Question

I’m a beginner in Android and am trying to run the Hello World but when the Emulator shows up, only the Android image is shown. My output “Hello World” never shows up.

MainActivity.class

public class MainActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        TextView text = new TextView(this);
        text.setText("Hello World, Android");
        setContentView(text);
       // setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
}

When the Emulator pops up i can wait for 5-10mins but yet the output never shows up. I haven’t change anything in any of the XML files. Am trying to test the “hello world” program.

I am using Eclipse.

Edit

activity_main.xml

<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" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/hello_world"
        tools:context=".MainActivity" />

</RelativeLayout>

androidManifest.XML

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myfirstapp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="15" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

Did you add your Activity to the AndroidManifest file?

Example

<application android:label="@string/app_name"
    android:icon="@drawable/ic_launcher">
    <activity android:name=".YourActivity">
        <intent-filter >
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Update

Change

setContentView(text)

to

setContentView(R.layout.activity_main) 

This means you will use your predefined XML file as the layout for this Activity.

If you want to change the TextView inside your xml:

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

    // find the TextView in the XML file defined by setContentView
    TextView text = (TextView) findViewById(R.id.mTextView);
    text.setText("Your text");
}

Do not forget to add the attribute `android:id=”@+id/mTextView” to the TextView in your XML.