18 Loader代码案例

• 目录结构:
  
  

• MainActivity.java 代码:

  package com.qf.day18_loader_demo2;
  
  import android.app.Activity;
  import android.app.LoaderManager.LoaderCallbacks;
  import android.content.Loader;
  import android.database.ContentObserver;
  import android.database.Cursor;
  import android.net.Uri;
  import android.os.Bundle;
  import android.os.Handler;
  import android.widget.ListView;
  import android.widget.SearchView;
  import android.widget.SearchView.OnQueryTextListener;
  import android.widget.SimpleCursorAdapter;
  
  public class MainActivity extends Activity implements LoaderCallbacks<Cursor>{
  
      private ListView lv;
      private SimpleCursorAdapter adapter;
  
      private SearchView sv;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          lv = (ListView) findViewById(R.id.lv);
          sv = (SearchView) findViewById(R.id.sv);
  
          sv.setOnQueryTextListener(new OnQueryTextListener() {
  
              @Override
              public boolean onQueryTextSubmit(String query) {
                  // TODO Auto-generated method stub
                  return false;
              }
  
              @Override
              public boolean onQueryTextChange(String newText) {
                  // TODO Auto-generated method stub
  
                  Bundle bundle = new Bundle();
                  bundle.putString("key", newText.toString());
  
                  getLoaderManager().restartLoader(1, bundle, MainActivity.this);
                  return false;
              }
          });
  
          adapter = new SimpleCursorAdapter(
                  MainActivity.this, R.layout.item,null,
                  new String[]{"address","body"},
                  new int[]{R.id.tv_adress,R.id.tv_body},
                  SimpleCursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);
  
          lv.setAdapter(adapter);
  
          //初始化Loader对象
          getLoaderManager().initLoader(1, null, this);
  
          /**
           * 注册观察者对象    给当前Uri
           * 参数1:Uri对象
           * 参数2:   如果返回true    检测到 content:sms    content:sms/address   content:sms/address/iii
           *        如果返回false    只能检测到当前的content:sms
           *
           * 参数3:观察者
           *
           */
          getContentResolver().registerContentObserver(
                  Uri.parse("content://sms"), true, new MyContentObserver(null));
      }
  
      @Override
      public Loader<Cursor> onCreateLoader(int id, Bundle args) {
          // 实例化Loader对象  并返回
          SmsLoader smsLoader = new SmsLoader(MainActivity.this,args);
          return smsLoader;
          //看个人喜好情况使用 两种方式 如果使用以下方式 请删除上面的
  //       Uri smsUri = Uri.parse("content://sms");
  //       String[] colums = {"_id","address","body"};
  //       String selection = null;
  //       String[] selectionArgs = null;
  //
  //      CursorLoader cursorLoader = new CursorLoader(MainActivity.this, smsUri, colums, selection, selectionArgs, null);
  //      return cursorLoader;
      }
  
      @Override
      public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
          // TODO Auto-generated method stub
          adapter.swapCursor(data);
      }
  
      @Override
      public void onLoaderReset(Loader<Cursor> loader) {
          // TODO Auto-generated method stub
          adapter.swapCursor(null);
      }
  
      /**
       * 自定义的观察者
       * @author sxy
       *
       */
      class MyContentObserver extends ContentObserver{
  
          public MyContentObserver(Handler handler) {
              super(handler);
              // TODO Auto-generated constructor stub
          }
  
          //当你的数据发生改变时  调用此方法
          @Override
          public void onChange(boolean selfChange) {
              // TODO Auto-generated method stub
              super.onChange(selfChange);
              //重启Loader
              getLoaderManager().restartLoader(1, null, MainActivity.this);
          }
  
      }
  
  }
  

• SmsLoader.java

  package com.qf.day18_loader_demo2;
  
  import android.content.AsyncTaskLoader;
  import android.content.Context;
  import android.database.Cursor;
  import android.net.Uri;
  import android.os.Bundle;
  import android.util.Log;
  
  /**
   * 自定义的AsyncTaskLoader
   *
   *
   */
  public class SmsLoader extends AsyncTaskLoader<Cursor> {
  
      private Uri smsUri = Uri.parse("content://sms");
      private String[] colums = {"_id","address","body"};
      private String selection = null;
      private String[] selectionArgs = null;
  
  //  private Bundle bundle;
  
      public SmsLoader(Context context,Bundle bundle) {
          super(context);
          // TODO Auto-generated constructor stub
  //      this.bundle = bundle;
          if(bundle!=null){
              selection = "body like ?";
              selectionArgs = new String[]{"%"+bundle.getString("key")+"%"};
          }
      }
  
      /**
       * Ui线程执行
       */
      @Override
      protected void onStartLoading() {
          // TODO Auto-generated method stub
          super.onStartLoading();
  
          Log.e("AAA", "==>"+Thread.currentThread().getName());
          forceLoad();//必须执行    强制向下执行 不然此类无效
      }
  
      /**
       * 耗时操作  工作线程   可以执行查询操作
       */
      @Override
      public Cursor loadInBackground() {
          // TODO Auto-generated method stub
  
          Log.e("AAA", "==>"+Thread.currentThread().getName());
  //      Log.e("AAA", "=selection=>"+selection);
  //      Log.e("AAA", "=selectionArgs=>"+selectionArgs[0]);
          Cursor cursor = getContext().getContentResolver().query(
                  smsUri, colums, selection, selectionArgs, null);
  
          return cursor;
      }
  
  }
  

• activity_main.xml

  <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"
      tools:context=".MainActivity" >
  
      <SearchView
          android:id="@+id/sv"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          ></SearchView>
  
      <ListView
          android:id="@+id/lv"
          android:layout_width="match_parent"
          android:layout_height="match_parent" />
  
  </LinearLayout>

• item.xml

  <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"
      tools:context=".MainActivity" >
  
      <SearchView
          android:id="@+id/sv"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          ></SearchView>
  
      <ListView
          android:id="@+id/lv"
          android:layout_width="match_parent"
          android:layout_height="match_parent" />
  
  </LinearLayout>