一个简单的Loading控件

实现效果如下：

使用方法：

在layout文件中添加以下代码：

   <com.example.jack.ui.widget.RingLoading
        android:layout_width="20.0dip"
        android:layout_height="20.0dip"
   />

具体代码如下：

package com.example.jack.ui.widget;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.SweepGradient;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by pengf on 2017/4/10.
 */

public class RingLoading extends View
{
    private static final int PROGRESS = 5;
    private int centerX;
    private int centerY;
    private Context context;
    private int mProgressColor ;
    private Matrix matrix;
    private final Paint paint;
    private int roundWidth = 10;
    private int start = 0;

    public RingLoading(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        this.context = context;
        this.paint = new Paint();
        this.paint.setAntiAlias(true);
        this.paint.setStyle(Paint.Style.STROKE);
        this.paint.setStrokeWidth(this.roundWidth);
        this.mProgressColor =Color.parseColor("#ffffcc00");

    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        int center = getWidth() / 2;
        int radius = center - this.roundWidth / 2;
        SweepGradient sweepGradient = new SweepGradient(this.centerX, this.centerY, Color.TRANSPARENT, this.mProgressColor);
        this.paint.setShader(sweepGradient);
        this.matrix = new Matrix();
        this.matrix.postRotate(this.start, this.centerX, this.centerY);
        canvas.concat(this.matrix);
        canvas.drawCircle(center, center, radius, this.paint);
        this.start = (PROGRESS + this.start);
        invalidate();
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh)
    {
        super.onSizeChanged(w, h, oldw, oldh);
        this.centerX = (w / 2);
        this.centerY = (h / 2);
    }
}