I have implemented a ListView in my Android application. I bind to this ListView using a custom subclass of the ArrayAdapter class. Inside the overridden ArrayAdapter.getView(...)开发者_运维知识库 method, I assign an OnClickListener. In the onClick method of the OnClickListener, I want to launch a new activity. I get the exception:

Calling startActivity() from outside of an Activity  context requires the  
FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?

How can I get the Context that the ListView(the current Activity) is working under?

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Either

• cache the Context object via constructor in your adapter, or
• get it from your view.

Or as a last resort,

• add - FLAG_ACTIVITY_NEW_TASK flag to your intent:

_

myIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

Edit - i would avoid setting flags as it will interfere with normal flow of event and history stack.

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You can achieve it with addFlags instead of setFlags

myIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

According to the documentation it does:

Add additional flags to the intent (or with existing flags value).

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EDIT

Be careful when you are using flags that you may change the history stack as Alex Volovoy's answer says:

...avoid setting flags as it will interfere with normal flow of event and history stack.

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Instead of using (getApplicationContext) use YourActivity.this

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If you got error because of using create chooser like below:

Intent sharingIntent = new Intent(Intent.ACTION_VIEW);
sharingIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
sharingIntent.setData(Uri.parse("http://google.com"));
startActivity(Intent.createChooser(sharingIntent, "Open With"));

Set the flag to create chooser like this :

Intent sharingIntent = new Intent(Intent.ACTION_VIEW);
sharingIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
sharingIntent.setData(Uri.parse("http://google.com"));

Intent chooserIntent = Intent.createChooser(sharingIntent, "Open With");
chooserIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

startActivity(chooserIntent);

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In addition: if you show links in listview in fragment, do not create it like this

adapter = new ListAdapter(getActivity().getApplicationContext(),mStrings);

instead call

adapter = new ListAdapter(getActivity(),mStrings);

adapter works fine in both cases, but links work only in last one.

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I think maybe you are implementing the OnClickListener in the wrong place - usually you should definitely implement an OnItemClickListener in your Activity and set it on the ListView instead, or you will get problems with your events...

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At the Android 28(Android P) startActivity

if ((intent.getFlags() & Intent.FLAG_ACTIVITY_NEW_TASK) == 0
        && (targetSdkVersion < Build.VERSION_CODES.N
                || targetSdkVersion >= Build.VERSION_CODES.P)
        && (options == null
                || ActivityOptions.fromBundle(options).getLaunchTaskId() == -1)) {
    throw new AndroidRuntimeException(
            "Calling startActivity() from outside of an Activity "
                    + " context requires the FLAG_ACTIVITY_NEW_TASK flag."
                    + " Is this really what you want?");
}

So the best way is add FLAG_ACTIVITY_NEW_TASK

Intent intent = new Intent(context, XXXActivity.class);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
}
context.startActivity(intent);

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CustomAdapter mAdapter = new CustomAdapter( getApplicationContext(), yourlist);

or

Context mContext = getAppliactionContext();
CustomAdapter mAdapter = new CustomAdapter( mContext, yourlist);

change to below

CustomAdapter mAdapter = new CustomAdapter( this, yourlist);

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See, if you are creating an intent within a listiner in some method

override onClick (View v).

then call the context through this view as well:

v.getContext ()

There will not even need SetFlags ...

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For anybody getting this on Xamarin.Android (MonoDroid) even when StartActivity is called from activity - this is actually Xamarin bug with new ART runtime, see https://bugzilla.xamarin.com/show_bug.cgi?id=17630

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Elaborating Alex Volovoy's answer a little more -

in case u are getting this problem with fragments, getActivity() works fine to get the context

In Other Cases:

If you don't want to use-

myIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);//not recommend

then make a function like this in your OutsideClass -

public void gettingContext(Context context){
    real_context = context;//where real_context is a global variable of type Context
}

Now,in your main activity when ever you make a new OutsideClass call the above method immediately after you define the OutsideClass giving the activity's context as argument. Also in your main activity make a function-

public void startNewActivity(final String activity_to_start) {
    if(activity_to_start.equals("ACTIVITY_KEY"));
    //ACTIVITY_KEY-is a custom key,just to
    //differentiate different activities
    Intent i = new Intent(MainActivity.this, ActivityToStartName.class);
    activity_context.startActivity(i);      
}//you can make a if-else ladder or use switch-case

now come back to your OutsideClass,and to start new activity do something like this-

@Override
public void onClick(View v) {
........
case R.id.any_button:

            MainActivity mainAct = (MainActivity) real_context;             
            mainAct.startNewActivity("ACTIVITY_KEY");                   

        break;
    }
........
}

This way you will be able to start different activities called from different OutsideClass without messing up with flags.

Note-Try not to cache context object via constructor for fragment(with adapter,its fine).A fragment should have a empty constructor otherwise application crashes in some scenarios.

remember to call

OutsideClass.gettingContext(Context context);

in the onResume() function as well.

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This error goes when startactivity doesn't know which is his activity. So you must add activity before startActivity()

you must set

context.startActivity(yourIntent);

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In my opinion, it's better to use the method of startActivity() just in the your code of the Activity.class. If you use that in the Adapter or other class, it will result in that.

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I also had the same problem. Check all the context that you have passed. For 'links' it needs Activity Context not Application context.

This are the place where you should check :

1.) If you used LayoutInflater then check what context you have passed.

2.) If you are using any Adapter check what context you have passed.

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Use this code in your Adapter_Activity and use context.startActivity(intent_Object) and intent_Object.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

Like this:

Intent n_act = new Intent(context, N_Activity.class);
n_act.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(n_act);

It Works....

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In your Activity (where you're calling the adapter) just change getActivityContext() with YourActivity.this. Here's an exemple:

yourAdapter = new YourAdapter(yourList, YourActivity.this); // Here YourActivity.this is the Context instead of getActivityContext()
recyclerView.setAdapter(yourAdapter);

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Intent viewIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);    
viewIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);    
startActivity(viewIntent);   

i hope this will work.

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Faced the same issue then implemented

intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

and got solved the problem.

There may be an another reason which is related to list view adapter.
You can see This blog, described it very well.

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Use this code. Works fine for me. Share Something from Outside of an activity:

Intent intent = new Intent(Intent.ACTION_SEND);
intent.setType("text/plain");

// Append Text
String Text = "Your Text Here"

intent.putExtra(Intent.EXTRA_TEXT, Text);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

Intent shareIntent = Intent.createChooser(intent,"Share . . . ");
shareIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
G.context.getApplicationContext().startActivity(shareIntent);

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Since adding flags affect event_flow and stack_history it is better to pass the 'application context' to the non-activity from where you need to call an activity class in the following way:

"ActivityClassName.this" (While you pass the context in this manner it will contain all the detail and info that you need to call an Activity from a non-activity scenario)

So there is no need to set or add flags, this will work fine in every case.

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If you use databinding, just get your context with

binding.root.context

This solved my problem.

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Intent i= new Intent(context, NextActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_SINGLE_TOP);

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If you are invoking share Intent in Cordova plugin, setting the Flag will not help. Instead use this -

cordova.getActivity().startActivity(Intent.createChooser(shareIntent, "title"));

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My situation was a little different, I'm testing my app using Espresso and I had to launch my Activity with ActivityTestRule from the instrumentation Context (which is not the one coming from an Activity).

fun intent(context: Context) = 
    Intent(context, HomeActivity::class.java)
        .addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)

I had to change the flags and add an or bitwise ( | in Java) with Intent.FLAG_ACTIVITY_NEW_TASK

So it results in:

fun intent(context: Context) = 
    Intent(context, HomeActivity::class.java)
        .addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP or Intent.FLAG_ACTIVITY_NEW_TASK)

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Kotlin version

val intent = Intent(Intent.ACTION_EDIT, ContactsContract.Profile.CONTENT_URI)
intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK
this.startActivity(intent)

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Calling startActivity() from outside of an Activity context get from your view

Don't

val context = activity.applicationContext
openBrowser(context, MenuUrl.TERM_CONDITION)

Do

   1. val context = binding.root.context // If you are using view binding
   2. val context = yourView.context // If you are not use view binding
    openBrowser(context, MenuUrl.TERM_CONDITION)

Thank You.

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For people coming from Xamarin.Forms or Xamarin.Android, In your Xamarin.Android project, use:

Xamarin.Essentials.Platform.CurrentActivity.StartActivity(intent);

Note that this might require Xamarin.Essentials v1.5 or above

As @Alex Volovoy mentioned, setting flags should be avoided as it will interfere with normal flow of event and history stack.