我的应用程序未显示应有的内容-为什么？

Question

我有一个歌词应用程序，该应用程序应显示正在播放的歌曲的歌词。 但不幸的是，它不起作用，显示为“正在加载”，并且不加载任何歌词。 但是我试图找出原因。 而且我发现BroadcastReceiver mReceiver无法正常工作，因为它没有在控制台中显示Log消息，而且我也不明白为什么它不能正常工作。 请你帮助我好吗？ 在这里，我附加了应用程序的两个Java类：MainActivity.java：

package com.example.trackslyrics;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.media.AudioManager;
import android.net.Uri;
import android.os.AsyncTask;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.logging.Logger;

public class MainActivity extends AppCompatActivity {

TextView status = null;
private BroadcastReceiver mReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        String cmd = intent.getStringExtra("command");

        Log.d("Music", cmd + " : " + action);

        String artist = intent.getStringExtra("artist");

        String track = intent.getStringExtra("track");
        boolean playing = intent.getBooleanExtra("playing", false);

        Log.d("Music", artist + " : " + track);

        if (!playing) {

            status.setText("No music playing");
        } else {
            status.setText(artist + "\n" + track);

            String uri = Uri.parse("http://www.stands4.com/services/v2/lyrics.php")
                    .buildUpon()
                    .appendQueryParameter("mus", track)
                    .appendQueryParameter("art", artist)
                    .build().toString();

            if (uri != null) {
                new VagalumeAsyncTask().execute(uri);
            }
        }
    }
};

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

    IntentFilter iF = new IntentFilter();
    iF.addAction("com.android.music.musicservicecommand");
    iF.addAction("com.android.music.metachanged");
    iF.addAction("com.android.music.playstatechanged");
    iF.addAction("com.android.music.updateprogress");

    this.status = (TextView) this.findViewById(R.id.status);

    registerReceiver(mReceiver, iF);

    AudioManager manager = (AudioManager) this.getSystemService(Context.AUDIO_SERVICE);
    if (!manager.isMusicActive()) {
        status.setText("No music playing");
    }

}

@Override
protected void onPause() {
    super.onPause();
    unregisterReceiver(mReceiver);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
   getMenuInflater().inflate(R.menu.menu_main, menu);
   return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

private class VagalumeAsyncTask extends AsyncTask<String, Void, JSONObject> {
    @Override
    protected JSONObject doInBackground(String... params) {
        JSONParser jParser = new JSONParser();
        return jParser.getJSONFromUrl(params[0]);
    }

    @Override
    protected void onPostExecute(JSONObject json) {
        super.onPostExecute(json);

        try {
            JSONObject mus = (JSONObject) json.getJSONArray("mus").get(0);
            status.setText(mus.getString("text"));
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}
}

和JSONParser.java：

package com.example.trackslyrics;

import android.util.Log;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.conn.ClientConnectionManager;
import org.apache.http.conn.scheme.PlainSocketFactory;
import org.apache.http.conn.scheme.Scheme;
import org.apache.http.conn.scheme.SchemeRegistry;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpConnectionParams;
import org.apache.http.params.HttpParams;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.security.KeyStore;

public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
HttpClient httpClient = createHttpClient();

public JSONParser() {

}

public static HttpClient createHttpClient() {
    try {
        KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
        trustStore.load(null, null);

        HttpParams params = new BasicHttpParams();
        HttpConnectionParams.setConnectionTimeout(params, 15000);
        HttpConnectionParams.setSoTimeout(params, 5000);

        SchemeRegistry registry = new SchemeRegistry();
        registry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));

        ClientConnectionManager ccm = new ThreadSafeClientConnManager(params, registry);

        return new DefaultHttpClient(ccm, params);
    } catch (Exception e) {
        return new DefaultHttpClient();
    }
}

public JSONObject getJSONFromUrl(String url) {
    try {
        HttpGet httpGet = new HttpGet(url);
        HttpResponse httpResponse = httpClient.execute(httpGet);
        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "ISO-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "n");
        }
        is.close();
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    return jObj;
}

}