I’ve just started working on my first Android app and my focus is the main activity of the app, MathleteIDActivity
, which includes a fragment TextFragment
which displays some text.
The project builds fine, but crashes as soon as the app is launched. This happens on two different phones running Android 4.x.x
, so fragment support shouldn’t be the issue. The stacktrace from adb logcat
looks like this (package redacted):
java.lang.RuntimeException: Unable to start activity ComponentInfo{foo.bar.baz.id.MathleteIDActivity} ... ... Caused by: android.view.InflateException: Binary XML file line #12: Error inflating class fragment ... Caused by: android.app.Fragment$InstantiationException: Unable to instantiate fragment .fragments.TextFragment: make sure class name exists, is public, and has an empty constructor that is public ... Caused by: java.lang.ClassNotFoundException: .fragments.TextFragment ...
My directory structure seems kosher: I’ve got the package directories foo/bar/baz/
inside src/main/java/
in the project root, and within that package:
fragments/ TextFragment.java id/ NFCIDActivity.java MathleteIDActivity.java ... ...
MathleteIDActivity.java
reads as follows:
package foo.bar.baz.id;
import android.widget.TextView;
import android.os.Bundle;
import foo.bar.baz.R;
public final class MathleteIDActivity extends NFCIDActivity {
@Override
public void onCreate(Bundle savedState) {
super.onCreate(savedState);
TextView textView = (TextView) findViewById(R.id.fragment_text);
textView.setText("Scan mathlete tag");
}
}
NFCIDActivity
is an abstract class that extends Android’s Activity
. Its only method is an override of onCreate
:
@Override
public void onCreate(Bundle savedState) {
super.onCreate(savedState);
setContentView(R.layout.id_activity);
}
And TextFragment.java
reads as follows:
package foo.bar.baz.fragments;
import android.app.Fragment;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.LayoutInflater;
import foo.bar.baz.R;
public final class TextFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.text_fragment, container, false);
}
}
In src/main/res/layout/id_activity.xml
I have the activity layout defined:
<?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" >
<fragment
android:name=".fragments.TextFragment"
android:id="@+id/id_message" >
</fragment>
</LinearLayout>
In the same directory, text_fragment.xml
defines TextFragment
‘s layout:
<?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" >
<TextView
android:id="@+id/fragment_text"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</TextView>
</LinearLayout>
I’ve already tried:
- Adding a public, no-parameter constructor to
TextFragment
. Same errors. - Referencing the fragment in the layout file by its fully-qualified package name
foo.bar.baz.fragments.TextFragment
. Same errors, now naming the new package. - Moving
TextFragment
‘s source file to the top-level packagefoo.bar.baz
and adjusting references. Same errors, now naming the new package.
Any ideas?
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Answer
Instantiate your fragment programatically using FragmentManager
as a quick solution:
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
TextFragment tf = new TextFragment();
ft.replace(R.id.container, tf);
ft.commit();
As for your approach, use a canonical package name instead and clean-build your project. Then pay attention to the error message (it can’t be “same error” since it should at least mention different package name).