Question

代码：

double percentage = 0.7711627906976745;
mSweepAngle = (float)(360*(percentage/(double)100));

我已经google了一下，但没有找到答案，afaik我正确地输入它，但它仍然评估为0.0。我甚至尝试在计算过程中将360，percentage和100强制转换为float，但它仍然不起作用...

EDIT1： 完整的代码：

package se.kiendys.petrus.da171a.uppg3.budgetapp;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Paint.Style;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;

public class PieChartView extends View {

    private Paint piechartItem1Paint;
    private Paint piechartItem2Paint;
    private Paint piechartBorderPaint;
    private Paint infoBorderPaint;
    private Paint infoBackgroundPaint;
    private Paint infoTextPaint;
    private RectF oval;

    private int mWidth;
    private int mHeight;
    private int mMarginLeft;
    private int mMarginTop;
    private float mStartAngle;
    private float mSweepAngle;

    private double percentage;

    public PieChartView(Context context) {
        super(context);
        init();
    }

    public PieChartView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public void init() {
        piechartItem1Paint = new Paint();                   // the piechart items color
        piechartItem2Paint = new Paint();                   // the piechart items color
        piechartBorderPaint = new Paint();                  // the piechart border color
        infoTextPaint = new Paint();                        // the info text color
        infoBackgroundPaint = new Paint();                  // the info background color
        infoBorderPaint = new Paint();                      // the info border color

        mWidth = 200;       // circle width
        mHeight = 200;      // circle height
        mMarginLeft = 10;   // circle and info margin
        mMarginTop = 10;    // circle and info margin
        mStartAngle = 0;    // the starting angle of the arc, begins at the rightmost part of the circle (an angle of 0 degrees correspond to the geometric angle of 0 degrees, or 3 o'clock on a watch)
                            // and through incrementation moves clockwise, the units are degrees

        oval = new RectF(mMarginLeft, mMarginTop, mWidth, mHeight); // sets the shape and size (boundaries) of the drawn circle

        piechartItem1Paint.setAntiAlias(true);
        piechartItem1Paint.setStyle(Style.FILL);
        piechartItem1Paint.setStrokeWidth(0.5f);
        piechartItem2Paint.setAntiAlias(true);
        piechartItem2Paint.setStyle(Style.FILL);
        piechartItem2Paint.setStrokeWidth(0.5f);

        piechartItem1Paint.setColor(0xCCFEFEFE);    // blue color
        piechartItem2Paint.setColor(0xCC343434);    // green color

//      double temp = (360*((double)percentage/(double)100));
//      Log.d(BudgetConstants.DEBUG_TAG, "temp: "+temp);
//      mSweepAngle = (float)temp;
//      Log.d(BudgetConstants.DEBUG_TAG, "init mSweepAngle: "+mSweepAngle);
//      mSweepAngle = (float)(360*(percentage/(double)100));
//      mSweepAngle = (float)(percentage/100.0*360);
        Log.d(BudgetConstants.DEBUG_TAG, "init mSweepAngle: "+mSweepAngle);
    }

    public void setDistributionPercentage(double percentage) {
        this.percentage = percentage;
        Log.d(BudgetConstants.DEBUG_TAG, "percentage: "+percentage);
    }

    protected void onDraw(Canvas canvas) {
        Log.d(BudgetConstants.DEBUG_TAG, "onDraw fired!");

        canvas.drawArc(oval, mStartAngle, mSweepAngle, true, piechartItem1Paint);
        Log.d(BudgetConstants.DEBUG_TAG, "startAngle1: "+mStartAngle+", sweepAngle1: "+mSweepAngle);
        canvas.drawArc(oval, mSweepAngle, (360-mSweepAngle), true, piechartItem2Paint);
        Log.d(BudgetConstants.DEBUG_TAG, "startAngle2: "+mSweepAngle+", sweepAngle2: "+(360-mSweepAngle));
    }

}

请注意，百分比已成功从另一项活动传递，目前正在通过0.7711627906976745.

Answer 1

您正在从构造函数中调用init，并且正在进行此计算的init。因此，无论您使用什么机制来设置percentage，它都不会发生，直到计算完成后才会发生。

我认真地建议学习使用调试器。单步执行代码会立即告诉您发生了什么。

float type-casting工作不正常，总是求值为0.0

1 个答案: