Develop Reference

How to launch a certain activity of an Android app

I would like to launch, from my app, two specific activities A_Activity and B_Activity from apps Aapp and Bapp
I inserted two buttons and in the two OnClickListener I wrote
Intent intent = new Intent();
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setAction("com.Acompany.Aapp.A_Activity");
ctx.startActivity(intent);
Intent intent = new Intent();
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setAction("com.Bcompany.Bapp.B_Activity");
ctx.startActivity(intent);
Moreover I added to AndroidManifest.xml the following lines
<activity
android:name="com.Acompany.Aapp.A_Activity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="com.Acompany.Aapp.A_Activity" />
</intent-filter>
</activity>
<activity
android:name="com.Bcompany.Bapp.B_Activity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="com.Bcompany.Bapp.B_Activity" />
</intent-filter>
</activity>
But my app crashes and in the logcat I read "No Activity found to handle Intent"
Where is my mistake?
EDIT: More precisely the two activities are not in my own app

More precisely the two activities are not in my own app
You should investigate target app's manifest file first, to check if these activities are available to others by being exported or offering publicly accessible intent filters. It looks you may simply be not allowed to do what you attempt to.

Try like this. For your home activity(first launch activity) do like this in your manifest file.xml
<activity
android:name="com.Acompany.LaunchHomeActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="com.Acompany.LaunchHomeActivity" />
</intent-filter>
</activity>
<activity android:name="com.Acompany.Aapp.A_Activity">
</activity>
<activity android:name="com.Bcompany.Bapp.B_Activity">
</activity>
don't include <intent-filter> to all activities

Intent intent = new Intent(myFirstClass.this, MySecondClassA.class);
startActivity(intent);
Class B
Intent intent = new Intent(myFirstClass.this, MySecondClassB.class);
startActivity(intent);

How to start an activity using a custom intent?

I have a very simple application (an example from a textbook) that consists of 2 activities: The first activity UsingIntentActivity has a button. When this button is clicked it must lead to the second activity called SecondActivity which will show a text on the screen.
I can achieve this using startActivity(new Intent(this, SecondActivity.class));
However in the textbook where I met this example another form of the same method is used:
startActivity(new Intent("net.dreamingpixel.SecondActivity"));
And in the Manifest File a matching custom intent is created (as I understood):
<activity
android:name=".UsingIntentActivity"
android:label="#string/title_activity_using_intent" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".SecondActivity"
android:label="Second Activity" >
<intent-filter>
<action android:name="net.dreamingpixel.SecondActivity" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
So there is an intent-filter and its category is set to DEFAULT. But when I try to run the app like this and click the button of the UsingIntentActivity the app crashes. In the log cat I can see the following messages:
FATAL EXCEPTION: main
java.lang.IllegalStateException: Could not execute the method of the activity
And then it points to the call of the startActivity method that I wrote at the beginning of this post.
Did anyone have a similar problem? Did I make a mistake somewhere?
UPDATE: Also I noticed that there is a warning in the Manifest file on the line where I open the second activity tag. It says: Exported activity does not require permission
Maybe this warning has to do something with my problem..

As you send that you have created second activity in manifest file as per
startActivity(new Intent("net.dreamingpixel.SecondActivity"));
Here net.dreamingpixel.SecondActivity means, here you need to provide the activity name with the package you created in your project...
In manifest at the top you will find package name. You need to use that package name with your activity...
Here as per above code..
net.dreamingpixel ----- is a package
SecondActivity ----- is an Activity in that package.

Unable to find explicit activity class in android

I have an android project with several packages. The structure of the packages in this case is com.siva.restorative is the package that contains the activity I want to run.
My activities are declared in my manifest as
<activity android:theme="#style/YtdTheme" android:name="com.siva.restorativecare.RestorativeCare">
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
The mainScreen activity displays fine, since it is inside the com.WAPP package. But when I try to run the setLocationActivity, I get the unable to find explicit class error. Here is how I have the intent parameters:
Intent i = new Intent(this,SecondActivity.class);

I guess first you should change the action string in manifest as:
<action android:name="com.siva.restorativecare.RestorativeCare" />
and then start running your activity as:
Intent i = new Intent("com.siva.restorativecare.RestorativeCare");
startActivity(i);

ActivityNotFoundException?

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

launch activities from different package

I have activity A in package one, and I want to run an intent which will up an activity B which is in package two.
How can I do this? Any samples will be welcome.
this is what ive done, and the error i get:
first activity ("MainActivity") in a package: com.abelski.currencyclient
and second activity("SecondActivity" in a diffrent package: com.idan.second
now i wanna call from MainActivity to SecondActivity.
ive added this line at the manifest of the MainActivity:
<activity android:name="com.idan.second.SecondApplicationActivity"></activity>
now in main Activity i got this button which run this line:
Intent intent = new Intent(MainActivity.this,SecondApplicationActivity.class);
and this is the rror:
04-29 09:20:59.197: ERROR/AndroidRuntime(399): Uncaught handler: thread main exiting due to uncaught exception
04-29 09:20:59.276: ERROR/AndroidRuntime(399): java.lang.NoClassDefFoundError: com.idan.second.SecondApplicationActivity
04-29 09:20:59.276: ERROR/AndroidRuntime(399):

I am assuming that by "packages" you mean applications.
We have:
- ApplicationA with FirstActivity
- ApplicationB with SecondActivity
If, in the ApplicationB's AndroidManifest.xml file, in the declaration of SecondActivity you add an intent filter such as:
<activity android:name=".SecondActivity">
<intent-filter>
<action android:name="applicationB.intent.action.Launch" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
You can create an Intent to launch this SecondActivity from the FirstActivity with:
Intent intent = new Intent("applicationB.intent.action.Launch");
startActivity(intent);
What this all means is:
The SecondActivity has a filter for the intent action of "applicationB.intent.action.Launch"
When you create an intent with that action and call 'startActivity' the system will find the activity (if any) that responds to it
The documentation for this is at: https://developer.android.com/reference/android/content/Intent.html

I had the same problem and the solution was another level in the root of your package name.
If you have two packages "com.first...." and "com.second...", and the manifest is referencing "com.first". Then you can refactor both packages in order to reuse the first part. For instance, "com.package.first" and "com.package.second". Then your manifest has to be also updated
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.package">
...
<activity android:name=".first.FirstPackageActivity" android:label="FirstPackageActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<activity android:name=".second.SecondPackageActivity" android:label="SecondPackageActivity">
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
Your java code can create an intent and start the activity in the usual way:
Intent intent = new Intent(this,ActivityClassName.class);
startActivity(intent);

If the package you mentioned here is same to application,I think the answer in the question Android: Starting An Activity For A Different Third Party App is simpler。With the first answer to that question, you don't need to make any modification to your second application.

Use explicit intents:
Intent intent = new Intent(context,ClassName.class);
where ClassName is from another package.
Sometimes, you will not know the name of the class in such cases you will have to rely on the Intent that the target class advertises to handle.

First, you need to declare both packages and activities on Manifest :
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
and for the second activities, on android:name --> .Packages name.activity, assuming your second packages name com.iden.second :
<activity android:name=".second.SecondActivity">
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value=".MainActivity" />
<intent-filter>
<action android:name="android.intent.action.SECOND" />
<category android:name="android.intent.category.SECOND" />
</intent-filter>
</activity>
then on the MAINACTIVITY JAVA CLASS, asuming you will start second activity using a button :
public class MainActivity extends AppCompatActivity {
private Button mButtonSecond;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mButtonSecond = findViewById(R.id.btn_second);
mButtonSecond.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent newActivity = new Intent(MainActivity.this,com.iden.second.SECOND.class);
startActivity(newActivity);
}
});
}
}
hope that can help, since i am not clear with the question structure