Starting activities with intents in Android - why does this work? - android

Previously I've been looking at existing code to display a map in a tab, and this time I've tried to write it myself to see if I understood it.
It runs fine without errors (screenshot), but I don't completely understand why, and whether I'm doing this in the best way.
The part that I don't quite understand is in the manifest.
I would have thought that android:label should be maptabview_name, but that gives me an error saying no matching resource was found.
Why does it run when using app_name for that activity?
Why can't it find the maptabview_name resource?
Also, in MapTab2, is this the best way to start an intent?
What exactly is this telling the system? "I intend to start an activity from this class"?
Here's my code
(It's based on this):
MapTab2.java
package com.test.maptab2;
import android.app.TabActivity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TabHost;
public class MapTab2 extends TabActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Intent i = new Intent(this,MapTabView.class);
TabHost.TabSpec spec;
spec = getTabHost().newTabSpec("tab1");
spec.setContent(i);
spec.setIndicator("Map");
getTabHost().addTab(spec);
spec = getTabHost().newTabSpec("tab2");
spec.setContent(R.id.detailstub);
spec.setIndicator("Detail");
getTabHost().addTab(spec);
getTabHost().setCurrentTab(0);
}
}
MapTabView.java
package com.test.maptab2;
import android.os.Bundle;
import com.google.android.maps.MapActivity;
public class MapTabView extends MapActivity {
#Override
public void onCreate (Bundle icicle){
super.onCreate(icicle);
setContentView(R.layout.maptabview);
}
#Override
public boolean isRouteDisplayed(){
return false;
}
}
Main.xml
<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#android:id/tabhost"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<!-- Tab-switch panel -->
<TabWidget android:id="#android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
<!-- Tab contents -->
<FrameLayout android:id="#android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<!-- Map here -->
<RelativeLayout android:id="#+id/mapstub"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
<!-- Other stuff -->
<TextView android:id="#+id/detailstub"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="detail"/>
</FrameLayout>
</LinearLayout>
</TabHost>
maptabview.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/maptablayout"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<com.google.android.maps.MapView android:id="#+id/mapview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true"
android:apiKey="0HRMcD5o6WrBVhmwbWpeyeavZ67PXWOvJeeCx2g"/>
</RelativeLayout>
MapTab2.Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.test.maptab2"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="3" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:icon="#drawable/ic_launcher"
android:label="#string/app_name" >
<uses-library android:name="com.google.android.maps" />
<!-- Main -->
<activity android:name=".MapTab2"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<!-- Map -->
<activity android:name=".MapTabView"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.EMBED" />
</intent-filter>
</activity>
</application>
</manifest>

Q1: maptabview_name has to be in a string resource file, usually at res/values/string.xml, in case you have it there and still it's not in the resources generated file (gen/package/R.java), try removing it and let eclipse generate it again.
Q2: AFAIK, TabHost.TabSpec.setContent(Intent intent) it's like starting the Activity within the specified tab. I think that's the way do do it when you deal with tabs. Since Intents are used to do a lot of things, this is a basic usage, in this case just to specify the class.

Related

How to make application rotate in AVD

This is for a school project, but i didn't understand many parts of this.
I am leaving the handling of the rotation to the system, but after describing 2 layouts (standart and landscape mode)
But the landscape mode layout won't be taken into account when I rotate the screen.
(source: hostingpics.net)
(I have pressed the 4th button, in case it is the issue ...)
The mainactivity extends AppCompatActivity, (Because our teacher told us to), and all I do (for now) in the MainActivity is
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d(TAG,"Test");
}
then I described 2 LinearLayouts, one in layout/activity_main.xml :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:baselineAligned="false"
android:divider="#drawable/empty_divider_tall"
android:showDividers="middle"
android:background="#color/fl_concrete"
>
<fragment
class="com.example.g20901528.androidproject.fragment.TopFragment"
android:id="#+id/fragment_top"
android:layout_weight="1"
android:layout_height="match_parent"
android:layout_width="match_parent"
/>
<fragment
class="com.example.g20901528.androidproject.fragment.BottomFragment"
android:id="#+id/fragment_bottom"
android:layout_weight="1"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
and another in layout-land/activity-main.xml which is almost the same :
edit : layout-land/activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:baselineAligned="false"
android:divider="#drawable/empty_divider_wide"
android:showDividers="middle"
android:background="#color/fl_concrete"
>
<fragment
class="com.example.g20901528.androidproject.fragment.TopFragment"
android:id="#+id/fragment_top"
android:layout_weight="1"
android:layout_height="match_parent"
android:layout_width="match_parent"
/>
<fragment
class="com.example.g20901528.androidproject.fragment.BottomFragment"
android:id="#+id/fragment_bottom"
android:layout_weight="1"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
I did not change my manifest aside describing the MainActivity :
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.g20901528.androidproject">
<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>
My question is : how to make it so the two fragments rotate when i rotate the phone ?
I'm ready to provide any information.
Github Link of the project, if you really need it.
dude your layout xml name is different please change that
layout/activity_main.xml
layout-land/activity-main.xml make it -->
layout-land/activity_main.xml
and run

error in running application on android emulator

I have written an app with XML and still I don't write Classes by java code. But the emulator can show my app by its name and after that it says " unfortunately, app has stopped." What I have to do for this problem??!
This is my code:
<?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="#string/hello"/>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/TextView2"/>
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/Button"
/>
</LinearLayout>
You must have at least one activity (Java class) in your application so that manifest.xml could recognize that and run it.
You have to use an activity to show this xml :
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
As you can see your xml is called by the setContentView method.
This activity must be declared in your AndroidManifest.xml with
<activity
android:name="YOURPACKAGE.ACTIVITY_NAME"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

Displaying another Activity after clicking a menu item

I am writing my first Android app. I have three Activities: BaseballCardList, BaseballCardDetails, and FilterBaseballCards. BaseballCardList loads as the main Activity. It has a menu with two options to display one of the other two activities. BaseballCardDetails loads just fine. However, when I try to load FilterBaseballCards, I get a "Unfortunately, BBCT for Android has stopped." error message. I am running my app in the Android emulator. Here is the relavant code:
res/layout/card_list.xml:
<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/card_list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
res/layout/filter_cards.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
>
<TextView android:text="#string/filter_by_label" />
<RadioGroup android:id="#+id/filter_by">
<RadioButton android:id="#+id/year"
android:text="#string/year_radio_button"
/>
<RadioButton android:id="#+id/number"
android:text="#string/number_radio_button"
/>
<RadioButton android:id="#+id/year_and_number"
android:text="#string/year_and_number_radio_button"
/>
<RadioButton android:id="#+id/player_name"
android:text="#string/player_name_radio_button"
/>
</RadioGroup>
<Button android:id="#+id/ok"
android:text="#string/ok_button"
/>
<Button android:id="#+id/cancel"
android:text="#string/cancel_button"
/>
</LinearLayout>
BaseballCardList.java:
package bbct.android;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
public class BaseballCardList extends Activity {
private static final String DEBUG_TAG = "BaseballCardList";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.card_list);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
new MenuInflater(this).inflate(R.menu.option, menu);
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.add:
Log.d(DEBUG_TAG, "Starting BaseballCardDetails");
this.startActivity(new Intent(this, BaseballCardDetails.class));
return true;
case R.id.filter:
Log.d(DEBUG_TAG, "Starting FilterBaseballCards");
this.startActivity(new Intent(this, FilterBaseballCards.class));
return true;
}
return super.onOptionsItemSelected(item);
}
}
FilterBaseballCards.java:
package bbct.android;
import android.app.Activity;
import android.os.Bundle;
public class FilterBaseballCards extends Activity{
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.filter_cards);
}
}
AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="bbct.android"
android:versionCode="1"
android:versionName="1.0">
<application android:label="#string/app_name" android:icon="#drawable/ic_launcher">
<activity android:name=".BaseballCardList"
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=".BaseballCardDetails" />
<activity android:name=".FilterBaseballCards" />
</application>
</manifest>
BaseballCardDetails.java is nearly identical to FilterBaseballCards.java, so I won't post it.
Why am I getting this error message? More importantly, how do I go about tracking down the problem myself? I am using the Android command-line tools, not Eclipse. I started adding some logging messages, but I don't know how to view the logging output that might help me trace the source of the problem.
Update:
I changed the setContentView() in FilterBaseballCards to setContentView(R.layout.card_details); and the card_details view loads just fine. This narrows down the problem to my filter_cards.xml file.
Another Update:
I simplified filter_cards.xml down to:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
>
<TextView android:text="#string/filter_by_label" />
</LinearLayout>
and continue to get the same error as before.
use
adb logcat
to view logging from command prompt
probably you have not added entries to manifest file for your new activities, for more on starting one activity from another look here:
http://developer.android.com/training/basics/firstapp/starting-activity.html
Ok I think your view is right mostly. Except I didn't like this line
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content" //Here wrap_content? Shouldn't it be fill_parent?
android:orientation="vertical"
>
Other than that your resources might be messed up (not accessing the right ones / names are wrong) #string/name Or #+id/name
EDIT:
I also noticed you don't assign an ID to the TextView probably should do that ;)
Sounds like you forgot to add the activies you are starting to the manifest.
More on Intent Filters: http://developer.android.com/guide/components/intents-filters.html
As #Nate noted, and I verified, the problem was in the view for my FilterBaseballCards activity. In particular, I modified the filter_cards.xml layout to
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/filter_by_label"
/>
</LinearLayout>
Note that I added android:layout_width and android:layout_height attributes to the TextView tag. After doing this, the app compiles and runs correctly in the Android emulator.

SurfaceView: ClassCastException, unable to start activity

Trying to get an Android 2.2 application to start up with a SurfaceView as the base view with a button placed atop it located near the bottom of the screen. So far, no luck. It crashes every time it attempts to launch. I've checked to make sure that the activity is registered in the manifest.
Here's my java code:
public class Dragable extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
and here's my main.xml:
<?xml version="1.0" encoding="utf-8"?>
<SurfaceView xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/surface_home"
>
<Button
android:id="#+id/add_new"
android:text="#string/add_new"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
/>
</SurfaceView>
and my manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name=".Dragable"
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>
<uses-sdk android:minSdkVersion="8" />
</manifest>
and here's my error:
11-29 11:58:52.620: ERROR/AndroidRuntime(512): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example/com.example.Dragable}: java.lang.ClassCastException: android.view.SurfaceView
Can't seem to find anything related doing searches on SO. My appologies if this has been asked before.
Now I see the problem. SurfaceView is not a container, I mean it does not extends ViewGroup, so you can't put a Button inside a SurfaceView. What you can do is wrapping the SurfaceView and the Button within a RelativeLayout.
You are not using any container to place components. Use this and make changes
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<SurfaceView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/surface_home"
>
<Button
android:id="#+id/add_new"
android:text="#string/add_new"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
/>
</SurfaceView>
</FrameLayout>

A new button to Android screen

How can I display a button on screen? I have defined it as
final Button nappi = (Button) findViewById(R.id.soita);
and
<Button
android:layout_width="100px"
android:layout_height="wrap_content"
android:text="#+string/Soita"
android:id="#+id/soita"
/>
You need to create the layout of the view in which you want the button to appear. Even something like
Let's say you're storing the definition in a file called main.xml in your res/layout directory.
<?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"
>
<Button android:text="Button01" android:id="#+id/Button01" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
</LinearLayout>
Then within your activity, you need to do the following:
public class Main extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Replace this with the name of your xml file dictating layout
setContentView(R.layout.main);
}
}
See the Hello Views tutorial; very useful. http://developer.android.com/guide/tutorials/views/index.html
If you're asking something different, like programmatically adding a button to an existing view, I'm not sure about that. In that case you might want to have the button start off as hidden and then reveal it when you need it.
I don't see why this displays nothing. I tried to make my own simple user interface.
main:
package com.xyz;
import android.app.Activity;
import android.os.Bundle;
public class NewHomeScreen extends Activity {
/** Called when the activity is first created. */
#Override public void onCreate(Bundle state) {
super.onCreate(state);
setContentView(R.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="fill_parent"
android:text="#string/hello"
>
</TextView>
<Button android:text="Soita"
android:id="#+id/soita"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
>
</Button>
</LinearLayout>
Manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.xyz"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name="NewHomeScreen">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.HOME"/>
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
<uses-sdk android:minSdkVersion="3" />
</manifest>
Your textview gets all screen place...
try this
XML:
<TextView
android:text="#string/hello"
android:layout_width="match_parent" android:layout_height="291dp">
</TextView>

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