17. MarkerView (Popup View)(MPAndroidChart中文翻译)

2023年12月7日 328次阅读来源: xiaobug

v3.0.0版本后出现,图表中的标记由IMarker接口表示.

IMarker interface (IMarker接口)
该接口允许你创建图表中显示突出条目时显示的自定义标识.该接口提供的方法如下所示:

public interface IMarker {

    /**
     * @return The desired (general) offset you wish the IMarker to have on the x- and y-axis.
     *         By returning x: -(width / 2) you will center the IMarker horizontally.
     *         By returning y: -(height / 2) you will center the IMarker vertically.
     */
    MPPointF getOffset();

    /**
     * @return The offset for drawing at the specific `point`. This allows conditional adjusting of the Marker position.
     *         If you have no adjustments to make, return getOffset().
     *
     * @param posX This is the X position at which the marker wants to be drawn.
     *             You can adjust the offset conditionally based on this argument.
     * @param posY This is the X position at which the marker wants to be drawn.
     *             You can adjust the offset conditionally based on this argument.
     */
    MPPointF getOffsetForDrawingAtPos(float posX, float posY);

    /**
     * This method enables a specified custom IMarker to update it's content every time the IMarker is redrawn.
     *
     * @param e         The Entry the IMarker belongs to. This can also be any subclass of Entry, like BarEntry or
     *                  CandleEntry, simply cast it at runtime.
     * @param highlight The highlight object contains information about the highlighted value such as it's dataset-index, the
     *                  selected range or stack-index (only stacked bar entries).
     */
    void refreshContent(Entry e, Highlight highlight);

    /**
     * Draws the IMarker on the given position on the screen with the given Canvas object.
     *
     * @param canvas
     * @param posX
     * @param posY
     */
    void draw(Canvas canvas, float posX, float posY);
}

Creating a MarkerView (创建一个标识视图)

为了创建自定义的标记视图,你需要创建一个类并实现IMarker接口:

public class YourMarkerView implements IMarker { ... }

接口中提供的方法的返回值取决于个人需求.为了更好的理解,请看看上面展示的方法文档.

除了实现IMarker接口之外,你可以创建自己的类并通过下面提到的预定义标记继承它.这种方法更简单,不要求实现IMarker接口所有的方法.只有特殊的方法需要重写和自定义的.最终要的是重写refreshContent(…)方法来调整标记绘制的数据.一个简单的例子可能是这样的:

public class YourMarkerView extends MarkerView {

    private TextView tvContent;

    public MyMarkerView(Context context, int layoutResource) {
        super(context, layoutResource);

        // find your layout components
        tvContent = (TextView) findViewById(R.id.tvContent);
    }

    // callbacks everytime the MarkerView is redrawn, can be used to update the
    // content (user-interface)
    @Override
    public void refreshContent(Entry e, Highlight highlight) {

        tvContent.setText("" + e.getY());

        // this will perform necessary layouting
        super.refreshContent(e, highlight);
    }

    private MPPointF mOffset; 

    @Override
    public MPPointF getOffset() {

        if(mOffset == null) {
           // center the marker horizontally and vertically
           mOffset = new MPPointF(-(getWidth() / 2), -getHeight());
        }

        return mOffset;
    }
}

Getting / Setting the Marker(获取/设置标记)

为了给图表设置自己的标记,请使用setMarker(…)方法:

IMarker marker = new YourMarkerView();
chart.setMarker(marker);

为了获取图表中设置的标记,使用geMarker()方法:

IMarker marker = chart.getMarker();

Predefined Markers (预定的标记)

除了创建你自己的标记视图,为了更简单更快的使用,该库提供了一些自定义标记.这些标记包括:

MarkerView: 基本标记.允许提供一个资源布局在图表表面上显示标记.集成该类并重写refreshContent(…)方法来调整标记数据.
MarkerImage: 一个绘制图片的标记.允许提供一个图片资源在图表表面上显示标记.集成该类并重写refreshContent(…)方法来调整标记数据.

Legacy MarkerView (传统标记视图)

在v3.0.0之前的版本中,MarkerView类负责在图表中突出显示的位置绘制标记.关于该类的详细信息请访问旧的MarkerView wiki page.

    原文作者：xiaobug
    原文地址: https://www.jianshu.com/p/214e27b43583
    本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。

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17. MarkerView (Popup View)(MPAndroidChart中文翻译)

目录

Creating a MarkerView (创建一个标识视图)

Getting / Setting the Marker(获取/设置标记)

Predefined Markers (预定的标记)

Legacy MarkerView (传统标记视图)