Android片段未显示

Question

I have the following codes in my android application:

main.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="fill_parent"
android:orientation="vertical" >

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="activity" />

<fragment
    android:id="@+id/list"
    android:name="com.hugo.test.FragmentA"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="1" />

</LinearLayout>

fragmenta.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="fill_parent"
android:orientation="vertical" >

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="helloA" />

</LinearLayout>

FragmentA.java :

package com.hugo.test;

//some imports here

public class FragmentA extends Fragment {
    /** Called when the activity is first created. */
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
    {
        //super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);

        return inflater.inflate(R.layout.fragmenta, container, false);
    }
}

FragmentActivity.java :

    package com.hugo.test;

    //some imports here

public class FragmentActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
}

The layout of the activity should display "activity" and the fragment should display "helloA". When I run my project I only see "activity", so it seems to me that the fragment is ignored at all.

The error I see is :

12-19 09:01:05.370: E/AndroidRuntime(1352): FATAL EXCEPTION: main
12-19 09:01:05.370: E/AndroidRuntime(1352): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.hugo.test/com.hugo.test.FragmentActivity}: android.view.InflateException: Binary XML file line #12: Error inflating class fragment
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1751)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1767)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.ActivityThread.access$1500(ActivityThread.java:122)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1005)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.os.Looper.loop(Looper.java:132)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.ActivityThread.main(ActivityThread.java:4028)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at java.lang.reflect.Method.invokeNative(Native Method)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at java.lang.reflect.Method.invoke(Method.java:491)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:844)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at dalvik.system.NativeStart.main(Native Method)
12-19 09:01:05.370: E/AndroidRuntime(1352): Caused by: android.view.InflateException: Binary XML file line #12: Error inflating class fragment
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:688)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.view.LayoutInflater.rInflate(LayoutInflater.java:724)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.view.LayoutInflater.inflate(LayoutInflater.java:479)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.view.LayoutInflater.inflate(LayoutInflater.java:391)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.view.LayoutInflater.inflate(LayoutInflater.java:347)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:245)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.Activity.setContentView(Activity.java:1780)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at com.hugo.test.FragmentActivity.onCreate(FragmentActivity.java:11)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1715)
12-19 09:01:05.370: E/AndroidRuntime(1352):     ... 11 more
12-19 09:01:05.370: E/AndroidRuntime(1352): Caused by: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.hugo.test.fragmenta: make sure class name exists, is public, and has an empty constructor that is public
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.Fragment.instantiate(Fragment.java:500)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.Fragment.instantiate(Fragment.java:468)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.Activity.onCreateView(Activity.java:4132)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:664)
12-19 09:01:05.370: E/AndroidRuntime(1352):     ... 20 more
12-19 09:01:05.370: E/AndroidRuntime(1352): Caused by: java.lang.ClassNotFoundException: com.hugo.test.fragmenta in loader dalvik.system.PathClassLoader[/data/app/com.jochen.test-1.apk]
12-19 09:01:05.370: E/AndroidRuntime(1352):     at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:251)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at java.lang.ClassLoader.loadClass(ClassLoader.java:540)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at java.lang.ClassLoader.loadClass(ClassLoader.java:500)
12-19 09:01:05.370: E/AndroidRuntime(1352):     at android.app.Fragment.instantiate(Fragment.java:490)
12-19 09:01:05.370: E/AndroidRuntime(1352):     ... 23 more

Because of that error I added a constructor to FragmentA.java

public FragmentA()
{

}

This error is not gone, the fragment still doesn't show up, same behavior as before. Anyone an idea?

Answer 1

这是由于 0dp 我没有看到，当我从 Android 页面复制该部分时。

Answer 2

use this, it works for me

public class FragmentA extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View returnView = inflater.inflate(R.layout.fragmenta, container, false);
    return returnView;

}

}

Answer 3

This

public class FragmentActivity extends Activity {

should be

public class FragmentActivity extends FragmentActivity {

This is also discussed at here