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MediaPlayer App is crashing when i try to run

I'm beginner in android development and tried to create a simple mediaplayer app which plays media from local source.
But it's crashing when i try to open it.
This is my java code.
package com.example.media;
import androidx.appcompat.app.AppCompatActivity;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;
public class MainActivity extends AppCompatActivity {
Button play,pause;
SeekBar s;
MediaPlayer m;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
m=MediaPlayer.create(this,R.raw.live);
play=findViewById(R.id.button3);
pause=findViewById(R.id.button4);
s.findViewById(R.id.seekBar);
s.setMax(m.getDuration());
s.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
#Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
if(fromUser)m.seekTo(progress);
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
play.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
m.start();
}
});
pause.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
m.pause();
}
});
}
}

You need to initialize the seekbar object instead of calling the findViewById method.
So just replace the dot with equal sign :
s=findViewById(R.id.seekBar);

Losing state of the activity when navigating from notification to activity

I have an activity named Player Activity in which I am streaming music with the help of MediaPlayer API. Whenever my activity is created a notification is displayed which has some basic control of the music player.
So when I tap on my notification it jumps back to the Player Activity, but the state of the activity is lost.
Before tapping on notification :
After tapping on notification :
Here is the code of my notification's Pending Intent
Intent notifyIntent = new Intent(context, PlayerActivity.class);
notifyIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
notifyIntent.setAction("android.intent.action.MAIN");
notifyIntent.addCategory("android.intent.category.LAUNCHER");
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, notifyIntent, PendingIntent.FLAG_UPDATE_CURRENT);
Here is the code for PlayerActivity.java :
package com.example.user.musicplayer;
import android.app.ProgressDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.media.MediaMetadataRetriever;
import android.media.MediaPlayer;
import android.os.AsyncTask;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;
import com.squareup.picasso.Picasso;
import java.util.concurrent.TimeUnit;
import de.hdodenhof.circleimageview.CircleImageView;
public class PlayerActivity extends AppCompatActivity implements MediaPlayer.OnBufferingUpdateListener,MediaPlayer.OnCompletionListener{
private static Button btn_play_pause;
private Button btnToggleRepeat;
private Button btnStop;
private SeekBar seekBar;
private TextView textView;
public static MediaPlayer mediaPlayer;
private int mediaFileLength;
private int realtimeLength;
private String musicUrl;
private String imageUrl;
final Handler handler = new Handler();
private boolean isRepeat;
private CircleImageView musicImage;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_player);
Log.d("TAG", "onCreate");
NotificationGenerator.customBigNotification(getApplicationContext());
musicUrl = getIntent().getStringExtra("musicUrl");
imageUrl = getIntent().getStringExtra("imageUrl");
seekBar = (SeekBar)findViewById(R.id.seekbar);
seekBar.setMax(99); // 100% (0~99)
seekBar.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
if(mediaPlayer.isPlaying())
{
SeekBar seekBar = (SeekBar)v;
int playPosition = (mediaFileLength/100)*seekBar.getProgress();
mediaPlayer.seekTo(playPosition);
}
return false;
}
});
textView = (TextView)findViewById(R.id.txtTime);
btnToggleRepeat = findViewById(R.id.btnRepeat);
btnStop = findViewById(R.id.btnStop);
musicImage = findViewById(R.id.musicImgView);
Picasso.get().load(imageUrl).placeholder(R.drawable.music).error(R.drawable.music).into(musicImage);
btn_play_pause = (Button) findViewById(R.id.btnTogglePlay);
btn_play_pause.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final ProgressDialog mDialog = new ProgressDialog(PlayerActivity.this);
AsyncTask<String,String,String> mp3Play = new AsyncTask<String, String, String>() {
#Override
protected void onPreExecute() {
mDialog.setMessage("Please wait");
mDialog.show();
}
#Override
protected String doInBackground(String... params) {
try{
mediaPlayer.setDataSource(params[0]);
mediaPlayer.prepare();
}
catch (Exception ex)
{
}
return "";
}
#Override
protected void onPostExecute(String s) {
mediaFileLength = mediaPlayer.getDuration();
realtimeLength = mediaFileLength;
if(!mediaPlayer.isPlaying())
{
playMusic();
}
else
{
pauseMusic();
}
updateSeekBar();
mDialog.dismiss();
}
};
mp3Play.execute(musicUrl); // direct link mp3 file
}
});
btnToggleRepeat.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(isRepeat){
isRepeat = false;
mediaPlayer.setLooping(false);
btnToggleRepeat.setText("Repeat");
}
else{
isRepeat = true;
mediaPlayer.setLooping(true);
btnToggleRepeat.setText("Single");
}
}
});
btnStop.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
mediaPlayer.pause();
mediaPlayer.stop();
}
catch (Exception e){
Toast.makeText(PlayerActivity.this, "Opps! sorry something bad happened", Toast.LENGTH_SHORT).show();
}
}
});
mediaPlayer = new MediaPlayer();
mediaPlayer.setOnBufferingUpdateListener(this);
mediaPlayer.setOnCompletionListener(this);
}
public void pauseMusic() {
mediaPlayer.pause();
btn_play_pause.setText("Play");
}
public void playMusic() {
mediaPlayer.start();
btn_play_pause.setText("Pause");
}
private void updateSeekBar() {
seekBar.setProgress((int)(((float)mediaPlayer.getCurrentPosition() / mediaFileLength)*100));
if(mediaPlayer.isPlaying())
{
Runnable updater = new Runnable() {
#Override
public void run() {
updateSeekBar();
realtimeLength-=1000; // declare 1 second
textView.setText(String.format("%d:%d",TimeUnit.MILLISECONDS.toMinutes(realtimeLength),
TimeUnit.MILLISECONDS.toSeconds(realtimeLength) -
TimeUnit.MILLISECONDS.toSeconds(TimeUnit.MILLISECONDS.toMinutes(realtimeLength))));
}
};
handler.postDelayed(updater,1000); // 1 second
}
}
#Override
protected void onResume() {
super.onResume();
Log.d("TAG", "onResume");
}
#Override
protected void onStart() {
super.onStart();
Log.d("TAG", "onStart");
}
#Override
public void onBufferingUpdate(MediaPlayer mp, int percent) {
seekBar.setSecondaryProgress(percent);
}
#Override
public void onCompletion(MediaPlayer mp) {
if(!mediaPlayer.isLooping())
btn_play_pause.setText("Play");
}
#Override
protected void onStop() {
super.onStop();
}
#Override
protected void onPause() {
super.onPause();
}
public static class DownloadCancelReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
Log.d("notificationPlayer","Received Cancelled Event");
}
}
}
Thanks in advance. Pardon me if the explanation is not clear, because if i might have right words to explain it, I would have googled it.

Add this to your PlayerActivity activity in manifest :
android:launchMode="singleTask"
And use these flags in the intent for pendingintent :
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);

Runtime error in thread of music app

**Down here I am trying to build a music app in android studio,my app is working fine displaying all my SD card songs and play too ,all button works but when I click on next button it works normally but don't know why app sometimes gets stopped working and shows runtime exception ->>please open the image of run log of the application.
package com.example.ramandeepsingh.tunes;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Build;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.Toast;
import java.io.File;
import java.util.ArrayList;
import java.util.jar.Manifest;
public class PlayerActivity extends AppCompatActivity{
static MediaPlayer mp;//assigning memory loc once or else multiple songs will play at once
int position;
SeekBar sb;
ArrayList<File> mySongs;
Thread updateSeekBar;
Button pause,forward,reverse,next,previous;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_player);
pause = (Button)findViewById(R.id.pause);
forward = (Button)findViewById(R.id.forward);
previous = (Button)findViewById(R.id.previous);
next = (Button)findViewById(R.id.next);
reverse = (Button)findViewById(R.id.reverse);
sb=(SeekBar)findViewById(R.id.seekBar);
updateSeekBar=new Thread(){
#Override
public void run(){
int totalDuration = mp.getDuration();
int currentPosition = 0;
// sb.setMax(totalDuration);
while(currentPosition < totalDuration){
try{
sleep(500);
currentPosition=mp.getCurrentPosition();
}
catch (InterruptedException e){
e.printStackTrace();
System.out.println(e);
}
sb.setProgress(currentPosition);
}
}
};
if(mp != null){
mp.stop();
mp.release();
}
Intent i = getIntent();
Bundle b = i.getExtras();
mySongs = (ArrayList) b.getParcelableArrayList("songs");
position = b.getInt("pos",0);
Uri u = Uri.parse(mySongs.get(position).toString());
mp = MediaPlayer.create(getApplicationContext(),u);
mp.start();
sb.setMax(mp.getDuration());
updateSeekBar.start();
sb.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
#Override
public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
mp.seekTo(seekBar.getProgress());
}
});
pause.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
sb.setMax(mp.getDuration());
if(mp.isPlaying()){
pause.setText(">");
mp.pause();
}
else {
pause.setText("||");
mp.start();
}
}
});
forward.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
sb.setMax(mp.getDuration());
mp.seekTo(mp.getCurrentPosition()+5000);
}
});
reverse.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
sb.setMax(mp.getDuration());
mp.seekTo(mp.getCurrentPosition()-5000);
}
});
next.setOnClickListener(new
View.OnClickListener() {
#Override
public void onClick(View v) {
mp.stop();
mp.reset();
position=((position+1)%mySongs.size());
Uri u = Uri.parse(mySongs.get( position).toString());
mp = MediaPlayer.create(getApplicationContext(),u);
mp.start();
sb.setMax(mp.getDuration());
updateSeekBar.start();
}
});
previous.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mp.stop();
mp.release();
position=((position-1)<0)?(mySongs.size()-1):(position-1);
Uri u = Uri.parse(mySongs.get( position).toString());//%mysongs so that it do not go to invalid position
mp = MediaPlayer.create(getApplicationContext(),u);
mp.start();
}
});
}}

Change the image transparency using a SeekBar

I have to do an Android Studio project that it has to change the transparency of an ImageView using a SeekBar.
I have this program:
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private int seekTransparent;
ImageView color;
SeekBar seekBarTransparent;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
color = (ImageView)findViewById(R.id.changeColor);
seekBarTransparent = (SeekBar) findViewById(R.id.seekBar);
updateNow();
seekBarTransparent.setOnSeekBarChangeListener(seekBarChangeListener);
}
private SeekBar.OnSeekBarChangeListener seekBarChangeListener = new
SeekBar.OnSeekBarChangeListener() {
#Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean
fromUser) {
updateNow();
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
Toast.makeText(getApplicationContext(), "toast in uso",
Toast.LENGTH_SHORT).show();
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
Toast.makeText(getApplicationContext(), "toast non in uso",
Toast.LENGTH_SHORT).show();
}
};
private void updateNow(){
seekTransparent = seekBarTransparent.getProgress();
color.getBackground().setAlpha(192 + seekTransparent * 0x10000);
}
}
I run the application but on my smartphone it doesn't work anyone can help me?

This is the xml of the seekbar
<SeekBar
android:id="#+id/opacitybar"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:max="10"
android:progress="10"
android:layout_alignTop="#+id/opacitylbl"
android:layout_centerHorizontal="true" />
And this is the code of the Activity
logoseekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
int opacity = 100; // from 0 to 255
#Override
public void onProgressChanged(SeekBar seekBar, int progresValue, boolean fromUser) {
im_move_zoom_rotate.setAlpha(progresValue * 25);
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
You can change the values if you want

Android SeekBar extension

I have multiple Seek Bars on my activity (4) and for each there is a textView that suppose to show the progress of each SeekBar. I thought to extend the SeekBar Class and add to it's constructor a TextView Parameter so I can bind the two -> SeekBar and TextView . Here is my extended SeekBar class:
import android.content.Context;
import android.widget.SeekBar;
import android.widget.TextView;
public class SeekBarPlus extends SeekBar {
private TextView numberOfDrills;
public SeekBarPlus(Context context, TextView text) {
super(context);
// TODO Auto-generated constructor stub
numberOfDrills = (TextView) text;
}
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
numberOfDrills.setText(progress);
}
}
What is the Context option?
Now here is my MainActivity:
package com.simplemathgame;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
import com.simplemathgame.SeekBarPlus;
public class MainActivity extends Activity{
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView numberOfAddDrills = (TextView) findViewById(R.id.add_drills_number);
TextView numberOfSubDrills = (TextView) findViewById(R.id.sub_drills_number);
TextView numberOfMulDrills = (TextView) findViewById(R.id.mul_drills_number);
TextView numberOfDivDrills = (TextView) findViewById(R.id.div_drills_number);
SeekBarPlus addSeekBar = SeekBarPlus((SeekBar) findViewById(R.id.add_seek_bar), numberOfAddDrills);
SeekBarPlus subSeekBar = SeekBarPlus((SeekBar) findViewById(R.id.sub_seek_bar), numberOfAddDrills);
SeekBarPlus mulSeekBar1 = SeekBarPlus((SeekBar) findViewById(R.id.mul_seek_bar), numberOfAddDrills);
SeekBarPlus divSeekBar1 = SeekBarPlus((SeekBar) findViewById(R.id.div_seek_bar), numberOfAddDrills);
}
}
I don't know how to it wright! Any suggestions would be appreciated!!!

try to use setter instead of constructor in your custom SeekBar:
public void setTextView(TextView text) {
numberOfDrills = text;
}
then in your activity, use
SeekBarPlus subSeekBar = (SeekBarPlus) findViewById(R.id.sub_seek_bar);
subSeekBar.setTextView(numberOfAddDrills);
you can also use normal Seekbar with OnSeekBarChangeListener:
SeekBar subSeekBar = (SeekBar) findViewById(R.id.sub_seek_bar);
subSeekBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
#Override
public void onStopTrackingTouch(SeekBar seekBar) { }
#Override
public void onStartTrackingTouch(SeekBar seekBar) { }
#Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
numberOfDrills.setText(String.valueOf(progress));
}
});