引起原因：java.lang.IllegalArgumentException：二进制XML文件第9行：必须指定唯一的android：id，android：tag或具有ID的父对象

Question

I am trying to learn Android from head first Android book , and this is one of it's codes, but I don't why it gives me this strange error? As I am new in Android couldn't solve the problem and posted it here. I don't know if this data enough or not? Detail activity is an activity that has a fragment on it's .xml file and points to a fragment activity with a layout includes two text view on it.

DetailActivity.java:

package com.example.m.workoutapp;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class DetailActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_detail);
    }
}

activity_detail.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.m.workoutapp.DetailActivity">

    <fragment
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:name="com.example.m.workoutapp.WorkoutDetailFragment" />

</android.support.constraint.ConstraintLayout>

The error happens in this line: android:name="com.example.m.workoutapp.WorkoutDetailFragment"

WorkoutDetailFragment.java:

package com.example.m.workoutapp;


import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;


public class WorkoutDetailFragment extends Fragment {


    public WorkoutDetailFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_workout_detail, container, false);
    }

}

fragment_workout_detail:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.m.workoutapp.WorkoutDetailFragment">

    <TextView
        android:id="@+id/text_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="workout title"
        android:textAppearance="?android:attr/textAppearanceLarge"/>

    <TextView
        android:id="@+id/text_desciption"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="workout description"
        />

</LinearLayout>

Full error message:

01-30 21:38:45.386 25393-25393/com.example.m.workoutapp E/AndroidRuntime: FATAL EXCEPTION: main
                                                                          Process: com.example.m.workoutapp, PID: 25393
                                                                          java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.m.workoutapp/com.example.m.workoutapp.DetailActivity}: android.view.InflateException: Binary XML file line #10: Binary XML file line #10: Error inflating class fragment
                                                                              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
                                                                              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
                                                                              at android.app.ActivityThread.-wrap12(ActivityThread.java)
                                                                              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
                                                                              at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                              at android.os.Looper.loop(Looper.java:154)
                                                                              at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                              at java.lang.reflect.Method.invoke(Native Method)
                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
                                                                           Caused by: android.view.InflateException: Binary XML file line #10: Binary XML file line #10: Error inflating class fragment
                                                                           Caused by: android.view.InflateException: Binary XML file line #10: Error inflating class fragment
                                                                           Caused by: java.lang.IllegalArgumentException: Binary XML file line #10: Must specify unique android:id, android:tag, or have a parent with an id for com.example.m.workoutapp.WorkoutDetailFragment
                                                                              at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:3385)
                                                                              at android.support.v4.app.FragmentController.onCreateView(FragmentController.java:120)
                                                                              at android.support.v4.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:378)
                                                                              at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:33)
                                                                              at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:79)
                                                                              at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:777)
                                                                              at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
                                                                              at android.view.LayoutInflater.rInflate(LayoutInflater.java:858)
                                                                              at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)
                                                                              at android.view.LayoutInflater.inflate(LayoutInflater.java:518)
                                                                              at android.view.LayoutInflater.inflate(LayoutInflater.java:426)
                                                                              at android.view.LayoutInflater.inflate(LayoutInflater.java:377)
                                                                              at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:288)
                                                                              at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140)
                                                                              at com.example.m.workoutapp.DetailActivity.onCreate(DetailActivity.java:11)
                                                                              at android.app.Activity.performCreate(Activity.java:6679)
                                                                              at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
                                                                              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
                                                                              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
                                                                              at android.app.ActivityThread.-wrap12(ActivityThread.java)
                                                                              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
                                                                              at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                              at android.os.Looper.loop(Looper.java:154)
                                                                              at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                              at java.lang.reflect.Method.invoke(Native Method)
                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

Answer 1

The error is in your activity_detail.xml file:

 <?xml version="1.0" encoding="utf-8"?> <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.example.m.workoutapp.DetailActivity"> <fragment android:layout_width="match_parent" android:layout_height="match_parent" android:name="com.example.m.workoutapp.WorkoutDetailFragment" /> </android.support.constraint.ConstraintLayout> 

When you use the <fragment> tag, the system will automatically create an instance of your WorkoutDetailFragment and add it to the activity's FragmentManager . To do this, the system needs some way to identify your fragment to the fragment manager. You have three choices:

1. Add an android:id attribute to the <fragment> tag's parent (the ConstraintLayout )

2. Add an android:id attribute to the <fragment> tag itself

3. Add an android:tag attribute to the <fragment> tag itself

Any of these will allow the fragment manager to identify and track the fragment, which will solve your crash.

It doesn't even really matter what tag or id you use, either (though it's always good to pick descriptive names). As long as you don't re-use the id or tag somewhere else in your activity's layout, it will be fine.