AsyncQueryHandler

AsyncQueryHandler是Handler的子类，文档上说，如果处理ContentProvider相关的内容，不用需要自行定义一套东西， 而可以简单的使用async方式。我想指代的就应该是AsyncQueryHandler类。该类是一个典型的模板类，为ContentProvider 的增删改查提供了很好的接口，提供了一个解决架构，final了一些方法，置空了一些方法。通过派生，实例化一些方法（不是每个对 ContentProvider的处理多需要全部做增删改查，我想这也是该类默认置空一些方法而不是抽象一些方法的原因），来达到这个目的。在内部，该类 隐藏了多线程处理的细节，当你使用时，你会感觉异常便利。以query为例，你可以这么来用：

    // 定义一个handler，采用的是匿名类的方式，只处理query，因此只重写了onQueryComplete函数：
    queryHandler = new AsyncQueryHandler(this.getContentResolver()){ // 传入的是一个ContentResolver实例，所以必须在OnCreate后实例化该Handler类
    @Override
    protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
            // 在这里你可以获得一个cursor和你传入的附加的token和cookie。
            // 该方法在当前线程下（如果传入的是默认的Looper话），可以自由设定UI信息
        }
    };

    // 调用时只需要调用startQuery(int token, Object cookie, ContentURI uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)函数即可：

    queryHandler.startQuery(token, cookie, uri, projection, selection, selectionArgs, sortBy);

    1. 当你实例化一个AsyncQueryHandler类时（包括其子类...），它会单件构造一个线程（后面会详述...），这个线程里面会构建一个消息循环。
    2. 获得该消息循环的指针，用它做参数实例化另一个Handler类，该类为内部类。至此，就有了两个线程，各自有一个Handler来处理消息。
    3. 当调用onXXX的时候，在XXX函数内部会将请求封装成一个内部的参数类，将其作为消息的参数，将此消息发送至另一个线程。
    4. 在该线程的Handler中，接受该消息，并分析传入的参数，用初始化时传入的ContentResolver进行XXX操作，并返回Cursor或其他返回值。
    5. 构造一个消息，将上述返回值以及其他相关内容绑定在该消息上，发送回主线程。
    6. 主线程默认的AsyncQueryHandler类的handleMessage方法（可自定义，但由于都是内部类，基本没有意义...）会分析该消息，并转发给对应的onXXXComplete方法。
    7. 用户重写的onXXXComplete方法开始工作。

好了 直接上代码：

package org.dxt.list;

import static android.view.Window.PROGRESS_VISIBILITY_OFF;
import static android.view.Window.PROGRESS_VISIBILITY_ON;
import android.app.ListActivity;
import android.content.AsyncQueryHandler;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.widget.CursorAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
import android.widget.Toast;

public class AsyncQueryActivity extends ListActivity {

	private ListView myListView;
	private EditText myEditText_Name;
	private EditText myEditText_Tel;
	private String name = null;
	private String tel = null;
	
	private MyQueryHandler mAsyncQueryActivity;
	private CursorAdapter mCursorAdapter;
	private Cursor mCursor = null;
	private TextView mEmptyText;
	protected final static int MENU_ADD = Menu.FIRST;
	protected final static int MENU_UPDATE = Menu.FIRST + 1;
	protected final static int MENU_DELETE = Menu.FIRST + 2;
	protected final static int MENU_SEARCH = Menu.FIRST + 3;
	protected final static int MENU_SEARCH_ALL = Menu.FIRST + 4;
	protected final static int MENU_DELETE_ALL = Menu.FIRST + 5;

	protected static final String ADD = "add";
	protected static final String UPDATE = "update";
	protected static final String DELETE = "delete";
	protected static final String SEARCH = "search";
	protected static final String SEARCH_ALL = "search_all";
	protected static final String DELETE_ALL = "delete_all";

	
	private static final String[] COLUMN_NAMES = new String[] { MyUsers.User.USER_NAME, MyUsers.User.USER_TEL };
	protected static final int QUERY_TOKEN = 0;
	protected static final int INSERT_TOKEN = 1;
	protected static final int UPDATE_TOKEN = 2;
	protected static final int DELETE_TOKEN = 3;
	protected static final int DELETE_TOKEN_ALL = 4;
	protected static final int SEARCH_TOKEN = 5;
	protected int mInitialSelection = -1;
	
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// TODO Auto-generated method stub
		super.onCreateOptionsMenu(menu);
		menu.add(Menu.NONE, MENU_ADD, 0, R.string.ADD);
		menu.add(Menu.NONE, MENU_UPDATE, 0, R.string.EDIT);
		menu.add(Menu.NONE, MENU_DELETE, 0, R.string.DELETE);
		menu.add(Menu.NONE, MENU_SEARCH, 0, R.string.SEARCH);
		menu.add(Menu.NONE, MENU_SEARCH_ALL, 0, R.string.SEARCH_ALL);
		menu.add(Menu.NONE, MENU_DELETE_ALL, 0, R.string.DELETE_ALL);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// TODO Auto-generated method stub

		super.onOptionsItemSelected(item);
		switch (item.getItemId()) {
		case MENU_ADD:
			operation(ADD);
			break;
		case MENU_UPDATE:
			operation(UPDATE);
			break;
		case MENU_DELETE:
			operation(DELETE);
			break;
		case MENU_SEARCH:
			operation(SEARCH);
			break;
		case MENU_SEARCH_ALL:
			operation(SEARCH_ALL);
			break;
		case MENU_DELETE_ALL:
			operation(DELETE_ALL);
			break;
		default:
			break;
		}
		return true;
	}

	private void initWidget() {
//		int ScreenWidth = getWindowManager().getDefaultDisplay().getWidth();
//		int ScreenHight = getWindowManager().getDefaultDisplay().getHeight();
//		Log.d("tag", "ScreenWidth = " + ScreenWidth + "ScreenHight =  "
//				+ ScreenHight);
		myEditText_Name = (EditText) findViewById(R.id.EditText_Name);
		myEditText_Tel = (EditText) findViewById(R.id.EditText_Tel);
		myListView = (ListView) findViewById(android.R.id.list);
	}

	private void getUserInput() {
		name = myEditText_Name.getText().toString().trim();//  除去两头的空格
		tel = myEditText_Tel.getText().toString().trim();
	}

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.asnyclist);
		initWidget();
		mEmptyText = (TextView) findViewById(android.R.id.empty);
		mAsyncQueryActivity = new MyQueryHandler(getContentResolver());

	}

	@Override
	protected void onListItemClick(ListView l, View v, int position, long id) {
		// TODO Auto-generated method stub
		super.onListItemClick(l, v, position, id);
		Log.d("tag", "position------>" + position);// 在这个view上的位置
	}

	@Override
	protected void onResume() {
		// TODO Auto-generated method stub
		super.onResume();
		query();
	}

	@Override
	protected void onStop() {
		// TODO Auto-generated method stub
		super.onStop();
		if (mCursor != null) {
			mCursor.deactivate();
		}
	}
	
	private void query() {
		mAsyncQueryActivity.startQuery(QUERY_TOKEN, null,MyUsers.User.CONTENT_URI,null, null, null, "_id desc");
		displayProgress(true);
	}

	private void reQuery() {
		query();
	}

	private void displayProgress(boolean flag) {
		mEmptyText.setText(flag ? R.string.simContacts_emptyLoading
				: R.string.simContacts_empty);
		getWindow().setFeatureInt(Window.FEATURE_INDETERMINATE_PROGRESS,
				flag ? PROGRESS_VISIBILITY_ON : PROGRESS_VISIBILITY_OFF);
	}

	private void setAdapter() {

		if (mCursorAdapter == null) {
			mCursorAdapter = newAdapter();
			myListView.setAdapter(mCursorAdapter);
//			setListAdapter(mCursorAdapter);
		} else {
			mCursorAdapter.changeCursor(mCursor);
			myListView.invalidateViews();// 更新listview
		}

		if (mInitialSelection >= 0
				&& mInitialSelection < mCursorAdapter.getCount()) {
			setSelection(mInitialSelection);
			getListView().setFocusableInTouchMode(true);
			boolean gotfocus = getListView().requestFocus();
		}
	}

	protected CursorAdapter newAdapter() {
		return new SimpleCursorAdapter(this, R.layout.testlist, mCursor,
				COLUMN_NAMES, new int[] { R.id.name_text,
						R.id.tel_text });
	}

	private void operation(String cmd) {
		getUserInput();

		if (cmd.equals(ADD)) {
			insert();
		} else if (cmd.equals(UPDATE)) {
			update();
		} else if (cmd.equals(DELETE)) {
			delete();
		} else if (cmd.equals(SEARCH)) {
			search();
		} else if (cmd.equals(SEARCH_ALL)) {
			query();
		} else if (cmd.equals(DELETE_ALL)) {
			deleteAll();
//			reQuery();
		}

		myEditText_Name.setText("");
		myEditText_Tel.setText("");

	}

	private void insert() {
		if (name.equals("") || tel.equals("")) {
			Toast.makeText(this, "请输入您要插入数据的用户名！", Toast.LENGTH_SHORT).show();
		} else {
			ContentValues values = new ContentValues();
			values.put(MyUsers.User.USER_NAME, name);
			values.put(MyUsers.User.USER_TEL, tel);
			mAsyncQueryActivity.startInsert(INSERT_TOKEN, null,MyUsers.User.CONTENT_URI,values);
		}
	}

	private void delete() {
		if (name.equals("")) {
			Toast.makeText(this, "请输入您要删除数据的用户名！", Toast.LENGTH_SHORT).show();
		} else {
			mAsyncQueryActivity.startDelete(DELETE_TOKEN, null, MyUsers.User.CONTENT_URI, 
					MyUsers.User.USER_NAME+"=?", new String[]{name});
			Toast.makeText(this, "删除" + name + " 成功！", Toast.LENGTH_SHORT).show();
		}
	}

	private void update() {
		if (name.equals("")) {
			Toast.makeText(this, "请输入您要更新数据的用户名！", Toast.LENGTH_SHORT).show();
		} else if (tel.equals("")) {
			Toast.makeText(this, "请输入您要更新数值", Toast.LENGTH_SHORT).show();
		} else {
			ContentValues values = new ContentValues();
//			values.put(MyUsers.User.USER_NAME, name);
			values.put(MyUsers.User.USER_TEL, tel);
			mAsyncQueryActivity.startUpdate(UPDATE_TOKEN, null, MyUsers.User.CONTENT_URI, values,
					MyUsers.User.USER_NAME + "=?", new String[]{name});
				Toast.makeText(this, "更新为" + tel + " 成功！", Toast.LENGTH_SHORT).show();
		}
	}
	private void search() {
		if (name.equals("")) {
			Toast.makeText(this, "请输入您要查找数据的用户名！", Toast.LENGTH_SHORT).show();
		} else {
			mAsyncQueryActivity.startQuery(SEARCH_TOKEN, null, 
					MyUsers.User.CONTENT_URI, null,
					MyUsers.User.USER_NAME+"=?", new String[]{name}, null);
		}
	}

	private void deleteAll() {
		mAsyncQueryActivity.startDelete(DELETE_TOKEN_ALL, null, MyUsers.User.CONTENT_URI, null, null);
		Toast.makeText(this, "清空成功喽！", Toast.LENGTH_SHORT).show();
	}

	private class MyQueryHandler extends AsyncQueryHandler {

		public MyQueryHandler(ContentResolver cr) {
			super(cr);
			// TODO Auto-generated constructor stub
		}

		@Override
		protected void onDeleteComplete(int token, Object cookie, int result) {
			// TODO Auto-generated method stub
			super.onDeleteComplete(token, cookie, result);
			Log.d("tag", "onDeleteComplete--->"+result);
			reQuery();
		}

		@Override
		protected void onInsertComplete(int token, Object cookie, Uri uri) {
			// TODO Auto-generated method stub
			super.onInsertComplete(token, cookie, uri);
			Log.d("tag", "onInsertComplete--->");
			reQuery();
		}

		@Override
		protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
			// TODO Auto-generated method stub
			super.onQueryComplete(token, cookie, cursor);
			Log.d("tag", "onQueryComplete--->");
			
			mCursor = cursor;
			setAdapter();
			if(cursor.getCount()>0){
				displayProgress(false);
			}else{
				displayProgress(true);
			}
			
		}

		@Override
		protected void onUpdateComplete(int token, Object cookie, int result) {
			// TODO Auto-generated method stub
			super.onUpdateComplete(token, cookie, result);
			Log.d("tag", "onUpdateComplete--->");
			reQuery();
		}

	}
}