自定义View模板

附：完整代码

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.View;


public class RoundProgressBar extends View
{

    private int mRadius;
    private int mColor;
    private int mLineWidth;
    private int mTextSize;
    private int mProgress;

    private Paint mPaint;


    public RoundProgressBar(Context context, AttributeSet attrs)
    {
        super(context, attrs);

        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.RoundProgressBar);

        mRadius = (int) ta.getDimension(R.styleable.RoundProgressBar_radius, dp2px(30));
        mColor = ta.getColor(R.styleable.RoundProgressBar_color, 0xffff0000);
        mLineWidth = (int) ta.getDimension(R.styleable.RoundProgressBar_line_width, dp2px(3));
        mTextSize = (int) ta.getDimension(R.styleable.RoundProgressBar_android_textSize, dp2px(36));
        mProgress = ta.getInt(R.styleable.RoundProgressBar_android_progress, 30);

        ta.recycle();

        initPaint();
    }

    private float dp2px(int dpVal)
    {
        return TypedValue.applyDimension(
                TypedValue.COMPLEX_UNIT_DIP, dpVal, getResources().getDisplayMetrics());
    }

    private void initPaint()
    {
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setColor(mColor);
    }

    public void setProgress(int progress)
    {
        mProgress = progress;
        invalidate();
    }

    public int getProgress()
    {
        return mProgress;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);

        int width = 0;
        if (widthMode == MeasureSpec.EXACTLY)
        {
            width = widthSize;
        } else
        {
            int needWidth = measureWidth() + getPaddingLeft() + getPaddingRight();
            if (widthMode == MeasureSpec.AT_MOST)
            {
                width = Math.min(needWidth, widthSize);
            } else
            {
                width = needWidth;
            }
        }

        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int height = 0;

        if (heightMode == MeasureSpec.EXACTLY)
        {
            height = heightSize;
        } else
        {
            int needHeight = measureHeight() + getPaddingTop() + getPaddingBottom();
            if (heightMode == MeasureSpec.AT_MOST)
            {
                height = Math.min(needHeight, heightSize);
            } else //MeasureSpec.UNSPECIFIED
            {
                height = needHeight;
            }
        }
        setMeasuredDimension(width, height);

    }

    private int measureHeight()
    {
        return mRadius * 2;
    }

    private int measureWidth()
    {
        return mRadius * 2;
    }


    @Override
    protected void onDraw(Canvas canvas)
    {
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(mLineWidth * 1.0f / 4);

        int width = getWidth();
        int height = getHeight();

        canvas.drawCircle(width / 2, height / 2,
                width / 2 - getPaddingLeft() - mPaint.getStrokeWidth() / 2, mPaint);

        mPaint.setStrokeWidth(mLineWidth);
        canvas.save();
        canvas.translate(getPaddingLeft(), getPaddingTop());
        float angle = mProgress * 1.0f / 100 * 360;
        canvas.drawArc(new RectF(0, 0, width - getPaddingLeft() * 2, height - getPaddingLeft() * 2), 0, angle, false, mPaint);
        canvas.restore();

        String text = mProgress + "%";
//        text = "张鸿洋";
        mPaint.setStrokeWidth(0);
        mPaint.setTextAlign(Paint.Align.CENTER);
        mPaint.setTextSize(mTextSize);
        int y = getHeight() / 2;
        Rect bound = new Rect();
        mPaint.getTextBounds(text, 0, text.length(), bound);
        int textHeight = bound.height();
        canvas.drawText(text, 0, text.length(), getWidth() / 2, y + textHeight / 2, mPaint);

        mPaint.setStrokeWidth(0);
//        canvas.drawLine(0, height / 2, width, height / 2, mPaint);

    }


    private static final String INSTANCE = "instance";
    private static final String KEY_PROGRESS = "key_progress";

    @Override
    protected Parcelable onSaveInstanceState()
    {
        Bundle bundle = new Bundle();
        bundle.putInt(KEY_PROGRESS, mProgress);
        bundle.putParcelable(INSTANCE, super.onSaveInstanceState());
        return bundle;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state)
    {
        if (state instanceof Bundle)
        {
            Bundle bundle = (Bundle) state;
            Parcelable parcelable = bundle.getParcelable(INSTANCE);
            super.onRestoreInstanceState(parcelable);
            mProgress = bundle.getInt(KEY_PROGRESS);
            return;
        }
        super.onRestoreInstanceState(state);
    }
}

自定义View的步骤
一：新建资源文件（res/values/attrs.xml）
二：创建子类继承View。
1.覆写父类构造方法(Context context, AttributeSet attrs)
1.1加载文件并从资源文件获取属性值
···
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.RoundProgressBar);

    mRadius = (int) ta.getDimension(R.styleable.RoundProgressBar_radius, dp2px(30));
    mColor = ta.getColor(R.styleable.RoundProgressBar_color, 0xffff0000);
    mLineWidth = (int) ta.getDimension(R.styleable.RoundProgressBar_line_width, dp2px(3));
    mTextSize = (int) ta.getDimension(R.styleable.RoundProgressBar_android_textSize, dp2px(36));
    mProgress = ta.getInt(R.styleable.RoundProgressBar_android_progress, 30);

2.测量(模板)

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int width = 0;
        if (widthMode == MeasureSpec.EXACTLY)
        {
            width = widthSize;
        } else
        {
            int needWidth = measureWidth() + getPaddingLeft() + getPaddingRight();
            if (widthMode == MeasureSpec.AT_MOST)
            {
                width = Math.min(needWidth, widthSize);
            } else
            {
                width = needWidth;
            }
        }

        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int height = 0;

        if (heightMode == MeasureSpec.EXACTLY)
        {
            height = heightSize;
        } else
        {
            int needHeight = measureHeight() + getPaddingTop() + getPaddingBottom();
            if (heightMode == MeasureSpec.AT_MOST)
            {
                height = Math.min(needHeight, heightSize);
            } else //MeasureSpec.UNSPECIFIED
            {
                height = needHeight;
            }
        }
        setMeasuredDimension(width, height);

    }
/**  实际书写该方法*/
    private int measureHeight()
    {
        return mRadius * 2;     
    }
 /**  实际书写该方法*/
    private int measureWidth()
    {
        return mRadius * 2;  
    }

3.绘制onDraw
4.保存状态与恢复(模板)

  private static final String INSTANCE = "instance";
    private static final String KEY_PROGRESS = "key_progress";

    @Override
    protected Parcelable onSaveInstanceState()
    {
        Bundle bundle = new Bundle();
        bundle.putInt(KEY_PROGRESS, mProgress);
        bundle.putParcelable(INSTANCE, super.onSaveInstanceState());
        return bundle;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state)
    {
        if (state instanceof Bundle)
        {
            Bundle bundle = (Bundle) state;
            Parcelable parcelable = bundle.getParcelable(INSTANCE);
            super.onRestoreInstanceState(parcelable);
            mProgress = bundle.getInt(KEY_PROGRESS);
            return;
        }
        super.onRestoreInstanceState(state);
    }