MPAndroidChart-如何最好地将X轴值设置为字符串/日期? [英] MPAndroidChart - How can I best set the X-axis values as strings/dates?

问题描述

这个 MPAndroid图表库让我有点迷茫.

我从此处开始了初学者示例，该示例建议创建一个数组/使用getValueX()和getValueY()方法的对象列表，然后将其添加为条目，如下所示:

I began the beginner example here, which recommends creating an array/list of objects with getValueX() and getValueY() methods, which you would then add as entries, like this:

List<Entry> entries = new ArrayList<Entry>(); // entry list    

for(ValueAndDateObject data : valueAndDateArrayList){ 

    // valueAndDateArrayList is the list of my own data 
    //(objects with a String X-value, and a double Y-value)

    entries.add(new Entry(data.getValueX(), data.getValueY())); //error here
 }

那里是一个错误，因为Entry仅采用(浮点数x，浮点数y).显然，我可以将double转换为浮点数，但是我需要x轴具有非浮点的日期.因此，我进行了更多搜索，发现了很多有关Github的问题，但是那里的解决方案似乎无法理解.多数指向类似于文档中的此.我遇到的问题是我不明白如何将此方法应用于Entry(float x，float y)问题.我找不到文档/解决方案说何时/何地适用于Entry().

There's an error there because Entry only takes (float x, float y). Obviously I can cast the double as a float, but I need the x-axis to have dates not floats. So I did some more searching and found a lot of Github issues about it, but the solutions there I can't seem to understand. Most point to something like this in the docs. The problem I'm having is I don't understand how this gets applied to the Entry(float x, float y) issue. I can't find when/where the docs/solutions say to apply to Entry().

因此，当我看有关创建格式化程序然后对其进行设置的示例时，我不知道entry.add(new Entry())东西的出现位置.该技术可以代替它吗?我会以某种方式通过吗?

So when I look at the example about creating the formatter and then setting it, I don't get where the entries.add(new Entry()) stuff comes in. Does that technique replace it? Do I somehow pass it in?

作为参考，这是我的完整方法，它是根据前面提到的初学者示例设计的.

For reference, here's my full method, designed after the beginner example mentioned previously.

public void updateUI(final ArrayList<ValueAndDateObject> valueAndDateArrayList){
    List<Entry> entries = new ArrayList<Entry>();



    for(ValueAndDateObject data : valueAndDateArrayList){

    /** for the sake of the example, let's say there's only one 
    *   ValueAndDataObject in the list and getValueX() returns "02-27-2016"
    *   and getValueY() returns 12,345.0
    */

        entries.add(new Entry(data.getValueX(), data.getValueY())); //error obviously 
    }        

    // would I add the formatter somewhere in here? And what would I "add" it to?

    LineDataSet dataSet = new LineDataSet(entries, "Label");
    dataSet.setColor(Color.YELLOW);
    dataSet.setValueTextColor(Color.BLACK);

    LineData lineData = new LineData(dataSet);
    lineChart.setData(lineData);
    lineChart.invalidate();
}

据我所知，我将必须创建自己的格式化程序类，该类将基于格式化程序doc链接中的string []示例进行建模.我的电话挂在设置格式程序"部分.只是不确定如何更改/交互与Entry(float x，float y)问题.

From what I can tell, I'll have to make my own formatter class, which I'll model off of the string[] example in the formatter doc link. My hang up is on the "Setting the formatter" section. Just not sure about how that will change/interact with the Entry(float x, float y) issue.

推荐答案

在创建 Entry 对象时，您只需要将 Date 作为时间戳即可，例如:

You simply need to treat your Date as a timestamp when creating the Entry object, e.g.:

entries.add(new Entry(new Long(data.getDate().getTime()).floatValue(), new Double(data.getValueY()).floatValue()));

在上面，我们假设 data.getDate()返回一个 java.util.Date 和 data.getValueY()返回 double .

In the above, we assume that data.getDate() returns a java.util.Date and that data.getValueY() returns a double.

然后，在您的 IAxisValueFormatter 中要做的就是将时间戳记表示形式转换回 Date ，然后转换为人类可读的格式，例如:

Then all you have to do in your IAxisValueFormatter is to convert the timestamp representation back to a Date and then into something human readable, like so:

public class DateValueFormatter implements IAxisValueFormatter {

    @Override
    public String getFormattedValue(float value, AxisBase axis) {
        // Simple version. You should use a DateFormatter to specify how you want to textually represent your date.
        return new Date(new Float(value).longValue()).toString();
    }
    // ...
}

更新:

设置值格式器:

XAxis xAxis = chart.getXAxis();
xAxis.setValueFormatter(new DateValueFormatter());

更新:

用户'Yasir-Ghunaim'在该线程在github上.

User 'Yasir-Ghunaim' provides a very good step-by-step guide as a response in this thread on github.

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