学习Android的第十一天-Android ProgressBar 自定义圆环进度条

在Android中，可以通过自定义绘制来实现一个圆环进度条。这可以通过自定义View来实现。

例子：

1、自定义一个 View 类 RingProgressBar.java

package com.example.myapplication;

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

public class RingProgressBar extends View {

    private Paint mBackPaint;
    private Paint mFrontPaint;
    private Paint mTextPaint;
    private float mStrokeWidth = 50;
    private float mRadius = 200;
    private RectF mRect;
    private int mProgress = 0;
    private int mTargetProgress = 90;
    private int mMax = 100;
    private int mWidth;
    private int mHeight;

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

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

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

    private void init() {
        mBackPaint = new Paint();
        mBackPaint.setColor(Color.WHITE);
        mBackPaint.setAntiAlias(true);
        mBackPaint.setStyle(Paint.Style.STROKE);
        mBackPaint.setStrokeWidth(mStrokeWidth);

        mFrontPaint = new Paint();
        mFrontPaint.setColor(Color.GREEN);
        mFrontPaint.setAntiAlias(true);
        mFrontPaint.setStyle(Paint.Style.STROKE);
        mFrontPaint.setStrokeWidth(mStrokeWidth);

        mTextPaint = new Paint();
        mTextPaint.setColor(Color.GREEN);
        mTextPaint.setAntiAlias(true);
        mTextPaint.setTextSize(80);
        mTextPaint.setTextAlign(Paint.Align.CENTER);
    }

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

        mWidth = resolveSizeAndState(widthSize, widthMeasureSpec, 0);
        mHeight = resolveSizeAndState(heightSize, heightMeasureSpec, 0);
        setMeasuredDimension(mWidth, mHeight);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        float angle = mProgress / (float) mMax * 360;
        canvas.drawCircle(mWidth / 2, mHeight / 2, mRadius, mBackPaint);
        canvas.drawArc(getRect(), -90, angle, false, mFrontPaint);
        canvas.drawText(mProgress + "%", mWidth / 2, mHeight / 2 + mStrokeWidth / 4, mTextPaint);
        if (mProgress < mTargetProgress) {
            mProgress += 1;
            invalidate();
        }
    }

    private RectF getRect() {
        if (mRect == null) {
            mRect = new RectF();
            int viewSize = (int) (mRadius * 2);
            int left = (mWidth - viewSize) / 2;
            int top = (mHeight - viewSize) / 2;
            int right = left + viewSize;
            int bottom = top + viewSize;
            mRect.set(left, top, right, bottom);
        }
        return mRect;
    }
}

2、然后修改 activity_main.xml 添加我们的 RingProgressBar

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:gravity="center">
        <com.example.myapplication.RingProgressBar
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
</LinearLayout>