Android MediaPlayer(多媒體播放)

Android提供了許多方法來控制播放的音訊/視訊檔案和流。其中該方法是通過一類稱為MediaPlayer。

Android是提供MediaPlayer類存取內建的媒體播放器的服務，如播放音訊，視訊等為了使用MediaPlayer，我們要呼叫這個類的靜態create() 方法。此方法返回MediaPlayer類的一個範例。它的語法如下：

MediaPlayer mediaPlayer = MediaPlayer.create(this, R.raw.song);

第二個引數是要播放的歌曲的名字。必須做出一個新的檔案夾下的專案名稱為raw，然後將音樂檔案轉換成它。

建立了MediaPlayer物件之後，可以呼叫一些方法來啟動或停止音樂。這些方法在下面列出。

mediaPlayer.start();
mediaPlayer.pause();

在呼叫start()方法時，音樂將從頭開始播放。如果此方法是pause() 方法之後再次呼叫時，音樂將開始從那裡被停住，而不是從頭開始播放。 

要從一開始啟動音樂，必須呼叫 reset()方法。其語法如下給出：

mediaPlayer.reset();

除了start和pause方法，有用於與音訊/視訊檔案更好處理提供的此類其他方法。這些方法如下：

例子

這裡有一個例子演示如何使用的MediaPlayer類。它建立了一個基本的媒體播放器，可以前進，後退，播放和暫停播放歌曲。

為了試驗這個例子，需要一個實際的裝置上執行這聽聽聲音。

Following is the content of the modifed main activity filesrc/com.yiibai.mediaplayer/MainActivity.java.

package com.example.mediaplayer;

import java.util.concurrent.TimeUnit;

import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

   public TextView songName,startTimeField,endTimeField;
   private MediaPlayer mediaPlayer;
   private double startTime = 0;
   private double finalTime = 0;
   private Handler myHandler = new Handler();;
   private int forwardTime = 5000; 
   private int backwardTime = 5000;
   private SeekBar seekbar;
   private ImageButton playButton,pauseButton;
   public static int oneTimeOnly = 0;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      songName = (TextView)findViewById(R.id.textView4);
      startTimeField =(TextView)findViewById(R.id.textView1);
      endTimeField =(TextView)findViewById(R.id.textView2);
      seekbar = (SeekBar)findViewById(R.id.seekBar1);
      playButton = (ImageButton)findViewById(R.id.imageButton1);
      pauseButton = (ImageButton)findViewById(R.id.imageButton2);
      songName.setText("song.mp3");
      mediaPlayer = MediaPlayer.create(this, R.raw.song);
      seekbar.setClickable(false);
      pauseButton.setEnabled(false);

   }

   public void play(View view){
   Toast.makeText(getApplicationContext(), "Playing sound", 
   Toast.LENGTH_SHORT).show();
      mediaPlayer.start();
      finalTime = mediaPlayer.getDuration();
      startTime = mediaPlayer.getCurrentPosition();
      if(oneTimeOnly == 0){
         seekbar.setMax((int) finalTime);
         oneTimeOnly = 1;
      } 

      endTimeField.setText(String.format("%d min, %d sec", 
         TimeUnit.MILLISECONDS.toMinutes((long) finalTime),
         TimeUnit.MILLISECONDS.toSeconds((long) finalTime) - 
         TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.
         toMinutes((long) finalTime)))
      );
      startTimeField.setText(String.format("%d min, %d sec", 
         TimeUnit.MILLISECONDS.toMinutes((long) startTime),
         TimeUnit.MILLISECONDS.toSeconds((long) startTime) - 
         TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.
         toMinutes((long) startTime)))
      );
      seekbar.setProgress((int)startTime);
      myHandler.postDelayed(UpdateSongTime,100);
      pauseButton.setEnabled(true);
      playButton.setEnabled(false);
   }

   private Runnable UpdateSongTime = new Runnable() {
      public void run() {
         startTime = mediaPlayer.getCurrentPosition();
         startTimeField.setText(String.format("%d min, %d sec", 
            TimeUnit.MILLISECONDS.toMinutes((long) startTime),
            TimeUnit.MILLISECONDS.toSeconds((long) startTime) - 
            TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.
            toMinutes((long) startTime)))
         );
         seekbar.setProgress((int)startTime);
         myHandler.postDelayed(this, 100);
      }
   };
   public void pause(View view){
      Toast.makeText(getApplicationContext(), "Pausing sound", 
      Toast.LENGTH_SHORT).show();

      mediaPlayer.pause();
      pauseButton.setEnabled(false);
      playButton.setEnabled(true);
   }	
   public void forward(View view){
      int temp = (int)startTime;
      if((temp+forwardTime)<=finalTime){
         startTime = startTime + forwardTime;
         mediaPlayer.seekTo((int) startTime);
      }
      else{
         Toast.makeText(getApplicationContext(), 
         "Cannot jump forward 5 seconds", 
         Toast.LENGTH_SHORT).show();
      }

   }
   public void rewind(View view){
      int temp = (int)startTime;
      if((temp-backwardTime)>0){
         startTime = startTime - backwardTime;
         mediaPlayer.seekTo((int) startTime);
      }
      else{
         Toast.makeText(getApplicationContext(), 
         "Cannot jump backward 5 seconds",
         Toast.LENGTH_SHORT).show();
      }

   }

   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
   // Inflate the menu; this adds items to the action bar if it is present.
   getMenuInflater().inflate(R.menu.main, menu);
   return true;
   }

 }

Following is the modified content of the xml res/layout/activity_main.xml.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:paddingBottom="@dimen/activity_vertical_margin"
   android:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   tools:context=".MainActivity" >

   <ImageButton
      android:id="@+id/imageButton3"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentBottom="true"
      android:layout_alignParentLeft="true"
      android:layout_marginBottom="14dp"
      android:onClick="forward"
      android:src="@android:drawable/ic_media_ff" />

   <ImageButton
      android:id="@+id/imageButton4"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentRight="true"
      android:layout_alignTop="@+id/imageButton2"
      android:layout_marginLeft="22dp"
      android:layout_toRightOf="@+id/imageButton2"
      android:onClick="rewind"
      android:src="@android:drawable/ic_media_rew" />

   <ImageButton
      android:id="@+id/imageButton2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignTop="@+id/imageButton1"
      android:layout_marginLeft="14dp"
      android:layout_toRightOf="@+id/imageButton1"
      android:onClick="pause"
      android:src="@android:drawable/ic_media_pause" />

   <ImageButton
      android:id="@+id/imageButton1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignTop="@+id/imageButton3"
      android:layout_marginLeft="24dp"
      android:layout_toRightOf="@+id/imageButton3"
      android:onClick="play"
      android:src="@android:drawable/ic_media_play" />

   <SeekBar
      android:id="@+id/seekBar1"
      android:layout_width="match_parent"
      android:layout_height="wrap_content" 
      android:layout_above="@+id/imageButton3"
      android:layout_toLeftOf="@+id/textView2"
      android:layout_toRightOf="@+id/textView1" />

   <TextView
      android:id="@+id/textView1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignRight="@+id/imageButton3"
      android:layout_alignTop="@+id/seekBar1"
      android:text="@string/inital_Time"
      android:textAppearance="?android:attr/textAppearanceSmall" />

   <TextView
      android:id="@+id/textView2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignLeft="@+id/imageButton4"
      android:layout_alignTop="@+id/seekBar1"
      android:text="@string/inital_Time"
      android:textAppearance="?android:attr/textAppearanceSmall" />

   <TextView
      android:id="@+id/textView3"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignLeft="@+id/imageButton3"
      android:text="@string/hello_world"
      android:textAppearance="?android:attr/textAppearanceMedium" />

   <ImageView
      android:id="@+id/imageView1"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:layout_alignParentBottom="true"
      android:layout_alignParentLeft="true"
      android:layout_below="@+id/textView3"
      android:src="@drawable/ic_launcher" />

   <TextView
      android:id="@+id/textView4"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignBaseline="@+id/textView3"
      android:layout_alignBottom="@+id/textView3"
      android:layout_toRightOf="@+id/imageButton1"
      android:text="TextView" />

</RelativeLayout>

Following is the content of the res/values/string.xml.

<?xml version="1.0" encoding="utf-8"?>
<resources>

   <string name="app_name">MediaPlayer</string>
   <string name="action_settings">Settings</string> 
   <string name="hello_world">Now Playing:</string>
   <string name="inital_Time">0 min, 0 sec</string>

</resources>

Following is the content of AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.yiibai.mediaplayer"
   android:versionCode="1"
   android:versionName="1.0" >

   <uses-sdk
      android:minSdkVersion="8"
      android:targetSdkVersion="17" />

   <application
      android:allowBackup="true"
      android:icon="@drawable/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >
      <activity
         android:name="com.yiibai.mediaplayer.MainActivity"
         android:label="@string/app_name" >
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your MediaPlayer application. I assume you have connected your actual Android Mobile device with your computer. To run the app from Eclipse, open one of your project's activity files and click Run  icon from the toolbar. Before starting your application, Eclipse will display following window to select an option where you want to run your Android application.

Select your mobile device as an option and then check your mobile device which will display your default screen:

By default you would see the pause button disabled. Now press play button and it would become disable and pause button become enable. It is shown in the picture below:

Uptill now , the music has been playing. Now press the pause button and see the pause notification. This is shown below:

Now when you press the play button again, the song will not play from the begining but from where it was paused. Now press the fast forwad or backward button to jump the song forward or backward 5 seconds. A time came when the song cannot be jump forward. At this yiibai , the notification would appear which would be something like this:

Your music would remain playing in the background while you are doing other tasks in your mobile. In order to stop it , you have to exit this application from background activities.

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• Android登入範例