java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView

Question

Not sure why I am getting a ClassCastException in the code below. Changing ListActivity to Activity corrects the error but I want ListActivity as this is a part of the bigger code I am trying to build. Any help will be appreciated. Thanks

MainActivity.java

package com.example.debug;

import android.app.ListActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;


public class MainActivity extends ListActivity {

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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

activity_main.xml:

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

    <LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >
    <!-- Name Label -->
    <TextView 
     android:id="@+id/vehicleType"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:textColor="#43bd00"
     android:textSize="16sp"
     android:textStyle="bold"
     android:paddingTop="6dip"
     android:text="Mobile1"
     android:paddingBottom="2dip" />
    <!-- Description Label -->
    <TextView 
     android:id="@+id/vehicleColor"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:textColor="#acacac"
     android:text="Mobile2"
     android:paddingBottom="2dip" />


    <LinearLayout 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal" >
    <!-- Cost Label -->
    <TextView 
     android:id="@+id/fuel"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:textColor="#000000"
     android:gravity="left"
     android:textStyle="bold"
     android:text="Mobile3" />
    <!-- Price Label -->
    <TextView 
     android:id="@+id/treadType"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:textColor="#acacac"
     android:text="Mobile4" 
     android:paddingBottom="2dip" />
    </LinearLayout> 
    </LinearLayout> 
    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>
</LinearLayout>

Stacktrace

FATAL EXCEPTION: main
Process: com.example.debug, PID: 1370
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.debug/com.example.debug.MainActivity}: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
    at android.app.ActivityThread.access$800(ActivityThread.java:135)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:136)
    at android.app.ActivityThread.main(ActivityThread.java:5017)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView
    at android.app.ListActivity.onContentChanged(ListActivity.java:241)
    at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:293)
    at android.app.Activity.setContentView(Activity.java:1929)
    at com.example.debug.MainActivity.onCreate(MainActivity.java:14)
    at android.app.Activity.performCreate(Activity.java:5231)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
    ... 11 more

Answer 1

your problem is with the root of your layout

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

you give it the android:id="@android:id/list" the id the android reserves for the ListView widget. Change it in something else. E.g

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/my_linear_layout"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

Answer 2

In a ListActivity android looks for the widget with android:id="@android:id/list" and expects a ListView but in your case it finds the root LinearLayout and tries to cast it to a ListView hence the exception :

Caused by: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView

To solve it, you just need to provide a different id as mentioned by Blackbelt.

Answer 3

Your linear layout id should be as follows

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/my_linear_layout"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal" >