Hi every body I just wanna ask a question, when you define some thing like this in your android manifest file :
<activity android:name= "com.example.myapp.ExampleActivity">
<intent-filter>
<action android:name= "some.custom.action" />
<category android:name= "android.intent.category.DEFAULT"/>
</intent-filter>
</activity>
and you gonna start it by this way :
val intent = Intent()
intent.action = "some.custom.action"
startActivity(intent)
so is it implicit calling activity?
Yes, this is an implicit intent. An explicit intent specifies the exact component that it calls. Because this doesn't, it's implicit (and therefore might resolve to multiple components if more than one matches).
Related
To specify my "Home" activity at compile-time, I can use the following code in my AndroidManifest.
<activity
android:name=".HomeActivity"
<intent-filter android:label="#string/home_activity">
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.HOME" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
I have a requirement though where I need to be able to specify the activity I would like to use as my "Home" screen at "run-time". Does anyone know if this is possible? Basically, I want to replace "HomeActivity" with something else.
I looked into using an "activity-alias" where I can specify the target activity using the "targetActivity" attribute but I didn't quite get how I can use this.
Thanks!
#Jon you can conditionally call separate activity from splash.Like you have a condition that on first app launch you need to open a tutorial screen and then onwards your home Activity then you can create different intents.
if (!sharedPreferences.contains(DiceConstants.FIRST_TIME_PREFS)) {
intent = new Intent(this, TutorialActivity.class);
sharedPreferences.edit().putBoolean(DiceConstants.FIRST_TIME_PREFS, true).commit();
} else {
intent = new Intent(this, HomeActivity.class);
}
I know I need to use to enable an activity to receive an Intent like this (not main activity).
<activity android:name=".MyApp_2ndActivity">
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
However, I found it can be triggered too if "intent-filter" is removed, like this.
<activity android:name=".MyApp_2ndActivity">
</activity>
I am wondering what difference is in these 2 formats?
See here: http://developer.android.com/guide/components/intents-filters.html
The difference is the second one can only be started using an explicit Intent -- one which names the component it wants to start. The first one can be started by an implicit Intent -- one which does not specify the exact component but contains information for the system to find an appropriate match for. The intent filters are used by the system for resolving such intents.
Difference is the when we use this code:
<activity android:name=".MyApp_2ndActivity">
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
This will be the first activity triggered when you starts your application.It doesnot need any explicit intents
and when we use this code:
<activity android:name=".MyApp_2ndActivity">
</activity>
the activity will be started with the use of Explicit intent
Intent filters are used, for example, when the activity starts from a specific event on the device. Your main activity has specific intent filters. If you want your application start when NFC tag is scanned, you can specify that via intent filters.
You can read more here for example.
http://developer.android.com/guide/components/intents-filters.html
Well I searched a lot, but I didn't find a precise answer how to export an Activity, so an app can start it with startActivityforResult.
How do I achieve that? Do I have to change the Manifest in some ways?
As an alternate to Dalmas' answer, you can actually export an Activity without creating an <intent-filter> (along with the hassle of coming up with a custom action).
In the Manifest edit your Activity tag like so:
<activity
android:name=".SomeActivity"
....
android:exported="true" />
The important part is android:exported="true", this export tag determines "whether or not the activity can be launched by components of other applications". If your <activity> contains an <intent-filter> then this tag is set to true automatically, if it does not then it is set to false by default.
Then to launch the Activity do this:
Intent i = new Intent();
i.setComponent(new ComponentName("package name", "fully-qualified name of activity"));
startActivity(i);
Of course with this method you will need to know the exact name of the Activity you are trying to launch.
You need to declare an intent-filter in your Manifest (I took the following example from Barcode Scanner) :
<activity android:name="...">
<intent-filter>
<action android:name="com.google.zxing.client.android.SCAN" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
Then create an intent with the same action string :
Intent intent = new Intent("com.google.zxing.client.android.SCAN");
startActivityForResult(intent, code);
Android should start your activity (or it will show a drop-down box if there are multiple apps sharing the same action string).
I am getting an ActivityNotFoundException in the following code:
Main.java
Intent intent = new Intent();
intent.setAction("com.test.app.TEST");
startActivity(intent); // ActivityNotFoundException
Manifest.xml
<activity android:name=".MainActivity" android:theme="#android:style/Theme.Dialog">
<intent-filter>
<action android:name="com.test.app.TEST" />
</intent-filter>
</activity>
I've had this issue too, as perfectly concisely described by jpahn.
the period at the front did not give any help to me.
even with exactly this (a copy of the original question including edits), I would still get ActivityNotFoundException.
Main.java
Intent intent = new Intent();
intent.setAction("com.test.app.TEST");
startActivity(intent); // ActivityNotFoundException
Manifest.xml
<activity android:name=".MainActivity" android:theme="#android:style/Theme.Dialog">
<intent-filter>
<action android:name="com.test.app.TEST" />
</intent-filter>
</activity>
This was resolved, after much trial-and-error, by simply adding this to the intent-filter in the manifest:
<category android:name="android.intent.category.DEFAULT" />
So the final manifest file contained:
<activity android:name=".MainActivity" android:theme="#android:style/Theme.Dialog">
<intent-filter>
<action android:name="com.test.app.TEST" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
I got this error after moving an activity class from one package to another.
Clean build solved it (Project -> Clean).
Be sure to declare your activity in the manifest.xml within the aplication:
<application>
<activity android:name=".YourNewActivity"/>
</application>
To start the new Activity:
Intent intent = new Intent(main.this, YourNewActivity.class);
startActivity(intent);
Where main stands for the current activity,
Add a . (dot) before your activity name in Android Manifest. So it should be android:name=".WordsToSpeakMainActivity"
I have some addition to the #Tom Pace answer. The answer is completely right, but to make it more clear:
ActivityNotFoundException occurs because of absence of
<category android:name="android.intent.category.DEFAULT" />
Because when Android OS see this in the manifest file, understands that this activity can receive intent.
The point ActivityNotFoundException thrown is that, when activity(intent-creator-activity) tries to create intent for other activity(intent-receiver-activity), Android OS sees there is intent for receiver activity but receiver activity does not receive anyone. Then Android OS returns null or empty intent to intent-creator-activity. And startActivity throws that exception.
I have found a code from android developers to avoid this exception:
// Verify the original intent will resolve to at least one activity
if (sendIntent.resolveActivity(getPackageManager()) != null) {
startActivity(chooser);
}
Android Developers: Intent Filters
To be safe you can also call your new activity like this:
Intent intent = new Intent();
intent.setClass(this, THECLASSNAME);
startActivity(intent); //
However, you must add the activity to the androidmanifest - and write a . in front of it, e.g.
<activity android:name=".YOURACTIVITYNAME"></activity>
There two types of intents in android framework,
1-Implicit intents that you are using,
<activity android:name=".MainActivity" android:theme="#android:style/Theme.Dialog">
<intent-filter>
<action android:name="com.test.app.TEST" />
</intent-filter>
</activity>
just add one line in intent filter
<intent-filter>
<action android:name="com.test.app.TEST" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
2- Explicit Intents
Intent i=new Intent(CurrentActivity.this,WhereWeWantToGoActivity.class);
startActivity(i);
To launch an activity by a string definition, use:
Intent intent = new Intent();
intent.setComponent(
new ComponentName("com.app", "com.app.activity.TheActivity"));
startActivity(intent);
At the very top of your AndroidManifest.xml, you'll see the package attribute
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.android.example"
and then, in the activity tag, you'll see the name attribute:
<activity
android:name=".Something"
Make sure that the package name and activity name, when joined together, make the full package specification of your Activity i.e.
com.android.example + .Something = com.android.example.Something
Otherwise, you'll get a ActivityNotFoundException.
I found a solution to this problem... I´m using 2 modules in a android studio project, the thing here is that I needed to add the activity to the main manifest file
<activity android:name="com.HeadApp.ARTry.UnityPlayerActivity"
android:clearTaskOnLaunch="false" android:label="#string/app_name"
android:screenOrientation="portrait"
android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen"
/>
I had that in the unity activity manifest, I just copied the activity and paste it in the main manifest and that was it, hope it helps, eve been struggling a lot with this for the past 3 weeks
I don't get the Android Intent matching concept! I must be missing something, but I read and re-read the docs and don't get it. Maybe some kind soul can shed some light on this?
I am able to start an Activity if I specify a Category filter android.intent.category.DEFAULT in the manifest:
...
<activity
android:name="mmmo.android.test.ItemDetails"
<intent-filter>
<action android:name="android.intent.action.INSERT" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
...
and if I then don't add any Category to the Intent object:
...
Intent intent = new Intent(Intent.ACTION_INSERT);
startActivity(intent);
...
That works. However, as soon as I define any other category than android.intent.category.DEFAULT I am only getting ActivityNotFoundExceptions. E.g. if I specify:
...
<activity
android:name="mmmo.android.test.ItemDetails"
<intent-filter>
<action android:name="android.intent.action.INSERT" />
<category android:name="foo.bar" />
</intent-filter>
</activity>
...
and then try to start that Activity using:
...
Intent intent = new Intent(Intent.ACTION_INSERT);
intent.addCategory("foo.bar");
startActivity(intent);
...
this does not work. The doc reads "... every category in the Intent object must match a category in the filter. ...". The category name I add to the Intent matches the category I specified in the filter. So why does this not match up and just throws an exception???
Michael
You must also add
<category android:name="android.intent.category.DEFAULT"></category>
to the intent filter for the intent to be resolved.
See Intent:
Activities will very often need to support the CATEGORY_DEFAULT so that they can be found by Context.startActivity().
From the documentation:
In principle, therefore, an Intent object with no categories should
always pass this test, regardless of what's in the filter. That's
mostly true. However, with one exception, Android treats all implicit
intents passed to startActivity() as if they contained at least one
category: "android.intent.category.DEFAULT" (the CATEGORY_DEFAULT
constant). Therefore, activities that are willing to receive implicit
intents must include "android.intent.category.DEFAULT" in their intent
filters
A "bug" is present if the observable behaviour does not match its documented one. This one does not a bug make.