自定义视图中未调用 onDraw() [英] onDraw() is not called in custom View

问题描述

对于我正在开发的应用程序，我想绘制计步器的结果.计步器使用 service 来测量某人在后台执行的步数.我有一个名为 DrawView 的自定义视图，我想在其中绘制结果.每当测量一个步骤时，我都会从我的 service 调用 drawPoint 方法.然后从我的 drawPoint 方法中，我尝试使用 invalidate() 调用 onDraw().根据我的日志， drawPoint 被调用但 onDraw() 不是.所以我的问题是:

For an app I am developing, I want to graph the results from a pedometer. The pedometer uses a service to measure the amount of steps someone makes in the background. I have a custom view called DrawView, in which I want to draw my results. I call the drawPoint method from my service whenever a step is measured. Then from my drawPoint method I try to call onDraw() using invalidate(). According to my logs, drawPoint is being called but onDraw() is not. So my question is:

为什么没有调用 onDraw()，我应该如何让 DrawView 调用它?

public class DrawView extends View {

...

@Override
public void onDraw(Canvas canvas) {
    for (Point point : points) {
        canvas.drawCircle(point.x, point.y, 5, paint);
        Log.d("Checks", "onDraw is called");
    }
}

public void drawPoint(int counter) {
    Log.d("Checks", "Point coordinates: " + 40 + ", " + counter);

    Point point = new Point();
    point.y = 40;
    point.x = counter;
    points.add(point);
    invalidate();
}
}

推荐答案

不是直接从 service 调用 view.drawPoint()，而是使用 handler 来更新 ui.

Instead calling directly view.drawPoint() from service, use handler to update the ui.

检查链接 从后台服务更新用户界面

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