android 自定义控件 方式三 重写View来实现全新的控件

本质理解

1. 通过 onMeasure(int widthMeasureSpec, int heightMeasureSpec) 来获取控件的尺寸设置

2. 通过 onDraw(Canvas canvas)，调用Canvas接口来绘制控件

代码位置： https://github.com/RichardKuma/AndroidHeroes/blob/master/3AndroidView/SystemWidget/app/src/main/java/com/imooc/systemwidget/CircleProgressView.java

 

package com.imooc.systemwidget;

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

public class CircleProgressView extends View {

    private int mMeasureHeigth;
    private int mMeasureWidth;

    private Paint mCirclePaint;
    private float mCircleXY;
    private float mRadius;

    private Paint mArcPaint;
    private RectF mArcRectF;
    private float mSweepAngle;
    private float mSweepValue = 66;

    private Paint mTextPaint;
    private String mShowText;
    private float mShowTextSize;

    public CircleProgressView(Context context, AttributeSet attrs,
                              int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

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

    public CircleProgressView(Context context) {
        super(context);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec,
                             int heightMeasureSpec) {
        mMeasureWidth = MeasureSpec.getSize(widthMeasureSpec);
        mMeasureHeigth = MeasureSpec.getSize(heightMeasureSpec);
        setMeasuredDimension(mMeasureWidth, mMeasureHeigth);
        initView();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // 绘制圆
        canvas.drawCircle(mCircleXY, mCircleXY, mRadius, mCirclePaint);
        // 绘制弧线
        canvas.drawArc(mArcRectF, 270, mSweepAngle, false, mArcPaint);
        // 绘制文字
        canvas.drawText(mShowText, 0, mShowText.length(),
                mCircleXY, mCircleXY + (mShowTextSize / 4), mTextPaint);
    }

    private void initView() {
        float length = 0;
        if (mMeasureHeigth >= mMeasureWidth) {
            length = mMeasureWidth;
        }
        else {
            length = mMeasureHeigth;
        }

        mCircleXY = length / 2;
        mRadius = (float) (length * 0.5 / 2);
        mCirclePaint = new Paint();
        mCirclePaint.setAntiAlias(true);
        mCirclePaint.setColor(getResources().getColor(
                android.R.color.holo_blue_bright));

        mArcRectF = new RectF(
                (float) (length * 0.1),
                (float) (length * 0.1),
                (float) (length * 0.9),
                (float) (length * 0.9));
        mSweepAngle = (mSweepValue / 100f) * 360f;
        mArcPaint = new Paint();
        mArcPaint.setAntiAlias(true);
        mArcPaint.setColor(getResources().getColor(
                android.R.color.holo_blue_bright));
        mArcPaint.setStrokeWidth((float) (length * 0.1));
        mArcPaint.setStyle(Style.STROKE);

        mShowText = setShowText();
        mShowTextSize = setShowTextSize();
        mTextPaint = new Paint();
        mTextPaint.setTextSize(mShowTextSize);
        mTextPaint.setTextAlign(Paint.Align.CENTER);
    }

    private float setShowTextSize() {
        this.invalidate();
        return 50;
    }

    private String setShowText() {
        this.invalidate();
        return "Android Skill";
    }

    public void forceInvalidate() {
        this.invalidate();
    }

    public void setSweepValue(float sweepValue) {
        if (sweepValue != 0) {
            mSweepValue = sweepValue;
        } 
        else {
            mSweepValue = 25;
        }
        this.invalidate();
    }
}