Android镂空字体,TextvView实现镂空字体效果

前言：

本来朋友问我镂空字体怎么实现，刚开始以为是简简单单调整背景色和透明度，后来发现是我想多了。记录一下

效果图:

看了几个整体思路都是

自定义HolloTextView继承自View，重写onDraw方法，绘制背景，使用PorterDuff.Mode.DST_OUT的画笔调用canvas.drawText方法绘制文字

其实有些背景可以用别的方法实现：

透明背景可以用

binding.btMySignOut.setTextColor(Color.alpha(100));等等

alpha范围是0-250

第一步：

1、创建HollowTextView

public class HollowTextView extends AppCompatTextView {private Paint mTextPaint, mBackgroundPaint;private Bitmap mBackgroundBitmap, mTextBitmap;private Canvas mBackgroundCanvas, mTextCanvas;private RectF mBackgroundRect;private int mBackgroundColor;private float mCornerRadius;public HollowTextView(Context context) {this(context, null);}public HollowTextView(Context context, AttributeSet attrs) {super(context, attrs);initAttrs(attrs, 0);initPaint();}public HollowTextView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);initAttrs(attrs, defStyleAttr);initPaint();}private void initAttrs(AttributeSet attrs, int defStyleAttr) {if (attrs == null) {return;}TypedArray typedArray = getContext().obtainStyledAttributes(attrs, R.styleable.HollowTextView, defStyleAttr, 0);mBackgroundColor = typedArray.getColor(R.styleable.HollowTextView_hollowTextView_background_color, Color.TRANSPARENT);mCornerRadius = typedArray.getDimension(R.styleable.HollowTextView_hollowTextView_corner_radius, 0);typedArray.recycle();}/**** 初始化画笔属性*/private void initPaint() {//画文字的paintmTextPaint = new Paint();//这是镂空的关键mTextPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));mTextPaint.setAntiAlias(true);mBackgroundPaint = new Paint();mBackgroundPaint.setColor(mBackgroundColor);mBackgroundPaint.setAntiAlias(true);}@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);mBackgroundBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_4444);mBackgroundCanvas = new Canvas(mBackgroundBitmap);mTextBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_4444);mTextCanvas = new Canvas(mTextBitmap);mBackgroundRect = new RectF(0, 0, getWidth(), getHeight());}@Overrideprotected void onDraw(Canvas canvas) {//这里给super传入的是mTextCanvas，把一些基本属性都支持进去super.onDraw(mTextCanvas);drawBackground(mBackgroundCanvas);int sc;if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {sc = canvas.saveLayer(0, 0, getMeasuredWidth(), getMeasuredHeight(), null);} else {sc = canvas.saveLayer(0, 0, getMeasuredWidth(), getMeasuredHeight(), null, Canvas.ALL_SAVE_FLAG);}canvas.drawBitmap(mBackgroundBitmap, 0, 0, null);canvas.drawBitmap(mTextBitmap, 0, 0, mTextPaint);canvas.restoreToCount(sc);}private void drawBackground(Canvas canvas) {if (mCornerRadius > 0) {canvas.drawRoundRect(mBackgroundRect, mCornerRadius, mCornerRadius, mBackgroundPaint);} else {canvas.drawColor(mBackgroundColor);}}
}

第二步：创建values下styleable的xml（attrs）

<?xml version="1.0" encoding="utf-8"?>
<resources><declare-styleable name="HollowTextView"><attr name="hollowTextView_background_color" format="color|reference"/><attr name="hollowTextView_corner_radius" format="dimension|reference"/></declare-styleable>
</resources>

最后就是引用HollowTextView

<com.test.aaa.activitys.HollowTextViewandroid:id="@+id/hollowtext"android:layout_width="wrap_content"android:layout_height="50dp"android:gravity="center"android:text="镂空文本"android:textSize="30sp"android:layout_marginTop="230dp"android:layout_marginLeft="@dimen/dp_200"android:layout_marginRight="50dp"android:textStyle="bold"app:hollowTextView_background_color="#4CAF50"app:hollowTextView_corner_radius="5dp"/>