Android 水印效果

本文主要介绍下android 中水印的实现效果.

实现的方式有多种,就不一一赘述了, 本文就是通过自定义drawable来实现水印.

不多说,直接上代码吧:

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.drawable.Drawable;
import android.util.DisplayMetrics;public class WatermarkDrawable extends Drawable {private String watermarkText;private Paint paint;private boolean isOne;private int numX, numY;private int mWidth, mHeight, mOffSet, textWidth, textHeight;private Context mContext;public WatermarkDrawable(Context context, String text, boolean isOne) {watermarkText = text;mContext = context;this.isOne = isOne;paint = new Paint();paint.setColor(Color.GRAY);paint.setTextSize(50);paint.setAlpha(100);textWidth = (int) paint.measureText(watermarkText);Paint.FontMetrics fontMetrics = paint.getFontMetrics();textHeight = (int) (fontMetrics.descent - fontMetrics.ascent);Resources resources = mContext.getResources();DisplayMetrics dm = resources.getDisplayMetrics();mWidth = dm.widthPixels;mHeight = dm.heightPixels;mOffSet = ((mHeight - mWidth) >> 1);int max = Math.max(mWidth, mHeight);numX = max / (textWidth + 50) + 2;numY = max / (textHeight + 100) + 2;}@Overridepublic void draw(Canvas canvas) {if (isOne) {drawOneWaterMark(canvas);} else {drawFullWaterMark(canvas);}}private void drawOneWaterMark(Canvas canvas) {int width = getBounds().width();int height = getBounds().height();float textWidth = paint.measureText(watermarkText);float x = (width - textWidth) / 2;float y = height / 2;canvas.drawText(watermarkText, x, y, paint);}private void drawFullWaterMark(Canvas canvas) {for (int i = 0; i < numY; i++) {int yy = (100 >> 1) + (100 + textHeight) * i;for (int j = 0; j < numX; j++) {float xx = (i % 2) * (50 + textWidth) / 2 + j * (50 + textWidth);canvas.drawText(watermarkText, xx, yy, paint);}}}@Overridepublic void setAlpha(int alpha) {paint.setAlpha(alpha);}@Overridepublic void setColorFilter(ColorFilter colorFilter) {paint.setColorFilter(colorFilter);}@Overridepublic int getOpacity() {return PixelFormat.TRANSLUCENT;}
}

这里只是简单实现下单个水印以及全局多个水印的效果, 后续水印的效果:如 旋转角度,水印的多少,水印文案的限制在继续优化吧.

设置水印的方式也很简单:

  WatermarkDrawable watermarkDrawable = new WatermarkDrawable(this,"测试", false);

获取acitvity的根布局, 设置背景drawable即可.

我们可以通过调用setForeground方法, 让水印在整个页面的前台,从而不被页面中的组件遮挡.
效果如下: