My mainactivity
package com.example.vivek.trackblue;
import android.bluetooth.BluetoothAdapter;
import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
Context context = getApplicationContext();
CharSequence text = "Bluetooth is not supported";
int duration = Toast.LENGTH_SHORT;
Toast toast1 = Toast.makeText(context, text, duration);
Button b1 = (Button)findViewById(R.id.button);
private final static int REQUEST_ENABLE_BT=1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1.setOnClickListener(new View.OnClickListener()
{
public void onClick(View view)
{
if(bt == null){
toast1.show();
}
if(bt.isEnabled())
{
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
}
});
}
}
and this is my AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.vivek.trackblue">
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<permission android:name="android.permission.BLUETOOTH" android:label="BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
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>
I am Trying to create an application where the user would press a button to start Bluetooth.
My code shows no errors on the ide but when it gets installed in the device, it crashes with an error "Unfortunately TrackBlue stopped working". Here trackblue is my application's name.
Simply because you have assigned value to button variable before setting content view for the screen.
Error is because it tries to find the view by the given button's ID even before it is set on to screen.
Solution:
Write the findViewById() line after setContentView() inside onCreate()
Related
I am building 2 NFC enabled apps, one is supposed to send a message and the other to receive it.
Sending app Android Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.joyride.nfc_merchant">
<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.NFC_Merchant">
<activity
android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Sending app Main Activity
package com.joyride.nfc_merchant;
import androidx.appcompat.app.AppCompatActivity;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
String message;
NdefRecord ndefRecord;
NdefMessage ndefMessage;
NfcAdapter nfcAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nfcAdapter = NfcAdapter.getDefaultAdapter(this);
}
public void sendMessage(View view) {
message = ((EditText) findViewById(R.id.text_message)).getText().toString();
ndefRecord = NdefRecord.createTextRecord(null, message);
ndefMessage = new NdefMessage(ndefRecord);
nfcAdapter.setNdefPushMessage(ndefMessage, this);
}
}
Receiving app android Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.joyride.nfc_customer">
<uses-permission android:name="android.permission.NFC" />
<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.NFC_Customer">
<activity
android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Receiving app Main Activity
package com.joyride.nfc_customer;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.nfc.NdefMessage;
import android.nfc.NfcAdapter;
import android.os.Bundle;
import android.os.Parcelable;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
TextView messageView = (TextView)findViewById(R.id.messageView);
if (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent.getAction())) {
Parcelable[] rawMessages =
intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
if (rawMessages != null) {
NdefMessage[] messages = new NdefMessage[rawMessages.length];
for (int i = 0; i < rawMessages.length; i++) {
messageView.setText(((NdefMessage) rawMessages[i]).toString());
}
}
}
}
}
I've installed each app on another phone. Off course the receiving app is not registering the message. Am I missing something here? How do I go about debugging this?
I have external package class (my custom library), which I want to include in the project. It uses Activity, but shows error as you see.
If I place this command in main project class, it works well... What to do?
Here is the code:
package com.__MyDefaultLibrary;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.preference.PreferenceManager;
import android.view.View;
import android.view.animation.AlphaAnimation;
import android.view.animation.Animation;
import android.view.animation.LinearInterpolator;
import android.view.animation.ScaleAnimation;
import android.widget.*;
import java.io.File;
import java.util.Calendar;
//
import android.app.Activity;
import com.oceanesa.samplevideorecorder.R;
public class __MyDefaultFunctions{
public android.app.Activity actv1 = android.app.Activity;
public void Initt(){
PreferenceManager.setDefaultValues(actv1.getBaseContext(), R.xml.mypreferences, false);
}
// ========== MY CUSTOM LIBRARY =============//
//button find
public Button fvb(int id) {
return (Button) actv1.findViewById(id);
}
//message show
public void msg(String text) {
Toast.makeText(actv1.getApplicationContext(), text, Toast.LENGTH_LONG).show();
}
public View.OnClickListener optionsListener2 = new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent i = new Intent(actv1.getBaseContext(), com.__MyDefaultLibrary.__MyDefaultPreferencesInit1.class);
actv1.startActivity(i);
}
};
}
And AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.oceanesa.samplevideorecorder"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="16"
android:targetSdkVersion="19" />
<uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<uses-feature
android:name="android.hardware.camera.front"
android:required="false" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:screenOrientation="landscape"
android:theme="#style/AppTheme"
>
<activity
android:name="com.oceanesa.samplevideorecorder.VideoCaptureExample"
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.__MyDefaultLibrary.__MyDefaultPreferencesInit1"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN_ACTIVITY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
Update Answer just passing context to class
public class MyClass {
private static Context mContext;
private static Activity mActivity;
public MyClass(Context c) {
mContext= c;
}
public MyClass(Activity act) {
mActivity= act;
}
public static void showToastMethod() {
// then passing context or activity to
Toast.makeText(mContext, "mymessage ", Toast.LENGTH_SHORT).show();
// or Toast.makeText(mActivity, "mymessage ", Toast.LENGTH_SHORT).show();
}
}
Finally I got it working with the help of topic: How to display a Toast message in from a class that doesn't extend Activity
Problem was in my code. There was no need to call andorid.app at all. I didnt pass Activity to my external file, from where I couldnt call anything..
I had to pass activity like this (from main project file):
public MyExternalClass myEx = new MyExternalClass(Activity);
and needed some modifications...
I'm using intent method to make a simple app that takes you from main screen [with an enter button] to another screen which has three options. Code sourced online and seems to be error free, though my app crashes saying "Unfortunately [yourapp], has stopped" immediately after i press the button which is meant to take to the the other screen.
This is my first activity code:
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Button;
import android.view.View;
import android.view.View.OnClickListener;
public class MainActivity extends Activity {
Button button;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addListenerOnButton();
}
public void addListenerOnButton() {
final Context context = this;
button = (Button) findViewById(R.id.enterBtn);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent = new Intent(context, HomeActivity.class);
startActivity(intent);
}
});
}
}`
And this is my landing screen's activity code:
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
public class HomeActivity extends Activity {
Button button;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.home);
}
}
I'm really stuck with this issue and any help would be much appreciated. Many thanks in advance.
Every activity needs to be added in your manifest file under application tag. This seems to be the problem in your case.
Try to post you LogCat so that we might get some more information and if you have not yet added your Activity in the manifest, this is the way of adding it (Activities go under application tag)
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.southmp3"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="21" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<application
android:allowBackup="true"
android:icon="#drawable/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=".HomeActivity"
android:label="#string/app_name" >
</activity>
</application>
all the Activities should be going under the application tag
I had forgotten to register my new activity on the androidmanifest.xml file. That's what sorted my app crash issue.
I am a new android developer and encountered a problem while following the tutorial on Android's site - http://developer.android.com/training/basics/firstapp/starting-activity.html
My program loads on the emulator fine, but when you type something into the EditText and then hit the send button, a window pops up saying "App has stopped working". It seems as though my new activity isn't being created and I'm not sure as to why. I've scoured the web (and my code) to see if I could get a solution but did so to no avail. Any help would be appreciated.
The code for my first activity:
package com.example.appli;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.myapp.MESSAGE";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.testlayout);
//////Button myButton = (Button) findViewById(R.id.my_button); //Told in tutorial to put this in onCreate
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
/** Called when the user selects the Send button */
public void sendMessage(View view) {
// Do something in response to button
Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editText = (EditText) findViewById(R.id.edit_message);
String message = editText.getText().toString();
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
}
}
The code for my second activity (the one being called)
package com.example.appli;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class DisplayMessageActivity extends Activity{
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//get message from intent
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
// Create the text view
TextView textView = new TextView(this);
textView.setTextSize(40);
textView.setText(message);
setContentView(textView);
}
}
The Manifest
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.appli"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<application
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity android:name="com.example.myapp.DisplayMessageActivity" />
<activity
android:name=".MainActivity"
android:label="#string/title_activity_main" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
In AndroidManifest File you have declared incorrect package
change
<activity android:name="com.example.myapp.DisplayMessageActivity" />
to
<activity android:name="com.example.appli.DisplayMessageActivity" />
or just
<activity android:name=".DisplayMessageActivity" />
you have declared only one Activity that's also wrong package name
already your manifest has the package name
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.appli"
so just declare like this
<activity android:name=".DisplayMessageActivity" />
and you need to add this in your manifest also
<activity android:name=".MainActivity />
remove the target SDK version that you mentioned
android:targetSdkVersion="15"
Try this
<activity android:name=".DisplayMessageActivity"/>
Instead of
<activity android:name="com.example.myapp.DisplayMessageActivity" />
in your Manifest.xml file.
You has defined the package package com.example.appli; in your activities.
Why have you defined you activity in manifest like <activity android:name="com.example.myapp.DisplayMessageActivity" />?
Replace this line with
<activity android:name=".DisplayMessageActivity" />.
I am trying to display messages from C2DM so When I start an Activity from a non activity it works but only first time. My activity contains View and close button so if the user is not inside the app when he receive the push notification then it should start the app when he press view button or close it on close this works as well but when user press view button and enters the app after than I am unable to start the activity again, it seems like the activity is there but its not visible to user. My code is as below , hope you understand what I am saying. The C2DM code example used is taken from here
C2DMReceiver
package com.mks.android.example;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import com.google.android.c2dm.C2DMBaseReceiver;
import com.google.android.c2dm.C2DMessaging;
import com.mks.android.example.activity.MessageDialogActivity;
public class C2DMReceiver extends C2DMBaseReceiver {
private static String senderId = "mysenderemail#gmail.com";
String registrationId;
public C2DMReceiver() {
super(senderId);
}
#Override
public void onRegistrered(Context context, String registrationId) {
this.registrationId = registrationId;
Log.e("Error", registrationId);
}
#Override
public void onUnregistered(Context context) {
C2DMessaging.register(context, senderId);
}
#Override
public void onError(Context context, String errorId) {
Log.w("Error", errorId);
}
#Override
protected void onMessage(Context context, Intent intent) {
Log.i("Error", "MessageReceived");
Bundle bundle = intent.getExtras();
intent = new Intent();
intent.putExtra("messageBundle", bundle);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT);
intent.setClass(context, MessageDialogActivity.class);
startActivity(intent);
// load message display activity here
}
}
MESSAGE DIALOG ACTIVITY CLASS
package com.mks.android.example.activity;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import com.mks.android.example.R;
import com.mks.android.example.activity.list.Functions;
public class MessageDialogActivity extends Activity {
private Functions func = new Functions();
private int isAppActive = 0;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
showMessages();
}
private void showMessages(){
Bundle bundle = getIntent().getBundleExtra("messageBundle");
String title = bundle.getString("title");
String message = bundle.getString("message");
setContentView(R.layout.c2dm_message);
TextView txtTitle = (TextView) findViewById(R.id.title);
TextView txtMessage = (TextView) findViewById(R.id.message);
Button btnView = (Button) findViewById(R.id.btnView);
Button btnClose = (Button) findViewById(R.id.btnClose);
txtTitle.setText(title);
txtMessage.setText(message);
this.isAppActive = func.getAppState(this);
if(isAppActive==1){
btnView.setVisibility(View.GONE);
}
btnView.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
if(isAppActive == 0){
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.setComponent(new ComponentName("com.mks.android.example","com.mks.android.example.activity.MainActivity"));
startActivity(intent);
}
MessageDialogActivity.this.finish();
}
});
btnClose.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
finish();
}
});
}
#Override
protected void onNewIntent(Intent intent) {
setIntent(intent);
showMessages();
}
}
AndroidManifest FIle
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.mks.android.example"
android:versionCode="1"
android:versionName="1.0" android:installLocation="preferExternal">
<uses-sdk android:minSdkVersion="4" />
<application android:label="#string/app_name" android:icon="#drawable/icon_launcher" android:debuggable="true">
<uses-library android:name="com.google.android.maps" />
<activity android:name=".activity.MainActivity"
android:label="#string/app_name"
android:screenOrientation="portrait"
android:theme="#android:style/Theme.NoTitleBar" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".activity.MessageDialogActivity" android:theme="#style/DialogNoTitle" android:activity android:launchMode="singleTop" />
<service android:name=".C2DMReceiver" />
<!-- Only C2DM servers can send messages for the app. If permission is not set - any other app can generate it -->
<receiver android:name="com.google.android.c2dm.C2DMBroadcastReceiver" android:permission="com.google.android.c2dm.permission.SEND">
<!-- Receive the actual message -->
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
<category android:name="com.mks.android.example" />
</intent-filter>
<!-- Receive the registration id -->
<intent-filter>
<action android:name="com.google.android.c2dm.intent.REGISTRATION" />
<category android:name="com.mks.android.example" />
</intent-filter>
</receiver>
</application>
<supports-screens android:smallScreens="true"
android:normalScreens="true"
android:largeScreens="true"
android:anyDensity="true" />
<permission android:name="com.mks.android.example.permission.C2D_MESSAGE" android:protectionLevel="signature" />
<uses-permission android:name="com.mks.android.example.permission.C2D_MESSAGE" />
<!-- This app has permission to register and receive message -->
<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.INTERNET" />
</manifest>
If i remove androidLaunchMode singleTop form manifest file and add set flag to multipleTask in C2DMReciver class it works but i get lots of dialog for each message. Thanks for help .
Set flag to singletop , the code to call messagedialogactivity is as under:
Intent intent = new Intent();
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.setClass(context, MessageDialogActivity.class);