广播的动态注册
先前我们的每个Activity都要在AndroidMainfest.xml文件中注册才能使用，这属于静态注册。现在我们学习一种新的注册方法，动态注册。
动态注册有很多好处，在新版本的安卓中，推荐全部使用动态注册，动态注册也利于大型项目的开发。
我们以Broadcast为例，我们需要在OnCreate和OnStop中注册和取消注册；取消注册是必要的，否则会导致内存溢出
声明广播
private SetTimeActivity.AlarmReceiver alarmReceiver;
注册广播
@Override public void onStart() { super.onStart(); alarmReceiver = new SetTimeActivity.AlarmReceiver(); // 创建一个闹钟的广播接收器 // 创建一个意图过滤器，只处理指定事件来源的广播 IntentFilter filter = new IntentFilter("ALARM"); registerReceiver(alarmReceiver, filter); // 注册接收器，注册之后才能正常接收广播 }
取消注册：
@Override public void onStop() { super.onStop(); unregisterReceiver(alarmReceiver); // 注销接收器，注销之后就不再接收广播 }
在此次的安卓打卡app中，我发现必须使用动态注册，才能成功使用广播触发AlertDialog
下面是我用AlertDialog实现定时提醒的具体代码:
package com.example.clockappliction; import static android.icu.text.DateTimePatternGenerator.DAY; import static androidx.constraintlayout.helper.widget.MotionEffect.TAG; import android.annotation.SuppressLint; import android.app.AlarmManager; import android.app.AlertDialog; import android.app.PendingIntent; import android.app.TimePickerDialog; import android.content.BroadcastReceiver; import android.content.Context; import android.content.DialogInterface; import android.content.Intent; import android.content.IntentFilter; import android.content.SharedPreferences; import android.icu.util.TimeZone; import android.os.Bundle; import android.os.SystemClock; import android.util.Log; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; import android.widget.TimePicker; import android.widget.Toast; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import androidx.appcompat.app.AppCompatActivity; import java.util.Calendar; public class SetTimeActivity extends AppCompatActivity implements View.OnClickListener , TimePickerDialog.OnTimeSetListener { private int hour,minute; private TextView tv_time; private Button btn_send; private EditText et_remind; public String mess = null; private SetTimeActivity.AlarmReceiver alarmReceiver; @SuppressLint("MissingInflatedId") @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_time_picker); tv_time = findViewById(R.id.tv_time); findViewById(R.id.btn_time).setOnClickListener(this); btn_send = (Button) findViewById(R.id.btn_send); btn_send.setOnClickListener(this); et_remind = (EditText) findViewById(R.id.et_remind); } @Override public void onStart() { super.onStart(); alarmReceiver = new SetTimeActivity.AlarmReceiver(); // 创建一个闹钟的广播接收器 // 创建一个意图过滤器，只处理指定事件来源的广播 IntentFilter filter = new IntentFilter("ALARM"); registerReceiver(alarmReceiver, filter); // 注册接收器，注册之后才能正常接收广播 } @Override public void onStop() { super.onStop(); unregisterReceiver(alarmReceiver); // 注销接收器，注销之后就不再接收广播 } @Override public void onClick(View view) { if (view.getId()==R.id.btn_time){ Calendar calendar = Calendar.getInstance(); TimePickerDialog dialog = new TimePickerDialog(this,this, calendar.get(Calendar.HOUR_OF_DAY), calendar.get(Calendar.MINUTE), true); dialog.show(); } else if (view.getId()==R.id.btn_send) { Intent intent = new Intent("ALARM"); mess = et_remind.getText().toString(); PendingIntent sender = PendingIntent.getBroadcast(this,0, intent,PendingIntent.FLAG_MUTABLE); long firstTime = SystemClock.elapsedRealtime(); // 开机之后到现在的运行时间(包括睡眠时间) long systemTime = System.currentTimeMillis(); android.icu.util.Calendar calendar = android.icu.util.Calendar.getInstance(); calendar.setTimeInMillis(System.currentTimeMillis()); // 这里时区需要设置一下，不然会有8个小时的时间差 calendar.setTimeZone(TimeZone.getTimeZone("GMT+8")); calendar.set(android.icu.util.Calendar.MINUTE,getMinute()); calendar.set(android.icu.util.Calendar.HOUR_OF_DAY,getHours()); calendar.set(android.icu.util.Calendar.SECOND,0); calendar.set(android.icu.util.Calendar.MILLISECOND,0); // 选择的定时时间 long selectTime = calendar.getTimeInMillis(); // 如果当前时间大于设置的时间，那么就从第二天的设定时间开始 if(systemTime > selectTime) { Toast.makeText(this," ", Toast.LENGTH_SHORT).show();//设置的时间小于当前时间 calendar.add(android.icu.util.Calendar.DAY_OF_MONTH,0); selectTime = calendar.getTimeInMillis(); } // 计算现在时间到设定时间的时间差 long time = selectTime - systemTime; firstTime += time; // 进行闹铃注册 AlarmManager manager = (AlarmManager)getSystemService(ALARM_SERVICE); manager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, time, DAY, sender); Log.i(TAG,"time ==== " + time +", selectTime ===== " + selectTime + ", systemTime ==== " + systemTime +", firstTime === " + firstTime); Toast.makeText(this,"设置提醒闹铃成功! ", Toast.LENGTH_LONG).show(); } } @Override public void onTimeSet(TimePicker timePicker, int hours_of_day, int minute) { String desc = String.format("你选择的时间是%d时%d分",hours_of_day,minute); tv_time.setText(desc); setHours(hours_of_day); setMinute(minute); } public int getHours(){ return hour; } public int getMinute(){ return minute; } public void setHours(int hour){ this.hour=hour; } public void setMinute(int minute){ this.minute=minute; } public void tipDialog(Context context) { AlertDialog.Builder builder = new AlertDialog.Builder(context); builder.setTitle("事件闹钟："); builder.setMessage("提醒您:"+mess); builder.setIcon(R.mipmap.ic_launcher); builder.setCancelable(false); //点击对话框以外的区域是否让对话框消失 //设置正面按钮 builder.setPositiveButton("确定", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); AlertDialog dialog = builder.create(); //创建AlertDialog对象 dialog.show(); //显示对话框 } public class AlarmReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { tipDialog(context); } } }
