android 添加文字水印 支持多行水印

android 添加文字水印 支持多行水印

特点

支持多行水印，支持自定义角度，支持自定义文字大小。

原理：

使用一个TextView 占据整个页面。在TextView基础上面打水印。

用法：

具体的view在

package cn.fulushan.watermark.view;

import android.content.Context;
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.support.annotation.IntRange;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;


import java.util.List;

/**
 * Created by fulushan on 18/4/5.
 */

public class WaterMarkBg extends Drawable {

    private Paint paint = new Paint();
    private List labels;
    private Context context;
    private int degress;//角度
    private int fontSize;//字体大小 单位sp

    /**
     * 初始化构造
     * @param context 上下文
     * @param labels 水印文字列表 多行显示支持
     * @param degress 水印角度
     * @param fontSize 水印文字大小
     */
    public WaterMarkBg(Context context,List labels,  int degress,int fontSize) {
        this.labels = labels;
        this.context = context;
        this.degress = degress;
        this.fontSize = fontSize;
    }

    @Override
    public void draw(@NonNull Canvas canvas) {


        int width = getBounds().right;
        int height = getBounds().bottom;

        canvas.drawColor(Color.parseColor("#40F3F5F9"));
        paint.setColor(Color.parseColor("#50AEAEAE"));

        paint.setAntiAlias(true);
        paint.setTextSize(sp2px(context,fontSize));
        canvas.save();
        canvas.rotate(degress);
        float textWidth = paint.measureText(labels.get(0));
        int index = 0;
        for (int positionY = height / 10; positionY <= height; positionY += height / 10+80) {
            float fromX = -width + (index++ % 2) * textWidth;
            for (float positionX = fromX; positionX < width; positionX += textWidth * 2) {
                int spacing  = 0;//间距
                for(String label:labels){
                    canvas.drawText(label, positionX, positionY+spacing, paint);
                    spacing = spacing+50;
                }

            }
        }
        canvas.restore();
    }

    @Override
    public void setAlpha(@IntRange(from = 0, to = 255) int alpha) {

    }

    @Override
    public void setColorFilter(@Nullable ColorFilter colorFilter) {

    }

    @Override
    public int getOpacity() {
        return PixelFormat.UNKNOWN;
    }


    public static int sp2px(Context context, float spValue) {
        final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
        return (int) (spValue * fontScale + 0.5f);
    }
}

具体的用法

public class MainActivity extends AppCompatActivity {
    private TextView bg_tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bg_tv = findViewById(R.id.bg_tv);

        SimpleDateFormat createTimeSdf1 = new SimpleDateFormat("yyyy-MM-dd");

        List labels = new ArrayList<>();
        labels.add("用户名：张三");
        labels.add("日期："+ createTimeSdf1.format(new Date()));
        labels.add("不可扩散");
        bg_tv.setBackgroundDrawable(new WaterMarkBg(MainActivity.this,labels,-30,13));


    }
}

效果图

github源码地址
https://github.com/fulushan/watermark-android

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