android - 广播接收器和警报管理器

Question

您好，我正在用 android 构建一个新闻应用程序，因此每次将新数据输入数据库时​​，用户都必须在通知栏中收到通知。所以经过研究我发现我必须使用广播接收器和警报管理器。但我无法理解的是，当应用程序关闭时，它如何知道输入了新数据？以及如何让警报管理器激活应用程序以检查新数据，比方说每 5 分钟一次？谢谢。

Answer 1

这个项目可以在使用AlarmManager设置时间后每10000秒显示一次通知。

AlarmActivityActivity.java:

package co.in.technoguys.AlarmActivity;

import java.util.Calendar;

import android.app.Activity;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.DatePicker;
import android.widget.TimePicker;
import android.widget.Toast;

public class AlarmActivityActivity extends Activity {
    int notifyID=1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

    }
    public void startAlert(View view) {
        TimePicker tp=(TimePicker)findViewById(R.id.timePicker1);
        DatePicker dp=(DatePicker)findViewById(R.id.datePicker1);
        Calendar Cal = Calendar.getInstance();
        Cal.set(Calendar.YEAR, dp.getYear());  
        Cal.set(Calendar.MONTH, dp.getMonth());         
        Cal.set(Calendar.DAY_OF_MONTH, dp.getDayOfMonth());         
        Cal.set(Calendar.HOUR_OF_DAY, tp.getCurrentHour());            
        Cal.set(Calendar.MINUTE, tp.getCurrentMinute());                
        Cal.set(Calendar.SECOND, 00);
        long when=Cal.getTimeInMillis();
        Intent intent = new Intent(this, MyBroadcastReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), 234324243, intent, 0);
        AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
        alarmManager.setRepeating(AlarmManager.RTC_WAKEUP,when,20000,pendingIntent);
        Toast.makeText(this, "Notification Triggered on"+tp.getCurrentHour()+":"+tp.getCurrentMinute(),
                Toast.LENGTH_LONG).show();

              }
}

MyBroadcastReceiver.java:

package co.in.technoguys.AlarmActivity;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class MyBroadcastReceiver extends BroadcastReceiver {
    int notifyID=1;

  @Override
  public void onReceive(Context context, Intent intent) {
    Intent i=new Intent();
    PendingIntent pi=PendingIntent.getBroadcast(context,0,i,0);
    NotificationManager nm=(NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
    Notification notify=new Notification(R.drawable.ic_launcher,"Notification Triggered",System.currentTimeMillis());
    CharSequence from="Remainder";
    CharSequence message="Meeting Starts at 9 A.M";
    notify.setLatestEventInfo(context, from, message, pi);
    nm.notify(notifyID,notify);
  }

} 

ma​​in.xml:

        <TimePicker
            android:id="@+id/timePicker1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_centerVertical="true" />

        <DatePicker
            android:id="@+id/datePicker1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_above="@+id/timePicker1"
            android:layout_alignLeft="@+id/timePicker1"
            android:layout_marginBottom="27dp" />

        <Button
            android:id="@+id/startAlert"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignLeft="@+id/timePicker1"
            android:layout_below="@+id/timePicker1"
            android:layout_marginTop="36dp"
            android:onClick="startAlert"
            android:text="@string/count" />

    </RelativeLayout>

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="co.in.technoguys.AlarmActivity"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="10" />
<uses-permission android:name="android.permission.VIBRATE" >
    </uses-permission>
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".AlarmActivityActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver android:name="MyBroadcastReceiver" >
        </receiver>
    </application>

</manifest>