Android自定义组件系列【9】——Canvas绘制折线图

有时候我们在项目中会遇到使用折线图等图形，Android的开源项目中为我们提供了很多插件，但是很多时候我们需要根据具体项目自定义这些图表，这一篇文章我们一起来看看如何在Android中使用Canvas绘制折线图。先看看绘制的效果：



实现原理很简单，我就直接给出代码：
package com.example.testcanvasdraw;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.View;

public class MyView extends View{
private int XPoint = 60;
private int YPoint = 260;
private int XScale = 8; //刻度长度
private int YScale = 40;
private int XLength = 380;
private int YLength = 240;

private int MaxDataSize = XLength / XScale;

private List<Integer> data = new ArrayList<Integer>();

private String[] YLabel = new String[YLength / YScale];

private Handler handler = new Handler(){
public void handleMessage(Message msg) {
if(msg.what == 0x1234){
MyView.this.invalidate();
}
};
};
public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
for(int i=0; i<YLabel.length; i++){
YLabel[i] = (i + 1) + "M/s";
}

new Thread(new Runnable() {

@Override
public void run() {
while(true){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
if(data.size() >= MaxDataSize){
data.remove(0);
}
data.add(new Random().nextInt(4) + 1);
handler.sendEmptyMessage(0x1234);
}
}
}).start();
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint = new Paint();
paint.setStyle(Paint.Style.STROKE);
paint.setAntiAlias(true); //去锯齿
paint.setColor(Color.BLUE);

//画Y轴
canvas.drawLine(XPoint, YPoint - YLength, XPoint, YPoint, paint);

//Y轴箭头
canvas.drawLine(XPoint, YPoint - YLength, XPoint - 3, YPoint-YLength + 6, paint); //箭头
canvas.drawLine(XPoint, YPoint - YLength, XPoint + 3, YPoint-YLength + 6 ,paint);

//添加刻度和文字
for(int i=0; i * YScale < YLength; i++) {
canvas.drawLine(XPoint, YPoint - i * YScale, XPoint + 5, YPoint - i * YScale, paint); //刻度

canvas.drawText(YLabel[i], XPoint - 50, YPoint - i * YScale, paint);//文字
}

//画X轴
canvas.drawLine(XPoint, YPoint, XPoint + XLength, YPoint, paint);
System.out.println("Data.size = " + data.size());
if(data.size() > 1){
for(int i=1; i<data.size(); i++){
canvas.drawLine(XPoint + (i-1) * XScale, YPoint - data.get(i-1) * YScale,
XPoint + i * XScale, YPoint - data.get(i) * YScale, paint);
}
}
}
}
上面绘制折线部分我们还有一种方式同样可以实现：
if(data.size() > 1){
Path path = new Path();
path.moveTo(XPoint, YPoint - data.get(0) * YScale);
for(int i=1; i<data.size(); i++){
path.lineTo(XPoint + i * XScale, YPoint - data.get(i) * YScale);
}
canvas.drawPath(path, paint);
}下面我们将上面代码修改，让折线下面的区域颜色填充



package com.example.testcanvasdraw;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.View;
/**
*
* @author 阳光小强
* http://blog.csdn.net/dawanganban *
*/
public class MyView extends View {
private int XPoint = 60;
private int YPoint = 260;
private int XScale = 8; // 刻度长度
private int YScale = 40;
private int XLength = 380;
private int YLength = 240;

private int MaxDataSize = XLength / XScale;

private List<Integer> data = new ArrayList<Integer>();

private String[] YLabel = new String[YLength / YScale];

private Handler handler = new Handler() {
public void handleMessage(Message msg) {
if (msg.what == 0x1234) {
MyView.this.invalidate();
}
};
};

public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
for (int i = 0; i < YLabel.length; i++) {
YLabel[i] = (i + 1) + "M/s";
}

new Thread(new Runnable() {

@Override
public void run() {
while (true) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (data.size() >= MaxDataSize) {
data.remove(0);
}
data.add(new Random().nextInt(4) + 1);
handler.sendEmptyMessage(0x1234);
}
}
}).start();
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint = new Paint();
paint.setStyle(Paint.Style.STROKE);
paint.setAntiAlias(true); // 去锯齿
paint.setColor(Color.BLUE);

// 画Y轴
canvas.drawLine(XPoint, YPoint - YLength, XPoint, YPoint, paint);

// Y轴箭头
canvas.drawLine(XPoint, YPoint - YLength, XPoint - 3, YPoint - YLength
+ 6, paint); // 箭头
canvas.drawLine(XPoint, YPoint - YLength, XPoint + 3, YPoint - YLength
+ 6, paint);

// 添加刻度和文字
for (int i = 0; i * YScale < YLength; i++) {
canvas.drawLine(XPoint, YPoint - i * YScale, XPoint + 5, YPoint - i
* YScale, paint); // 刻度

canvas.drawText(YLabel[i], XPoint - 50, YPoint - i * YScale, paint);// 文字
}

// 画X轴
canvas.drawLine(XPoint, YPoint, XPoint + XLength, YPoint, paint);

// 绘折线
/*
* if(data.size() > 1){ for(int i=1; i<data.size(); i++){
* canvas.drawLine(XPoint + (i-1) * XScale, YPoint - data.get(i-1) *
* YScale, XPoint + i * XScale, YPoint - data.get(i) * YScale, paint); }
* }
*/
paint.setStyle(Paint.Style.FILL);
if (data.size() > 1) {
Path path = new Path();
path.moveTo(XPoint, YPoint);
for (int i = 0; i < data.size(); i++) {
path.lineTo(XPoint + i * XScale, YPoint - data.get(i) * YScale);
}
path.lineTo(XPoint + (data.size() - 1) * XScale, YPoint);
canvas.drawPath(path, paint);
}
}
}
上面的效果有时候还是达不到我们的要求，我们将代码修改后效果如下：



package com.example.testcanvasdraw;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.View;

/**
*
* @author 阳光小强 http://blog.csdn.net/dawanganban *
*/
public class MyView extends View {
private int XPoint = 60;
private int YPoint = 260;
private int XScale = 8; // 刻度长度
private int YScale = 40;
private int XLength = 380;
private int YLength = 240;

private int MaxDataSize = XLength / XScale;

private List<Integer> data = new ArrayList<Integer>();

private String[] YLabel = new String[YLength / YScale];

private Handler handler = new Handler() {
public void handleMessage(Message msg) {
if (msg.what == 0x1234) {
MyView.this.invalidate();
}
};
};

public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
for (int i = 0; i < YLabel.length; i++) {
YLabel[i] = (i + 1) + "M/s";
}

new Thread(new Runnable() {

@Override
public void run() {
while (true) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (data.size() >= MaxDataSize) {
data.remove(0);
}
data.add(new Random().nextInt(4) + 1);
handler.sendEmptyMessage(0x1234);
}
}
}).start();
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint = new Paint();
paint.setStyle(Paint.Style.STROKE);
paint.setAntiAlias(true); // 去锯齿
paint.setColor(Color.BLUE);

// 画Y轴
canvas.drawLine(XPoint, YPoint - YLength, XPoint, YPoint, paint);

// Y轴箭头
canvas.drawLine(XPoint, YPoint - YLength, XPoint - 3, YPoint - YLength
+ 6, paint); // 箭头
canvas.drawLine(XPoint, YPoint - YLength, XPoint + 3, YPoint - YLength
+ 6, paint);

// 添加刻度和文字
for (int i = 0; i * YScale < YLength; i++) {
canvas.drawLine(XPoint, YPoint - i * YScale, XPoint + 5, YPoint - i
* YScale, paint); // 刻度

canvas.drawText(YLabel[i], XPoint - 50, YPoint - i * YScale, paint);// 文字
}

// 画X轴
canvas.drawLine(XPoint, YPoint, XPoint + XLength, YPoint, paint);

// 绘折线
/*
* if(data.size() > 1){ for(int i=1; i<data.size(); i++){
* canvas.drawLine(XPoint + (i-1) * XScale, YPoint - data.get(i-1) *
* YScale, XPoint + i * XScale, YPoint - data.get(i) * YScale, paint); }
* }
*/
paint.setColor(Color.RED);
paint.setStrokeWidth(5);

Paint paint2 = new Paint();
paint2.setColor(Color.BLUE);
paint2.setStyle(Paint.Style.FILL);
if (data.size() > 1) {
Path path = new Path();
Path path2 = new Path();
path.moveTo(XPoint, YPoint - data.get(0) * YScale);
path2.moveTo(XPoint, YPoint);
for (int i = 0; i < data.size(); i++) {
path.lineTo(XPoint + i * XScale, YPoint - data.get(i) * YScale);
path2.lineTo(XPoint + i * XScale, YPoint - data.get(i) * YScale);
}
path2.lineTo(XPoint + (data.size() - 1) * XScale, YPoint);
canvas.drawPath(path, paint);
canvas.drawPath(path2, paint2);
}
}
}
感谢你对“阳光小强"的关注，我的另一篇博文很荣幸参加了CSDN举办的博文大赛，如果你觉的小强的博文对你有帮助，请为小强投上你宝贵的一票，投票地址：http://vote.blog.csdn.net/Article/Details?articleid=30101091