Android编程实现canvas绘制柱状统计图功能【自动计算宽高及分度值、可左右滑动】

本文实例讲述了Android编程实现canvas绘制柱状统计图功能。分享给大家供大家参考，具体如下：

这里实现了一个简单的柱状统计图，如下：

特点：

1.根据数据源自动计算每个条目的高度、宽度、间距，自动计算分度值。

2.当条目数较多时，可左右滑动查看全部内容，图形、文字同步滑动，并且松手后会渐渐的停下来（而不是立刻停下来）。

代码：

（1）核心代码：BarChartView.Java

package com.sina.appbarchart;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Rect;
import android.support.annotation.NonNull;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
/**
 * 自定义组件：条形统计图
 * Created by hanj on 14-12-30.
 */
public class BarChartView extends View {
 private int screenW, screenH;
 private BarChartItemBean[] mItems;
 //max value in mItems.
 private float maxValue;
 //max height of the bar
 private int maxHeight;
 private int[] mBarColors = new int[]{Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW, Color.MAGENTA, Color.CYAN};
 private Paint barPaint, linePaint, textPaint;
 private Rect barRect, leftWhiteRect, rightWhiteRect;
 private Path textPath;
 private int leftMargin, topMargin, smallMargin;
 //the width of one bar item
 private int barItemWidth;
 //the spacing between two bar items.
 private int barSpace;
 //the width of the line.
 private int lineStrokeWidth;
 /**
  * The x-position of y-index and the y-position of the x-index..
  */
 private float x_index_startY, y_index_startX;
 private Bitmap arrowBmp;
 private Rect x_index_arrowRect, y_index_arrowRect;
 private static final int BG_COLOR = Color.parseColor("#E5E5E5");
 public BarChartView(Context context, AttributeSet attrs) {
  super(context, attrs);
  init(context);
 }
 private void init(Context context) {
  screenW = ScreenUtils.getScreenW(context);
  screenH = ScreenUtils.getScreenH(context);
  leftMargin = ScreenUtils.dp2px(context, 16);
  topMargin = ScreenUtils.dp2px(context, 40);
  smallMargin = ScreenUtils.dp2px(context, 6);
  barPaint = new Paint();
  barPaint.setColor(mBarColors[0]);
  linePaint = new Paint();
  lineStrokeWidth = ScreenUtils.dp2px(context, 1);
  linePaint.setStrokeWidth(lineStrokeWidth);
  textPaint = new Paint();
  textPaint.setAntiAlias(true);
  barRect = new Rect(0, 0, 0, 0);
  textPath = new Path();
  leftWhiteRect = new Rect(0, 0, 0, screenH);
  rightWhiteRect = new Rect(screenW - leftMargin, 0, screenW, screenH);
  arrowBmp = BitmapFactory.decodeResource(context.getResources(), R.drawable.arrow_up);
 }
 //标记是否已经获取过状态拉的高度
 private boolean statusHeightHasGet;
 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  if (!statusHeightHasGet) {
   subStatusBarHeight();
   statusHeightHasGet = true;
  }
  //draw background
  canvas.drawColor(BG_COLOR);
  //bounds
  checkLeftMoving();
  textPaint.setTextSize(ScreenUtils.dp2px(getContext(), 16));
  for (int i = 0; i < mItems.length; i++) {
   //draw bar rect
   barRect.left = (int) y_index_startX + barItemWidth * i + barSpace * (i + 1) - (int) leftMoving;
   barRect.top = topMargin * 2 + (int) (maxHeight * (1.0f - mItems[i].itemValue / maxValue));
   barRect.right = barRect.left + barItemWidth;
   barPaint.setColor(mBarColors[i % mBarColors.length]);
   canvas.drawRect(barRect, barPaint);
   //draw type text
   String typeText = mItems[i].itemType;
   float textPathStartX = barRect.left + barItemWidth / 2 -
     (float) (Math.sin(Math.PI / 6)) * textPaint.measureText("好") / 2;
   float textPathStartY = barRect.bottom;
   textPath.reset();
   textPath.moveTo(textPathStartX, textPathStartY);
   textPath.lineTo(textPathStartX + (float) (1000 * Math.tan(Math.PI / 6)), textPathStartY + 1000);
   canvas.drawTextOnPath(typeText, textPath, smallMargin * 1.5f, smallMargin * 2, textPaint);
   //draw value text
   String valueText = String.valueOf(mItems[i].itemValue);
   canvas.drawText(valueText, barRect.left - (textPaint.measureText(valueText) - barItemWidth) / 2,
     barRect.top - smallMargin, textPaint);
  }
  //draw left white space and right white space
  int c = barPaint.getColor();
  barPaint.setColor(BG_COLOR);
  leftWhiteRect.right = (int) y_index_startX;
  canvas.drawRect(leftWhiteRect, barPaint);
  canvas.drawRect(rightWhiteRect, barPaint);
  barPaint.setColor(c);
  //draw x-index line.
  canvas.drawLine(
    y_index_startX - lineStrokeWidth / 2,
    x_index_startY,
    screenW - leftMargin,
    x_index_startY,
    linePaint);
  //draw y-index line.
  canvas.drawLine(
    y_index_startX,
    x_index_startY + lineStrokeWidth / 2,
    y_index_startX,
    topMargin / 2,
    linePaint);
  canvas.drawBitmap(arrowBmp, null, y_index_arrowRect, null);
  canvas.save();
  canvas.rotate(90, (x_index_arrowRect.left + x_index_arrowRect.right) / 2, (x_index_arrowRect.top + x_index_arrowRect.bottom) / 2);
  canvas.drawBitmap(arrowBmp, null, x_index_arrowRect, null);
  canvas.restore();
  //draw division value
  int maxDivisionValueHeight = (int) (maxHeight * 1.0f / maxValue * maxDivisionValue);
  textPaint.setTextSize(ScreenUtils.dp2px(getContext(), 10));
  for (int i = 1; i <= 10; i++) {
   float startY = barRect.bottom - maxDivisionValueHeight * 0.1f * i;
   if (startY < topMargin / 2) {
    break;
   }
   canvas.drawLine(y_index_startX, startY, y_index_startX + 10, startY, linePaint);
   String text = String.valueOf(maxDivisionValue * 0.1f * i);
   canvas.drawText(text,
     y_index_startX - textPaint.measureText(text) - 5,
     startY + textPaint.measureText("0") / 2,
     textPaint);
  }
 }
 private float leftMoving;
 private float lastPointX;
 private float movingLeftThisTime = 0.0f;
 @Override
 public boolean onTouchEvent(@NonNull MotionEvent event) {
  int type = event.getAction();
  switch (type) {
   case MotionEvent.ACTION_DOWN:
    lastPointX = event.getRawX();
    break;
   case MotionEvent.ACTION_MOVE:
    float x = event.getRawX();
    movingLeftThisTime = lastPointX - x;
    leftMoving += movingLeftThisTime;
    lastPointX = x;
    invalidate();
    break;
   case MotionEvent.ACTION_UP:
    //smooth scroll
    new Thread(new SmoothScrollThread(movingLeftThisTime)).start();
    break;
   default:
    return super.onTouchEvent(event);
  }
  return true;
 }
 /**
  * Check the value of leftMoving to ensure that the view is not out of the screen.
  */
 private void checkLeftMoving() {
  if (leftMoving < 0) {
   leftMoving = 0;
  }
  if (leftMoving > (maxRight - minRight)) {
   leftMoving = maxRight - minRight;
  }
 }
 public BarChartItemBean[] getItems() {
  return mItems;
 }
 public void setItems(BarChartItemBean[] items) {
  if (items == null) {
   throw new RuntimeException("BarChartView.setItems(): the param items cannot be null.");
  }
  if (items.length == 0) {
   return;
  }
  this.mItems = items;
  //Calculate the max value.
  maxValue = items[0].itemValue;
  for (BarChartItemBean bean : items) {
   if (bean.itemValue > maxValue) {
    maxValue = bean.itemValue;
   }
  }
  //Calculate the max division value.
  getRange(maxValue, 0);
  //Get the width of each bar.
  getBarItemWidth(screenW, items.length);
  //Refresh the view.
  invalidate();
 }
 private int maxRight, minRight;
 /**
  * Get the width of each bar which is depended on the screenW and item count.
  */
 private void getBarItemWidth(int screenW, int itemCount) {
  //The min width of the bar is 50dp.
  int minBarWidth = ScreenUtils.dp2px(getContext(), 40);
  //The min width of spacing.
  int minBarSpacing = ScreenUtils.dp2px(getContext(), 30);
  barItemWidth = (screenW - leftMargin * 2) / (itemCount + 3);
  barSpace = (screenW - leftMargin * 2 - barItemWidth * itemCount) / (itemCount + 1);
  if (barItemWidth < minBarWidth || barSpace < minBarSpacing) {
   barItemWidth = minBarWidth;
   barSpace = minBarSpacing;
  }
  maxRight = (int) y_index_startX + lineStrokeWidth + (barSpace + barItemWidth) * mItems.length;
  minRight = screenW - leftMargin - barSpace;
 }
 /**
  * Sub the height of status bar and action bar to get the accurate height of screen.
  */
 private void subStatusBarHeight() {
  //The height of the status bar
  int statusHeight = ScreenUtils.getStatusBarHeight((Activity) getContext());
  //The height of the actionBar
  ActionBar ab = ((ActionBarActivity) getContext()).getSupportActionBar();
  int abHeight = ab == null ? 0 : ab.getHeight();
  screenH -= (statusHeight + abHeight);
  barRect.top = topMargin * 2;
  barRect.bottom = screenH - topMargin * 3;
  maxHeight = barRect.bottom - barRect.top;
  x_index_startY = barRect.bottom;
  x_index_arrowRect = new Rect(screenW - leftMargin, (int) (x_index_startY - 10),
    screenW - leftMargin + 10, (int) (x_index_startY + 10));
 }
 //The max and min division value.
 private float maxDivisionValue, minDivisionValue;
 //Get the max and min division value by the max and min value in mItems.
 private void getRange(float maxValue, float minValue) {
  //max
  int scale = Utility.getScale(maxValue);
  float unscaledValue = (float) (maxValue / Math.pow(10, scale));
  maxDivisionValue = (float) (getRangeTop(unscaledValue) * Math.pow(10, scale));
  y_index_startX = getDivisionTextMaxWidth(maxDivisionValue) + 10;
  y_index_arrowRect = new Rect((int) (y_index_startX - 5), topMargin / 2 - 20,
    (int) (y_index_startX + 5), topMargin / 2);
 }
 private float getRangeTop(float value) {
  //value: [1,10)
  if (value < 1.2) {
   return 1.2f;
  }
  if (value < 1.5) {
   return 1.5f;
  }
  if (value < 2.0) {
   return 2.0f;
  }
  if (value < 3.0) {
   return 3.0f;
  }
  if (value < 4.0) {
   return 4.0f;
  }
  if (value < 5.0) {
   return 5.0f;
  }
  if (value < 6.0) {
   return 6.0f;
  }
  if (value < 8.0) {
   return 8.0f;
  }
  return 10.0f;
 }
 /**
  * Get the max width of the division value text.
  */
 private float getDivisionTextMaxWidth(float maxDivisionValue) {
  Paint textPaint = new Paint();
  textPaint.setTextSize(ScreenUtils.dp2px(getContext(), 10));
  float max = textPaint.measureText(String.valueOf(maxDivisionValue * 0.1f));
  for (int i = 2; i <= 10; i++) {
   float w = textPaint.measureText(String.valueOf(maxDivisionValue * 0.1f * i));
   if (w > max) {
    max = w;
   }
  }
  return max;
 }
 /**
  * Use this thread to create a smooth scroll after ACTION_UP.
  */
 private class SmoothScrollThread implements Runnable {
  float lastMoving;
  boolean scrolling = true;
  private SmoothScrollThread(float lastMoving) {
   this.lastMoving = lastMoving;
   scrolling = true;
  }
  @Override
  public void run() {
   while (scrolling) {
    long start = System.currentTimeMillis();
    lastMoving = (int) (0.9f * lastMoving);
    leftMoving += lastMoving;
    checkLeftMoving();
    postInvalidate();
    if (Math.abs(lastMoving) < 5) {
     scrolling = false;
    }
    long end = System.currentTimeMillis();
    if (end - start < 20) {
     try {
      Thread.sleep(20 - (end - start));
     } catch (InterruptedException e) {
      e.printStackTrace();
     }
    }
   }
  }
 }
 /**
  * A model class to keep the bar item info.
  */
 static class BarChartItemBean {
  private String itemType;
  private float itemValue;
  public BarChartItemBean(String itemType, float itemValue) {
   this.itemType = itemType;
   this.itemValue = itemValue;
  }
 }
}

（2）该自定义组件的使用：

package com.sina.appbarchart;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
public class MainActivity extends ActionBarActivity {
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  BarChartView barChartView = (BarChartView) findViewById(R.id.bar_chart);
  BarChartView.BarChartItemBean[] items = new BarChartView.BarChartItemBean[]{
    new BarChartView.BarChartItemBean("餐饮", 300),
    new BarChartView.BarChartItemBean("学习", 200),
    new BarChartView.BarChartItemBean("旅行", 270),
    new BarChartView.BarChartItemBean("购物", 110),
    new BarChartView.BarChartItemBean("人际关系", 120),
    new BarChartView.BarChartItemBean("娱乐", 80),
    new BarChartView.BarChartItemBean("投资", 110),
    new BarChartView.BarChartItemBean("教育", 280)
  };
  barChartView.setItems(items);
 }
}

完整实例代码点击此处本站下载。

更多关于Android相关内容感兴趣的读者可查看本站专题：《Android图形与图像处理技巧总结》、《Android开发入门与进阶教程》、《Android调试技巧与常见问题解决方法汇总》、《Android基本组件用法总结》、《Android视图View技巧总结》、《Android布局layout技巧总结》及《Android控件用法总结》

希望本文所述对大家Android程序设计有所帮助。