finish the java code

app/src/main/java/me/jj97181818/ch06_energycalculator/MainActivity.java

@@ -2,12 +2,63 @@ package me.jj97181818.ch06_energycalculator;
 
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
+import android.view.View;
+import android.widget.AdapterView;
+import android.widget.EditText;
+import android.widget.Spinner;
+import android.widget.TextView;
+
+public class MainActivity extends AppCompatActivity implements AdapterView.OnItemClickListener, AdapterView.OnItemSelectedListener {
+    double[] energyRate = {3.1, 4.4, 13.2, 9.7, 5.1, 3.7};
+    EditText weight, time;
+    TextView total, txvRate;
+    Spinner sports;
 
-public class MainActivity extends AppCompatActivity {
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
+
+        //設定初值
+        weight = findViewById(R.id.weight);
+        time = findViewById(R.id.timeSpan);
+        total = findViewById(R.id.total);
+        txvRate = findViewById(R.id.txvRate);
+        sports = findViewById(R.id.sports);
+
+        //註冊監聽器
+        sports.setOnItemSelectedListener(this);
+    }
+
+
+    @Override
+    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
+
+    }
+
+    @Override
+    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
+        txvRate.setText(String.valueOf(energyRate[position]));
+    }
+
+    @Override
+    public void onNothingSelected(AdapterView<?> parent) {
+
+    }
+
+    public void calc(View v) {
+        String w = weight.getText().toString();
+        String t = time.getText().toString();
+        if (w.isEmpty() || w.equals(".") || t.isEmpty() || t.equals(".")) {
+            total.setText("請輸入體重及運動時間");
+            return;
+        }
+
+        int pos = sports.getSelectedItemPosition();
+
+        long kcal = Math.round(energyRate[pos] * Double.parseDouble(w) * Double.parseDouble(t));
+
+        total.setText(String.format("消耗能量 %d 仟卡", kcal));
     }
 }