最近看到一些应用在下载文件的时候，并没有额外弹出进度条，而是很炫的使用启动下载任务的Button直接显示文件的下载进度，通过改变其背景色，从左向右推进，直到填满整个Button时，意味着下载任务的完成。

除了这种效果，还看到某酷的视频客户端，在观看过的视频对应的按钮上，会给该按钮添加一个描边效果，4条边，每条边代表25%的进度，由上沿开始，顺时针最终到左边沿，则代表100%的进度，这种效果也很不错。

自己也研究了一下，写了个自定义的button，下面是效果，

普通的填充效果：

描边的效果：

自定义Button的主要实现就是继承Button，并重写onDraw()方法，填充的效果实现起来相对简单一点：

if(currentType == TYPE_FILL) { mPaint.setColor(getContext().getResources().getColor(R.color.green_yellow)); mPaint.setAntiAlias(true); mPaint.setAlpha(128); mPaint.setStrokeWidth(1.0f); Rect rect = new Rect(); //先获取Button的边框 canvas.getClipBounds(rect); rect.left += getPaddingLeft(); //填充条的右边界根据当前进度来计算 rect.top += getPaddingTop(); rect.right = (rect.left - getPaddingLeft()) + (mProgress * getWidth() / 100) - getPaddingRight(); rect.bottom -= getPaddingBottom(); //绘制一个圆角的长条，这样相对好看一点 canvas.drawRoundRect(new RectF(rect), 8.0f, 8.0f, mPaint); }

描边效果实现起来相对复杂一点，确切说是繁琐：

else if(currentType == TYPE_STROKE) { //初始化画笔 mPaint.setAntiAlias(true); mPaint.setColor(getContext().getResources().getColor(R.color.green_yellow)); mPaint.setAlpha(255); //获取Button的边框 Rect rect = new Rect(); canvas.getClipBounds(rect); Paint paint1, paint2, paint3, paint4; //根据当前进度，确定是绘制哪条边，其实也是绘制一个矩形，只不过这个矩形比较扁或是比较窄而已，类似一条边 if(mProgress >= 0 && mProgress < 25) { paint1 = new Paint(mPaint); Rect temp = new Rect(rect.left + getPaddingLeft(), rect.top + getPaddingTop(), rect.left + mProgress * (getWidth() - getPaddingLeft() - getPaddingRight()) / 25 - getPaddingRight(), rect.top + getPaddingTop() + 2); canvas.drawRect(temp, paint1); } else if(mProgress < 50) { paint1 = new Paint(mPaint); Rect rect1 = new Rect(rect.left + getPaddingLeft(), rect.top + getPaddingTop(), rect.right - getPaddingRight(), rect.top + getPaddingTop() + 2); canvas.drawRect(rect1, paint1); paint2 = new Paint(mPaint); Rect rect2 = new Rect(rect.right - getPaddingRight() - 2, rect.top + getPaddingTop(), rect.right - getPaddingRight(), rect.top + getPaddingTop() + (mProgress - 25) * (getHeight() - getPaddingTop() - getPaddingBottom()) / 25); canvas.drawRect(rect2, paint2); } else if(mProgress < 75) { paint1 = new Paint(mPaint); Rect rect1 = new Rect(rect.left + getPaddingLeft(), rect.top + getPaddingTop(), rect.right - getPaddingRight(), rect.top + getPaddingTop() + 2); canvas.drawRect(rect1, paint1); paint2 = new Paint(mPaint); Rect rect2 = new Rect(rect.right - getPaddingRight() - 2, rect.top + getPaddingTop(), rect.right - getPaddingRight(), rect.bottom - getPaddingBottom()); canvas.drawRect(rect2, paint2); paint3 = new Paint(mPaint); Rect rect3 = new Rect( rect.right - getPaddingRight() - (mProgress - 50) * (getWidth() - getPaddingLeft() - getPaddingRight()) / 25, rect.bottom - getPaddingBottom() - 2, rect.right - getPaddingRight(), rect.bottom - getPaddingBottom()); canvas.drawRect(rect3, paint3); } else if(mProgress <= 100) { paint1 = new Paint(mPaint); Rect rect1 = new Rect( rect.left + getPaddingLeft(), rect.top + getPaddingTop(), rect.right - getPaddingRight(), rect.top + getPaddingTop() + 2); canvas.drawRect(rect1, paint1); paint2 = new Paint(mPaint); Rect rect2 = new Rect( rect.right - getPaddingRight() - 2, rect.top + getPaddingTop(), rect.right - getPaddingRight(), rect.bottom - getPaddingBottom()); canvas.drawRect(rect2, paint2); paint3 = new Paint(mPaint); Rect rect3 = new Rect( rect.left + getCompoundPaddingLeft(), rect.bottom - getPaddingBottom() - 2, rect.right - getPaddingRight(), rect.bottom - getPaddingRight()); canvas.drawRect(rect3, paint3); paint4 = new Paint(mPaint); Rect rect4 = new Rect( rect.left + getCompoundPaddingLeft(), rect.bottom - getPaddingBottom() - (mProgress - 75) * (getHeight() - getPaddingTop() - getPaddingBottom()) / 25, rect.left + getPaddingLeft() + 2, rect.bottom - getPaddingBottom()); canvas.drawRect(rect4, paint4); } }

记得最后执行 super.onDraw(canvas);

这样会让填充或是描边绘制在最底层，不会挡住Button原有的内容。

然后添加一个API，用于更新进度：

public void updateProgress(int progress) { if(progress >= 0 && progress <= 100) { mProgress = progress; invalidate(); } else if(progress < 0) { mProgress = 0; invalidate(); } else if(progress > 100) { mProgress = 100; invalidate(); } }

Demo的代码上传到了github上：https://github.com/YoungLeeForeverBoy/ProgressButton

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。