Develop Reference

How do I activate NFC without a readable/writable device nearby?

For an engineering project I need to basically trick my phone to come out of NFC searching mode and into a mode where the phone is continuously putting out energy. Obviously I have activated NFC in the settings, but the only way I can trick it into leaving the searching mode and have it put out energy continuously is if I leave it on top of a blank tag.
I was thinking of implementing this NFC beam function: public boolean invokeBeam (Activity activity) and implanting it into the BeamLargeFiles sample code provided in Android studio, posted below.
I'm new to app development (though I have a fair bit of coding experience) so I'm just not sure if it's feasible, or if I'm looking in the right places. Any thoughts, ideas and help is appreciated!
package com.example.android.beamlargefiles;
import android.graphics.Color;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.text.Html;
import android.widget.TextView;
import android.view.Menu;
import com.example.android.common.activities.SampleActivityBase;
import com.example.android.common.logger.Log;
import com.example.android.common.logger.LogFragment;
import com.example.android.common.logger.LogWrapper;
import com.example.android.common.logger.MessageOnlyLogFilter;
/**
* A simple launcher activity containing a summary sample description
* and a few action bar buttons.
*/
public class MainActivity extends SampleActivityBase {
public static final String TAG = "MainActivity";
public static final String FRAGTAG = "BeamLargeFilesFragment";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView sampleOutput = (TextView) findViewById(R.id.sample_output);
sampleOutput.setText(Html.fromHtml(getString(R.string.intro_message)));
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
BeamLargeFilesFragment fragment = new BeamLargeFilesFragment();
transaction.add(fragment, FRAGTAG);
transaction.commit();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
/** Create a chain of targets that will receive log data */
#Override
public void initializeLogging() {
// Wraps Android's native log framework.
LogWrapper logWrapper = new LogWrapper();
// Using Log, front-end to the logging chain, emulates android.util.log method signatures.
Log.setLogNode(logWrapper);
// Filter strips out everything except the message text.
MessageOnlyLogFilter msgFilter = new MessageOnlyLogFilter();
logWrapper.setNext(msgFilter);
// On screen logging via a fragment with a TextView.
LogFragment logFragment = (LogFragment) getSupportFragmentManager()
.findFragmentById(R.id.log_fragment);
msgFilter.setNext(logFragment.getLogView());
logFragment.getLogView().setTextAppearance(this, R.style.Log);
logFragment.getLogView().setBackgroundColor(Color.WHITE);
Log.i(TAG, "Ready");
}
}
From the beamlargedata sample code provided by android studio

When no suitable NFC device is in range the NFC controller will constantly search all technologies for a tag or peer-to-peer device. It does this by sending out short bursts separated by no field activity (to save power).
If you have a newer device it is also very likely that the NFC Controller will only generate a very weak RF field to save power. This field is not strong enough to power a NFC tag but is strong enough for the chip to detect if there is something resonating at 13.56Mhz.
With standard Android you cannot change this behaviour. There is no programatical way in the API to enable the mode you're looking for.
However, if you can stretch your requirements a bit you can likely get something close to what you want.
Option 1:
Enable the Reader-Mode. Call enableReaderMode using the EXTRA_READER_PRESENCE_CHECK_DELAY extra. Set this to the a very high value.
Now, if a tag enters the RF field the NFC controller won't check for presence that often anymore. You can activate your RF field by touching a tag, then removing it.
The RF field will be stable until the presence check delay expires.
Option 2:
If rooting the device is an option, you can hack yourself into the low level NFC stack. Each NFC controller that I've worked with so far has one or more test modes for antenna calibration. Just outputting an RF field is one of the very common test modes.
Reading the source-code of the nfc-stack will likely show you how to enable such a mode. That takes some digging in the source-code and is not for the faint heart, but it is doable.

Android App Is Causing Battery Drain

I have two issues with this, my very first android app. The first is that I noticed after I installed the app the battery started draining about twice as fast as before. I read an article on this that stated sometimes programmers make an error which causes this. This being my first app, the probability is pretty high that this is the case.
The second issue is that I can save my variables when the app is turned off, but when the phone is turned off the data is lost.
As for the code, it's mostly bits and pieces from stuff I've found online and tried to incorporate. It's a simple calculator with three variables. Ideally, I'd like to store b and c, but allow the user to overwrite them. Variable a will change with each use, so no need to store that.
Here's my Main:
package com.kwagz.calc;
import android.app.Activity;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends Activity {
String g, e;
String b; //changed(sorry)
String c; //changed
SharedPreferences sh_Pref;
Editor toEdit;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
loadSavedPreferences();
}
public void calculateClickHandler(View view) {
if (view.getId() == R.id.button1) {
EditText a = (EditText)findViewById(R.id.a);
EditText b = (EditText)findViewById(R.id.b);
EditText c = (EditText)findViewById(R.id.c);
TextView output = (TextView)findViewById(R.id.textView9);
double gp = Double.parseDouble(a.getText().toString());
int ab = Integer.parseInt(b.getText().toString());
int ac = Integer.parseInt(c.getText().toString());
double t = ((gp / ab) * ac);
output.setText(String.format("%.2f", t));
}
}
public void sharedPreferences() {
SharedPreferences saved_values =//there's no linebreak here in my code
PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
SharedPreferences.Editor editor=saved_values.edit();
editor.putString("b", b);
editor.putString("c", c);
editor.commit();
}
private void loadSavedPreferences() {
SharedPreferences saved_values =//there's no linebreak here in my code
PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
b = saved_values.getString("b", g);
}
}

From reading what you said, the only logical explanation forming in my head is: You are starting background service from your App, while background service is running it makes app run all the time which explains why variables are stored until phone is turned off (when background service gets killed).

Okay, let's take your questions one at a time. The battery problem could be a number of things, without knowing more details about your program I couldn't possibly diagnose it completely. Android does have some good power saving tips. The key item is to minimize the use of connectivity devices to no more than is required. The two biggest culprits are GPS and Internet connections. If your app isn't running, then the only way it could be running the batteries is if there's threads in the background, or maybe something like an AlarmService.
You are using SharedPreferences correctly, the value should be saved, but I think you should but the saving code in onSaveInstanceState(). If you do that, it should work fine.
EDIT
Upon closer inspection, you're fundementally saving the wrong thing. You should save the value of the EditText, not the EditText itself. In fact, I'd simply remove all references to String a,b,c, move the EditText definitions to the top to replace them, and do something like this:
editor.putString("b", b.getText().toString());
b.setText(saved_values.getString("b", g));

I've conducted several tests in an effort to recreate the issue, with no success. I'm still working on the sharedPreferences thing, but the battery drain (I suspect) was caused by another app which just happened to coincide with the installation of mine.
As I mentioned in my note to arleitiss, my Y!Mail was showing the highest amount of battery drain. A day or two after posting the note my account started acting up and then became "inactive". Once I reset it, the app no longer appears on the Battery list.
Thanks for all the input!

How to run Monkeyrunner script on multiple devices at the same time

I am trying to run a monkeyrunner script on multiple devices to do some basic operations.I figured out that initialy I will start of writing a script to perform basic action in two connected devices.
from com.android.monkeyrunner import MonkeyRunner, MonkeyDevice
import time
import sys
import time
devices = os.popen('adb devices').read().strip().split('\n')[1:]
device1 = MonkeyRunner.waitForConnection( devices[0].split('\t')[0])
package = 'com.android.browser'
activity = 'com.android.browser.BrowserActivity'
runComponent = package + '/' + activity
device1.startActivity(component=runComponent)
MonkeyRunner.sleep(1)
device2 = MonkeyRunner.waitForConnection( devices[1].split('\t')[0])
package = 'com.android.browser'
activity = 'com.android.browser.BrowserActivity'
runComponent = package + '/' + activity
device2.startActivity(component=runComponent)
When i run this script, it never finish executing. The browser action happen on one of the connected device but not on other. Can you guys help me fix this or if you have a better code(ideas) to run an activity on multiple devices, Please do let me know~ I am newbie and completely new to the programming world!Thanks in advance

you can give like
device1 = MonkeyRunner.waitForConnection('', devices[0].split('\t')[0])
this will help

A better way to do it is to write a script that explicitly binds to the devices. The link below shows how for emulators
http://chanakaudaya.wordpress.com/2012/04/10/monkeyrunner-tutorial-running-tests-on-multiple-devices-with-monkeyrunner-13/
also seems similar to this question(Which i answered):
Can not simultaneously run monkeyrunner scripts (e.g. two monkeyrunner process) on multi device

Android App crashes in emulator - logs blank

I am completely new to android, and pretty much a Java newb.
I have a simple app that I am building to get the hang of android's development environment - and things like click events, etc..
The app loads, and I am able to change the text in a textfield using a button handler. However, when I import the location class, and try to do a simple GPS call, the application crashes.
The problem is, everything looks good in Eclipse (error console) - and I'm not seeing any exceptions in the android emulator (DevTools). I have the logcat window open, but I haven't done anything in eclipse/code to send logcat anything (do I need to?)
Can anyone see something wrong with this? Is there a better way to troubleshoot?
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.*;
import android.location.*;
public class locationDisplay extends Activity {
private EditText text;
private Location GPSLocation;
double dblLat;
double dblong;
String strLat;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main); // bind the layout to the activity
text = (EditText) findViewById(R.id.EditText01);
text.setText("No button pressed");
}
// Handler for each button -- Button01 is when it crashes
public void myClickHandler(View view) {
switch (view.getId()) {
case R.id.Button01:
dblLat = GPSLocation.getLatitude();
strLat = Double.toString(dblLat);
text.setText(strLat);
break;
case R.id.Button02:
text.setText("Button 2 was clicked");
break;
case R.id.Button03:
text.setText("Button 3 was clicked");
break;
}
}

You shouldn't need to write anything to get the default messages in LogCat; uncaught exception reports should appear automatically when your program crashes. However, sometimes LogCat and your emulator get disconnected from each other and the messages simply all disappear. Simply close Eclipse and the emulator, restart them both, and the messages should reappear. An easy way to tell whether the link has been re-established is during the boot-up of the emulator. Just as the flashing "ANDROID" text in the fancy font disappears bringing you to the lockscreen, you should see about a hundred lines of text flash by on LogCat. If that doesn't happen, then LogCat isn't getting its messages.
The way to display debugging messages in Android is to use the Log.d("some name for your log statements so you can filter the LogCat messages", "The actual debug statement here");. You'll often find people using things like a static final String LOG_TAG in their application so that they can make sure their logs always have the same tag, and hence, the filter never misses a message.
As for your actual code here, Rpond is right, you never initialised your GPSLocation object.

You GPSLocation object is null. You need to access the LocationService to get a current location. And with the emulator you will need to manually send locations.
Location Services

Sometimes LogCat 'forgets' you have a device/emulator connected and running. It seems like this happens after you have a device and an emulator online at the same time and then you disconnect one of them. If you are getting nothing from LogCat, go to Window>Show View>Other>Devices and then click the device that you want to log.

GPS on emulator doesn't get the geo fix - Android

I'm developing an application for the android OS, I'm just starting, but I can't get the GPS on the emulator to work.
I've read on the internet that you need to send a geo fix to the emulator in order to enable the gps locationProvider. I'm both using the DDMS and telnet to try to send it, but logcat never tells me the it recived a new fix, and my apolication still sees the gps as disabled
here's my code
package eu.mauriziopz.gps;
import java.util.Iterator;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.location.LocationManager;
import android.os.Bundle;
import android.util.Log;
public class ggps extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LocationManager l =(LocationManager) getSystemService(Context.LOCATION_SERVICE);
List<String> li = l.getAllProviders();
for (Iterator<String> iterator = li.iterator(); iterator.hasNext();) {
String string = iterator.next();
Log.d("gps", string);
}
if (l.getLastKnownLocation("gps")==null)
Log.d("gps", "null");
}
}
I've read that the DDMS may not work properly on a non english OS, but telnet should work!
update: the gps is enabled in the settings

Turns out, that since I was developing for Android 1.5 (and not Google API 1.5) the map (and looks like other features) were disabled.
As soon as I changed the target platform, my error disappeared.
btw thanks all

To test if the geofix is working you could use the Google Maps app with "My Location"

Make sure that the gps in enabled in the settings. If still the problem persists, you just go to the application named Navigation in the main menu, run it and exit. Now try your application.
You can enable location controls under emulator control in DDMS perspective by selecting a particular device. without selecting a device it will not work

I supose is fixed yet, but in the code you should use as provider a string returned by the LocationManager service, instead of "gps" as you put in l.getLastKnownLocation("gps").