7.数据库、Contentobserver

public class MySqliteHelper extends SQLiteOpenHelper{
	public MySqliteHelper(Context context, String name, int version) {
		super(context, name, null, version);
	}
	public static final String TABLE_GROUPS = "groups";
	public static final String TABLE_THREAD_GROUPS = "thread_groups";
	
	@Override
	public void onCreate(SQLiteDatabase db) {
		
		db.execSQL("create table groups(_id integer primary key autoincrement, group_name varchar(20));");
		
		db.execSQL("create table thread_groups(_id integer primary key autoincrement, group_id integer, thread_id integer);");
		
	}
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		
	}
}

public class DBUtils {
	/**
	 * 用于更新cursor 的URI
	 */
	private static final Uri uri = Uri.parse("content://www.itheima.com");
	private Context ctx;
	
	private MySqliteHelper sqlHelper;
	
	private DBUtils(Context ctx){
		this.ctx = ctx;
		sqlHelper = new MySqliteHelper(ctx, "heima39", 1);
		
	}
	
	private  static DBUtils instance;
	
	public static synchronized DBUtils getInstance(Context ctx){
		
		if(instance == null){
			instance = new DBUtils(ctx);
		}
		return instance;
	}
	/**
	 * 创建新群组
	 * @param name 群组的名称
	 */
	public void createNewGroup(String name) {
		SQLiteDatabase db = sqlHelper.getWritableDatabase();
		
		ContentValues values = new ContentValues();
		
		values.put("group_name", name);
		
		db.insert(MySqliteHelper.TABLE_GROUPS, "_id", values);
		
		notifyCursor();
		
	}
	/**
	 * 查询所有的群组信息
	 * @return
	 */
	public Cursor getAllGroup() {
		SQLiteDatabase db = sqlHelper.getReadableDatabase();
		
		Cursor cursor = db.query(MySqliteHelper.TABLE_GROUPS, null, null, null, null, null, null);
		// android.database.sqlite.SQLiteCursor
		System.out.println(cursor);
		
		//为cursor 设置 通知提醒的URI 
		cursor.setNotificationUri(ctx.getContentResolver(), uri);
		
		return cursor;
	}
	/**
	 * 通知cursor 群组表中的内容已经发生变化
	 * @param cursor
	 */
	private void notifyCursor() {
		// 让内容处理者，根据URI 发出更新通知
		ctx.getContentResolver().notifyChange(uri, null);
	}
	/**
	 * 通过群组ID删除群组
	 * @param groupId
	 */
	public void deleteGroupById(int groupId) {
		SQLiteDatabase db = sqlHelper.getWritableDatabase();
		
		db.delete(MySqliteHelper.TABLE_GROUPS, " _id = "+groupId, null);
		
		notifyCursor();
	}
	/**
	 * 更新群组名称
	 * @param groupId 群组的ID
	 * @param name 群组的新名
	 */
	public void updateGroupById(int groupId, String name) {
		SQLiteDatabase db = sqlHelper.getWritableDatabase();
		
		ContentValues values = new ContentValues();
		
		values.put("group_name", name);
		
		db.update(MySqliteHelper.TABLE_GROUPS, values, " _id = "+groupId , null);
		
		notifyCursor();
	}
	/**
	 * 将会话ID和群组ID 插入到会话群组关系 表中
	 * @param threadId
	 * @param groupId
	 */
	public void insertThradIdAndGroupId(int threadId, int groupId) {
		SQLiteDatabase db = sqlHelper.getWritableDatabase();
		
		ContentValues values = new ContentValues();
		
		values.put("thread_id", threadId);
		values.put("group_id", groupId);
		
		db.insert(MySqliteHelper.TABLE_THREAD_GROUPS,null, values);
		
	}
	/**
	 * 返回所有的指定群组ID的会话信息
	 * @param groupId
	 * @return
	 */
	public Cursor getAllThreadIdByGroupId(int groupId) {
		SQLiteDatabase db = sqlHelper.getReadableDatabase();
		Cursor cursor = db.query(MySqliteHelper.TABLE_THREAD_GROUPS, null, " group_id = "+groupId, null, null, null, null);
		return cursor;
	}
}

public class GroupUI extends ListActivity implements OnItemLongClickListener, OnItemClickListener{
	
	private ListView listView;
	private Context ctx;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		ctx = this;
		listView = getListView();
		adapter = new GropListAdapter(this, null);
		listView.setAdapter(adapter);
		
		listView.setOnItemLongClickListener(this);
		
		listView.setOnItemClickListener(this);
		
		prepareData();
	}
	private void prepareData() {
		
		DBUtils dbu = DBUtils.getInstance(ctx);
		Cursor cursor = dbu.getAllGroup();
		adapter.changeCursor(cursor);
		
	}
	private GropListAdapter adapter;
	
	class GropListAdapter extends CursorAdapter{
		public GropListAdapter(Context context, Cursor c) {
			super(context, c);
		}
		@Override
		public View newView(Context context, Cursor cursor, ViewGroup parent) {
			View view = View.inflate(context, R.layout.list_item_group, null);
			
			TextView name = (TextView) view.findViewById(R.id.tv_name_group);
			
			view.setTag(name);
			
			return view;
		}
		@Override
		public void bindView(View view, Context context, Cursor cursor) {
			
			TextView name = (TextView) view.getTag();
			
			name.setText(cursor.getString(cursor.getColumnIndex("group_name")));
			
		}
	}
	
	
	@Override
	/**
	 * 创建菜单
	 */
	public boolean onCreateOptionsMenu(Menu menu) {
		// 将 资料ID对应的文件转换为 菜单条目 ，并添加至  menu 中
		getMenuInflater().inflate(R.menu.activity_group, menu);
		return true;
	}
	
	@Override
	/**
	 * 响应菜单的点击事件
	 */
	public boolean onOptionsItemSelected(MenuItem item) {
		switch (item.getItemId()) {
		case R.id.menu_new_group:
			
			showCreateGroupDialog();
			
			break;
		}
		return true;
	}
	private AlertDialog dialog;
	
	/**
	 * 显示新建群组对话框
	 */
	private void showCreateGroupDialog() {
		AlertDialog.Builder adb =new AlertDialog.Builder(ctx);
		dialog = adb.create();
		View view = View.inflate(ctx, R.layout.dialog_new_group, null);
		final EditText etInputName = (EditText) view.findViewById(R.id.et_input_new_group);
		Button btnOk = (Button) view.findViewById(R.id.btn_ok);
		btnOk.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				String name = etInputName.getText().toString();
				if(TextUtils.isEmpty(name)){
					Toast.makeText(ctx, "请输入群组名称", 0).show();
					return ;
				}
				// 将群组名称保存至数据库
				DBUtils dbu = DBUtils.getInstance(ctx);
				dbu.createNewGroup(name);
				dialog.dismiss();
			}
		});
		dialog.setView(view,0,0,0,0);
		dialog.show();
		
	}
	@Override
	/**
	 * 响应listview条目的长按事件
	 */
	public boolean onItemLongClick(AdapterView<?> parent, View view,
			int position, long id) {
		
		showEditGroupDialog(position);
		
		return true;
	}
	/**
	 * 显示编辑群组对话框 
	 * @param position
	 */
	private void showEditGroupDialog(final int position) {
		
		AlertDialog.Builder adb = new AlertDialog.Builder(ctx);
		
		String items[]=new String[]{"编辑","删除"};
		
		adb.setItems(items, new DialogInterface.OnClickListener() {
			@Override
			/**
			 * which 是点击的条目的位置
			 */
			public void onClick(DialogInterface dialog, int which) {
				if(which == 0){ // “编辑”
					showUpdateGroupDialog(position);
				}else{ // 删除
					showConfirmDeleteDialog(position);
				}
				
			}
		});
		
		adb.show();
		
	}
	/**
	 * 显示确认删除的对话框
	 * @param position
	 */
	protected void showConfirmDeleteDialog(final int position) {
		AlertDialog.Builder adb = new AlertDialog.Builder(ctx);
		adb.setTitle("删除群组");
		adb.setMessage("确定要删除这个群吗？");
		adb.setNegativeButton("确定", new DialogInterface.OnClickListener() {
			
			@Override
			public void onClick(DialogInterface dialog, int which) {
				// 删除对应的群组
				DBUtils dbu = DBUtils.getInstance(ctx);
				Cursor cursor = adapter.getCursor();
				cursor.moveToPosition(position);
				int groupId = cursor.getInt(0); // 获得第0列的值，即，_id 这一列的值
				dbu.deleteGroupById(groupId);
				
				dialog.dismiss();
			}
		});
		adb.setPositiveButton("取消", null);
		adb.show();
		
	}
	/**
	 * 显示更新群组的对话框 
	 * @param position
	 */
	protected void showUpdateGroupDialog(final int position) {
		
		AlertDialog.Builder adb =new AlertDialog.Builder(ctx);
		dialog = adb.create();
		
		View view = View.inflate(ctx, R.layout.dialog_new_group, null);
		
		TextView title = (TextView) view.findViewById(R.id.tv_title_dialog);
		title.setText("更新群组名称");
		
		final EditText etInputName = (EditText) view.findViewById(R.id.et_input_new_group);
		Button btnOk = (Button) view.findViewById(R.id.btn_ok);
		
		btnOk.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				String name = etInputName.getText().toString();
				if(TextUtils.isEmpty(name)){
					Toast.makeText(ctx, "请输入群组名称", 0).show();
					return ;
				}
				// 将群组名称保存至数据库
				DBUtils dbu = DBUtils.getInstance(ctx);
				
				Cursor cursor = adapter.getCursor();
				cursor.moveToPosition(position);
				
				int groupId = cursor.getInt(0); // 获得群组ID
				
				dbu.updateGroupById(groupId,name);
				
				dialog.dismiss();
			}
		});
		dialog.setView(view,0,0,0,0);
		dialog.show();
	}
	@Override
	/**
	 * 响应listview条目点击事件
	 */
	public void onItemClick(AdapterView<?> parent, View view, int position,
			long id) {
		
		Cursor cursor = adapter.getCursor();
		cursor.moveToPosition(position);
		int groupId = cursor.getInt(0); // 返回群组ID
		
		DBUtils dbu =DBUtils.getInstance(ctx);
		Cursor cursor2 =  dbu.getAllThreadIdByGroupId(groupId);
		if(cursor2.getCount() == 0){ // 该群组没有人
			Toast.makeText(ctx, "该群还没有人，快回点人气吧", 0).show();
		}else{
			// 如果有人的话，希望能过cursor2 拼凑出如： thread_id in (1,2);
			
			String subSql = convertCursor2Str(cursor2);
			
			System.out.println("subSql"+subSql);
			
			Intent intent = new Intent(this,ConversationUI.class);
			intent.putExtra("subSql", subSql);
			
			startActivity(intent);
			
		}
	}
	/**
	 * 根据cursor中的内容，拼凑出 如   thread_id in (1,2); 的字符串
	 * @param cursor2
	 * @return
	 */
	private String convertCursor2Str(Cursor cursor) {
		cursor.moveToPosition(-1);
		StringBuilder sb=new StringBuilder("  thread_id in ( ");
		while(cursor.moveToNext()){
			String threadId = cursor.getString(cursor.getColumnIndex("thread_id"));
			sb.append(threadId+",");  //  thread_id in (1,
		}
	//  thread_id in (1,2,3,4,
		sb.replace(sb.lastIndexOf(","), sb.length(), ")");
		
		return sb.toString();
	}
}