折线图(四)计算坐标轴文字大小，确定准确位置

Paint xValuePaint = new Paint(); //画笔
xValuePaint.setColor(Color.BLACK);
xValuePaint.setTextSize(textSize);
xValuePaint.getTextBounds(xName, 0, xName.length(), nRect);
int nWith = nRect.width();//获取x轴名字长度
int nHeight = nRect.height();//获取x轴名字高度

<?xml version="1.0" encoding="utf-8"?>
<resources>

<declare-styleable name="LineChartView">

<!-- 视图padding -->
<attr name="chartPadding" format="dimension"></attr>

<!-- x轴单位 长度-->
<attr name="xUnit" format="dimension"></attr>

<!-- x轴单位值-->
<attr name="xValue" format="integer"></attr>

<!-- 单位字体大小-->
<attr name="unitTextSize" format="dimension"></attr>

<!-- y轴单位名称-->
<attr name="xName" format="string"></attr>

<!-- x轴单位 长度-->
<attr name="yUnit" format="dimension"></attr>

<!-- x轴单位值-->
<attr name="yValue" format="integer"></attr>

<!-- x轴单位名称-->
<attr name="yName" format="string"></attr>

</declare-styleable>

</resources>

/**
* 绘制折线图详情
*/
public class LineChartView extends View

{

/**
* 折线图padding
*/
private float chardPading;

/**
* x单位长度
*/
private float xUnit;

/**
* y单位长度
*/
private float yUnit;

private float textSize;

/**
* 单位名字
*/
private String xName;

/**
* 单位值
*/
private int xValue;

private String yName;

private int yValue;

public LineChartView(Context context, AttributeSet attrs) {
super(context, attrs);
//获取提供的chardPading长度， 如果不提供，默认为100px. 注意，拿到的dip单位最终会转化为px
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.LineChartView);
chardPading = typedArray.getDimension(R.styleable.LineChartView_chartPadding, 100);//默认视图距离边界的长度
xUnit = typedArray.getDimension(R.styleable.LineChartView_xUnit, 50);//默认单位长度为50px
xName = typedArray.getString(R.styleable.LineChartView_xName);//x 轴 名字
xName = null != xName ? xName : "x";//如果不提供名字，则默认为x
xValue = typedArray.getInt(R.styleable.LineChartView_xValue, 10);//默认单位值为10
textSize = typedArray.getDimension(R.styleable.LineChartView_unitTextSize, 25);//默认25px字体大小
yUnit =  typedArray.getDimension(R.styleable.LineChartView_yUnit, xUnit);//默认单位值为与xUnit一样
yName = typedArray.getString(R.styleable.LineChartView_yName);//y 轴 名字
yName = null != yName ? yName : "y";//如果不提供名字，则默认为y
yValue = typedArray.getInt(R.styleable.LineChartView_yValue, xValue);//默认单位值与xValue一样
}

@Override
protected void onDraw(Canvas canvas) {
//绘制坐标轴
drawAxis(canvas);
//绘制x坐标轴详情
drawX_AxisState(canvas);
drawY_AxisState(canvas);

}

/**
* 为了不遮住坐标轴，给予100padding给它
*/
int arrowPadding = 40;

/**
* 绘制x轴名称，按提供的长度来标识长度值
*
* @param canvas
*/
private void drawX_AxisState(Canvas canvas) {
Paint paint = new Paint(); //直线画笔

paint.setColor(Color.BLACK);//设置画笔为黑色
paint.setStrokeWidth(2);//设置画笔尖大小为2px
int height = getMeasuredHeight() - (int) chardPading;
int drawXlengh = getMeasuredWidth() - (int) chardPading * 2 - arrowPadding;//保留能看到箭头
int xUnit = (int) this.xUnit;
Rect nRect = new Rect();
Paint xValuePaint = new Paint(); //画笔
xValuePaint.setColor(Color.BLACK);
xValuePaint.setTextSize(textSize);
xValuePaint.getTextBounds(xName, 0, xName.length(), nRect);
int nWith = nRect.width();//获取x轴名字长度
int nHeight = nRect.height();//获取x轴名字高度
canvas.drawText(xName, getMeasuredWidth() - chardPading - nWith / 2, height + nHeight + 15, xValuePaint);
for (int i = xUnit, j = 1; i < drawXlengh; i += xUnit, j++) {
canvas.drawLine(chardPading + i, height, chardPading + i, height - 15, paint);
int drawvalue = xValue * j;
Rect rect = new Rect();
xValuePaint.getTextBounds(drawvalue + "", 0, (drawvalue + "").length(), rect);
int txtWith = rect.width();
int txtHeght = rect.height();
canvas.drawText(drawvalue + "", chardPading + i - txtWith / 2, height + txtHeght + 15, xValuePaint);
}
}

/**
* 绘制y轴名称，按提供的长度来标识长度值
*
* @param canvas
*/
private void drawY_AxisState(Canvas canvas) {
Paint paint = new Paint(); //直线画笔
Paint yValuePaint = new Paint(); //画笔
yValuePaint.setColor(Color.BLACK);
yValuePaint.setTextSize(textSize);
paint.setColor(Color.BLACK);//设置画笔为黑色
paint.setStrokeWidth(2);//设置画笔尖大小为2px
int height = getMeasuredHeight() - (int) chardPading;
int drawYlengh = getMeasuredHeight() - (int) chardPading * 2 - arrowPadding;//保留能看到箭头
int yUnit = (int) this.yUnit;
Rect nRect = new Rect();
yValuePaint.getTextBounds(yName, 0, yName.length(), nRect);
int nWith = nRect.width();
int nHeight = nRect.height();
canvas.drawText(yName, chardPading - nWith - 15, chardPading + nHeight / 2, yValuePaint);
for (int i = yUnit, j = 1; i < drawYlengh; i += yUnit, j++) {
int drawvalue = yValue * j;
Rect rect = new Rect();
yValuePaint.getTextBounds(drawvalue + "", 0, (drawvalue + "").length(), rect);
int txtWith = rect.width();
int txtHeght = rect.height();
canvas.drawLine(chardPading, height - i, chardPading + 15, height - i, paint);
canvas.drawText(drawvalue + "", chardPading - txtWith - 15, height - i + txtHeght / 2, yValuePaint);
}
}

/**
* 绘制坐标轴， 并且设置100padding给LineChartView
*
* @param canvas
*/
private void drawAxis(Canvas canvas) {
int chartViewHeight = getMeasuredHeight(); //获取LineChartView高度
int charViewWidth = getMeasuredWidth(); //获取LineChartView宽度
Paint paint = new Paint(); //画笔
paint.setColor(Color.BLACK);//设置画笔为黑色
paint.setStrokeWidth(4);//设置画笔尖大小为4px

/*
* 绘制直线.在2点之间连线
* startX 起点的x坐标
* startY 起点的y坐标
* endX 终点的x坐标
* endY 终点的y坐标
* canvas.drawLine（startX, startY, endX, endY）
*/

//绘制直线paddingTop 了chardPading的y轴
canvas.drawLine(chardPading, chartViewHeight - chardPading, chardPading, chardPading, paint);

//绘制y轴左边半边箭头
canvas.drawLine(chardPading, chardPading, chardPading - 10, chardPading + 10, paint);

//绘制y轴右边半边箭头
canvas.drawLine(chardPading, chardPading, chardPading + 10, chardPading + 10, paint);

//绘制直线paddingLeft 了chardPading的x轴,
canvas.drawLine(chardPading, chartViewHeight - chardPading, charViewWidth - chardPading, chartViewHeight - chardPading, paint);

//绘制x轴上半部分箭头
canvas.drawLine(charViewWidth - chardPading, chartViewHeight - chardPading, charViewWidth - chardPading - 10, chartViewHeight - chardPading - 10, paint);

//绘制x轴下半部分箭头
canvas.drawLine(charViewWidth - chardPading, chartViewHeight - chardPading, charViewWidth - chardPading - 10, chartViewHeight - chardPading + 10, paint);
}

}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="折线图(四)"
android:layout_centerHorizontal="true"
/>

<sam.android.utils.widget.LineChartView
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:chartPadding="30dp"
app:xValue="10"
app:xUnit="30dp"
app:xName="x轴"
app:unitTextSize="12sp"
app:yValue="10"
app:yUnit="30dp"
app:yName="y轴"
/>

</RelativeLayout>