Android自绘View界面布局实现文字水印效果

一、需求分析

（1）水印文字旋转
（2）水印效果处于内容布局之下
（3）水印文字的具体位置
（4）水印文字的特殊效果,例如图中的空心字体效果

二、功能实现

1. 自定义view(大家瞬间就能想到Canvas工具),直接上代码

package com.newbjgoodwill.mobilecwr.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by zhangjianmin on 2017/7/4.
 */

public class WaterView extends View {
    private String water_name;//需要回传的值

    public WaterView(Context context, String user_name) {
        super(context);
        this.water_name = user_name;
    }

    public WaterView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public WaterView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);
    }

    public WaterView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.save();
        Paint paint = new Paint();
        paint.setColor(Color.argb(191, 200, 215, 200));
        //设置字体大小
        paint.setTextSize(46);
        //让画出的图形是空心的
        paint.setStyle(Paint.Style.STROKE);
        //设置画出的线的 粗细程度
        paint.setStrokeWidth(1);
        // 以文字中心轴旋转
        canvas.rotate(-20, this.getWidth() / 2f, this.getHeight() / 2f);
        // 按照指定点的坐标绘制文本(在这里画了四个);water_name 不能为空
        canvas.drawText(water_name + "", this.getWidth() / 4f, this.getHeight() / 2f, paint);
        canvas.drawText(water_name + "", this.getWidth() / 1.5f, this.getHeight() / 2f, paint);
        canvas.drawText(water_name + "", this.getWidth() / 1.5f, this.getHeight() / 4f, paint);
        canvas.drawText(water_name + "", this.getWidth() / 4f, this.getHeight() / 4f, paint);
        super.onDraw(canvas);
        canvas.restore();
    }

    public void setWater_name(String water_name) {
        this.water_name = water_name;
    }
}

2. 添加水印到当前布局

如何将水印布局添加到内容布局之下，我们可以利用DecoerView来实现。在onCreate中设置了根布局后，会生成DecoerView，那么我们可以通过addView的方式，将水印布局添加，通过第二个参数来控制布局层次即可

package com.newbjgoodwill.mobilecwr;

import android.app.Activity;
import android.os.Bundle;
import android.view.ViewGroup;

import watermark.WaterView;

public class MainActivity extends Activity {
    private WaterView view;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onStart() {
        addWaterMarkView();
        super.onStart();
    }

    private void addWaterMarkView() {
        view=new WaterView(this,"水印");
        getRootView().addView(view,-1);
    }

    private ViewGroup getRootView() {
        ViewGroup rootView = (ViewGroup)findViewById(android.R.id.content);
        return rootView;
    }
}

好了，水印效果实现就是这么简单,效果图如下:

20170705162251110.jpg