寫在前面的話

1、參考自：https://b23.tv/0mHcF5
2、內容如果有不對的，希望可以指出或補充，
3、由于這部分卡了很久，也算是個完整的練習，所以單獨提出來了，
4、新知識，

一、概述

通信方式：

1、本地服務通信：是指應用程式內部的通信，需要使用IBinder物件進行本地服務，

2、遠程服務通信：是指兩個應用程式間的通信，遠程服務通信是通過AIDL（Android Interface Definition Language，Android介面定義語言，定義了客戶端與服務端的一個標準）實作的，

這里測驗的是本地服務通信，

二、遇到的問題

以下都是在Android Studio4.1.1里進行的，

報錯資訊：
在這里插入圖片描述
最侄訓成以下這種虛擬機（成功解決了問題）：

三、步驟展示

1、準備

檔案：
在這里插入圖片描述
匯入音頻檔案：

宣告：

2、布局

activity_play.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@mipmap/bg"
    android:gravity="center_vertical"
    >
    <!--拖動條-->
    <SeekBar
        android:id="@+id/seek_bar"

        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:max="100"/>
    <!--按鈕-->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:layout_marginTop="20dp">
        <Button
            android:id="@+id/play_or_pause_btn"

            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="播放" />
        <Button
            android:id="@+id/close_btn"

            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="停止" />
    </LinearLayout>

</LinearLayout>

3、介面

activity與服務間通過介面連接，
在這里插入圖片描述

4、服務

PlayerService.java

package com.example.testservice.services;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import androidx.annotation.Nullable;
import com.example.testservice.presenter.PlayerPresenter;

public class PlayerService extends Service {

    private static final String TAG = "PlayerService";
    private PlayerPresenter mplayerPresenter;

    @Override
    public void onCreate(){
        Log.d(TAG,"onCreate...");
        super.onCreate();
        if (mplayerPresenter == null) {
            mplayerPresenter = new PlayerPresenter();
        }
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        Log.d(TAG,"onBind...");
        return mplayerPresenter;
    }

    @Override
    public void onDestroy() {
        Log.d(TAG,"onDestroy...");
        super.onDestroy();
        mplayerPresenter = null;
    }
}

5、功能實作部分

PlayerPresenter.java

package com.example.testservice.presenter;

import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Binder;
import android.util.Log;

import com.example.testservice.interfaces.IPlayerControl;
import com.example.testservice.interfaces.IPlayerViewControl;

import java.io.IOException;
import java.util.Timer;
import java.util.TimerTask;

//實作邏輯層的服務
public class PlayerPresenter extends Binder implements IPlayerControl {

    private static final String TAG = "PlayerPresenter";
    private IPlayerViewControl mViewController;
    private int mCurrentState = PLAY_STATE_STOP;//記錄當前的播放狀態 默認停止
    private MediaPlayer mMediaPlayer;
    private Timer mTimer;
    private SeekTimeTask mTimeTask;

    @Override
    public void registerViewController(IPlayerViewControl viewControl) {
        this.mViewController = viewControl;
    }

    @Override
    public void unRegisterViewController() {
        mViewController = null;
    }

    @Override
    public void playOrPause() {
        Log.i(TAG,"playOrPause...");
        if (mCurrentState==PLAY_STATE_STOP) {
            //創建播放器
            initPlayer();
            //設定資料源
            try {
                mMediaPlayer.setDataSource("/mnt/sdcard/testsong.mp3");
                mMediaPlayer.prepare();
                mMediaPlayer.start();
                mCurrentState = PLAY_STATE_PLAY;
                startTimer();//拖動條開始動
            }catch (IOException e){
                e.printStackTrace();
            }
        }else if(mCurrentState == PLAY_STATE_PLAY){
            //如果當前狀態為播放則暫停
            if (mMediaPlayer != null) {
                mMediaPlayer.pause();
                mCurrentState = PLAY_STATE_PAUSE;
                stopTimer();//拖動條停止
            }
        }else if(mCurrentState == PLAY_STATE_PAUSE){
            //如果當前狀態為暫停就繼續播放
            if (mMediaPlayer != null) {
                mMediaPlayer.start();
                mCurrentState = PLAY_STATE_PLAY;
                startTimer();
            }
        }
        //通知ui更新界面按鈕文字
        if (mViewController != null) {
            mViewController.onPlayStateChange(mCurrentState);
        }
    }

    //初始化播放器
    private void initPlayer() {
        if (mMediaPlayer == null) {
            //音頻播放器
            mMediaPlayer = new MediaPlayer();
            //播放型別 因為播放的mp3
            mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        }
    }

    // 停止過后再播放就是從頭開始
    @Override
    public void stopPlay() {
        Log.i(TAG,"stopPlay...");
        if (mMediaPlayer != null && mMediaPlayer.isPlaying()) {
            mMediaPlayer.stop();
            mCurrentState = PLAY_STATE_STOP;
            stopTimer();
            if (mViewController != null) {
                mViewController.onPlayStateChange(mCurrentState);//更新播放狀態
            }
            mMediaPlayer.release();
            mMediaPlayer = null;
        }
    }

    @Override
    public void seekTo(int seek) {
        Log.i(TAG,"seekTo..."+seek);
        //seek是0~100
        //轉換 得到seek百分比
        if (mMediaPlayer != null) {
            //.getDuration()取到的是音頻的真實“長度”
            int tarSeek = (int) (seek * 1.0f / 100 * mMediaPlayer.getDuration());
            mMediaPlayer.seekTo(tarSeek);
        }
    }

    //開啟一個timerTask
    private void startTimer(){
        if (mTimer == null) {
            mTimer = new Timer();
        }
        if (mTimeTask == null) {
            mTimeTask = new SeekTimeTask();
        }
        mTimer.schedule(mTimeTask,0,500);//500毫秒
    }
    //停止
    private void stopTimer(){
        if (mTimeTask != null) {
            mTimeTask.cancel();
            mTimeTask = null;//置空
        }
        if (mTimer != null) {
            mTimer.cancel();
            mTimer = null;
        }
    }

    private class SeekTimeTask extends TimerTask{
        @Override
        public void run() {
            if (mMediaPlayer != null && mViewController != null) {
                //獲取當前的播放進度
                int currentPosition = mMediaPlayer.getCurrentPosition();
                //Log.d(TAG,"current play position..."+currentPosition);
                //當前的播放進度/總的播放進度
                int curPosition = (int) (currentPosition * 1.0f / mMediaPlayer.getDuration() *100);
                //改變ui界面拖動條
                mViewController.onSeekChange(curPosition);
            }
        }
    }
}

6、活動視窗

PlayerActivity.java

package com.example.testservice;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;

import androidx.annotation.Nullable;

import com.example.testservice.interfaces.IPlayerControl;
import com.example.testservice.interfaces.IPlayerViewControl;
import com.example.testservice.services.PlayerService;

import static com.example.testservice.interfaces.IPlayerControl.PLAY_STATE_PAUSE;
import static com.example.testservice.interfaces.IPlayerControl.PLAY_STATE_PLAY;
import static com.example.testservice.interfaces.IPlayerControl.PLAY_STATE_STOP;

//ui的展示
//activity與服務間通過介面連接
public class PlayerActivity extends Activity {

    private static final String TAG = "PlayerActivity";
    private SeekBar mSeekBar;
    private Button mPlayOrPause,mClose;
    private PlayerConnection mPlayerConnection;
    private IPlayerControl mIPlayerControl;
    private boolean isUserTouchProgressBar = false;//默認用戶沒觸摸到拖動條

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_play);
        initView();
        //設定相關事件
        initEvent();

        //另需開啟服務 這樣服務才能長期運行
        initService();
        //系結服務
        initBindService();
    }

    //開啟播放的服務
    private void initService() {
        Log.d(TAG,"initService");
        startService(new Intent(this,PlayerService.class));
    }

    //系結服務
    private void initBindService() {
        Log.d(TAG,"initBindService");
        Intent intent = new Intent(this, PlayerService.class);
        if(mPlayerConnection == null) {
            mPlayerConnection = new PlayerConnection(); //ctrl+alt+f抽取成員變數
        }
        bindService(intent,mPlayerConnection,BIND_AUTO_CREATE);
    }
    private class PlayerConnection implements ServiceConnection{
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            Log.d(TAG,"onServiceConnected------>"+service);
            mIPlayerControl = (IPlayerControl) service;//這樣才能進行下面的控制元件事件
            //按鈕功能的介面連接
            mIPlayerControl.registerViewController(mIPlayerViewControl);
        }
        @Override
        //斷開連接(系結
        public void onServiceDisconnected(ComponentName name) {
            Log.d(TAG,"onServiceDisconnected");
            mIPlayerControl = null;
        }
    }

    //初始化控制元件事件
    private void initEvent() {
        mSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                //進度條發生改變
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                //拖動進度條
                isUserTouchProgressBar = true;
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                int touchProgress = seekBar.getProgress();
                Log.d(TAG,"touchProgress------>"+touchProgress);
                //停止拖動
                if (mIPlayerControl != null) {
                    mIPlayerControl.seekTo(touchProgress);
                }
                isUserTouchProgressBar = false;//沒用觸摸到拖動條
            }
        });
        mPlayOrPause.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //播放或暫停
                if(mIPlayerControl != null){
                    mIPlayerControl.playOrPause();
                }
            }
        });
        mClose.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //點擊關閉按鈕
                //需要判空，否則容易崩掉
                if(mIPlayerControl != null) {
                    mIPlayerControl.stopPlay();
                }
            }
        });
    }

    //初始化各控制元件
    private void initView() {
        mSeekBar = (SeekBar) this.findViewById(R.id.seek_bar);
        mPlayOrPause = (Button) this.findViewById(R.id.play_or_pause_btn);
        mClose = (Button) this.findViewById(R.id.close_btn);
    }

    //釋放服務
    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(mPlayerConnection != null){
            mIPlayerControl.unRegisterViewController();//釋放資源
            Log.d(TAG,"unbind service------>onDestroy");
            unbindService(mPlayerConnection);
        }
    }

    //ui狀態
    private IPlayerViewControl mIPlayerViewControl = new IPlayerViewControl() {
        @Override
        public void onPlayStateChange(int state) {
            //根據播放狀態來修改ui(按鈕上顯示的文字)
            switch (state){
                case PLAY_STATE_PLAY:
                    mPlayOrPause.setText("暫停");
                    break;
                case PLAY_STATE_PAUSE:
                case PLAY_STATE_STOP:
                    mPlayOrPause.setText("播放");
                    break;
            }
        }
        @Override
        public void onSeekChange(final int seek) {
            //在Android中progressBar、surfaceView控制元件可以用子執行緒更新(不是主執行緒但也沒問題原因)
            Log.d(TAG,"current thread-----"+Thread.currentThread().getName());//從結果得出不是主執行緒
            //所以進行如下操作：
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    //改變播放進度（拖動條）
                    if (!isUserTouchProgressBar) {
                        mSeekBar.setProgress(seek);
                    }
                }
            });
        }
    };
}

四、結果展示

可在后臺運行，
在這里插入圖片描述

五、補充

1、MediaPlayer播放音頻與視頻

2、seekBar屬性詳解

轉載請註明出處，本文鏈接：https://www.uj5u.com/yidong/252015.html

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