MP3下载致命异常

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运行得很好。现在当我尝试的时候，它会给我一个错误，当我点击一首歌下载它，从搜索结果。下面是错误:

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)

Downloader.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

原因是您设置为Downloader的id(或者可能从未设置过id)是错误的，并且在soundcloud中没有这样的id跟踪。track变量不能初始化，保持null。
之前之所以有效，是因为你使用的是有效的轨道id