android 炫酷倒计时连接数据库，并使用广播接收器的完整代码

以下是一个简单的 Android 炫酷倒计时应用的完整代码，其中包括了连接数据库和使用广播接收器的相关代码。

首先，我们需要创建一个数据库帮助类 `CountdownDBHelper`，用于创建和管理数据库：

public class CountdownDBHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "countdown.db";
    private static final int DATABASE_VERSION = 1;

    public static final String TABLE_COUNTDOWNS = "countdowns";
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_TITLE = "title";
    public static final String COLUMN_DATE = "date";

    private static final String CREATE_TABLE_COUNTDOWNS =
            "CREATE TABLE " + TABLE_COUNTDOWNS + "(" +
                    COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                    COLUMN_TITLE + " TEXT, " +
                    COLUMN_DATE + " TEXT);";

    public CountdownDBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE_COUNTDOWNS);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_COUNTDOWNS);
        onCreate(db);
    }
}

接下来，我们需要创建一个 `Countdown` 类，用于表示一个倒计时对象，并实现相关的数据库操作：

public class Countdown {
    private long id;
    private String title;
    private Date date;

    public Countdown(long id, String title, Date date) {
        this.id = id;
        this.title = title;
        this.date = date;
    }

    public long getId() {
        return id;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getTitle() {
        return title;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public Date getDate() {
        return date;
    }

    public static List<Countdown> getAllCountdowns(Context context) {
        List<Countdown> countdowns = new ArrayList<>();
        CountdownDBHelper dbHelper = new CountdownDBHelper(context);
        SQLiteDatabase db = dbHelper.getReadableDatabase();

        Cursor cursor = db.query(CountdownDBHelper.TABLE_COUNTDOWNS,
                new String[]{CountdownDBHelper.COLUMN_ID, CountdownDBHelper.COLUMN_TITLE, CountdownDBHelper.COLUMN_DATE},
                null, null, null, null, null);

        while (cursor.moveToNext()) {
            long id = cursor.getLong(cursor.getColumnIndex(CountdownDBHelper.COLUMN_ID));
            String title = cursor.getString(cursor.getColumnIndex(CountdownDBHelper.COLUMN_TITLE));
            String dateString = cursor.getString(cursor.getColumnIndex(CountdownDBHelper.COLUMN_DATE));
            Date date = new Date(Long.parseLong(dateString));
            countdowns.add(new Countdown(id, title, date));
        }

        cursor.close();
        db.close();
        dbHelper.close();

        return countdowns;
    }

    public static long addCountdown(Context context, String title, Date date) {
        CountdownDBHelper dbHelper = new CountdownDBHelper(context);
        SQLiteDatabase db = dbHelper.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(CountdownDBHelper.COLUMN_TITLE, title);
        values.put(CountdownDBHelper.COLUMN_DATE, String.valueOf(date.getTime()));

        long id = db.insert(CountdownDBHelper.TABLE_COUNTDOWNS, null, values);

        db.close();
        dbHelper.close();

        return id;
    }

    public static void deleteCountdown(Context context, long id) {
        CountdownDBHelper dbHelper = new CountdownDBHelper(context);
        SQLiteDatabase db = dbHelper.getWritableDatabase();

        db.delete(CountdownDBHelper.TABLE_COUNTDOWNS,
                CountdownDBHelper.COLUMN_ID + " = ?",
                new String[]{String.valueOf(id)});

        db.close();
        dbHelper.close();
    }
}

接下来，我们需要创建一个 `CountdownAdapter` 类，用于将倒计时对象列表展示在 `RecyclerView` 中：

public class CountdownAdapter extends RecyclerView.Adapter<CountdownAdapter.ViewHolder> {
    private List<Countdown> countdowns;
    private Context context;

    public CountdownAdapter(Context context, List<Countdown> countdowns) {
        this.context = context;
        this.countdowns = countdowns;
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        public TextView titleTextView;
        public TextView countdownTextView;

        public ViewHolder(View itemView) {
            super(itemView);

            titleTextView = itemView.findViewById(R.id.titleTextView);
            countdownTextView = itemView.findViewById(R.id.countdownTextView);
        }
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.list_item_countdown, parent, false);

        return new ViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        Countdown countdown = countdowns.get(position);

        holder.titleTextView.setText(countdown.getTitle());
        holder.countdownTextView.setText(getCountdownString(countdown.getDate()));
    }

    @Override
    public int getItemCount() {
        return countdowns.size();
    }

    private String getCountdownString(Date date) {
        long diff = date.getTime() - new Date().getTime();
        long days = TimeUnit.MILLISECONDS.toDays(diff);
        diff -= TimeUnit.DAYS.toMillis(days);
        long hours = TimeUnit.MILLISECONDS.toHours(diff);
        diff -= TimeUnit.HOURS.toMillis(hours);
        long minutes = TimeUnit.MILLISECONDS.toMinutes(diff);
        diff -= TimeUnit.MINUTES.toMillis(minutes);
        long seconds = TimeUnit.MILLISECONDS.toSeconds(diff);

        return String.format("%02dd %02dh %02dm %02ds", days, hours, minutes, seconds);
    }
}

接下来，我们需要创建一个 `CountdownActivity` 类，用于处理倒计时的各种操作：

public class CountdownActivity extends AppCompatActivity {
    private RecyclerView countdownRecyclerView;
    private CountdownAdapter countdownAdapter;

    private BroadcastReceiver countdownReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            countdownAdapter.notifyDataSetChanged();
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_countdown);

        countdownRecyclerView = findViewById(R.id.countdownRecyclerView);
        countdownRecyclerView.setLayoutManager(new LinearLayoutManager(this));

        List<Countdown> countdowns = Countdown.getAllCountdowns(this);
        countdownAdapter = new CountdownAdapter(this, countdowns);
        countdownRecyclerView.setAdapter(countdownAdapter);

        LocalBroadcastManager.getInstance(this).registerReceiver(countdownReceiver,
                new IntentFilter("countdown-updated"));

        FloatingActionButton addCountdownButton = findViewById(R.id.addCountdownButton);
        addCountdownButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showAddCountdownDialog();
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        LocalBroadcastManager.getInstance(this).unregisterReceiver(countdownReceiver);
    }

    private void showAddCountdownDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Add Countdown");

        View view = LayoutInflater.from(this).inflate(R.layout.dialog_add_countdown, null);
        final EditText titleEditText = view.findViewById(R.id.titleEditText);
        final DatePicker datePicker = view.findViewById(R.id.datePicker);
        final TimePicker timePicker = view.findViewById(R.id.timePicker);
        timePicker.setIs24HourView(true);

        builder.setView(view);

        builder.setPositiveButton("Add", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                String title = titleEditText.getText().toString();
                Calendar calendar = Calendar.getInstance();
                calendar.set(datePicker.getYear(), datePicker.getMonth(), datePicker.getDayOfMonth(),
                        timePicker.getCurrentHour(), timePicker.getCurrentMinute());

                long id = Countdown.addCountdown(CountdownActivity.this, title, calendar.getTime());
                countdownAdapter.notifyDataSetChanged();

                Intent intent = new Intent("countdown-updated");
                LocalBroadcastManager.getInstance(CountdownActivity.this).sendBroadcast(intent);
            }
        });

        builder.setNegativeButton("Cancel", null);

        builder.show();
    }
}

最后，我们需要创建一个 `BroadcastReceiver` 类，用于在倒计时结束时发送通知：

public class CountdownReceiver extends BroadcastReceiver {
    private static final int NOTIFICATION_ID = 1;

    @Override
    public void onReceive(Context context, Intent intent) {
        NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, "default")
                .setSmallIcon(R.drawable.ic_notification)
                .setContentTitle(intent.getStringExtra("title"))
                .setContentText("Countdown has ended!")
                .setPriority(NotificationCompat.PRIORITY_HIGH)
                .setAutoCancel(true);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel("default", "Countdown", NotificationManager.IMPORTANCE_HIGH);
            notificationManager.createNotificationChannel(channel);
        }

        notificationManager.notify(NOTIFICATION_ID, builder.build());
    }
}

以上就是一个简单的 Android 炫酷倒计时应用的完整代码，其中包括了连接数据库和使用广播接收器的相关代码。