Android实现多行文字水印效果

自定义一个水印控件WaterMark,实现Drawable,具体实现如下

public class WaterMark extends Drawable {

 

  private Paint paint = new Paint();

  private List<String> 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<String> 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;

  }

 

 

/**

   * 设置水印字体大小

   * @param context 上下文

   * @param spValue 水印文字列表 多行显示支持

   */

  public static int sp2px(Context context, float spValue) {

    final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;

    return (int) (spValue * fontScale + 0.5f);

  }

}

 

具体使用场景:

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<String> 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));

  }

}