Android 筆記

2013年2月25日星期一

onCreate和onStart是不同的

onCreate和onStart是不同的

通过从客户端调用Context.startService(Intent)方法我们可以启动一个服务。如果这个服务还没有运行，Android将启动它并且在onCreate方法之后调用它的onStart方法。如果这个服务已经在运行，那么它的onStart方法将被新的Intent再次调用。所以对于单个运行的Service它的onStart方法被反复调用是完全可能的并且是很正常的。

@Override
public void onStart(Intent intent, int startId) {
Log.e(TAG, "start onStart~~~");
super.onStart(intent, startId);
}

2013年2月23日星期六

Alarm Manager Example

74down vote

This is working code. It wakes CPU every 10 minutes until the phone turns off.

Add to Manifest.xml:

...
<uses-permission android:name="android.permission.WAKE_LOCK"></uses-permission>
...
<receiver  android:process=":remote" android:name="Alarm"></receiver>
...

Code:

    package YourPackage;
    import android.app.AlarmManager;
    import android.app.PendingIntent;
    import android.content.BroadcastReceiver;
    import android.content.Context;
    import android.content.Intent;
    import android.os.PowerManager;
    import android.widget.Toast;

    public class Alarm extends BroadcastReceiver 
    {    
         @Override
         public void onReceive(Context context, Intent intent) 
         {   
             PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
             PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "");
             wl.acquire();

             // Put here YOUR code.
             Toast.makeText(context, "Alarm !!!!!!!!!!", Toast.LENGTH_LONG).show(); // For example

             wl.release();
         }

     public void SetAlarm(Context context)
     {
         AlarmManager am=(AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
         Intent i = new Intent(context, Alarm.class);
         PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0);
         am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 1000 * 60 * 10, pi); // Millisec * Second * Minute
     }

     public void CancelAlarm(Context context)
     {
         Intent intent = new Intent(context, Alarm.class);
         PendingIntent sender = PendingIntent.getBroadcast(context, 0, intent, 0);
         AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
         alarmManager.cancel(sender);
     }
 }

Set Alarm from Service:

package YourPackage;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;

public class YourService extends Service
{
    Alarm alarm = new Alarm();
    public void onCreate()
    {
        super.onCreate();       
    }

    public void onStart(Context context,Intent intent, int startId)
    {
        alarm.SetAlarm(context);
    }

    @Override
    public IBinder onBind(Intent intent) 
    {
        return null;
    }
}

If you want set alarm repeating at phone boot time:

Add permission to Manifest.xml:

<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"></uses-permission>
...
<receiver android:name=".AutoStart">
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED"></action>
    </intent-filter>
</receiver>
...

And create new class:

package YourPackage;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class AutoStart extends BroadcastReceiver
{   
    Alarm alarm = new Alarm();
    @Override
    public void onReceive(Context context, Intent intent)
    {   
        if (intent.getAction().equals("android.intent.action.BOOT_COMPLETED"))
        {
            alarm.SetAlarm(context);
        }
    }
}

2013年2月17日星期日

Saving image to sdcard from drawble resource

Saving image to sdcard from drawble resource:

Say you have an image namely ic_launcher in your drawable. Then get a bitmap object from this image like:

Bitmap bm = BitmapFactory.decodeResource( getResources(), R.drawable.ic_launcher);

The path to SD Card can be retrieved using:

String extStorageDirectory = Environment.getExternalStorageDirectory().toString();

Then save to sdcard on button click using:

File file = new File(extStorageDirectory, "ic_launcher.PNG");
    outStream = new FileOutputStream(file);
    bm.compress(Bitmap.CompressFormat.PNG, 100, outStream);
    outStream.flush();
    outStream.close();

Don't forget to add android.permission.WRITE_EXTERNAL_STORAGE permission.

2013年2月25日 星期一