Simple Android Application not working

Question

This is my 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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<ImageButton
    android:id="@+id/clicker"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:background="@android:color/transparent"
    android:onClick="increment"
    android:src="@drawable/crown"
     />

<TextView
    android:id="@+id/output"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_below="@+id/clicker"
    android:text="0" />

</RelativeLayout>

This is MainActivity.java:

package com.example.ProjectName;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.widget.TextView;

public class MainActivity extends Activity {

TextView output = (TextView) findViewById(R.id.output);
int clickCount = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

}

public void increment() {
    clickCount++;
    output.setText(clickCount);
}

@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;
}

 }

This application is supposed to have a button that when you click it, a textview underneath the button displays an integer which increments with each click.

However, when I run this on my AVD it just says "ProjectName has stopped working". The IDE is giving me no errors. I tried previously instead of using "onClick:" in the xml manifest I st onClickListeners in the onCreate method but I got the same errors.

I see no reason why this should error, I barely entered any code besides what is created by default. I am an inexperienced android programmer and this is getting frustrating. Thanks for your help.

Edit for Binghammer:

MainActivity.java:

public class MainActivity extends Activity {

TextView output;
int clickCount = 0;
Button clicker;

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    output = (TextView) findViewById(R.id.output);
    clicker = (Button) findViewById(R.id.clicker);

    clicker.setOnClickListener(new OnClickListener() {
        public void onClick(View v)
        {
            clickCount++;
            output.setText(clickCount);
        } 
    });


}

@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;
}

}

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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<ImageButton
    android:id="@+id/clicker"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:background="@android:color/transparent"        
    android:src="@drawable/crown" />

<TextView
    android:id="@+id/output"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_below="@+id/clicker"
    android:text="0" />

</RelativeLayout>

With the code for an onClickListener on Button clicker, app doesn't start.

Answer 1

Try

public class MainActivity extends Activity {
TextView output;
int clickCount = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    output = (TextView) findViewById(R.id.output);

}

You were trying to access the id before setting the content of the activity

For your 2nd problem, try

public void increment(View view) {
    output = (TextView) findViewById(R.id.output);
    clickCount++;
    output.setText("" + clickCount);
}

Use the one without onclicklistener and see if it works

Answer 2

In your original class, you defined the TextView before it was created in onCreate, so it crashed.

In your edited class, this could be the problem:

output.setText(clickCount);

may need to be:

output.setText("" + clickCount);