java - MPAndroidChart。如何播放scaleX动画来显示BarChart中实体的范围？

Question

我正在使用 MPAndroidChart。我需要做这样的事情:/image/AKgry.gif

我在用动画显示实体范围时遇到了问题。 我有一个条形图，xAxis - 月份，yAxis - 金钱。我需要用动画显示选定范围的实体(缩放到选定范围)。

诸如 setVisibleXRange(min, max) 或 setScaleMinima(scaleX, 1f); 之类的方法可以执行我想要的操作，但没有动画。 我尝试使用方法 zoomAndCenterAnimated() 缩放到选定范围:

private void showMonthRange(int monthCount) {
    //find center bar entry
    BarEntry centerBarEntry = null;
    ViewPortHandler handler = barChart.getViewPortHandler();
    MPPointD topLeft = barChart.getValuesByTouchPoint(handler.contentLeft(), handler.contentTop(), YAxis.AxisDependency.LEFT);
    MPPointD bottomRight = barChart.getValuesByTouchPoint(handler.contentRight(), handler.contentBottom(), YAxis.AxisDependency.LEFT);
    int index = (int) (topLeft.x + bottomRight.x) / 2;
    for (IBarDataSet set : barChart.getBarData().getDataSets()) {
        BarEntry entry = set.getEntryForIndex(index);
        if (entry != null) {
            centerBarEntry = entry;
            break;
        }
    }

    //perform scaling by X to show the range on entities for selected monthCount (for example 3, 6, 12..etc months)
    if (centerBarEntry != null) {
        float scaleX = (float) maxMonthCount / monthCount;
        barChart.zoomAndCenterAnimated(scaleX, 1f, entry.getX(), entry.getY(), YAxis.AxisDependency.RIGHT, 500);
    }
}

但我有一个异常(exception):

java.lang.NullPointerException: Attempt to read from field 'float com.github.mikephil.charting.components.AxisBase.mAxisRange' on a null object reference
at com.github.mikephil.charting.jobs.AnimatedZoomJob.onAnimationUpdate(AnimatedZoomJob.java:75)
at android.animation.ValueAnimator.animateValue(ValueAnimator.java:1522)
at android.animation.ObjectAnimator.animateValue(ObjectAnimator.java:987)
at android.animation.ValueAnimator.setCurrentFraction(ValueAnimator.java:654)
at android.animation.ValueAnimator.start(ValueAnimator.java:1048)
at android.animation.ValueAnimator.start(ValueAnimator.java:1065)
at android.animation.ObjectAnimator.start(ObjectAnimator.java:852)
at com.github.mikephil.charting.jobs.AnimatedViewPortJob.run(AnimatedViewPortJob.java:38)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

如果我使用方法barChart.zoom(scaleX, 1f,entry.getX(),entry.getY(), YAxis.AxisDependency.LEFT);而不是barChart.zoomAndCenterAnimated(scaleX, 1f,entry.getX(),entry.getY(),YAxis.AxisDependency.RIGHT,500);所有工作都很完美。 我的实现中有什么问题？为什么我会遇到这样的异常？ 我试图在现有问题中寻找答案，但没有找到任何解决方案。

Answer 1

我通过更改可见的 X 范围解决了我的问题:

    private void animateToRange(final int newRange) {
    final float visibleRange = barChart.getVisibleXRange();
    ValueAnimator animator = ValueAnimator.ofFloat(0.1f, 1f);
    animator.setDuration(300);
    animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            float ratio = (float) animation.getAnimatedValue();
            float range;
            if (visibleRange > newRange) {
                range = visibleRange - (visibleRange - newRange) * ratio;
            } else {
                range = visibleRange + (newRange - visibleRange) * ratio;
            }

            barChart.setVisibleXRange(range, deltaRange);
            barChart.invalidate();
        }
    });
    animator.start();
}

如果您不需要手动缩放，此解决方案适合。