Android：使用网页在媒体播放器中显示当前曲目信息

Question

我是一名学习者并正在开发Android应用以播放直播。它正常工作，除了1个问题。我想显示当前播放的曲目的标题，该标题可在webpge上获得。为此，我使用了一个textView并尝试使用Asynchronous Task并在该异步任务中调用一个包含Runnable的方法，我可以用30秒的间隔更新textView的文本。在runnable中我调用了一个加载网页的方法并将其内容作为字符串。

问题：当它尝试更新textView的文本时，应用程序崩溃。感谢提前。

以下是我的代码：

import java.io.IOException;
import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
import android.app.ProgressDialog;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Handler;
import java.net.URLConnection;
import java.net.URL;
import java.io.InputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import android.util.Log;
import java.net.MalformedURLException;
import android.widget.TextView;
import android.os.AsyncTask;

public class MusicAndroidActivity extends Activity {



static MediaPlayer mPlayer;
    Button buttonPlay;
    Button buttonStop;
    Button buttonPause;
    public TextView txtMessage;
    private StringBuilder response;
    private String text="***";
    ProgressDialog progDailog;
    private final static int INTERVAL = 1000 * 30; //2 minutes
    Handler mHandler;
    int length=0;
    String url = "http://www.s8.voscast.com:9630/;stream.mp3";
    private final Handler handler = new Handler();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        buttonStop = (Button) findViewById(R.id.stop);
        txtMessage=(TextView)findViewById(R.id.txtMessage);
        buttonStop.setEnabled(false);
        buttonPause=(Button) findViewById(R.id.pause);
        buttonPause.setEnabled(false);
        buttonPlay = (Button) findViewById(R.id.play);

        buttonPlay.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {

                mPlayer = new MediaPlayer();
                mPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
                try {
                    buttonPlay.setEnabled(false);
                    buttonStop.setEnabled(true);
                    buttonPause.setEnabled(true);
                    //txtMessage.setText("Loading...");
                    progDailog = ProgressDialog.show(MusicAndroidActivity.this, "", "Buffering ... \n It can take upto 1 Minute, depending upon your internet speed", true);
                    mPlayer.setDataSource(url);
                } catch (IllegalArgumentException e) {
                    Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                } catch (SecurityException e) {
                    Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                } catch (IllegalStateException e) {
                    Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                try {

                    mPlayer.setOnPreparedListener(new OnPreparedListener() {

                        public void onPrepared(MediaPlayer mPlayer) {
                            // TODO Auto-generated method stub
                            mPlayer.start();
                            progDailog.dismiss();
                            LoadWebPageASYNC task = new LoadWebPageASYNC();
                            task.execute(new String[]{"http://khilare.com/swltest/sms.html"});

                        }
                    });
                    mPlayer.prepareAsync();
                } catch (IllegalStateException e) {
                    Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                } //catch (IOException e) {
                //Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                //}

            }

        });



        buttonStop.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                // TODO Auto-generated method stub
                if(mPlayer!=null && mPlayer.isPlaying()){
                    mPlayer.stop();
                    buttonPlay.setEnabled(true);
                    buttonStop.setEnabled(false);
                    buttonPause.setEnabled(false);
                }
            }
        });

        buttonPause.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                // TODO Auto-generated method stub
                if(mPlayer!=null && mPlayer.isPlaying()){
                    mPlayer.pause();
                    length=mPlayer.getCurrentPosition();
                    buttonPause.setText("Resume");
                    //buttonPlay.setEnabled(true);
                    buttonStop.setEnabled(true);
                    buttonPlay.setEnabled(false);
                    //sapp();
                    //getHTML();
                    //txtMessage.setText(text);
                    txtMessage.setText(text);
                }
                else {
                //mPlayer.seekTo(length);
                    mPlayer.start();
                //  mPlayer.seekTo(length);
                    buttonPause.setText("Pause");

                }
            }
        });

    }

    protected void onDestroy() {
        super.onDestroy();
        // TODO Auto-generated method stub
        if (mPlayer != null) {
            mPlayer.release();
            mPlayer = null;
        }
    }



    private class LoadWebPageASYNC extends AsyncTask<String, Void, String> {

        @Override
        protected String doInBackground(String... urls) {
            getHTML();
            //sapp();
            txtMessage.setText(text);
            return null;
        }
    }
    private void sapp()
    {
        //Runnable updater1 = new Runnable() {
            handler.postDelayed(new Runnable() {
                //@Override
                public void run() {
                    getHTML();
                    txtMessage.setText(text);
                }
            }, INTERVAL);


            /*public void run() {
                getHTML();
                txtMessage.setText(text);
            }
        };*/
        //handler.post(updater1);
    }
    private void getHTML()
    {
        try {
            URLConnection connection = new URL("http://khilare.com/swltest/sms.html").openConnection();
            connection.setRequestProperty("Accept-Charset", "UTF-8");
            InputStream responseStream = connection.getInputStream();

            BufferedReader br = new BufferedReader(new InputStreamReader(responseStream));
            response = new StringBuilder();
            String line;
            line = br.readLine();
            {
                response.append(line);
            }
            text = response.toString();
            //txtMessage.setText(text);
            //Log.i("Output", text);
        } catch (MalformedURLException e) {
            txtMessage.setText(e.getMessage());
            e.printStackTrace();
        } catch (IOException e) {
            txtMessage.setText(e.getMessage());
            e.printStackTrace();
        }
        //textStreamed.setText(text);
    }

}

这是Logcat：

    java.lang.SecurityException: Permission denial: writing to settings requires android.permission.WRITE_SETTINGS
            at com.android.providers.settings.SettingsProvider.callFromPackage(SettingsProvider.java:645)
            at android.content.ContentProvider$Transport.call(ContentProvider.java:279)
            at android.content.ContentProviderNative.onTransact(ContentProviderNative.java:273)
            at android.os.Binder.execTransact(Binder.java:388)
            at dalvik.system.NativeStart.run(Native Method)
05-29 10:56:45.772      302-302/? E/Parcel﹕ Reading a NULL string not supported here.
05-29 10:56:45.772      302-302/? E/Parcel﹕ Reading a NULL string not supported here.
05-29 10:56:48.462      302-302/? E/Parcel﹕ Reading a NULL string not supported here.
05-29 10:56:48.462      302-302/? E/Parcel﹕ Reading a NULL string not supported here.
05-29 10:56:50.702      302-302/? E/Parcel﹕ Reading a NULL string not supported here.
05-29 10:56:50.702      302-302/? E/Parcel﹕ Reading a NULL string not supported here.
05-29 10:56:50.712      302-302/? E/Parcel﹕ Reading a NULL string not supported here.
05-29 10:56:50.712      302-302/? E/Parcel﹕ Reading a NULL string not supported here.

05-29 10:57:01.772  28164-28569/com.prgguru.example E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
    java.lang.RuntimeException: An error occured while executing doInBackground()
            at android.os.AsyncTask$3.done(AsyncTask.java:299)
            at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
            at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
            at java.util.concurrent.FutureTask.run(FutureTask.java:239)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
            at java.lang.Thread.run(Thread.java:841)
     Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
            at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:5969)
            at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:921)
            at android.view.ViewGroup.invalidateChild(ViewGroup.java:4276)
            at android.view.View.invalidate(View.java:10552)
            at android.view.View.invalidate(View.java:10507)
            at android.widget.TextView.checkForRelayout(TextView.java:6531)
            at android.widget.TextView.setText(TextView.java:3789)
            at android.widget.TextView.setText(TextView.java:3643)
            at android.widget.TextView.setText(TextView.java:3618)
            at com.prgguru.example.MusicAndroidActivity$LoadWebPageASYNC.doInBackground(MusicAndroidActivity.java:158)
            at com.prgguru.example.MusicAndroidActivity$LoadWebPageASYNC.doInBackground(MusicAndroidActivity.java:152)
            at android.os.AsyncTask$2.call(AsyncTask.java:287)
            at java.util.concurrent.FutureTask.run(FutureTask.java:234)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
            at java.lang.Thread.run(Thread.java:841)

Answer 1

我明白了。

我使用了TimeTask，它每10秒调用一次方法 UpdateGUI（）; 。这种方法＆＃34; UpdateGUI（）; ＆＃34;进一步调用方法＆＃34; getHTML（）; ＆＃34;将网页内容加载到String文本。此方法也可通过 myHandler 调用 myRunnable

myHandler.post(myRunnable);

和 myRunnable 设置textView的文本 txtMessage

要完全了解此过程，请阅读this Article

代码现在是：

import java.io.IOException;
import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
import android.app.ProgressDialog;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Handler;
import java.net.URLConnection;
import java.net.URL;
import java.io.InputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import android.util.Log;
import java.net.MalformedURLException;
import android.widget.TextView;
import java.util.TimerTask;
import java.util.Timer;

public class MusicAndroidActivity extends Activity {

    static MediaPlayer mPlayer;
    Button buttonPlay;
    Button buttonStop;
    Button buttonPause;
    public TextView txtMessage;
    private StringBuilder response;
    private String text="***";
    ProgressDialog progDailog;
    final Handler myHandler = new Handler();
    int length=0;
    String url = "http://www.example.com:port/;stream.mp3";
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        buttonStop = (Button) findViewById(R.id.stop);
        txtMessage=(TextView)findViewById(R.id.txtMessage);
        buttonStop.setEnabled(false);
        buttonPause=(Button) findViewById(R.id.pause);
        buttonPause.setEnabled(false);
        buttonPlay = (Button) findViewById(R.id.play);

        buttonPlay.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                mPlayer = new MediaPlayer();
                mPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
                try {
                    buttonPlay.setEnabled(false);
                    buttonStop.setEnabled(true);
                    buttonPause.setEnabled(true);
                    progDailog = ProgressDialog.show(MusicAndroidActivity.this, "", "Buffering ... \n It can take upto 1 Minute, depending upon your internet speed", true);
                    mPlayer.setDataSource(url);
                } catch (IllegalArgumentException e) {
                    Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                } catch (SecurityException e) {
                    Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                } catch (IllegalStateException e) {
                    Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                try {
                    mPlayer.setOnPreparedListener(new OnPreparedListener() {
                            public void onPrepared(MediaPlayer mPlayer) {
                            // TODO Auto-generated method stub
                            mPlayer.start();
                            progDailog.dismiss();
                        }
                    });
                    mPlayer.prepareAsync();
                    Timer myTimer = new Timer();        // Declared Timer
                    myTimer.schedule(new TimerTask() {  // Started Time Task, it will repeat as per given duration (Ours is 1000 or 10 Second)
                        @Override
                        public void run() {
                            UpdateGUI();  // Called Method UdateGUI
                        }                 //   v
                    }, 0, 10000);         // After Every 10 Seconds

                } catch (IllegalStateException e) {
                    Toast.makeText(getApplicationContext(), "You might not set the URI correctly!", Toast.LENGTH_LONG).show();
                }
            }
        });

        buttonStop.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                // TODO Auto-generated method stub
                if(mPlayer!=null && mPlayer.isPlaying()){
                    mPlayer.stop();
                    buttonPlay.setEnabled(true);
                    buttonStop.setEnabled(false);
                    buttonPause.setEnabled(false);
                }
            }
        });

        buttonPause.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                if(mPlayer!=null && mPlayer.isPlaying()){
                    mPlayer.pause();
                    length=mPlayer.getCurrentPosition();
                    buttonPause.setText("Play");
                    buttonStop.setEnabled(true);
                    buttonPlay.setEnabled(false);
                }
                else {
                    mPlayer.start();
                    buttonPause.setText("Pause");
                }
            }
        });

    }

    protected void onDestroy() {
        super.onDestroy();
        // TODO Auto-generated method stub
        if (mPlayer != null) {
            mPlayer.release();
            mPlayer = null;
        }
    }

    private void UpdateGUI() {
        getHTML();
        myHandler.post(myRunnable);  // Posted MyRunnable  to myHandler
    }

    final Runnable myRunnable = new Runnable() {
        public void run() {
            txtMessage.setText(text);       //Set txtMessage's value to text (text is a string declared above)
        }
    };

    private void getHTML()
    {
        try {
            URLConnection connection = new URL("http://example.com/stats/index.php").openConnection();
            connection.setRequestProperty("Accept-Charset", "UTF-8");
            InputStream responseStream = connection.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(responseStream));
            response = new StringBuilder();
            String line;
            line = br.readLine();
            {
                response.append(line);
            }
            text = response.toString();
        } catch (MalformedURLException e) {
            txtMessage.setText(e.getMessage());
            e.printStackTrace();
        } catch (IOException e) {
            txtMessage.setText(e.getMessage());
            e.printStackTrace();
        }
    }
}