自定義CursorLoader基本原理簡單介紹

 

一、在配置清單添加須要的權限

 

 <uses-permission android:name="android.permission.READ_SMS"/>

 

 

二、res/layout下2個佈局activity_main.xml佈局和item_activity.xml佈局

 

activity_main.xml佈局

 

代碼

 

 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="${relativePackage}.${activityClass}" >

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
         />

</RelativeLayout>

 

 

================

 

 

item_activity.xml佈局

 

代碼

 

 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/text_phone"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
         />
    <TextView
        android:id="@+id/text_content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
         />

</LinearLayout>

 

 

 

==============================

 

 

三、MainActivity.java類

 

代碼

 

 

/**
 *
 * @author  Administrator
 * 自定義CursorLoader要實現LoaderCallbacks類觀察者的原理
 *
 */
public class MainActivity extends Activity {

 private String uri_sms = "content://sms";
 private ListView listView;
 private SimpleCursorAdapter adapter;
 private Cursor cursor;

 private boolean issameObject;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  this.listView = (ListView) this.findViewById(R.id.listview);

  adapter = new SimpleCursorAdapter(this, R.layout.item_activity, cursor,
    new String[] { "body", "address" }, new int[] {
      R.id.text_phone, R.id.text_content },
    CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);
  listView.setAdapter(adapter);
         
  new MyAsynTask().execute();
 }

 class MyAsynTask extends AsyncTask<Void, Void, Cursor> {

  @Override
  protected void onPreExecute() {
   super.onPreExecute();
  }

  @Override
  protected Cursor doInBackground(Void... params) {
   ContentResolver resolver = getContentResolver();
   // 查詢數據庫
   cursor = resolver.query(Uri.parse(uri_sms), new String[] { "_id",
     "body", "address" }, null, null, "date desc");
   return cursor;
  }

  @Override
  protected void onPostExecute(Cursor result) {
   super.onPostExecute(result);
   // 註冊一個觀察者
   result.registerContentObserver(new Observer(null));
   //交換數據
   adapter.swapCursor(result);
   issameObject = false;
  }

  // 觀察者類 要繼承ContentObserver類
  class Observer extends ContentObserver {

   public Observer(Handler handler) {
    super(handler);
   }
   @Override//註冊對象發生改變 都要觸發該方法
   public void onChange(boolean selfChange) {
    if (issameObject) {//若是註冊的對象 是同一個 什麼都不作
     return;
    }
    new MyAsynTask().execute();//若是註冊對象改變了 就從新啓動MyAsynTask類
    issameObject = true;//改變標誌
   }

  }

 }}