Develop Reference

Android Widget freezes after some time

I have made a counter widget. There are two buttons, one to increase and one to decrease the number. The number is displayed on a TextView. At first everything works just fine, but after some time (usually around an hour) the Textview freezes i.e. I click the buttons but the number doesen't change.
When I click the buttons, the "clicking animation" is still played, so the buttons might still work.
When I remove the widget and replace it again, the widget starts to work again but the same problem occurs after around the same time.
The code is here:
WidgetProvider
package com.example.myapplication;
import android.app.PendingIntent;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.widget.RemoteViews;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
public class WidgetProvider1 extends AppWidgetProvider {
String widgettextviewtext;
final String INCREASE= "sdfjkldjldkf";
final String DECREASE = "skdhbcvouweoaior";
#Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget_layout);
MainActivity.zahl = 15;
remoteViews.setTextViewText(R.id.textView, ""+MainActivity.zahl);
remoteViews.setOnClickPendingIntent(R.id.button3,onClickPendingIntent(context,ZAHLGROESSER) );
remoteViews.setOnClickPendingIntent(R.id.button2,onClickPendingIntent(context,ZAHLKLEINER) );
appWidgetManager.updateAppWidget(appWidgetIds, remoteViews);
updateWidgetNow(context,remoteViews);
super.onUpdate(context, appWidgetManager, appWidgetIds);
}
#Override
public void onReceive(Context context, Intent intent) {
RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget_layout);
//if increase button is clicked
if(intent.getAction().equals(INCREASE)){
if(MainActivity.zahl == 15) {
Toast.makeText(context, "STOOOP!!!", Toast.LENGTH_SHORT).show();
}else{
MainActivity.number = MainActivity.number+1;
String text=""+ MainActivity.number;
remoteViews.setTextViewText(R.id.textView, text);
updateWidgetNow(context, remoteViews);
}
}
//if decrease button is clicked
if(intent.getAction().equals(DECREASE)) {
if (MainActivity.number == 0) {
Toast.makeText(context, "Hurray!", Toast.LENGTH_SHORT).show();
}else{
MainActivity.number = MainActivity.number - 1;
String text = "" + MainActivity.number;
remoteViews.setTextViewText(R.id.textView, text);
updateWidgetNow(context, remoteViews);
}
}
super.onReceive(context, intent);
}
public void updateWidgetNow (Context context, RemoteViews remoteViews){
ComponentName widgetComponent = new ComponentName(context, WidgetProvider1.class);
AppWidgetManager.getInstance(context).updateAppWidget(widgetComponent, remoteViews);
}
public PendingIntent onClickPendingIntent (Context context, String stringAction){
Intent onClickIntent = new Intent(context, WidgetProvider1.class);
onClickIntent.setAction(stringAction);
return PendingIntent.getBroadcast(context,0,onClickIntent,PendingIntent.FLAG_UPDATE_CURRENT);
}
}
MainActivity:
package com.example.myapplication;
import android.appwidget.AppWidgetManager;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
public static int number = 15;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
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="com.example.myapplication">
<uses-permission android:name="android.permission.VIBRATE"/>
<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.MyApplication"
tools:targetApi="31">
<activity
android:name=".MainActivity"
android:exported="true"
android:label="#string/app_name"
android:theme="#style/Theme.MyApplication">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<receiver android:name="com.example.myapplication.WidgetProvider1"
android:label="Tutorial Widget"
android:exported="true"
>
<intent-filter>
<action android:name="android.appwidget.action.APPWIDGET_UPDATE"/>
</intent-filter>
<meta-data
android:name="android.appwidget.provider"
android:resource="#xml/widget_info"
/>
</receiver>
</application>
</manifest>
WidgetInfo:
<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider
xmlns:android="http://schemas.android.com/apk/res/android"
android:minHeight="180dp"
android:minWidth="180dp"
android:initialLayout="#layout/widget_layout"
android:previewImage="#drawable/widget_preview"
android:widgetCategory="home_screen"
android:resizeMode="horizontal|vertical"
>
</appwidget-provider>
WidgeLayout:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent"
android:theme="#style/Theme.AppCompat.Light"
android:id="#+id/widget_layout"
>
<TextView
android:id="#+id/textView"
android:layout_width="match_parent"
android:layout_height="220dp"
android:layout_centerInParent="true"
android:text="1"
android:textAlignment="center"
android:textSize="150dp"
android:textColor="#color/white"
/>
<Button
android:id="#+id/button3"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="#+id/textView"
android:layout_marginBottom="1dp"
android:text="increase"
android:bottomRightRadius="20dp"
android:bottomLeftRadius="20dp"
android:topLeftRadius="20dp"
android:topRightRadius="20dp"
android:textSize="30dp"
/>
<Button
android:id="#+id/button2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#+id/textView"
android:layout_marginTop="1dp"
android:text="decrease"
android:bottomRightRadius="20dp"
android:bottomLeftRadius="20dp"
android:topLeftRadius="20dp"
android:topRightRadius="20dp"
android:textSize="30dp"
/>
</RelativeLayout>

Why Isn't the Button responding to the Intent? Don't understand what's wrong here

I am trying to get the ABOUT button to listen for a click, in order to go from a screen displaying three buttons and a picture, to another screen just displaying some text.
This is my Main java file (MainActivity.java)
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addListenerOnButton();
}
public void addListenerOnButton() {
final Context cont = this;
Button aButton = (Button) findViewById(R.id.ab_button);
aButton.setOnClickListener(
new Button.OnClickListener(){
public void onClick(View v){
Intent intent = new Intent(cont, AboutActivity.class);
startActivity(intent);
}
});
}
This is my second java file for the about button (AboutActivity.java):
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.widget.TextView;
public class AboutActivity extends Activity {
public void onCreate(Bundle about){
super.onCreate(about);
setContentView(R.layout.activity_about);
TextView briText = (TextView) findViewById(R.id.about_b2);
briText.setText("Goodie");
}
}
This is the main xml file that displays the picture and the buttons (activity_main.xml):
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/about_b"
android:id="#+id/ab_button"
android:shadowColor="#8e2300"
android:background="#drawable/oval_button"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/share_button"
android:id="#+id/share_button"
android:shadowColor="#8e2300"
android:onClick="shareActivity"
android:background="#drawable/oval_button"
And this is the xml file that displays the text (activity_about.xml):
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
android:id="#+id/back_to_work_rel">
<TextView android:text="#string/about_bac"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/about_b2" />
</RelativeLayout>
Manifest file (AndroidManifest.xml):
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.brian.eggalong" >
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".AboutActivity"
android:parentActivityName=".MainActivity"
android:label="#string/about_bac">
</activity>
</application>
</manifest>
Every time I click the ABOUT button, nothing happens. Any help would be greatly appreciated.

Try to remove the background attribute of your button.
Otherwise you can try this
MainActivity.java
public void moveToAboutActivity(){
Intent i = new Intent(getApplicationContext(), AboutActivity.class);
startActivity(i);
}
activity_main.xml
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/about_b"
android:id="#+id/ab_button"
android:onClick="moveToAboutActivity"/>
good Luck

Ok, so, definetly the problem is that you need to put the activity in your manifest file like:
<activity
android:name=".activity.SplashScreen"
android:screenOrientation="portrait"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

Android Phone Call Intent

I am trying to make a call with the help of button, compiling time shows no errors but the application stops working as soon as i start the app, both on emulator and my android device. i have also set the permissions in the manifest file. but still :\
please help
activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<Button
android:id="#+id/makeCall"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/make_call" />
</LinearLayout>
MainActivity.java
package com.example.phonecalldemo;
import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public abstract class MainActivity extends Activity implements OnClickListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button startBtn = (Button) findViewById(R.id.makeCall);
startBtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
makeCall();
}
});
}
protected void makeCall() {
Log.i("Make call", "");
Intent phoneIntent = new Intent(Intent.ACTION_CALL);
phoneIntent.setData(Uri.parse("tel:8866158630"));
startActivity(phoneIntent);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
manifest file
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.phonecalldemo"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<permission android:name="android.permission.CALL_PHONE"></permission>
<uses-permission android:name="android.permission.CALL_PHONE"></uses-permission>
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.phonecalldemo.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

You can't instantiate abstract classes. Remove the 'abstract' from "public abstract class MainActivity", which will give you a different error telling you to implement the onClick method. Once you add that method that your app will launch.

Bluetooth adapter is remaining null in android

I have a problem while writing code of bluetooth adapter in android. Bluetooth adapter is always remains null. I have written code for that but I could not turn on the bluetooth.
My Code is as below
package com.example.bluetoothdemo;
import java.io.IOException;
import java.io.OutputStream;
import java.util.UUID;
import android.os.Bundle;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
#SuppressLint("NewApi")
public class MainActivity extends Activity {
String msg="Hello";/* Default message to be sent. */
BluetoothAdapter adpt=null;// Default it is set to null value.
public static String MacAddress;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btn=(Button)findViewById(R.id.button_send);
final TextView tv=(TextView)findViewById(R.id.disp_msg);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
adpt=BluetoothAdapter.getDefaultAdapter();
if(adpt==null){
// Always this portion is generating errors.
tv.append("Bluetooth Not Available in device");
Toast.makeText(getApplicationContext(), "Bluetooth is off",Toast.LENGTH_LONG).show();
}
else{
if(!adpt.isEnabled()){
//adpt.enable();
Intent i=new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
//startActivity(i);
startActivityForResult(i, 0);
tv.append("Bluetooth is turned on.");
}
}
byte[] toSend=msg.getBytes();
try{
final UUID applicationUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
BluetoothDevice device=adpt.getRemoteDevice(MacAddress);
BluetoothSocket socket=device.createInsecureRfcommSocketToServiceRecord(applicationUUID);
socket.connect();
OutputStream mmout=socket.getOutputStream();
mmout.write(toSend);
mmout.flush();
mmout.close();
socket.close();
Toast.makeText(getBaseContext(), MacAddress, Toast.LENGTH_SHORT).show();
}catch(IOException e){
e.printStackTrace();
}
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
My activity_main.xml file is as below:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal">
<EditText android:id="#+id/edit_message"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:hint="#string/edit_message" />
<Button android:id="#+id/button_send"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send"
android:onClick="sendMessage" />
<TextView android:id="#+id/disp_msg"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/display"
/>
</LinearLayout>
My AndroidMenifest.xml file is as below:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.bluetoothdemo"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="8" android:targetSdkVersion="18" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.bluetoothdemo.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>-
I have created the .apk file also and run on my Micromax A89 Ninja phone but the error says that "BluetoothDemo has been stopped unexpectedly."

Please write the below line
adpt=BluetoothAdapter.getDefaultAdapter();
in OnCreate() method after this line,
setContentView(R.layout.activity_main);

Null pointer exception using Time Pickers

I'm trying to make a simple app that opens the time picker dialog when you click the "Check" button, and once you set the time and tap "OK", it checks the system time and outputs whether it is correct. However, I am given a null pointer exception on line 21 of MainActivity.java. At the moment the code is simply set up to bring up the dialog once "Check" is tapped.
MainActivity.java
package com.example.timechecker;
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.support.v4.app.FragmentManager;
import android.view.View;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public FragmentManager getSupportFragmentManager() {
return null;
}
public void checkTime(View view) {
DialogFragment newFragment = new TimePickerFragment();
newFragment.show(getSupportFragmentManager(), "timePicker");
}
}
TimePickerFragment.java
package com.example.timechecker;
import java.util.Calendar;
import android.app.Dialog;
import android.app.TimePickerDialog;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.text.format.DateFormat;
import android.widget.TimePicker;
public class TimePickerFragment extends DialogFragment
implements TimePickerDialog.OnTimeSetListener {
#Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// Use the current time as the default values for the picker
final Calendar c = Calendar.getInstance();
int hour = c.get(Calendar.HOUR_OF_DAY);
int minute = c.get(Calendar.MINUTE);
// Create a new instance of TimePickerDialog and return it
return new TimePickerDialog(getActivity(), this, hour, minute,
DateFormat.is24HourFormat(getActivity()));
}
public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
// Do something with the time chosen by the user
}
}
Manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.timechecker"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.timechecker.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.example.timechecker.TimePickerFragment"
android:label="#string/app_name" >
</activity>
</application>
</manifest>
Activity_Main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:id="#+id/whatTime"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="What time is it?"
android:textAppearance="?android:attr/textAppearanceLarge" />
<Button
android:id="#+id/check"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="checkTime"
android:text="Check" />
</LinearLayout>

Ah i see what is happening here.
public FragmentManager getSupportFragmentManager() {
return null;
}
public void checkTime(View view) {
DialogFragment newFragment = new TimePickerFragment();
newFragment.show(getSupportFragmentManager(), "timePicker");
}
You are overriding getSupportFragmentManager to return null, and after that you call the method to show the dialog, looks like you created the nullpointer on purpose? =D