Question

My SherlockActivity, which inflates a layout with an EditText, Button, and a ListView.

<RelativeLayout 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=".MainActivity" >

<ListView
    android:id="@+id/listView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/editText1" >
</ListView>

<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBottom="@+id/editText1"
    android:layout_alignParentRight="true"
    android:layout_alignParentTop="true"
    android:text="Add"
    tools:ignore="HardcodedText" />

<EditText
    android:id="@+id/editText1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:layout_toLeftOf="@+id/button1"
    android:ems="10"
    android:hint="Click add!"
    android:inputType="text"
    tools:ignore="HardcodedText" >
</EditText>

My MainActivity extends BaseActivity which inflates a menu layout file of the following

<menu xmlns:android="http://schemas.android.com/apk/res/android" >

<item
    android:id="@+id/menu_settings"
    android:orderInCategory="100"
    android:showAsAction="never"
    android:title="@string/menu_settings"/>
<item
    android:id="@+id/add_item"
    android:orderInCategory="1"
    android:showAsAction="ifRoom"
    android:title="@string/add"/>
<item
    android:id="@+id/calendar"
    android:orderInCategory="2"
    android:showAsAction="ifRoom"
    android:title="@string/show_cal"/>
</menu>

I create a BaseActivity that extends SherlockActivity.

package com.courseorganizer;

import com.actionbarsherlock.app.SherlockActivity;
import com.actionbarsherlock.view.Menu;

public class BaseActivity extends SherlockActivity {
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getSupportMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
}

The MainActivity is where I have the problem. I extend BaseActivity and set up the onOptionsItemSelected() so that if the “Add” tab is selected, the input field is called. Then, I set up the OnClickListener to the button to add the user’s input to the ListView populated in an ArrayList that’s put into an ArrayAdapter.

Here is the MainActivity:

    package com.courseorganizer;

import java.util.ArrayList;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

import com.actionbarsherlock.view.MenuItem;

public class MainActivity extends BaseActivity {

private final String TAG = "Main Activity";

// LIST OF ARRAY STRINGS WHICH WILL SERVE AS LIST ITEMS
ArrayList<String> listItems = new ArrayList<String>();

// DEFINING STRING ADAPTER WHICH WILL HANDLE DATA OF LISTVIEW
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, listItems);

Button addItem = (Button)findViewById(R.id.button1);
EditText input = (EditText)findViewById(R.id.editText1);
ListView courseList = (ListView)findViewById(R.id.listView1);

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

    addItem.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            listItems.add(input.getText().toString());
            courseList.setAdapter(adapter);
        }
    });
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.add_item:
        input.requestFocus();
        Log.i(TAG, "Add Clicked");
        return true;
    case R.id.calendar:
        Log.i(TAG, "Calendar Clicked");
        return true;
    default:
        return super.onOptionsItemSelected(item);
    }
}
}

I appreciate your help!

EDIT: Here’s my logcat output:

11-04 19:16:24.517: D/AndroidRuntime(305): Shutting down VM
11-04 19:16:24.517: W/dalvikvm(305): threadid=1: thread exiting with uncaught exception     (group=0x4001d800)
11-04 19:16:24.569: E/AndroidRuntime(305): FATAL EXCEPTION: main
11-04 19:16:24.569: E/AndroidRuntime(305): java.lang.RuntimeException: Unable to     instantiate activity ComponentInfo{com.courseorganizer/com.courseorganizer.MainActivity}:     java.lang.IllegalStateException: System services not available to Activities before     onCreate()
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.app.ActivityThread.access$2300(ActivityThread.java:125)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.os.Handler.dispatchMessage(Handler.java:99)
11-04 19:16:24.569: E/AndroidRuntime(305):  at android.os.Looper.loop(Looper.java:123)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.app.ActivityThread.main(ActivityThread.java:4627)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     java.lang.reflect.Method.invokeNative(Native Method)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     java.lang.reflect.Method.invoke(Method.java:521)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-04 19:16:24.569: E/AndroidRuntime(305):  at dalvik.system.NativeStart.main(Native     Method)
11-04 19:16:24.569: E/AndroidRuntime(305): Caused by: java.lang.IllegalStateException:     System services not available to Activities before onCreate()
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.app.Activity.getSystemService(Activity.java:3526)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.widget.ArrayAdapter.init(ArrayAdapter.java:271)
11-04 19:16:24.569: E/AndroidRuntime(305):  at android.widget.ArrayAdapter.<init>    (ArrayAdapter.java:150)
11-04 19:16:24.569: E/AndroidRuntime(305):  at com.courseorganizer.MainActivity.<init>    (MainActivity.java:24)
11-04 19:16:24.569: E/AndroidRuntime(305):  at java.lang.Class.newInstanceImpl(Native     Method)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     java.lang.Class.newInstance(Class.java:1429)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.app.Instrumentation.newActivity(Instrumentation.java:1021)
11-04 19:16:24.569: E/AndroidRuntime(305):  at     android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
11-04 19:16:24.569: E/AndroidRuntime(305):  ... 11 more
11-04 19:16:26.998: I/Process(305): Sending signal. PID: 305 SIG: 9

Answer 1

findViewById() cannot be called before onCreate() and setContentView(), as there is no context or layout to search.

Move these lines into onCreate() after setContentView().

addItem = (Button)findViewById(R.id.button1);
input = (EditText)findViewById(R.id.editText1);
courseList = (ListView)findViewById(R.id.listView1);