25.分批加载数据

   /**
     * 分批加载数据
     * @param startIndex  开始的位置
     * @param maxCount    每页展示的最大的条目
     * @return
     */
    public List<BlackNumberInfo> findPar2(int startIndex, int maxCount) {
        SQLiteDatabase db = helper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select number,mode from blacknumber limit ? offset ?", new String[]{String.valueOf(maxCount),
                String.valueOf(startIndex)});
        List<BlackNumberInfo> blackNumberInfos = new ArrayList<BlackNumberInfo>();
        while (cursor.moveToNext()) {
            BlackNumberInfo blackNumberInfo = new BlackNumberInfo();
            blackNumberInfo.setMode(cursor.getString(1));
            blackNumberInfo.setNumber(cursor.getString(0));
            blackNumberInfos.add(blackNumberInfo);
        }
        cursor.close();
        db.close();
        return blackNumberInfos;
    }
    /**
     * 获取总的记录数
     * @return
     */
    public int getTotalNumber(){
        SQLiteDatabase db = helper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select count(*) from blacknumber", null);
        cursor.moveToNext();
        int count = cursor.getInt(0);
        cursor.close();
        db.close();
        return count;
    }

public class CallSafeActivity extends Activity {
    private ListView list_view;
    private List<BlackNumberInfo> blackNumberInfos;
    private LinearLayout ll_pb;
    private BlackNumberDao dao;
    private CallSafeAdapter adapter;
    /**
     * 开始的位置
     */
    private int mStartIndex = 0;
    /**
     * 每页展示20条数据
     */
    private int maxCount = 20;
    /**
     * 一共有多少页面
     */
    private int totalPage;
    private int totalNumber;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_call_safe2);
        initUI();
        initData();
    }
    private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            ll_pb.setVisibility(View.INVISIBLE);
让数据继续停留在当前位置，两种实现方式：
 第一种：lv_call_sms_safe.setSelection(startIndex);//不推荐
 第二种：重复利用适配器，数据变化通知一下就行了
  private CallSmsSafeAdapter adapter;
  Handler里面修改成：
   if(adapter == null){
			adapter = new CallSmsSafeAdapter();
			lv_call_sms_safe.setAdapter(adapter);
	}else{
			//通知数据适配器更新一下界面
		adapter.notifyDataSetChanged();
	}
            if(adapter == null){
                adapter = new CallSafeAdapter(blackNumberInfos, CallSafeActivity.this);
                list_view.setAdapter(adapter);
            }else{
                adapter.notifyDataSetChanged();
            }
        }
    };
    private void initData() {
        dao = new BlackNumberDao(CallSafeActivity.this);
        //一共有多少条数据
        totalNumber = dao.getTotalNumber();
        new Thread() {
            @Override
            public void run() {
                //分批加载数据
                if (blackNumberInfos == null) {
                    blackNumberInfos = dao.findPar2(mStartIndex, maxCount);
                } else {
                    //把后面的数据。追加到blackNumberInfos集合里面。防止黑名单被覆盖
                    blackNumberInfos.addAll(dao.findPar2(mStartIndex, maxCount));
                }
                handler.sendEmptyMessage(0);
            }
        }.start();
    }
    /**
     * 添加黑名单
     *
     * @param view
     */
    public void addBlackNumber(View view) {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        final AlertDialog dialog = builder.create();
        View dialog_view = View.inflate(this, R.layout.dialog_add_black_number, null);
        final EditText et_number = (EditText) dialog_view.findViewById(R.id.et_number);
        Button btn_ok = (Button) dialog_view.findViewById(R.id.btn_ok);
        Button btn_cancel = (Button) dialog_view.findViewById(R.id.btn_cancel);
        final CheckBox cb_phone = (CheckBox) dialog_view.findViewById(R.id.cb_phone);
        final CheckBox cb_sms = (CheckBox) dialog_view.findViewById(R.id.cb_sms);
        btn_cancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dialog.dismiss();
            }
        });
        btn_ok.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String str_number = et_number.getText().toString().trim();
                if(TextUtils.isEmpty(str_number)){
                  Toast.makeText(CallSafeActivity.this,"请输入黑名单号码",Toast.LENGTH_SHORT).show();
                    return;
                }
                String mode = "";
                if(cb_phone.isChecked()&& cb_sms.isChecked()){
                    mode = "1";
                }else if(cb_phone.isChecked()){
                    mode = "2";
                }else if(cb_sms.isChecked()){
                    mode = "3";
                }else{
                    Toast.makeText(CallSafeActivity.this,"请勾选拦截模式",Toast.LENGTH_SHORT).show();
                    return;
                }
                BlackNumberInfo blackNumberInfo = new BlackNumberInfo();
                blackNumberInfo.setNumber(str_number);
                blackNumberInfo.setMode(mode);
                blackNumberInfos.add(0,blackNumberInfo);
                //把电话号码和拦截模式添加到数据库。
                dao.add(str_number,mode);
                dialog.dismiss();
            }
        });
        dialog.setView(dialog_view);
        dialog.show();
    }
    private void initUI() {
        ll_pb = (LinearLayout) findViewById(R.id.ll_pb);
        //展示加载的圆圈
        ll_pb.setVisibility(View.VISIBLE);
        list_view = (ListView) findViewById(R.id.list_view);
        //设置listview的滚动监听
        list_view.setOnScrollListener(new AbsListView.OnScrollListener() {
            //状态改变时候回调的方法
            /**
             *
             * @param view
             * @param scrollState  表示滚动的状态
             *
             *                     AbsListView.OnScrollListener.SCROLL_STATE_IDLE 闲置状态
             *                     AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL 手指触摸的时候的状态
             *                     AbsListView.OnScrollListener.SCROLL_STATE_FLING 惯性
             */
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                switch (scrollState) {
                    case AbsListView.OnScrollListener.SCROLL_STATE_IDLE:
                        //获取到最后一条显示的数据
                        int lastVisiblePosition = list_view.getLastVisiblePosition();
                        System.out.println("lastVisiblePosition==========" + lastVisiblePosition);
                            if(lastVisiblePosition == blackNumberInfos.size() - 1){
                                // 加载更多的数据。 更改加载数据的开始位置
                                mStartIndex += maxCount;
                                if (mStartIndex >= totalNumber) {
                                    Toast.makeText(getApplicationContext(),
                                            "没有更多的数据了。", Toast.LENGTH_SHORT).show();
                                    return;
                                }
                                initData();
                            }
                        break;
                }
            }
            //listview滚动的时候调用的方法
            //时时调用。当我们的手指触摸的屏幕的时候就调用
            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            }
        });
    }
    private class CallSafeAdapter extends MyBaseAdapter<BlackNumberInfo> {
        private CallSafeAdapter(List lists, Context mContext) {
            super(lists, mContext);
        }
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder holder;
            if (convertView == null) {
                convertView = View.inflate(CallSafeActivity.this, R.layout.item_call_safe, null);
                holder = new ViewHolder();
                holder.tv_number = (TextView) convertView.findViewById(R.id.tv_number);
                holder.tv_mode = (TextView) convertView.findViewById(R.id.tv_mode);
                holder.iv_delete = (ImageView) convertView.findViewById(R.id.iv_delete);
                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }
            holder.tv_number.setText(lists.get(position).getNumber());
            String mode = lists.get(position).getMode();
            if (mode.equals("1")) {
                holder.tv_mode.setText("来电拦截+短信");
            } else if (mode.equals("2")) {
                holder.tv_mode.setText("电话拦截");
            } else if (mode.equals("3")) {
                holder.tv_mode.setText("短信拦截");
            }
            final BlackNumberInfo info = lists.get(position);
            holder.iv_delete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String number = info.getNumber();
                    boolean result = dao.delete(number);
                    if (result) {
                        Toast.makeText(CallSafeActivity.this, "删除成功", Toast.LENGTH_SHORT).show();
                        lists.remove(info);
                        //刷新界面
                        adapter.notifyDataSetChanged();
                    } else {
                        Toast.makeText(CallSafeActivity.this, "删除失败", Toast.LENGTH_SHORT).show();
                    }
                }
            });
            return convertView;
        }
    }
    static class ViewHolder {
        TextView tv_number;
        TextView tv_mode;
        ImageView iv_delete;
    }
}