MPAndroidChart - 为什么线不显示? [英] MPAndroidChart - why line not showing?

问题描述

我想创建一个带有时间表的小应用程序.但是由于某种原因，当我在图表中添加很多点时，它根本没有出现，尽管使用少量点一切正常.

I want to create a small application with a schedule. But for some reason, when I add a lot of points to the chart, it simply does not appear, although with a small number of points everything works.

   void f() {
 ArrayList<Entry> values = new ArrayList<>();

    for (int i = x1, index = 0, j = y; i < x2; ++i, ++index)
    {
        float waveLength = (float) calib_a * i +  (float) calib_b;
        int pixel = rotated.getPixel(i, j);
        float I = (Color.red(pixel) + Color.blue(pixel) + Color.green(pixel)) / 765.0f;
        values.add(new Entry((int) waveLength, I));
        Log.d("[SPECTRAl]", " WAVE:  " +waveLength + "  I: " + I);
       // i += 4;
    }



    LineDataSet lineValues = new LineDataSet(values, "");

    lineValues.setColor(Color.BLACK);
    lineValues.setLineWidth(2f);
    LineData line = new LineData(lineValues);
    chart.getXAxis().setGranularity(100f);
    chart.setData(line);
    chart.invalidate();
}

但与:

   void f() {
 ArrayList<Entry> values = new ArrayList<>();

 values.add(new Entry(100, 6));
 values.add(new Entry(200, 3));
 values.add(new Entry(300, 2));
 values.add(new Entry(400, 4));



    LineDataSet lineValues = new LineDataSet(values, "");

    lineValues.setColor(Color.BLACK);
    lineValues.setLineWidth(2f);
    LineData line = new LineData(lineValues);
    chart.getXAxis().setGranularity(100f);
    chart.setData(line);
    chart.invalidate();
}

推荐答案

以下代码创建问题:

 for (int i = x1, index = 0, j = y; i < x2; ++i, ++index)
{
    float waveLength = (float) calib_a * i +  (float) calib_b;
    int pixel = rotated.getPixel(i, j);
    float I = (Color.red(pixel) + Color.blue(pixel) + Color.green(pixel)) / 765.0f;
    values.add(new Entry((int) waveLength, I));
    Log.d("[SPECTRAl]", " WAVE:  " +waveLength + "  I: " + I);
   // i += 4;
}

首先，您需要将 int 转换为 float 更改为以下行，因为此库将 float 值作为输入:

First you need to change casting of int into float into following line as this library get float values as input:

values.add(new Entry((float) waveLength, I)); 

相反，您可以移除投射，因为您的波长已经是浮点数:

Instead you can remove casting as your wavelength is already a float:

values.add(new Entry(waveLength, I));

其次:values.add(new Entry(100, 6)); 这一行作为 values.add(new Entry(x, y));

因此您需要为图表提供适当的 x 值和相应的 y 值以生成图表.如果 n 处的 x 值(此处 n 是条目索引)在任何时候等于或小于 n-1 处的 x 值，则 x 值应按正确顺序创建图表，那么您将无法生成图表图表.因此，按照我描述的方式修复上面的 for 循环代码将可以正常工作.祝你好运:)

So you need to give chart proper x values and corresponding y values to generate a graph. x values should be in proper sequence to create a chart if the value of x at n (here n is index of entry) is equals or less than value of x at n-1 at any point then you will not be able to generate a chart. So fixing the code of for loop above as I described your chart will work properly. Best of luck :)

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