android - 如何使用 Switch 开启和关闭背景音乐？

package com.example.biowit; import android.app.Service; import android.content.Intent; import android.media.MediaPlayer; import android.os.IBinder; public class BgMusicService extends Service { MediaPlayer player; @Override public IBinder onBind(Intent intent) { return null; } @Override public void onCreate() { super.onCreate(); player = MediaPlayer.create(this, R.raw.bg_music); player.setLooping(true); player.setVolume(100, 100); } @Override public int onStartCommand(Intent intent, int flags, int startId) { player.start(); return super.onStartCommand(intent, flags, startId); } @Override public void onDestroy() { super.onDestroy(); player.stop(); player.release(); } @Override public void onLowMemory() { super.onLowMemory(); } }

package com.example.biowit; import androidx.appcompat.app.AppCompatActivity; import android.content.Intent; import android.media.MediaPlayer; import android.os.Bundle; import android.view.View; import android.view.Window; import android.view.WindowManager; import android.widget.Button; import com.google.firebase.auth.FirebaseAuth; public class HomeScreen extends AppCompatActivity { Button Chap1_btn, Achieve_btn, HowToPlay_btn, LogOut_btn, Settings_btn; FirebaseAuth home_FbAuth; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_home_screen); Chap1_btn = findViewById(R.id.btn_Chap1); Achieve_btn = findViewById(R.id.btn_Achievements); HowToPlay_btn = findViewById(R.id.btn_HowToPlay); LogOut_btn = findViewById(R.id.btn_Logout); Settings_btn = findViewById(R.id.btn_Settings); home_FbAuth = FirebaseAuth.getInstance(); startService(new Intent(this, BgMusicService.class)); Chap1_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent open_Chap1 = new Intent(getApplicationContext(), LessonScreen.class); startActivity(open_Chap1); } }); LogOut_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { home_FbAuth.signOut(); startActivity(new Intent(getApplicationContext(), LoginScreen.class)); finish(); } }); Settings_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent open_Settings = new Intent(getApplicationContext(), Settings.class); startActivity(open_Settings); } }); } }

package com.example.biowit; import androidx.annotation.NonNull; import androidx.appcompat.app.AppCompatActivity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.CompoundButton; import android.widget.EditText; import android.widget.Switch; import android.widget.TextView; import android.widget.Toast; import com.google.android.gms.tasks.OnFailureListener; import com.google.android.gms.tasks.OnSuccessListener; import com.google.firebase.auth.FirebaseAuth; import com.google.firebase.auth.FirebaseUser; public class Settings extends AppCompatActivity { Button Back_ST_btn, AboutUs_btn, VerEmail_btn, Res_Pass_btn, Con_Res_btn, Cancel_Res_btn; TextView VerEmail_txt; EditText NewPass_input, CoNewPass_input; FirebaseAuth set_FbAuth; FirebaseUser set_FbUser; String respass_set, conpass_set; Switch Music_swch; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_settings); AboutUs_btn = findViewById(R.id.btn_AboutUs); Back_ST_btn = findViewById(R.id.btn_ST_Back); Res_Pass_btn = findViewById(R.id.btn_Reset_Pass); Con_Res_btn = findViewById(R.id.btn_Confirm_Reset); Cancel_Res_btn = findViewById(R.id.btn_Cancel_Reset); NewPass_input = findViewById(R.id.txt_New_Pass); CoNewPass_input = findViewById(R.id.txt_CoNew_Pass); VerEmail_btn = findViewById(R.id.btn_Verify_Email); VerEmail_txt = findViewById(R.id.lbl_Verify_Email); Music_swch = findViewById(R.id.swch_ST_Music); set_FbAuth = FirebaseAuth.getInstance(); set_FbUser = set_FbAuth.getCurrentUser(); String pass_regex = "^(?=.*[a-zA-Z])(?=.*[@#$%^&+=])(?=\\S+$).{6,}$"; Music_swch.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { @Override public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { if(Music_swch.isChecked()){ //??? } else{ //??? } } }); //When email is not verified, a message and button will appear. if (!set_FbAuth.getCurrentUser().isEmailVerified()){ VerEmail_txt.setVisibility(View.VISIBLE); VerEmail_btn.setVisibility(View.VISIBLE); } //When the "Verify Now" button is clicked, a verification email will be sent to the user's email address. VerEmail_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //send verificaton email set_FbAuth.getCurrentUser().sendEmailVerification().addOnSuccessListener(new OnSuccessListener<Void>() { @Override public void onSuccess(Void unused) { Toast.makeText(getApplicationContext(),"Verification Email sent.", Toast.LENGTH_LONG).show(); VerEmail_txt.setVisibility(View.GONE); VerEmail_btn.setVisibility(View.GONE); } }); } }); Res_Pass_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // opens reset password. NewPass_input.setVisibility(View.VISIBLE); CoNewPass_input.setVisibility(View.VISIBLE); Con_Res_btn.setVisibility(View.VISIBLE); Cancel_Res_btn.setVisibility(View.VISIBLE); } }); Cancel_Res_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // cancels reset password. NewPass_input.setVisibility(View.GONE); CoNewPass_input.setVisibility(View.GONE); Con_Res_btn.setVisibility(View.INVISIBLE); Cancel_Res_btn.setVisibility(View.INVISIBLE); } }); Con_Res_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { respass_set = NewPass_input.getText().toString(); conpass_set = CoNewPass_input.getText().toString(); if(respass_set.isEmpty()){ // if new password field is empty, error message will be shown. NewPass_input.setError("This field cannot be empty."); return; } if(respass_set.matches(pass_regex)){ // if new password is weak and not follows the certain , this error message will be shown. NewPass_input.setError("Password is too weak. Password must contain at least 6 characters with at least one digit and a special character."); return; } if(conpass_set.isEmpty()){ // if confirm password field is empty, error message will be shown. CoNewPass_input.setError("This field cannot be empty."); return; } if (!conpass_set.equals(respass_set)){ // if the confirm password is not equals to new password, error message will be shown. CoNewPass_input.setError("Password does not match."); return; } set_FbUser.updatePassword(respass_set).addOnSuccessListener(new OnSuccessListener<Void>() { @Override public void onSuccess(Void unused) { Toast.makeText(getApplicationContext(),"New Password saved.", Toast.LENGTH_LONG).show(); NewPass_input.setVisibility(View.GONE); CoNewPass_input.setVisibility(View.GONE); Con_Res_btn.setVisibility(View.INVISIBLE); } }).addOnFailureListener(new OnFailureListener() { @Override public void onFailure(@NonNull Exception e) { Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show(); } }); } }); AboutUs_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // opens "About Us" screen. startActivity(new Intent(getApplicationContext(), AboutUsScreen.class)); } }); Back_ST_btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // returns to previous screen. finish(); } }); } public void PlayBackgroundSound(View view){ startService(new Intent(this, BgMusicService.class)); } }