有些App在点击下载按钮的时候，可以在按钮上显示进度，我们可以通过继承原生Button，重写onDraw来实现带进度条的按钮。
Github：https://github.com/imcloudfloating/ProgressBar
1.效果：
2.原理：
创建三个GradientDrawable作为按钮背景、进度条背景和进度条前景，通过计算进度条的百分比来设置宽度，然后调用invalidate()重绘。GradientDrawable设置颜色、圆角等参数，当然你也可以直接加载xml作为背景。
3.自定义参数：
在values目录建一个attrs.xml文件
<?xml version="." encoding="utf-"?> <resources> <attr name="progressColor" format="color" /> <attr name="progressBackColor" format="color" /> <attr name="progress" format="integer" /> <attr name="minProgress" format="integer" /> <attr name="maxProgress" format="integer" /> <declare-styleable name="ProgressButton"> <attr name="progressColor" /> <attr name="progressBackColor" /> <attr name="buttonColor" format="color" /> <attr name="cornerRadius" format="dimension" /> <attr name="progress" /> <attr name="minProgress" /> <attr name="maxProgress" /> <attr name="progressMargin" format="dimension" /> </declare-styleable> </resources>
3.按钮类：
在setProgress方法中改变mProgress的值，然后调用invalidate()重绘，因为我这里定义了一个minProgress(默认为0)，所以在计算进度条宽度的时候，当前进度和最大进度都要先减去minProgress再做除法。
if (progressWidth < mCornerRadius * 2) { progressWidth = mCornerRadius * 2;} 当进度条宽度小于2倍圆角半径的时候，进度条的圆角就和背景的圆角不一致，所以加上了上面这段代码。
获取宽度和高度其实用getWidth()和getHeight()也可以，只不过在设计器中没法看到效果，所以我用了getMeasuredWidth()和getMeasuredHeight()。
package com.cloud.customviews; import android.content.Context; import android.content.res.TypedArray; import android.graphics.Canvas; import android.graphics.drawable.GradientDrawable; import android.support.v.widget.AppCompatButton; import android.util.AttributeSet; public class ProgressButton extends AppCompatButton { private float mCornerRadius = ; private float mProgressMargin = ; private boolean mFinish; private int mProgress; private int mMaxProgress = ; private int mMinProgress = ; private GradientDrawable mDrawableButton; private GradientDrawable mDrawableProgressBackground; private GradientDrawable mDrawableProgress; public ProgressButton(Context context, AttributeSet attrs) { super(context, attrs); initialize(context, attrs); } public ProgressButton(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); initialize(context, attrs); } private void initialize(Context context, AttributeSet attrs) { //Progress background drawable mDrawableProgressBackground = new GradientDrawable(); //Progress drawable mDrawableProgress = new GradientDrawable(); //Normal drawable mDrawableButton = new GradientDrawable(); //Get default normal color int defaultButtonColor = getResources().getColor(R.color.colorGray, null); //Get default progress color int defaultProgressColor = getResources().getColor(R.color.colorGreen, null); //Get default progress background color int defaultBackColor = getResources().getColor(R.color.colorGray, null); TypedArray attr = context.obtainStyledAttributes(attrs, R.styleable.ProgressButton); try { mProgressMargin = attr.getDimension(R.styleable.ProgressButton_progressMargin, mProgressMargin); mCornerRadius = attr.getDimension(R.styleable.ProgressButton_cornerRadius, mCornerRadius); //Get custom normal color int buttonColor = attr.getColor(R.styleable.ProgressButton_buttonColor, defaultButtonColor); //Set normal color mDrawableButton.setColor(buttonColor); //Get custom progress background color int progressBackColor = attr.getColor(R.styleable.ProgressButton_progressBackColor, defaultBackColor); //Set progress background drawable color mDrawableProgressBackground.setColor(progressBackColor); //Get custom progress color int progressColor = attr.getColor(R.styleable.ProgressButton_progressColor, defaultProgressColor); //Set progress drawable color mDrawableProgress.setColor(progressColor); //Get default progress mProgress = attr.getInteger(R.styleable.ProgressButton_progress, mProgress); //Get minimum progress mMinProgress = attr.getInteger(R.styleable.ProgressButton_minProgress, mMinProgress); //Get maximize progress mMaxProgress = attr.getInteger(R.styleable.ProgressButton_maxProgress, mMaxProgress); } finally { attr.recycle(); } //Set corner radius mDrawableButton.setCornerRadius(mCornerRadius); mDrawableProgressBackground.setCornerRadius(mCornerRadius); mDrawableProgress.setCornerRadius(mCornerRadius - mProgressMargin); setBackgroundDrawable(mDrawableButton); mFinish = false; } @Override protected void onDraw(Canvas canvas) { if (mProgress > mMinProgress && mProgress <= mMaxProgress && !mFinish) { //Calculate the width of progress float progressWidth = (float) getMeasuredWidth() * ((float) (mProgress - mMinProgress) / mMaxProgress - mMinProgress); //If progress width less than x corner radius, the radius of progress will be wrong if (progressWidth < mCornerRadius * ) { progressWidth = mCornerRadius * ; } //Set rect of progress mDrawableProgress.setBounds((int) mProgressMargin, (int) mProgressMargin, (int) (progressWidth - mProgressMargin), getMeasuredHeight() - (int) mProgressMargin); //Draw progress mDrawableProgress.draw(canvas); if (mProgress == mMaxProgress) { setBackgroundDrawable(mDrawableButton); mFinish = true; } } super.onDraw(canvas); } /** * Set current progress */ public void setProgress(int progress) { if (!mFinish) { mProgress = progress; setBackgroundDrawable(mDrawableProgressBackground); invalidate(); } } public void setMaxProgress(int maxProgress) { mMaxProgress = maxProgress; } public void setMinProgress(int minProgress) { mMinProgress = minProgress; } public void reset() { mFinish = false; mProgress = mMinProgress; } } 使用：
<com.cloud.customviews.ProgressButton android:id="@+id/button_progress_green" android:layout_width="dp" android:layout_height="wrap_content" android:layout_marginTop="dp" android:textAllCaps="false" android:textColor="@color/colorWhite" android:text="@string/button_progress" app:cornerRadius="dp" app:progressMargin="dp" app:progressColor="@color/colorGreen" app:buttonColor="@color/colorGreen" />
总结
以上所述是小编给大家介绍的Android 进度条按钮ProgressButton的实现代码，希望对大家有所帮助，如果大家有任何疑问欢迎给我留言小编会及时回复大家的！
注：相关教程知识阅读请移步到Android开发频道。
