1. 编程圈首页
  2. 文库
  3. 移动开发

Android滚轮选择时间控件使用详解

滚轮选择控件Android自带的选择时间控件有点丑,往往产品和设计都比较嫌弃,希望做成ios一样的滚轮选择,下面是我在NumberPicker的基础上自定义的选择控件,效果如下: 原理 基于NumberPicker实现

滚轮选择控件

Android自带的选择时间控件有点丑,往往产品和设计都比较嫌弃,希望做成ios一样的滚轮选择,下面是我在NumberPicker的基础上自定义的选择控件,效果如下:

Android滚轮选择时间控件使用详解

原理

  • 基于NumberPicker实现
  • 动态填充数值
  • 联动
  • 接口监听回调

实现滚轮效果有github上mark比较多的WheelView,但是阅读源码发现数据是一次性填入的,选择时间的话,填入10年就是10*365=3650条数据,也就是new出三千多个TextView,想想都觉得恐怖,肯定是不行的,于是便想到用NumberPicker,动态填充数据,一次只设置5个数据,当选中变化时,重新设置数据填充,所以关键在于填充的数据的计算。

设置数据部分逻辑代码

  /**
   * 更新左侧控件
   * 日期:选择年控件
   * 时间:选择月份和日期控件
   *
   * @param timeMillis
   */
  private void updateLeftValue(long timeMillis) {
    SimpleDateFormat sdf;
    String str[] = new String[DATA_SIZE];
    if (mCurrentType == TYPE_PICK_DATE) {
      sdf = new SimpleDateFormat("yyyy");
      for (int i = 0; i < DATA_SIZE; i++) {
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(timeMillis);
        cal.add(Calendar.YEAR, (i - DATA_SIZE / 2));
        str[i] = sdf.format(cal.getTimeInMillis());
      }
    } else {
      sdf = new SimpleDateFormat("MM-dd EEE");
      for (int i = 0; i < DATA_SIZE; i++) {
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(timeMillis);
        cal.add(Calendar.DAY_OF_MONTH, (i - DATA_SIZE / 2));
        str[i] = sdf.format(cal.getTimeInMillis());
      }
    }
    mNpLeft.setDisplayedValues(str);
    mNpLeft.setValue(DATA_SIZE / 2);
    mNpLeft.postInvalidate();
  }

对滚轮的监听,并重新设置填充数据:

  @Override
  public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(mTimeMillis);
    int year = calendar.get(Calendar.YEAR);
    int month = calendar.get(Calendar.MONTH);
    int day = calendar.get(Calendar.DAY_OF_MONTH);
    int hour = calendar.get(Calendar.HOUR_OF_DAY);
    int offset = newVal - oldVal;
    if (picker == mNpLeft) {
      if (mCurrentType == TYPE_PICK_DATE) {
        calendar.add(Calendar.YEAR, offset);
      } else {
        calendar.add(Calendar.DAY_OF_MONTH, offset);
      }
      updateLeftValue(calendar.getTimeInMillis());
      mTimeMillis = calendar.getTimeInMillis();
    } else if (picker == mNpMiddle) {
      if (mCurrentType == TYPE_PICK_DATE) {
        calendar.add(Calendar.MONTH, offset);
        if (calendar.get(Calendar.YEAR) != year) {
          calendar.set(Calendar.YEAR, year);
        }
      } else {
        calendar.add(Calendar.HOUR_OF_DAY, offset);
        if (calendar.get(Calendar.DAY_OF_MONTH) != day) {
          calendar.set(Calendar.DAY_OF_MONTH, day);
        }
        if (calendar.get(Calendar.MONTH) != month) {
          calendar.set(Calendar.MONTH, month);
        }
        if (calendar.get(Calendar.YEAR) != year) {
          calendar.set(Calendar.YEAR, year);
        }
      }
      updateMiddleValue(calendar.getTimeInMillis());
      updateRightValue(calendar.getTimeInMillis());
      mTimeMillis = calendar.getTimeInMillis();
    } else if (picker == mNpRight) {
      if (mCurrentType == TYPE_PICK_DATE) {
        int days = getMaxDayOfMonth(year, month + 1);
        if(day == 1 && offset < 0){
          calendar.set(Calendar.DAY_OF_MONTH,days);
        }else if(day == days && offset > 0){
          calendar.set(Calendar.DAY_OF_MONTH,1);
        }else{
          calendar.add(Calendar.DAY_OF_MONTH, offset);
        }

        if (calendar.get(Calendar.MONTH) != month) {
          calendar.set(Calendar.MONTH, month);
        }
        if (calendar.get(Calendar.YEAR) != year) {
          calendar.set(Calendar.YEAR, year);
        }
        Log.e(TAG,"time:::"+test.format(calendar.getTimeInMillis()));
      } else {
        calendar.add(Calendar.MINUTE, offset);
        if (calendar.get(Calendar.HOUR_OF_DAY) != hour) {
          calendar.set(Calendar.HOUR_OF_DAY, hour);
        }
        if (calendar.get(Calendar.DAY_OF_MONTH) != day) {
          calendar.set(Calendar.DAY_OF_MONTH, day);
        }
        if (calendar.get(Calendar.MONTH) != month) {
          calendar.set(Calendar.MONTH, month);
        }
        if (calendar.get(Calendar.YEAR) != year) {
          calendar.set(Calendar.YEAR, year);
        }
      }
      updateRightValue(calendar.getTimeInMillis());
      mTimeMillis = calendar.getTimeInMillis();
    }
    /**
     * 向外部发送当前选中时间
     */
    if (mOnSelectedChangeListener != null) {
      mOnSelectedChangeListener.onSelected(this,mTimeMillis);
    }
    Log.e(TAG, "selected time:" + test.format(mTimeMillis));
  }

选择数值和字符串

同样的,使用NumberPicker进行封装,动态填充数值从而实现滚动变换的效果。

  • 考虑到通用性,传入的是Object类型的数组,在控件里进行判断。
  • 可以选择一列数值、两列数值、三列数值,字符串同理。每一列数值可以设置它的单位、标题等,默认是隐藏,需要自己设置。
  • 可以设置步长step

完整代码如下:

package com.example.moore.picktimeview.widget;

import android.content.Context;
import android.graphics.Color;
import android.util.AttributeSet;
import android.util.Log;
import android.view.Gravity;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.NumberPicker;
import android.widget.TextView;

/**
 * Created by Moore on 2016/10/21.
 */

public class PickValueView extends LinearLayout implements NumberPicker.OnValueChangeListener {
  private Context mContext;
  /**
   * 组件 标题、单位、滚轮
   */
  private TextView mTitleLeft, mTitleMiddle, mTitleRight;
  private TextView mUnitLeft, mUnitMiddle, mUnitRight;
  private MyNumberPicker mNpLeft, mNpMiddle, mNpRight;
  /**
   * 数据个数 1列 or 2列 or 3列
   */
  private int mViewCount = 1;
  /**
   * 一组数据长度
   */
  private final int DATA_SIZE = 3;

  /**
   * 需要设置的值与默认值
   */
  private Object[] mLeftValues;
  private Object[] mMiddleValues;
  private Object[] mRightValues;
  private Object mDefaultLeftValue;
  private Object mDefaultMiddleValue;
  private Object mDefaultRightValue;
  /**
   * 当前正在显示的值
   */
  private Object[] mShowingLeft = new Object[DATA_SIZE];
  private Object[] mShowingMiddle = new Object[DATA_SIZE];
  private Object[] mShowingRight = new Object[DATA_SIZE];

  /**
   * 步长
   */
  private int mLeftStep = 5;
  private int mMiddleStep = 1;
  private int mRightStep = 1;
  /**
   * 回调接口对象
   */
  private onSelectedChangeListener mSelectedChangeListener;

  public PickValueView(Context context) {
    super(context);
    this.mContext = context;
    generateView();
  }

  public PickValueView(Context context, AttributeSet attrs) {
    super(context, attrs);
    this.mContext = context;
    generateView();
  }

  public PickValueView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    this.mContext = context;
    generateView();
  }

  /**
   * 生成视图
   */
  private void generateView() {
    //标题
    LinearLayout titleLayout = new LinearLayout(mContext);
    LayoutParams titleParams = new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
    titleParams.setMargins(0, 0, 0, dip2px(12));
    titleLayout.setLayoutParams(new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
    titleLayout.setOrientation(HORIZONTAL);
    mTitleLeft = new TextView(mContext);
    mTitleMiddle = new TextView(mContext);
    mTitleRight = new TextView(mContext);

    LayoutParams params = new LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT, 1);
    TextView[] titles = new TextView[]{mTitleLeft, mTitleMiddle, mTitleRight};
    for (int i = 0; i < titles.length; i++) {
      titles[i].setLayoutParams(params);
      titles[i].setGravity(Gravity.CENTER);
      titles[i].setTextColor(Color.parseColor("#3434EE"));
    }
    titleLayout.addView(mTitleLeft);
    titleLayout.addView(mTitleMiddle);
    titleLayout.addView(mTitleRight);
    //内容
    LinearLayout contentLayout = new LinearLayout(mContext);
    contentLayout.setLayoutParams(new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
    contentLayout.setOrientation(HORIZONTAL);
    contentLayout.setGravity(Gravity.CENTER);
    mNpLeft = new MyNumberPicker(mContext);
    mNpMiddle = new MyNumberPicker(mContext);
    mNpRight = new MyNumberPicker(mContext);
    mUnitLeft = new TextView(mContext);
    mUnitMiddle = new TextView(mContext);
    mUnitRight = new TextView(mContext);

    MyNumberPicker[] nps = new MyNumberPicker[]{mNpLeft, mNpMiddle, mNpRight};
    for (int i = 0; i < nps.length; i++) {
      nps[i].setLayoutParams(params);
      nps[i].setDescendantFocusability(FOCUS_BLOCK_DESCENDANTS);
      nps[i].setOnValueChangedListener(this);
    }

    contentLayout.addView(mNpLeft);
    contentLayout.addView(mUnitLeft);
    contentLayout.addView(mNpMiddle);
    contentLayout.addView(mUnitMiddle);
    contentLayout.addView(mNpRight);
    contentLayout.addView(mUnitRight);

    this.setLayoutParams(new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
    this.setOrientation(VERTICAL);
    this.addView(titleLayout);
    this.addView(contentLayout);
  }

  /**
   * 初始化数据和值
   */
  private void initViewAndPicker() {
    if (mViewCount == 1) {
      this.mNpMiddle.setVisibility(GONE);
      this.mNpRight.setVisibility(GONE);
      this.mUnitMiddle.setVisibility(GONE);
      this.mUnitRight.setVisibility(GONE);
    } else if (mViewCount == 2) {
      this.mNpRight.setVisibility(GONE);
      this.mUnitRight.setVisibility(GONE);
    }

    //初始化数组值
    if (mLeftValues != null && mLeftValues.length != 0) {
      if (mLeftValues.length < DATA_SIZE) {
        for (int i = 0; i < mLeftValues.length; i++) {
          mShowingLeft[i] = mLeftValues[i];
        }
        for (int i = mLeftValues.length; i < DATA_SIZE; i++) {
          mShowingLeft[i] = -9999;
        }
      } else {
        for (int i = 0; i < DATA_SIZE; i++) {
          mShowingLeft[i] = mLeftValues[i];
        }
      }
      mNpLeft.setMinValue(0);
      mNpLeft.setMaxValue(DATA_SIZE - 1);
      if (mDefaultLeftValue != null)
        updateLeftView(mDefaultLeftValue);
      else
        updateLeftView(mShowingLeft[0]);
    }
    /**
     * 中间控件
     */
    if (mViewCount == 2 || mViewCount == 3) {
      if (mMiddleValues != null && mMiddleValues.length != 0) {
        if (mMiddleValues.length < DATA_SIZE) {
          for (int i = 0; i < mMiddleValues.length; i++) {
            mShowingMiddle[i] = mMiddleValues[i];
          }
          for (int i = mMiddleValues.length; i < DATA_SIZE; i++) {
            mShowingMiddle[i] = -9999;
          }
        } else {
          for (int i = 0; i < DATA_SIZE; i++) {
            mShowingMiddle[i] = mMiddleValues[i];
          }
        }
        mNpMiddle.setMinValue(0);
        mNpMiddle.setMaxValue(DATA_SIZE - 1);
        if (mDefaultMiddleValue != null)
          updateMiddleView(mDefaultMiddleValue);
        else
          updateMiddleView(mShowingMiddle[0]);
      }
    }

    /**
     * 右侧控件
     */
    if (mViewCount == 3) {
      if (mRightValues != null && mRightValues.length != 0) {
        if (mRightValues.length < DATA_SIZE) {
          for (int i = 0; i < mRightValues.length; i++) {
            mShowingRight[i] = mRightValues[i];
          }
          for (int i = mRightValues.length; i < DATA_SIZE; i++) {
            mShowingRight[i] = -9999;
          }
        } else {
          for (int i = 0; i < DATA_SIZE; i++) {
            mShowingRight[i] = mRightValues[i];
          }
        }
        mNpRight.setMinValue(0);
        mNpRight.setMaxValue(DATA_SIZE - 1);
        if (mDefaultRightValue != null)
          updateRightView(mDefaultRightValue);
        else
          updateRightView(mShowingRight[0]);
      }
    }


  }

  private void updateLeftView(Object value) {
    updateValue(value, 0);
  }

  private void updateMiddleView(Object value) {
    updateValue(value, 1);
  }

  private void updateRightView(Object value) {
    updateValue(value, 2);
  }

  /**
   * 更新滚轮视图
   *
   * @param value
   * @param index
   */
  private void updateValue(Object value, int index) {
    String showStr[] = new String[DATA_SIZE];
    MyNumberPicker picker;
    Object[] showingValue;
    Object[] values;
    int step;
    if (index == 0) {
      picker = mNpLeft;
      showingValue = mShowingLeft;
      values = mLeftValues;
      step = mLeftStep;
    } else if (index == 1) {
      picker = mNpMiddle;
      showingValue = mShowingMiddle;
      values = mMiddleValues;
      step = mMiddleStep;
    } else {
      picker = mNpRight;
      showingValue = mShowingRight;
      values = mRightValues;
      step = mRightStep;
    }

    if (values instanceof Integer[]) {
      for (int i = 0; i < DATA_SIZE; i++) {
        showingValue[i] = (int) value - step * (DATA_SIZE / 2 - i);
        int offset = (int) values[values.length - 1] - (int) values[0] + step;
        if ((int) showingValue[i] < (int) values[0]) {
          showingValue[i] = (int) showingValue[i] + offset;
        }
        if ((int) showingValue[i] > (int) values[values.length - 1]) {
          showingValue[i] = (int) showingValue[i] - offset;
        }
        showStr[i] = "" + showingValue[i];
      }
    } else {
      int strIndex = 0;
      for (int i = 0; i < values.length; i++) {
        if (values[i].equals(value)) {
          strIndex = i;
          break;
        }
      }
      for (int i = 0; i < DATA_SIZE; i++) {
        int temp = strIndex - (DATA_SIZE / 2 - i);
        if (temp < 0) {
          temp += values.length;
        }
        if (temp >= values.length) {
          temp -= values.length;
        }
        showingValue[i] = values[temp];
        showStr[i] = (String) values[temp];
      }
    }
    picker.setDisplayedValues(showStr);
    picker.setValue(DATA_SIZE / 2);
    picker.postInvalidate();
  }


  @Override
  public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
    if (picker == mNpLeft) {
      updateLeftView(mShowingLeft[newVal]);
    } else if (picker == mNpMiddle) {
      updateMiddleView(mShowingMiddle[newVal]);
    } else if (picker == mNpRight) {
      updateRightView(mShowingRight[newVal]);
    }
    if (mSelectedChangeListener != null) {
      mSelectedChangeListener.onSelected(this, mShowingLeft[DATA_SIZE / 2], mShowingMiddle[DATA_SIZE / 2], mShowingRight[DATA_SIZE / 2]);
    }
  }

  /**
   * 设置数据--单列数据
   *
   * @param leftValues
   * @param mDefaultLeftValue
   */
  public void setValueData(Object[] leftValues, Object mDefaultLeftValue) {
    this.mViewCount = 1;
    this.mLeftValues = leftValues;
    this.mDefaultLeftValue = mDefaultLeftValue;

    initViewAndPicker();
  }

  /**
   * 设置数据--两列数据
   *
   * @param leftValues
   * @param mDefaultLeftValue
   * @param middleValues
   * @param defaultMiddleValue
   */
  public void setValueData(Object[] leftValues, Object mDefaultLeftValue, Object[] middleValues, Object defaultMiddleValue) {
    this.mViewCount = 2;
    this.mLeftValues = leftValues;
    this.mDefaultLeftValue = mDefaultLeftValue;

    this.mMiddleValues = middleValues;
    this.mDefaultMiddleValue = defaultMiddleValue;

    initViewAndPicker();
  }

  /**
   * 设置数据--三列数据
   *
   * @param leftValues
   * @param mDefaultLeftValue
   * @param middleValues
   * @param defaultMiddleValue
   * @param rightValues
   * @param defaultRightValue
   */
  public void setValueData(Object[] leftValues, Object mDefaultLeftValue, Object[] middleValues, Object defaultMiddleValue, Object[] rightValues, Object defaultRightValue) {
    this.mViewCount = 3;
    this.mLeftValues = leftValues;
    this.mDefaultLeftValue = mDefaultLeftValue;

    this.mMiddleValues = middleValues;
    this.mDefaultMiddleValue = defaultMiddleValue;

    this.mRightValues = rightValues;
    this.mDefaultRightValue = defaultRightValue;

    initViewAndPicker();
  }

  /**
   * 设置左边数据步长
   *
   * @param step
   */
  public void setLeftStep(int step) {
    this.mLeftStep = step;
    initViewAndPicker();
  }

  /**
   * 设置中间数据步长
   *
   * @param step
   */
  public void setMiddleStep(int step) {
    this.mMiddleStep = step;
    initViewAndPicker();
  }

  /**
   * 设置右边数据步长
   *
   * @param step
   */
  public void setRightStep(int step) {
    this.mRightStep = step;
    initViewAndPicker();
  }

  /**
   * 设置标题
   *
   * @param left
   * @param middle
   * @param right
   */
  public void setTitle(String left, String middle, String right) {
    if (left != null) {
      mTitleLeft.setVisibility(VISIBLE);
      mTitleLeft.setText(left);
    } else {
      mTitleLeft.setVisibility(GONE);
    }
    if (middle != null) {
      mTitleMiddle.setVisibility(VISIBLE);
      mTitleMiddle.setText(middle);
    } else {
      mTitleMiddle.setVisibility(GONE);
    }
    if (right != null) {
      mTitleRight.setVisibility(VISIBLE);
      mTitleRight.setText(right);
    } else {
      mTitleRight.setVisibility(GONE);
    }
    this.postInvalidate();
  }

  public void setUnitLeft(String unitLeft) {
    setUnit(unitLeft, 0);
  }

  public void setmUnitMiddle(String unitMiddle) {
    setUnit(unitMiddle, 1);
  }

  public void setUnitRight(String unitRight) {
    setUnit(unitRight, 2);
  }

  private void setUnit(String unit, int index) {
    TextView tvUnit;
    if (index == 0) {
      tvUnit = mUnitLeft;
    } else if (index == 1) {
      tvUnit = mUnitMiddle;
    } else {
      tvUnit = mUnitRight;
    }
    if (unit != null) {
      tvUnit.setText(unit);
    } else {
      tvUnit.setText(" ");
    }
    initViewAndPicker();
  }

  /**
   * 设置回调
   *
   * @param listener
   */
  public void setOnSelectedChangeListener(onSelectedChangeListener listener) {
    this.mSelectedChangeListener = listener;
  }

  /**
   * dp转px
   *
   * @param dp
   * @return
   */
  private int dip2px(int dp) {
    float scale = mContext.getResources().getDisplayMetrics().density;
    return (int) (scale * dp + 0.5f);
  }

  /**
   * 回调接口
   */
  public interface onSelectedChangeListener {
    void onSelected(PickValueView view, Object leftValue, Object middleValue, Object rightValue);
  }
}

关于NumberPicker

默认的NumberPicker往往字体颜色、分割线颜色等都是跟随系统,不能改变,考虑到可能比较丑或者有其他需求,所以自定义的NumberPicker,通过反射的方式更改里面的一些属性,代码如下:

package com.example.moore.picktimeview.widget;

import android.content.Context;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.NumberPicker;

import java.lang.reflect.Field;

/**
 * Created by Moore on 2016/10/20.
 */

public class MyNumberPicker extends NumberPicker {
  private static int mTextSize = 16;
  private static int mTextColor = 0x000000;
  private static int mDividerColor = 0xFFFF00;

  public MyNumberPicker(Context context) {
    super(context);
    setNumberPickerDividerColor();
  }

  public MyNumberPicker(Context context, AttributeSet attrs) {
    super(context, attrs);
    setNumberPickerDividerColor();
  }

  public MyNumberPicker(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    setNumberPickerDividerColor();
  }

  @Override
  public void addView(View child) {
    super.addView(child);
    updateView(child);
  }

  @Override
  public void addView(View child, int index, ViewGroup.LayoutParams params) {
    super.addView(child, index, params);
    updateView(child);
  }

  @Override
  public void addView(View child, ViewGroup.LayoutParams params) {
    super.addView(child, params);
    updateView(child);
  }

  private void updateView(View view) {
    if (view instanceof EditText) {
//      ((EditText) view).setTextSize(mTextSize);
      ((EditText) view).setTextSize(17);
//      ((EditText) view).setTextColor(mTextColor);
      ((EditText) view).setTextColor(Color.parseColor("#6495ED"));
    }
  }

  private void setNumberPickerDividerColor() {
    Field[] pickerFields = NumberPicker.class.getDeclaredFields();
    /**
     * 设置分割线颜色
     */
    for (Field pf : pickerFields) {
      if (pf.getName().equals("mSelectionDivider")) {
        pf.setAccessible(true);
        try {
//          pf.set(this, new ColorDrawable(mDividerColor));
          pf.set(this, new ColorDrawable(Color.parseColor("#C4C4C4")));
        } catch (IllegalAccessException e) {
          e.printStackTrace();
        }
        break;
      }
    }
    /**
     * 设置分割线高度
     */
    for (Field pf : pickerFields) {
      if (pf.getName().equals("mSelectionDividerHeight")) {
        pf.setAccessible(true);
        try {
          pf.set(this, 2);
        } catch (IllegalAccessException e) {
          e.printStackTrace();
        }
        break;
      }
    }
    for (Field pf : pickerFields) {
      if (pf.getName().equals("mSelectorElementHeight")) {
        pf.setAccessible(true);
        try {
          pf.set(this, 2);
        } catch (IllegalAccessException e) {
          e.printStackTrace();
        }
        break;
      }
    }
  }

  public void setDividerColor(int color) {
    this.mDividerColor = color;
//    this.postInvalidate();
  }

  public void setTextColor(int color) {
    this.mTextColor = color;
//    this.postInvalidate();
  }

  public void setTextSize(int textSize) {
    this.mTextSize = textSize;
//    this.postInvalidate();
  }
}

完整Demo可前往github查看与下载,地址:https://github.com/lizebinbin/PickTimeView.git 谢谢!

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持编程圈

发布者:编程圈,转转请注明出处:https://www.bianchengquan.com/article/202342.html

发表评论

登录后才能评论