeekBarVol.setProgress(curV);

    mSeekBarVol.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

            mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, progress, 0);
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {

        }
    });


    //above seekbar volume
    //

    play.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mSeekBarTime.setMax(mMediaPlayer.getDuration());
            if (mMediaPlayer != null && mMediaPlayer.isPlaying()) {
                mMediaPlayer.pause();
                play.setImageResource(R.drawable.ic_playbtn_foreground);
            } else {
                mMediaPlayer.start();
                play.setImageResource(R.drawable.ic_pausebtn_foreground);
            }

            songNames();

        }
    });


    next.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (mMediaPlayer != null) {
                play.setImageResource(R.drawable.ic_pausebtn_foreground);
            }

            if (currentIndex < songs.size() - 1) {
                currentIndex++;
            } else {
                currentIndex = 0;
            }

            if (mMediaPlayer.isPlaying()) {
                mMediaPlayer.stop();
            }

            mMediaPlayer = MediaPlayer.create(getApplicationContext(), songs.get(currentIndex));

            mMediaPlayer.start();
            songNames();

        }
    });


    prev.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            if (mMediaPlayer != null) {
                play.setImageResource(R.drawable.ic_pausebtn_foreground);
            }

            if (currentIndex > 0) {
                currentIndex--;
            } else {
                currentIndex = songs.size() - 1;
            }
            if (mMediaPlayer.isPlaying()) {
                mMediaPlayer.stop();
            }

            mMediaPlayer = MediaPlayer.create(getApplicationContext(), songs.get(currentIndex));
            mMediaPlayer.start();
            songNames();

        }
    });

}

private void songNames() {
    if (currentIndex == 0) {
        songTitle.setText("Sound 1");
        imageView.setImageResource(R.drawable.gridbg3);
    }
    if (currentIndex == 1) {
        songTitle.setText("Sound 2");
        imageView.setImageResource(R.drawable.gridbg3);
    }
    if (currentIndex == 2) {
        songTitle.setText("Sound 3");
        imageView.setImageResource(R.drawable.gridbg3);
    }
    if (currentIndex == 3) {
        songTitle.setText("Sound 4");
        imageView.setImageResource(R.drawable.gridbg3);
    }
    if (currentIndex == 4) {
        songTitle.setText("Sound 5");
        imageView.setImageResource(R.drawable.gridbg3);
    }


    // seekbar duration
    mMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
        @Override
        public void onPrepared(MediaPlayer mp) {
            mSeekBarTime.setMax(mMediaPlayer.getDuration());
            mMediaPlayer.start();
        }
    });

    mSeekBarTime.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            if (fromUser) {
                mMediaPlayer.seekTo(progress);
                mSeekBarTime.setProgress(progress);
            }
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {

        }
    });

    new Thread(new Runnable() {
        @Override
        public void run() {
            while (mMediaPlayer != null) {
                try {
                    if (mMediaPlayer.isPlaying()) {
                        Message message = new Message();
                        message.what = mMediaPlayer.getCurrentPosition();
                        handler.sendMessage(message); //**ERROR IN THIS PART**
                        Thread.sleep(1000);
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }).start();
}
 //**ERROR IN THIS PART**
@SuppressLint("Handler Leak") Handler handler = new Handler () {
    public void handleMessage  (Message msg) {
        mSeekBarTime.setProgress(msg.what);
    }
};
}

Answer 1

您导入了错误的包。您所期待的Handler 出现在android.os.Handler 中。但是你已经导入了java.util.logging.Handler。

导入正确的包将解决这两个错误。

在 MusicPlayer.java 中，进行以下更改：

package com.example.serenityapplication;

import androidx.appcompat.app.AppCompatActivity;

...

import android.os.Handler;