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。
