ADD file via upload

OrderActivity.java

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+package com.example.drink_order_system;
+
+import android.annotation.SuppressLint;
+import android.app.Fragment;
+import android.app.FragmentManager;
+import android.app.FragmentTransaction;
+import android.os.Bundle;
+import android.widget.RadioButton;
+import android.widget.RadioGroup;
+
+import androidx.appcompat.app.AppCompatActivity;
+
+public class OrderActivity extends AppCompatActivity {
+
+    private RadioGroup rg_tab_bar;
+    private RadioButton rb_order;
+    private Fragment fg_order; //点餐界面
+    private Fragment fg_shop; //购物车界面
+    private FragmentManager fManager;
+    private String userName;
+    private String restaurantName;
+    Bundle bundle = new Bundle();
+    @SuppressLint("MissingInflatedId")
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_order);
+
+        userName = getIntent().getStringExtra("userName");
+        restaurantName = getIntent().getStringExtra("restaurantName");
+        bundle.putString("userName", userName);
+        bundle.putString("restaurantName", restaurantName);
+        System.out.println("username in onCreate in OrderActivity: " + userName);
+        fManager = getFragmentManager();
+        rg_tab_bar = (RadioGroup) findViewById(R.id.rg_tab);
+        rg_tab_bar.setOnCheckedChangeListener(this::onCheckedChanged); //对下方导航栏设置监听，实现界面切换
+        defaultFragment(); // 将点单界面设为默认界面
+    }
+    public void onCheckedChanged(RadioGroup group, int checkedId) { //界面切换函数
+        FragmentTransaction fTransaction = fManager.beginTransaction();
+        hideAllFragment(fTransaction); //先隐藏所有界面
+        switch (checkedId){
+            case R.id.rb_order:
+                if(fg_order==null)
+                {
+                    fg_order = OrderFragment.newInstance(restaurantName);
+                    fTransaction.add(R.id.ly_content,fg_order);
+                    fTransaction.show(fg_order);
+                }
+                else
+                    fTransaction.show(fg_order);
+                break;
+            case R.id.rb_shop:
+                if(fg_shop==null)
+                {
+                    fg_shop = ShopFragment.newInstance(userName,restaurantName);
+                    fTransaction.add(R.id.ly_content,fg_shop);
+                    fTransaction.show(fg_shop);
+                }
+                else
+                    fTransaction.show(fg_shop);
+                break;
+        }
+        fTransaction.commit();
+    }
+    public void defaultFragment() {
+        FragmentTransaction fTransaction = fManager.beginTransaction();
+        fg_order = OrderFragment.newInstance(restaurantName);
+        fTransaction.add(R.id.ly_content, fg_order);
+        fTransaction.show(fg_order);
+        fTransaction.commit();
+    }
+    private void hideAllFragment(FragmentTransaction fragmentTransaction){
+        if(fg_order!=null)fragmentTransaction.hide(fg_order);
+        if(fg_shop!=null)fragmentTransaction.hide(fg_shop);
+    }
+}