Increment/decrement counter

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

@@ -2,12 +2,55 @@ package edu.liu.floodgame;
 
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
+import android.view.View;
+import android.widget.Button;
+import android.widget.TextView;
 
-public class MainActivity extends AppCompatActivity {
+public class MainActivity extends AppCompatActivity implements View.OnClickListener {
+
+    final private String COUNTER = "counter";
+
+    private TextView textView;
+    private Button decrButton;
+    private int counter = 0;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
+        this.textView = findViewById(R.id.textView);
+        this.decrButton = findViewById(R.id.decrement);
+        if(savedInstanceState == null) {
+            System.out.println("No existing bundle");
+            setCounter(0);
+        }
+        else {
+            System.out.println("Using existing bundle");
+            setCounter(savedInstanceState.getInt(COUNTER));
+        }
+    }
+
+    @Override
+    protected void onSaveInstanceState(Bundle outState) {
+        super.onSaveInstanceState(outState);
+        outState.putInt(COUNTER, counter);
+    }
+
+    @Override
+    public void onClick(View view) {
+        switch(view.getId()) {
+            case R.id.increment:
+                setCounter(counter+1);
+                break;
+            case R.id.decrement:
+                setCounter(counter-1);
+                break;
+        }
+    }
+
+    private void setCounter(int newValue) {
+        counter = newValue;
+        textView.setText(getString(R.string.counter_is, counter));
+        decrButton.setEnabled(counter > 0);
     }
 }

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

@@ -7,12 +7,49 @@
     tools:context=".MainActivity">
 
     <TextView
+        android:id="@+id/textView"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:text="Hello World!"
+        android:layout_marginTop="8dp"
+        android:text="@string/greeting"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintLeft_toLeftOf="parent"
         app:layout_constraintRight_toRightOf="parent"
-        app:layout_constraintTop_toTopOf="parent" />
+        app:layout_constraintTop_toBottomOf="@+id/linearLayout" />
+
+    <LinearLayout
+        android:id="@+id/linearLayout"
+        style="?android:attr/buttonBarStyle"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:gravity="center"
+        android:orientation="horizontal"
+        app:layout_constraintBottom_toTopOf="@+id/textView"
+        app:layout_constraintTop_toTopOf="parent">
+
+        <Button
+            android:id="@+id/decrement"
+            style="?android:attr/borderlessButtonStyle"
+            android:layout_width="105dp"
+            android:layout_height="wrap_content"
+            android:onClick="onClick"
+            android:text="@string/decrement"
+            app:layout_constraintEnd_toStartOf="@+id/increment"
+            app:layout_constraintStart_toStartOf="parent"
+            tools:layout_editor_absoluteY="154dp" />
+
+        <Button
+            android:id="@+id/increment"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:onClick="onClick"
+            style="?android:attr/borderlessButtonStyle"
+            android:text="@string/increment"
+            app:layout_constraintBottom_toTopOf="@+id/textView"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toEndOf="@+id/decrement"
+            app:layout_constraintTop_toTopOf="parent" />
+
+    </LinearLayout>
 
 </android.support.constraint.ConstraintLayout>
\ No newline at end of file

app/src/main/res/values/strings.xml

 <resources>
     <string name="app_name">FloodGame</string>
+    <string name="greeting">Hello class, this is a test.</string>
+    <string name="counter_is">Counter is ((%d))</string>
+    <string name="decrement">Decrement</string>
+    <string name="increment">Increment</string>
 </resources>