title: Android App won't display in Android Studio Emulator
body: <p>I am very new to Android development. I have tried to recreate an app where if you press a button, a message "new text string" is displayed. However, when I run the AVD and choose the Virtual Device, it doesn't display it. Just an old TestApp I had. Can anyone suggest a fix? I'd really appreciate it.
  My code:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android=      "http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"&gt;
  
  &lt;TextView android:id="@+id/hello_text"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:text="@string/hello"
      /&gt;
  
  
  &lt;Button android:id="@+id/trigger"
      android:layout_width="100dip" android:layout_height="100dip"
      android:text="@string/button1"
      android:layout_below="@+id/hello_text"
      android:layout_alignParentLeft="true"
      android:layout_alignParentStart="true"
      android:layout_marginTop="111dp" /&gt;
   &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>SimpleActivity.java</p>
  
  <pre><code>package com.example.simpleactivityexample;
  import android.app.Activity;
  import android.os.Bundle;
  import android.widget.Toast;
  import android.widget.*;
  import android.view.View;
  public class SimpleActivity extends Activity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
      Toast.makeText(this, "onCreate", Toast.LENGTH_SHORT).show();
      Button startButton = (Button) findViewById(R.id.trigger);
      startButton.setOnClickListener(new View.OnClickListener()
      {
          private TextView tv = (TextView) findViewById(R.id.hello_text);
          public void onClick(View view)
          {
              tv.setText("new text string");
          }
      }
      );
  
  }
  @Override
  protected void onStart() {
      super.onStart();
      Toast.makeText(this, "onStart", Toast.LENGTH_SHORT).show();
  }
  @Override
  protected void onResume() {
      super.onResume();
      Toast.makeText(this, "onResume", Toast.LENGTH_SHORT).show();
  }
  @Override
  protected void onRestart() {
      super.onRestart();
      Toast.makeText(this, "onRestart", Toast.LENGTH_SHORT).show();
  }
  @Override
  protected void onPause() {
      Toast.makeText(this, "onPause", Toast.LENGTH_SHORT).show();
      super.onPause();
  }
  @Override
  protected void onStop() {
      Toast.makeText(this, "onStop", Toast.LENGTH_SHORT).show();
      super.onStop();
  }
  @Override
  protected void onDestroy() {
      Toast.makeText(this, "onDestroy", Toast.LENGTH_SHORT).show();
      super.onDestroy();
  }
  
  
  }
  </code></pre>
  
  <p>Manifest</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.example.simpleactivityexample" &gt;
  
  &lt;application
      android:debuggable="true"
      android:allowBackup="true"
      android:icon="@drawable/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" &gt;
      &lt;activity
          android:name="com.example.simpleactivityexample.SimpleActivity"
          android:configChanges="orientation|keyboardHidden|screenSize"
          android:label="@string/app_name"
          android:theme="@style/FullscreenTheme" &gt;
          &lt;intent-filter&gt;
              &lt;action android:name="android.intent.action.MAIN" /&gt;
              &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
          &lt;/intent-filter&gt;
      &lt;/activity&gt;
    &lt;/application&gt;
  
   &lt;/manifest&gt;
  </code></pre>
  
  <p>Strings.xml </p>
  
  <pre><code> &lt;?xml version="1.0" encoding="utf-8"?&gt;
   &lt;resources&gt;
   &lt;string name="app_name"&gt;Dietary Application&lt;/string&gt;
   &lt;string name="hello"&gt;Hello!&lt;/string&gt;
   &lt;string name="button1"&gt;This is a button!&lt;/string&gt;
   &lt;/resources&gt;
  </code></pre>