give RentActivity real functionality

app/src/main/java/com/example/hochi/nextcompanion/RentActivity.java

@@ -1,14 +1,51 @@
 package com.example.hochi.nextcompanion;
 
+import android.content.SharedPreferences;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
+import android.view.View;
+import android.widget.Button;
+import android.widget.TextView;
 
-public class RentActivity extends AppCompatActivity {
+public class RentActivity extends AppCompatActivity implements AsyncTaskCallbacks<String> {
-
+    private RequestHandler rentRequestTask = null;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_rent);
         getSupportActionBar().setDisplayHomeAsUpEnabled(true);
+        Button mRentSubmitButton = findViewById(R.id.rent_submit_button);
+        mRentSubmitButton.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+                rentRequest();
+            }
+        });
+    }
+
+    void rentRequest() {
+        TextView mBikeInput;
+        mBikeInput = findViewById(R.id.bike_id);
+        String bikeID = mBikeInput.getText().toString();
+        //get loginkey
+        SharedPreferences sharedPref = getSharedPreferences("persistence", MODE_PRIVATE);
+        String defaultValue = "nokey";
+        String loginKey = sharedPref.getString("loginKey", defaultValue);
+
+        String[] params = {
+                "apikey=", getString(R.string.apikey),
+                "loginkey=", loginKey,
+                "bike=", bikeID
+        };
+
+        rentRequestTask = new RequestHandler(this, "POST",
+                "api/rent.json", params);
+        rentRequestTask.execute((Void) null);
+    }
+
+    @Override
+    public void onTaskComplete(String response) {
+        //TODO: *any* response handling
+        finish();
     }
 }