android开发――内容观察者

ContentObserver――内容观察者，可以观察特定uri的数据库的变化，已达到监听的目的，进而对数据库的变化作出相应的反应。下面是一个监听短信变化的应用。

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Uri uri = Uri.parse("content://sms/");
        getContentResolver().registerContentObserver(uri, true, new SmsObserver(new Handler()));
    }
        
    public class SmsObserver extends ContentObserver{
        public SmsObserver(Handler handler) {
            super(handler);
        }
        //当短信数据库发生改变时，触发此方法
        @Override
        public void onChange(boolean selfChange) {
            System.out.println("您有新短信产生！");
            //获取游标，对数据库进行操作
            Cursor cursor = getContentResolver().query(Uri.parse("content://sms/outbox"), null, null, null, null);
            while(cursor.moveToNext()){
                StringBuilder sBuilder = new StringBuilder();
                sBuilder.append("id=").append(cursor.getInt(cursor.getColumnIndex("_id")));
                sBuilder.append(";address=").append(cursor.getString(cursor.getColumnIndex("address")));
                sBuilder.append(";body=").append(cursor.getString(cursor.getColumnIndex("body")));
                sBuilder.append(";time=").append(cursor.getString(cursor.getColumnIndex("date")));
                //Toast.makeText(MainActivity.this, sBuilder.toString(), Toast.LENGTH_LONG).show();
                String message = sBuilder.toString();
                System.out.println(message);
                TextView textView = (TextView) MainActivity.this.findViewById(R.id.tv_message);
                textView.setText("你有短信了\n"+message);
            }
            super.onChange(selfChange);
        }
            
            
            
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
}