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Android Studio – My Music Player App is crashing again and again

Below i have pasted the code of MainActivity

package com.example.tunifi;

import androidx.appcompat.app.AppCompatActivity;

import android.Manifest;
import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

import com.karumi.dexter.Dexter;
import com.karumi.dexter.PermissionToken;
import com.karumi.dexter.listener.PermissionDeniedResponse;
import com.karumi.dexter.listener.PermissionGrantedResponse;
import com.karumi.dexter.listener.PermissionRequest;
import com.karumi.dexter.listener.single.PermissionListener;

import java.io.File;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ListView listView;
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = findViewById(R.id.listView);
        Dexter.withContext(this)
                .withPermission(Manifest.permission.READ_EXTERNAL_STORAGE)
                .withListener(new PermissionListener() {
                    @Override
                    public void onPermissionGranted(PermissionGrantedResponse permissionGrantedResponse) {
                        //Toast.makeText(MainActivity.this, "Runtime permission given !", Toast.LENGTH_SHORT).show();
                        ArrayList<File> mySongs = fetchSongs(Environment.getExternalStorageDirectory());
                        String [] items = new String[mySongs.size()];
                        for (int i=0;i<mySongs.size();i++){
                            items[i] = mySongs.get(i).getName().replace(".mp3","");
                        }
                        ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_expandable_list_item_1,items);
                        listView.setAdapter(adapter);
                        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                            @Override
                            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                                Intent intent = new Intent(MainActivity.this, PlaySong.class);
                                String currentSong = listView.getItemAtPosition(position).toString();
                                intent.putExtra("SongList",mySongs);
                                intent.putExtra("CurrentSong",currentSong);
                                intent.putExtra("Position",position);
                                startActivity(intent);
                            }
                        });
                    }

                    @Override
                    public void onPermissionDenied(PermissionDeniedResponse permissionDeniedResponse) {

                    }

                    @Override
                    public void onPermissionRationaleShouldBeShown(PermissionRequest permissionRequest, PermissionToken permissionToken) {
                        permissionToken.continuePermissionRequest();
                    }
                })
                .check();
    }
    public ArrayList<File> fetchSongs(File file){
        ArrayList arrayList = new ArrayList();
        File [] songs = file.listFiles();
        if (songs != null){
            for (File myFile : songs){
                if (!myFile.isHidden() && myFile.isDirectory()){
                    arrayList.addAll(fetchSongs(myFile));
                }
                else{
                    if (myFile.getName().endsWith(".mp3") && !myFile.getName().startsWith(".")){
                        arrayList.add(myFile);
                    }
                }
            }
        }
        return arrayList;
    }
}

Below i have pasted the code of PlaySong

package com.example.tunifi;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.TextView;

import java.io.File;
import java.util.ArrayList;

public class PlaySong extends AppCompatActivity {

    TextView textView;
    ImageView previous, play, next;
    ArrayList<File> songs;
    MediaPlayer mediaPlayer;
    String textContent;
    int position;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_play_song);
        textView = findViewById(R.id.textView);
        previous = findViewById(R.id.previous);
        play = findViewById(R.id.play);
        next = findViewById(R.id.next);

        Intent intent = getIntent();
        Bundle bundle = intent.getExtras();
        songs = (ArrayList) bundle.getParcelableArrayList("songs");
        textContent = intent.getStringExtra("CurrentSong");
        textView.setText(textContent);
        position = intent.getIntExtra("Position",0);
        Uri uri = Uri.parse(songs.get(position).toString());
        mediaPlayer = MediaPlayer.create(this,uri);
        mediaPlayer.start();
    }
}

This is what my Logcat shows:

2021-08-13 13:05:25.898 23725-23725/? I/zygote: Not late-enabling -Xcheck:jni (already on)
2021-08-13 13:04:58.820 1538-23594/? I/AudioFlinger: AudioFlinger's thread 0xb1903c80 tid=23594 ready to run
2021-08-13 13:05:25.917 23725-23725/? W/zygote: Unexpected CPU variant for X86 using defaults: x86
2021-08-13 13:03:30.914 1697-2352/system_process W/ActivityManager: Slow operation: 566ms so far, now at getContentProviderImpl: done!
2021-08-13 13:05:25.898 23725-23725/? I/zygote: Not late-enabling -Xcheck:jni (already on)
2021-08-13 13:05:25.917 23725-23725/? W/zygote: Unexpected CPU variant for X86 using defaults: x86
2021-08-13 13:05:25.898 23725-23725/? I/zygote: Not late-enabling -Xcheck:jni (already on)
2021-08-13 13:05:25.917 23725-23725/? W/zygote: Unexpected CPU variant for X86 using defaults: x86
2021-08-13 13:05:26.244 23725-23749/com.example.tunifi D/OpenGLRenderer: HWUI GL Pipeline
2021-08-13 13:05:26.331 23725-23749/com.example.tunifi I/OpenGLRenderer: Initialized EGL, version 1.4
2021-08-13 13:05:26.332 23725-23749/com.example.tunifi D/OpenGLRenderer: Swap behavior 1
2021-08-13 13:05:26.334 23725-23749/com.example.tunifi W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
2021-08-13 13:05:26.334 23725-23749/com.example.tunifi D/OpenGLRenderer: Swap behavior 0
2021-08-13 13:05:26.382 23725-23749/com.example.tunifi D/EGL_emulation: eglCreateContext: 0xa0385120: maj 2 min 0 rcv 2
2021-08-13 13:05:26.405 23725-23749/com.example.tunifi D/EGL_emulation: eglMakeCurrent: 0xa0385120: ver 2 0 (tinfo 0xa0383280)
2021-08-13 13:05:26.544 23725-23749/com.example.tunifi D/EGL_emulation: eglMakeCurrent: 0xa0385120: ver 2 0 (tinfo 0xa0383280)
2021-08-13 13:05:28.347 23725-23725/com.example.tunifi D/AndroidRuntime: Shutting down VM
2021-08-13 13:05:28.351 23725-23725/com.example.tunifi E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.tunifi, PID: 23725
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tunifi/com.example.tunifi.PlaySong}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.ArrayList.get(int)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.ArrayList.get(int)' on a null object reference
        at com.example.tunifi.PlaySong.onCreate(PlaySong.java:38)
        at android.app.Activity.performCreate(Activity.java:6975)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593) 
        at android.os.Handler.dispatchMessage(Handler.java:105) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6541) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

Can someone please help me out in finding what is wrong and how to correct it, sice i am new to this android development world and i am really upset for this thing since i am trying from many days to correct it,but nothing is working. Thank You So Much in advance !

Tags:

3

Answers


  1. 0 
    
Uri uri = Uri.parse(songs.get(position).toString());

         Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.ArrayList.get(int)' on a null object reference

    from this error,we can know the this arraylist is null,you should check it first

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  2. 0

    The trick is to read the stacktrace, it says :

    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.ArrayList.get(int)' on a null object reference

    So looks like songs is null when you try to get a value of that list, can you make sure that songs is initialized before calling the

    Uri uri = Uri.parse(songs.get(position).toString());

    Edit

    Perhaps this is not the root cause of your bug but you are doing this

    intent.putExtra("SongList",mySongs);

    looks like you are sending your song list with this bundle name "SongList" but then you are trying to retrieve it with :

    songs = (ArrayList) bundle.getParcelableArrayList("songs");

    I guess it should be "SongList" instead of "songs"

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  3. 0

    change

    songs = (ArrayList) bundle.getParcelableArrayList("songs");

    to

     songs = (ArrayList) bundle.getParcelableArrayList("SongList");
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