Android ContentObserver监视未接电话,未读短信

ContentObserver有点类似于BroadcastReceiver,当某类事件发生时进行调用.ContentObserver一般和系统或第三方程序提供的Provider一起使用.

当为某个URI注册了ContentObserver后,对其进行操作后都会调用注册的回调函数,以监视未接电话为例（未读短信和未接电话类似,只需将URI改为短信的URI就可以了）：

// 注册ContentObserver
getContentResolver().registerContentObserver(CallLog.Calls.CONTENT_URI, false, new MissedCallContentObserver(this,    

new Handler()));   

// 当有call log时,就会对这个类进行回调
public class MissedCallContentObserver extends ContentObserver {   

    private Context ctx;   

    private static final String TAG = "MissedCallContentObserver";   

    public MissedCallContentObserver(Context context, Handler handler) {
        super(handler);
        ctx = context;
    }   

    @Override
    public void onChange(boolean selfChange) {   

        Cursor csr = ctx.getContentResolver().query(Calls.CONTENT_URI, new String[] {Calls.NUMBER,    

Calls.TYPE, Calls.NEW}, null, null, Calls.DEFAULT_SORT_ORDER);   

        if (csr != null) {
            if (csr.moveToFirst()) {
                int type = csr.getInt(csr.getColumnIndex(Calls.TYPE));
                switch (type) {
                case Calls.MISSED_TYPE:
                    Log.v(TAG, "missed type");
                    if (csr.getInt(csr.getColumnIndex(Calls.NEW)) == 1) {
                        Log.v(TAG, "you have a missed call");
                    }
                    break;
                case Calls.INCOMING_TYPE:
                    Log.v(TAG, "incoming type");
                    break;
                case Calls.OUTGOING_TYPE:
                    Log.v(TAG, "outgoing type");
                    break;
                }
            }
            // release resource
            csr.close();
        }
    }   

    @Override
    public boolean deliverSelfNotifications() {
        return super.deliverSelfNotifications();
    }
}