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How to fill the progress bar in the background while changing activities

I have 3 page application, in which the activities change every 10 secs (i.e., Activity1 -> Activity2 -> Activity3 -> Activity1 .......).
I have a progressbar in Activity2 which updates every 1 sec. The problem is, whenever the Activity2 is changing to Activity3 and then coming back to Activity 2 the progressbar is resetting and starting all over from zero.
I would like the progressbar to update continuously for the set time without interruptions. I tried using the services but the result is still the same.
I hope the code below helps in idenfying the issue and would really appreciate if anyone helps me out.
Activity1.java
package com.ossus.SC20;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.text.DateFormat;
import java.util.Calendar;
import java.util.Timer;
import java.util.TimerTask;
public class frame_6_activity extends Activity {
Timer timer;
private View _bg__frame_6;
private ImageView background_1;
private TextView text_view_date;
private ImageView logo_2_1;
private TextView H2Value;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.frame_6);
startService(new Intent(frame_6_activity.this, service.class));
Thread.setDefaultUncaughtExceptionHandler(new MyExceptionHandler(this));
if (getIntent().getBooleanExtra("crash", false)) {
Toast.makeText(this, "App restarted after crash", Toast.LENGTH_SHORT).show();
}
timer = new Timer();
timer.schedule(new TimerTask() {
#Override
public void run(){
Intent intent = new Intent(frame_6_activity.this, frame_2_activity.class);
startActivity(intent);
finish();
}
}, 10000);
Calendar calendar = Calendar.getInstance();
String currentDate = DateFormat.getDateInstance(DateFormat.FULL).format(calendar.getTime());
TextView textViewDate = findViewById(R.id.text_view_date);
textViewDate.setText(currentDate);
_bg__frame_6 = (View) findViewById(R.id._bg__frame_6);
background_1 = (ImageView) findViewById(R.id.background_1);
text_view_date = (TextView) findViewById(R.id.text_view_date);
logo_2_1 = (ImageView) findViewById(R.id.logo_2_1);
H2Value = (TextView) findViewById(R.id.H2Value);
}
}
Activity2.java
package com.ossus.SC20;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import androidx.annotation.NonNull;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import org.w3c.dom.Text;
import java.text.DateFormat;
import java.util.Calendar;
import java.util.Timer;
import java.util.TimerTask;
public class frame_2_activity extends Activity {
private ProgressBar mProgressBar;
private TextView mLoadingText;
private int mProgressStatus = 0;
// private Handler mHandler = new Handler();
Handler handler = new Handler();
Timer timer;
private View _bg__frame_2;
private ImageView background_1;
private TextView text_view_date;
private ImageView logo_2_1;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.frame_2_new);
startService(new Intent(frame_2_activity.this, service.class));
mProgressBar = (ProgressBar) findViewById(R.id.progressbar);
mLoadingText = (TextView) findViewById(R.id.LoadingCompleteTextView);
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
startProgress();
}
});
thread.start();
timer = new Timer();
timer.schedule(new TimerTask() {
#Override
public void run(){
Intent intent = new Intent(frame_2_activity.this, frame_3_activity.class);
startActivity(intent);
finish();
}
}, 10000);
Calendar calendar = Calendar.getInstance();
String currentDate = DateFormat.getDateInstance(DateFormat.FULL).format(calendar.getTime());
TextView textViewDate = findViewById(R.id.text_view_date);
textViewDate.setText(currentDate);
_bg__frame_2 = (View) findViewById(R.id._bg__frame_2);
background_1 = (ImageView) findViewById(R.id.background_1);
text_view_date = (TextView) findViewById(R.id.text_view_date);
logo_2_1 = (ImageView) findViewById(R.id.logo_2_1);
//custom code goes here
}
public void startProgress(){
for (mProgressStatus = 0; mProgressStatus < 100; mProgressStatus = mProgressStatus + 1){
try{
Thread.sleep(1000);
mProgressBar.setProgress(mProgressStatus);
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.post(new Runnable() {
#Override
public void run() {
mLoadingText.setText(String.valueOf(mProgressStatus + "% Completed"));
}
});
}
}
}
Service.java
package com.ossus.SC20;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.widget.Toast;
public class service extends Service {
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "Service started by user.", Toast.LENGTH_LONG).show();
return START_STICKY;
}
}
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="com.ossus.SC20">
<application
android:allowBackup="true"
android:dataExtractionRules="#xml/data_extraction_rules"
android:fullBackupContent="#xml/backup_rules"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/Theme.SC20"
tools:targetApi="31">
<activity
android:name=".frame_3_activity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:label="#string/app_name"
android:screenOrientation="landscape"
android:exported="true" >
</activity>
<activity
android:name=".frame_2_activity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:label="#string/app_name"
android:screenOrientation="landscape"
android:exported="true" >
</activity>
<activity
android:name=".frame_6_activity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:label="#string/app_name"
android:screenOrientation="landscape"
android:exported="true" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<meta-data
android:name="preloaded_fonts"
android:resource="#array/preloaded_fonts" />
<service android:name = ".service"/>
</application>
</manifest>

I can't start activity from service while app is hidden

I have two activities: MainActivity and ActivityTwo. When starting application, I start service serviceApp, which after some events should start ActivityTwo. For the test, I made the launch after 10 seconds and AsyncTask, but if the application is hidden, activity does not start
How do I launch activity even if the app is hidden?
MainActivity
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.SwitchCompat;
import android.app.ActivityManager;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
import java.security.Provider;
import java.util.List;
public class MainActivity extends AppCompatActivity {
SharedPreferences setting;
#Override
protected void onCreate(Bundle savedInstanceState) {
Intent service = new Intent(this, serviceApp.class);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setting = getSharedPreferences("settings", MODE_PRIVATE);
SwitchCompat switchCompat = findViewById(R.id.switchBLock);
switchCompat.setOnCheckedChangeListener((view, bool) -> {
SharedPreferences.Editor editor = setting.edit();
editor.putBoolean("block", bool);
editor.apply();
if(bool){
startService(service);
}else{
stopService(service);
}
});
if(setting.getBoolean("block", false)){
switchCompat.setChecked(true);
}
}
}
ActivityTwo
import android.app.ActivityManager;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Toast;
public class ActivityTwo extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_two);
}
}
serviceApp
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.IBinder;
public class serviceApp extends Service {
Context context;
public serviceApp() {
context = this;
}
#Override
public void onCreate() {
super.onCreate();
new Async().execute();
}
class Async extends AsyncTask<Void, Void, Void>{
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
Intent startMain = new Intent();
startMain.setClass(context, ActivityTwo.class);
startMain.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(startMain);
}
#Override
protected Void doInBackground(Void... voids) {
for(int i = 0; i < 2; i++) {
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return null;
}
}
#Override
public IBinder onBind(Intent intent) {
return null;
}
}
AndroidManifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.test">
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/Theme.AppCompat.NoActionBar">
<activity android:name="com.example.test.ActivityTwo"></activity>
<service
android:name=".serviceApp"/>
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

I found an easy way to fix this ailment, you need to give the application the SYSTEM_ALERT_WINDOW permission
https://developer.android.com/guide/components/activities/background-starts
AndroidManifest.xml
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
MainActivity
Intent myIntent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
startActivity(myIntent);

Playback position resets to zero after orientation change

Below is the code for my music player. I use Videoview to play a local list of selective songs.
I want to store and resume the playback position when orientation changes (portrait/landscape).
I have used onSaveInstanceState and onRestoreInstanceState methods. No errors on build, but still the songs reset every time.
I couldn't figure out what's wrong.
package io.automaton.android.morningbinge;
import androidx.appcompat.app.AlertDialog;
import android.app.Activity;
import android.content.DialogInterface;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.widget.Toast;
import android.widget.VideoView;
import android.widget.MediaController;
import java.util.ArrayList;
public class MainActivity extends Activity
implements MediaPlayer.OnCompletionListener {
VideoView vw;
ArrayList<Integer> videolist = new ArrayList<>();
int currvideo = 0;
int mPositionWhenPaused=0;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
vw = (VideoView)findViewById(R.id.videoView);
vw.setMediaController(new MediaController(this));
vw.setOnCompletionListener(this);
// video name should be in lower case alphabet.
videolist.add(R.raw.onbadhu_kolum);
videolist.add(R.raw.kala_bhairava_ashtakam);
videolist.add(R.raw.panchamukh_hanumath_kavacham);
videolist.add(R.raw.kandha_shashti_kavasam);
setVideo(videolist.get(0));
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
//we use onSaveInstanceState in order to store the video playback position for orientation change
savedInstanceState.putInt("Position", vw.getCurrentPosition());
vw.pause();
}
#Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
//we use onRestoreInstanceState in order to play the video playback from the stored position
mPositionWhenPaused = savedInstanceState.getInt("Position");
vw.seekTo(mPositionWhenPaused);
}
public void setVideo(int id)
{
String uriPath
= "android.resource://"
+ getPackageName() + "/" + id;
Uri uri = Uri.parse(uriPath);
vw.setVideoURI(uri);
vw.start();
}
public void onCompletion(MediaPlayer mediapalyer)
{
AlertDialog.Builder obj = new AlertDialog.Builder(this);
obj.setTitle("Playback Finished!");
obj.setIcon(R.mipmap.ic_launcher);
MyListener m = new MyListener();
obj.setPositiveButton("Replay", m);
obj.setNegativeButton("Next", m);
obj.setMessage("Want to replay or play next video?");
obj.show();
}
class MyListener implements DialogInterface.OnClickListener {
public void onClick(DialogInterface dialog, int which)
{
if (which == -1) {
vw.seekTo(0);
vw.start();
}
else {
++currvideo;
if (currvideo == videolist.size())
currvideo = 0;
setVideo(videolist.get(currvideo));
}
}
}
}

I sorted out the issue. I changed the way the list is being called to play with the setOnPreparedListener, seeking to last played position.
...
Main Activity
package io.automaton.android.morningbinge;
import androidx.appcompat.app.AlertDialog;
import android.app.Activity;
import android.content.DialogInterface;
import android.content.res.Configuration;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
import android.widget.VideoView;
import android.widget.MediaController;
import android.media.MediaPlayer.OnPreparedListener;
import java.util.ArrayList;
public class MainActivity extends Activity
implements MediaPlayer.OnCompletionListener {
VideoView vw;
ArrayList<Integer> videolist = new ArrayList<>();
int currvideo = 0;
int mPositionWhenPaused=0;
private static final String TAG = "MyActivity";
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
vw = (VideoView)findViewById(R.id.videoView);
vw.setMediaController(new MediaController(this));
vw.setOnCompletionListener(this);
videolist.add(R.raw.onbadhu_kolum);
videolist.add(R.raw.kala_bhairava_ashtakam);
videolist.add(R.raw.panchamukh_hanumath_kavacham);
videolist.add(R.raw.kandha_shashti_kavasam);
try {
//set the uri of the video to be played
vw.setVideoURI(Uri.parse("android.resource://" + getPackageName() + "/" + videolist.get(0)));
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);
vw.requestFocus();
vw.setOnPreparedListener(new OnPreparedListener() {
public void onPrepared(MediaPlayer mediaPlayer) {
vw.seekTo(mPositionWhenPaused);
if (mPositionWhenPaused == 0) {
vw.start();
} else {
vw.pause();
}
}
});
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
savedInstanceState.putInt("Position", vw.getCurrentPosition());
Log.i("Orientation Change", "Warn-orientation change and saved");
vw.pause();
}
#Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
mPositionWhenPaused = savedInstanceState.getInt("Position");
vw.seekTo(mPositionWhenPaused);
Log.i("restored", "restored after orientation change");
}
public void onCompletion(MediaPlayer mediapalyer)
{
++currvideo;
if (currvideo == videolist.size())
currvideo = 0;
setVideo(videolist.get(currvideo));
}
}
...
android manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="io.automaton.android.morningbinge">
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".MainActivity"
android:configChanges="orientation|screenSize|screenLayout|keyboardHidden">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
...

How to Handle Back Button on Android

I'm trying to make a app with WebView ,and i want to exit app if WebView Back History is finished.
This is the scenario what i want ,gif animation :
my Project Structure (my code):
AndroidManifest.xml
<?xml version = "1.0" encoding = "utf-8"?>
<manifest xmlns:android = "http://schemas.android.com/apk/res/android"
package = "com.example.myapplication">
<uses-permission android:name = "android.permission.INTERNET"/>
<application
android:allowBackup = "true"
android:icon = "#mipmap/ic_launcher"
android:label = "#string/app_name"
android:roundIcon = "#mipmap/ic_launcher_round"
android:supportsRtl = "true"
android:theme = "#style/AppTheme">
<activity android:name = ".MainActivity">
<intent-filter>
<action android:name = "android.intent.action.MAIN" />
<category android:name = "android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
layout: activity_main.xml
<?xml version = "1.0" encoding = "utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
xmlns:app = "http://schemas.android.com/apk/res-auto"
xmlns:tools = "http://schemas.android.com/tools"
android:layout_width = "match_parent"
android:gravity = "center"
android:layout_height = "match_parent"
tools:context = ".MainActivity"
android:orientation = "vertical">
<WebView
android:id = "#+id/web_view"
android:layout_width = "match_parent"
android:layout_height = "match_parent" />
</LinearLayout>
java: MainActivity.java
package com.example.myapplication;
import android.app.ProgressDialog;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
#RequiresApi(api = Build.VERSION_CODES.P)
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ProgressDialog progressDialog = new ProgressDialog(this);
progressDialog.setMessage("Loading Data...");
progressDialog.setCancelable(false);
WebView web_view = findViewById(R.id.web_view);
web_view.requestFocus();
web_view.getSettings().setJavaScriptEnabled(true);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
web_view.getSettings().setMixedContentMode(WebSettings.MIXED_CONTENT_COMPATIBILITY_MODE);
}
web_view.loadUrl("https://google.com");
web_view.setWebViewClient(new WebViewClient() {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
return true;
}
});
web_view.setWebChromeClient(new WebChromeClient() {
public void onProgressChanged(WebView view, int progress) {
if (progress < 100) {
progressDialog.show();
}
if (progress == 100) {
progressDialog.dismiss();
}
}
});
}
}
i found the code here How to Control Back Button in Android Scenario 3
I tried to make working my code and the code from that site , but it give me ERROR-S on Adobe Studio ,
what i tried is:
package com.example.myapplication;
import android.app.ProgressDialog;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
#RequiresApi(api = Build.VERSION_CODES.P)
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ProgressDialog progressDialog = new ProgressDialog(this);
progressDialog.setMessage("Loading Data...");
progressDialog.setCancelable(false);
WebView web_view = findViewById(R.id.web_view);
web_view.requestFocus();
web_view.getSettings().setJavaScriptEnabled(true);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
web_view.getSettings().setMixedContentMode(WebSettings.MIXED_CONTENT_COMPATIBILITY_MODE);
}
web_view.loadUrl("https://alltrafficcams.com/");
web_view.setWebViewClient(new WebViewClient() {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
return true;
}
});
web_view.setWebChromeClient(new WebChromeClient() {
public void onProgressChanged(WebView view, int progress) {
if (progress < 100) {
progressDialog.show();
}
if (progress == 100) {
progressDialog.dismiss();
}
}
});
#Override
public void onBackPressed() {
if(webView.canGoBack())
{
webView.goBack();
}
else
{
super.onBackPressed();
}
}
}
Pleas can somone help me to make my code working. thank you

Android ArrayAdapter NullPointerException getID

I'm having a bit of a problem with my code for a ListView, it is supposed to present a list of available devices that have not yet been paired with the device.
I've included the error below:
FATAL EXCEPTION: main
at com.zephyr.bolt.UnpairedDeviceViewer$StableArrayAdapter.getItemId(UnpairedDeviceViewer.java:110)
at android.widget.AbsListView.obtainView(AbsListView.java:2198)
(I didn't include the entire error sadly, the error is on my tablet, and I can't seem to copy it out of AIDE)
Below is the referenced class file and it's XML file
UnpairedDeviceViewer.java
package com.zephyr.bolt;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
public class UnpairedDeviceViewer extends Activity{
Activity a = this;
private ListView listview;
private Button b1;
public StableArrayAdapter adapter;
private ArrayList strings;
private BroadcastReceiver recv;
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.udv);
b1 = (Button) findViewById(R.id.b5);
listview = (ListView) findViewById(R.id.l2);
strings = new ArrayList<String>();
adapter = new StableArrayAdapter(this, android.R.layout.simple_list_item_1, strings);
recv = new BroadcastReceiver() {
#Override
public void onReceive(Context arg0, Intent arg1) {
String action = arg1.getAction();
if(BluetoothDevice.ACTION_FOUND.equals(action))
{
BluetoothDevice device = arg1.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
adapter.add(device.getName() + "\n" + device.getAddress());
adapter.notifyDataSetChanged();
}
else if(BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action))
{
Toast.makeText(a, "Device Discovery Started", Toast.LENGTH_LONG).show();
}
else if(BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action))
{
Toast.makeText(a, "Device Discovery Completed", Toast.LENGTH_LONG).show();
}
}
};
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(recv, filter);
listview.setAdapter(adapter);
b1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
MainActivity.bTAdapter.startDiscovery();
}
});
}
protected void onDestroy()
{
MainActivity.bTAdapter.cancelDiscovery();
unregisterReceiver(recv);
}
private class StableArrayAdapter extends ArrayAdapter<String> {
HashMap<String, Integer> mIdMap = new HashMap<String, Integer>();
public StableArrayAdapter(Context context, int textViewResourceId,
List<String> objects) {
super(context, textViewResourceId, objects);
for (int i = 0; i < objects.size(); ++i) {
mIdMap.put(objects.get(i), i);
}
}
#Override
public long getItemId(int position) {
String item = getItem(position);
return mIdMap.get(item);
}
#Override
public boolean hasStableIds() {
return true;
}
}
}
udv.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android" >
<Button
android:id = "#+id/b5"
android:layout_centerHorizontal="true"
android:layout_width = "match_parent"
android:layout_height = "wrap_content"
android:text = "Begin Discovery"
/>
<ListView
android:id = "#+id/l2"
android:layout_below="#+id/b5"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</ListView>
</RelativeLayout>

Your mIdMap is an overly complicated way of doing what ArrayAdapter already does. Its implementation of getItemId(pos) returns pos.
Note you are only building your mIdMap once, any items you add post-construct - like in your receiver callback - will not have ids, and will cause a NPE in your getItemId implementation trying to unbox null.
Also, calling notifyDataSetChanged() is unnecessary, ArrayAdapter will automatically call it after each add() by default.