java - MP3 下载器致命异常

Question

我有一个 mp3 下载应用程序的源代码，几个月前我上次使用它时效果很好。现在，当我尝试它时，当我从搜索结果中单击歌曲进行下载时，它会出现错误。错误如下:

08-01 13:06:09.227: E/AndroidRuntime(2075): FATAL EXCEPTION: main
08-01 13:06:09.227: E/AndroidRuntime(2075): Process: com.soundload, PID: 2075
08-01 13:06:09.227: E/AndroidRuntime(2075): java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Boolean de.voidplus.soundcloud.Track.isStreamable()' on a null object reference
08-01 13:06:09.227: E/AndroidRuntime(2075):     at com.baixavideos.Downloader.onPostExecute(Downloader.java:41)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at com.baixavideos.Downloader.onPostExecute(Downloader.java:1)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at android.os.AsyncTask.finish(AsyncTask.java:636)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at android.os.AsyncTask.access$500(AsyncTask.java:177)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at android.os.Handler.dispatchMessage(Handler.java:102)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at android.os.Looper.loop(Looper.java:135)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at android.app.ActivityThread.main(ActivityThread.java:5254)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at java.lang.reflect.Method.invoke(Native Method)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at java.lang.reflect.Method.invoke(Method.java:372)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
08-01 13:06:09.227: E/AndroidRuntime(2075):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
08-01 13:06:11.353: W/System.err(2174): java.io.IOException: open failed: EACCES (Permission denied)
08-01 13:06:11.353: W/System.err(2174):     at java.io.File.createNewFile(File.java:941)
08-01 13:06:11.354: W/System.err(2174):     at de.voidplus.soundcloud.SoundCloud.<init>(Unknown Source)
08-01 13:06:11.354: W/System.err(2174):     at com.baixavideos.ui.MainActivity.<clinit>(MainActivity.java:63)
08-01 13:06:11.354: W/System.err(2174):     at java.lang.reflect.Constructor.newInstance(Native Method)
08-01 13:06:11.354: W/System.err(2174):     at java.lang.Class.newInstance(Class.java:1606)
08-01 13:06:11.354: W/System.err(2174):     at android.app.Instrumentation.newActivity(Instrumentation.java:1066)

下载器.java:

package com.baixavideos;

import com.baixavideos.ui.SongDetails;

import de.voidplus.soundcloud.SoundCloud;
import de.voidplus.soundcloud.Track;

import android.os.AsyncTask;
import android.util.Log;

public class Downloader extends AsyncTask<String, Void, Track>{

    private int id;
    private SoundCloud soundcloud;
    private SongDetails ui;

    public Downloader(){
        soundcloud = new SoundCloud("cd07b57592f6d914f437f8ab2856363d", "841953bd718a3ceb427b3e3be170a014"); 
    }

    public int getId() {
        return id;
    }

    public Downloader setId(int id) {
        this.id = id;

        return this;
    }

    @Override
    protected Track doInBackground(String... arg0) {        
        Track track = soundcloud.getTrack(getId());
        return track;
    }

    @Override
    protected void onPostExecute(Track track) {
        super.onPostExecute(track);

        if(track.isStreamable()){
            getUi().onSongLoaded(track);
        } else {
            getUi().onStreamingError();
        }
    }

    public SongDetails getUi() {
        return ui;
    }

    public Downloader setUi(SongDetails ui) {
        this.ui = ui;

        return this;
    }   

}

Answer 1

原因是您为Downloader设置的id(或者可能根本没有设置过)是错误的，并且soundcloud中没有具有此类id的轨道。 track 变量无法初始化并保持为 null。
它以前起作用的原因是，当时您使用了有效的轨道 ID