Develop Reference

List Crashes App when updated

I'm trying to get a ListView to show the contents of a simple array but my program crashes at the setAdapeter line. As I understand this is supposed to be because the final value comes out as null but I don't see why that would be the case or how to fix it. I have already tried using ArrayAdapeter instead as well as catching the null exception with a try block. The former changes nothing and the latter simply shows a blank activity with no list to speak of. Please help.
Here's Main Activity
package ballton.fowdeckbuilder;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ListAdapter;
import android.widget.ArrayAdapter;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btnDecks = (Button) (findViewById(R.id.btnDecks));
Button btnCards = (Button) (findViewById(R.id.btnCards));
btnDecks.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, DeckCatalogue.class));
}
});
btnCards.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, CardCatalogue.class));
}
});
}
}
Here's the activity with the Problem
package ballton.fowdeckbuilder;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
public class DeckCatalogue extends AppCompatActivity {
ListView Ldecks;
String TAG = "TAG";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_deck_catalogue);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
Ldecks = (ListView) (findViewById(R.id.DeckList));
String Decks[] = new String[] {"Faria","Melgis"};
ListAdapter feed = (new ArrayAdapter<String>(this, R.layout.show_deck, Decks));
Ldecks.setAdapter(feed);
}
}
Here's the Layout for that activity
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="ballton.fowdeckbuilder.DeckCatalogue"
tools:showIn="#layout/activity_deck_catalogue">
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/DeckList"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
</RelativeLayout>
And Here's the layout XML I use for the list times
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:text="Small Text"
android:id="#+id/Deck" />
</LinearLayout>

Use this code instead of yours:
ListAdapter feed = (new ArrayAdapter<String>(this, R.layout.show_deck, R.id.Deck, Decks));
This happened because you must supply the resource ID (as your xml: R.id.Deck) for the TextView you used for ListView.

How to make two diffrent Activities to use the same layout Android

Below code works fine, but it opens a new layout and shows the toast message. but i wanted it to show toast & popup menus on the current layout. I'm working on popup menu project, i want to show popup menu on same layout. Thanks in Advance.
MainMactivity.java
package com.example.twoact;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainActivity extends Activity {
Button b1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1 = (Button) findViewById(R.id.button1);
b1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent openpopactivity = new Intent(MainActivity.this,
MainActivity2.class);
startActivity(openpopactivity);
}
});
}
}
MainActivity2.java
package com.example.twoact;
import android.widget.Toast;
import android.os.Bundle;
import android.os.Handler;
public class MainActivity2 extends MainActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
new Handler().postDelayed(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), "ya am in",
Toast.LENGTH_SHORT).show();
}
}, 1000);
}
}
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.twoact.MainActivity"
tools:ignore="MergeRootFrame" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="142dp"
android:text="Button" />
</RelativeLayout>

You can use Popup menu and Popup window. in this you can use your custom layout so you can get your view as window in same activity.
Popup window will be good option because it is since API LEVEL 1
please refer this docs and example 1,example 2
And Popup Menu is since API LEVEL 11. so you have to manage for lower version
docs for Popup Menu and example
popup window

Android-background change

So basically what I want to do is to change the background of the application when integer A value is greater than 50. I've tried using:
setBackgroundResource(R.drawable.imagename);
but it doesn't work.
I would really appreciate your help.
UPDATE:
My code:
package com.example.highhope;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.view.View;
import android.view.View.OnClickListener;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;
public class MainActivity extends ActionBarActivity {
Button button;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_main);
addListenerOnButton();
}
public void addListenerOnButton() {
button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
runOnUiThread(new Runnable() {
#Override
public void run() {
view.setBackgroundResource(R.drawable.i0);
}
});
}
});
}
}
My layout:
<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: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="com.example.highhope.MainActivity$PlaceholderFragment" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="90dp"
android:text="Button" />
So for starters I'm just trying to change application background on button click and I've tried everything and nothing seems to work.

You can make that with a Selector, Check this tutorial.
it's pretty easy, you just have to:
Add the images to your app resources
Create your background_button.xml (selector in the tutorial) in the drawable carpet
Set the background_button as your button background in your layout (android:background="#drawable/background_button")
Set an onClickListener to your button
Test it!.
When you do it this way, the background of your button will change with no need of handle it programmatically.

Are you making the background change in the UI thread? Try setBackgroundResource in the UI thread like below.
runOnUiThread(new Runnable() {
#Override
public void run() {
view.setBackgroundResource(R.drawable.bg);
}
});
Also, if you are using a Fragment. you would have to put getActivity(). in front of runOnUiThread.

Android Google Map API V2 - Buttons above fragment

I have managed to get a map to show on the screen. I am trying to create buttons above the map and then add actions to this. E.g. the button will change the location of the map. I am basically trying to adapt my code to this: https://www.youtube.com/watch?v=awX5T-EwLPc. However, I am using "extends Fragment Activity" which messes everything up.
My problem: I cannot create a button above the map, it is placed inside the map. I am trying to create a button above the map, and assign code so I can move to a location on the map etc. Here is my code:
MainActivity.java
package com.example.theapp;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends FragmentActivity implements OnClickListener
{
Button button;
TextView text;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button=(Button)findViewById(R.id.button1);
text=(TextView)findViewById(R.id.textView1);
}
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
text.setText("The button worked!");
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<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: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" >
<fragment
android:id="#+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
class="com.google.android.gms.maps.SupportMapFragment" />
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/map"
android:layout_alignTop="#+id/map"
android:text="Button" />
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="#+id/button1"
android:layout_alignBottom="#+id/button1"
android:layout_alignRight="#+id/map"
android:layout_marginRight="39dp"
android:text="TextView" />
</RelativeLayout>
From the code, my app displays a button on the map and a text view. When you click the button, its meant to change the text, but it doesn't do anything. I have researched tutorials and by the looks of it, I will have to create multiple fragments?
Question: How would I be able to create a button on that page, that will then pin point the user on the map?
Thank you in advance.

You are not setting any functionality to the Button... You should use
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
text.setText("that's how you do it!");
}
});

You need not to worry about "FragmentActivity" until and unless you use fragment class.
Just use this as normal Activity. it will work well.
package com.example.theapp;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends FragmentActivity implements OnClickListener
{
Button button;
TextView text;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button=(Button)findViewById(R.id.button1);
button.setOnClickListener(this);
text=(TextView)findViewById(R.id.textView1);
}
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
text.setText("The button worked!");
}
}

Runtime Android exception after pressing a button to go to next Activity

I have this code:
package com.problemio;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class ProblemioActivity extends Activity
{
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button addProblemButton = (Button)findViewById(R.id.add_problem_button);
Button browseProblemsButton = (Button)findViewById(R.id.browse_problems_button);
Button searchProblemsButton = (Button)findViewById(R.id.search_problems_button);
Button myProblemsButton = (Button)findViewById(R.id.my_problems_button);
addProblemButton.setOnClickListener(new Button.OnClickListener()
{
public void onClick(View v) {
Intent myIntent = new Intent(ProblemioActivity.this, AddProblemActivity.class);
ProblemioActivity.this.startActivity(myIntent);
}
});
}
}
It compiles fine and displays the addProblemButton button, but when that button is clicked, the system gives a runtime exception.
Here is the AddProblemActivity class:
package com.problemio;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class AddProblemActivity extends Activity
{
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//TextView text = (TextView) dialog.findViewById(R.id.addProblemText);
//text.setText(R.string.addProblemText);
TextView tv = new TextView(this);
tv.setText("Please Add a Problem");
setContentView(tv);
}
}
and here is the layout main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="First, add the problem you want to solve!"
/>
<TextView
android:id="#+id/add_problem_text"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Add a Problem You Want To See Solved"
/>
<Button
android:id="#+id/add_problem_button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Add a Problem"
/>
<Button
android:id="#+id/browse_problems_button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Browse Problems"
/>
<Button
android:id="#+id/search_problems_button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Search Problems"
/>
<Button
android:id="#+id/my_problems_button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="View My Problems"
/>
</LinearLayout>
any idea what might be going wrong? By the way, I can't seem to locate the stack trace of the exception. Where should I look for that in Eclipse? All it currently shows me is AndroidRuntimeException - dalvik.system.NativeStart.main
Thanks!!

The only problem I can think of is that your Activity "AddProblemActivity" is not register in the manifest.
See the logs under LogCat...you will find it in Window >Show View >Android > LogCat