Counter increment button

app/src/main/java/edu/liu/counter/MainActivity.java

@@ -2,12 +2,28 @@ package edu.liu.counter;
 
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
+import android.view.View;
+import android.widget.TextView;
 
 public class MainActivity extends AppCompatActivity {
 
+    private int count;
+    private TextView counterText;
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
+        counterText = findViewById(R.id.counterText);
+        setCount(0);
+    }
+
+    public void setCount(int count) {
+        this.count = count;
+        counterText.setText(Integer.toString(count));
+    }
+
+    public void onClickIncrement(View v) {
+        setCount(count+1);
     }
 }

app/src/main/res/layout/activity_main.xml

@@ -7,6 +7,7 @@
     tools:context=".MainActivity">
 
     <TextView
+        android:id="@+id/textView2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="Hello World!"
@@ -15,4 +16,28 @@
         app:layout_constraintRight_toRightOf="parent"
         app:layout_constraintTop_toTopOf="parent" />
 
+    <TextView
+        android:id="@+id/counterText"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="TextView"
+        android:textSize="30sp"
+        app:layout_constraintBottom_toTopOf="@+id/textView2"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.498"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintVertical_bias="0.872" />
+
+    <Button
+        android:id="@+id/incrButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="8dp"
+        android:onClick="onClickIncrement"
+        android:text="Increment"
+        app:layout_constraintBottom_toTopOf="@+id/counterText"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent" />
+
 </android.support.constraint.ConstraintLayout>
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