Android 学习笔记多媒体技术之 AsyncTask+实现音频播放...

 private class updateseekbar extends AsyncTask<Integer, Integer, String>{

        protected void onPostExecute(String result){}
        protected void onProgressUpdate(Integer...progress){
            seekbar.setProgress(progress[0]);
        }
        @Override
        protected String doInBackground(Integer... params) {
            // TODO Auto-generated method stub
            while(MainActivity.this.playflag){
                try {
                      Thread.sleep(params[0]);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                this.publishProgress(MainActivity.this.media.getCurrentPosition());
            }
            return null;
        }      
    }

//当在UI线程中调用execute（）方法以后,下面这个方法将被调用... 
public final AsyncTask<Params, Progress, Result> execute(Params... params) {
        return executeOnExecutor(sDefaultExecutor, params);//
    }
    /**
     * Executes the task with the specified parameters. The task returns
     * itself (this) so that the caller can keep a reference to it.
     * 
     * <p>This method is typically used with {@link #THREAD_POOL_EXECUTOR} to
     * allow multiple tasks to run in parallel on a pool of threads managed by
     * AsyncTask, however you can also use your own {@link Executor} for custom
     * behavior.
     * 
     * <p><em>Warning:</em> Allowing multiple tasks to run in parallel from
     * a thread pool is generally <em>not</em> what one wants, because the order
     * of their operation is not defined.  For example, if these tasks are used
     * to modify any state in common (such as writing a file due to a button click),
     * there are no guarantees on the order of the modifications.
     * Without careful work it is possible in rare cases for the newer version
     * of the data to be over-written by an older one, leading to obscure data
     * loss and stability issues.  Such changes are best
     * executed in serial; to guarantee such work is serialized regardless of
     * platform version you can use this function with {@link #SERIAL_EXECUTOR}.
     *
     * <p>This method must be invoked on the UI thread.
     *
     * @param exec The executor to use.  {@link #THREAD_POOL_EXECUTOR} is available as a
     *              convenient process-wide thread pool for tasks that are loosely coupled.
     * @param params The parameters of the task.
     *
     * @return This instance of AsyncTask.
     *
     * @throws IllegalStateException If {@link #getStatus()} returns either
     *         {@link AsyncTask.Status#RUNNING} or {@link AsyncTask.Status#FINISHED}.
     */
    public final AsyncTask<Params, Progress, Result> executeOnExecutor(Executor exec,
            Params... params) {
        if (mStatus != Status.PENDING) {
            switch (mStatus) {
                case RUNNING:
                    throw new IllegalStateException("Cannot execute task:"
                            + " the task is already running.");
                case FINISHED:
                    throw new IllegalStateException("Cannot execute task:"
                            + " the task has already been executed "
                            + "(a task can be executed only once)");
            }
        }

        mStatus = Status.RUNNING;

        onPreExecute();

        mWorker.mParams = params;
        exec.execute(mFuture);

        return this;
    }
    /**
     * Convenience version of {@link #execute(Object...)} for use with
     * a simple Runnable object.
     */
    public static void execute(Runnable runnable) {
        sDefaultExecutor.execute(runnable);
    }

<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity" >
    <TextView 
        android:id="@+id/info"
        android:layout_height="wrap_content"
        android:layout_width="fill_parent"
        android:text="等待播放"/>
    <LinearLayout 
        android:orientation="horizontal"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content">
        <ImageButton 
            android:id="@+id/play"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:src="@drawable/play"/>
        <ImageButton 
            android:id="@+id/pause"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:src="@drawable/pause"/>
        <ImageButton 
            android:id="@+id/stop"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:src="@drawable/stop"/>
    </LinearLayout>
    <SeekBar 
        android:id="@+id/seekbar"
        android:layout_height="wrap_content"
        android:layout_width="fill_parent"/>
</LinearLayout>

package com.example.exam7_2;

import java.io.IOException;

import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.SeekBar;
import android.widget.TextView;

public class MainActivity extends Activity implements View.OnClickListener, SeekBar.OnSeekBarChangeListener{
    private MediaPlayer media;
    private boolean playflag=true;
    private boolean pauseflag=false;
    private SeekBar seekbar=null;
    private TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv=(TextView) findViewById(R.id.info);
        findViewById(R.id.play).setOnClickListener(this);
        findViewById(R.id.pause).setOnClickListener(this);
        findViewById(R.id.stop).setOnClickListener(this);
        seekbar=(SeekBar) findViewById(R.id.seekbar);
        
    }
    private class updateseekbar extends AsyncTask<Integer, Integer, String>{

        protected void onPostExecute(String result){}
        protected void onProgressUpdate(Integer...progress){
            seekbar.setProgress(progress[0]);
        }
        @Override
        protected String doInBackground(Integer... params) {
            // TODO Auto-generated method stub
            while(MainActivity.this.playflag){
                try {
                    Thread.sleep(params[0]);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                this.publishProgress(MainActivity.this.media.getCurrentPosition());
            }
            return null;
        }
        
    }
    @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;
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch(v.getId()){
        case R.id.play:
        {
            media=MediaPlayer.create(MainActivity.this, R.raw.wind);
            MainActivity.this.media.setOnCompletionListener(new OnCompletionListener() {
                
                @Override
                public void onCompletion(MediaPlayer arg0) {
                    // TODO Auto-generated method stub
                    playflag=false;
                    media.release();
                }
            });
            seekbar.setMax(MainActivity.this.media.getDuration());
            updateseekbar update=new updateseekbar();
            //执行者execute
            update.execute(1000);
            seekbar.setOnSeekBarChangeListener(this);
            if(MainActivity.this.media!=null){
                MainActivity.this.media.stop();
            }
            try {
                MainActivity.this.media.prepare();
                MainActivity.this.media.start();
                tv.setText("正在播放文件...");
            } catch (Exception e) {
                // TODO Auto-generated catch block
                tv.setText("文件出现异常...");
                e.printStackTrace();
            } 
            break;
        }
        case R.id.pause:
            if(media!=null){
                if(pauseflag){
                    media.start();
                    pauseflag=false;
                }else{
                    media.pause();
                    pauseflag=true;
                }
            }
            break;
        case R.id.stop:
            if(media!=null){
                media.stop();
                tv.setText("停止播放文件...");
            }
            break;
        }
    }

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress,
            boolean fromUser) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {
        // TODO Auto-generated method stub
        media.seekTo(seekbar.getProgress());
    }
   
}