Android Canvas rotate() 旋转

Canvas 提供了 rotate() 方法用于旋转当前 Canvas 对象一定角度

void rotate(float degrees)
final void rotate(float degrees, float px, float py)

围绕坐标原点或指定坐标旋转 degrees 度，值为正顺时针

1. 创建一个 空的 Android 项目 cn.twle.android.CanvasRotate

2. 自定义一个 View 类 MsView.java

   package cn.twle.android.canvasrotate;
   
   import android.content.Context;
   import android.graphics.Canvas;
   import android.graphics.Paint;
   import android.support.v7.widget.AppCompatImageView;
   
   public class MsView extends AppCompatImageView {
   
       public MsView(Context context) {
   
           super(context, null);
       }
   
       @Override
       protected void onDraw(Canvas canvas) {
   
           super.onDraw(canvas);
   
           Paint mPaint = new Paint();
   
           mPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
           mPaint.setAntiAlias(true);// 抗锯尺
           mPaint.setColor(0xffff0000);
           mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
           mPaint.setTextSize(48.0f);
   
           canvas.translate(500, 500);
   
           for(int i = 0; i < 36;i++){
               canvas.rotate(10);
               canvas.drawText("简单教程，简单编程",0,0,mPaint);
           }
           invalidate();
       }
   }

3. 修改 MainActivity.java 设置 setContentView(new MsView(MainActivity.this))

   package cn.twle.android.canvasrotate;
   
   import android.support.v7.app.AppCompatActivity;
   import android.os.Bundle;
   
   public class MainActivity extends AppCompatActivity {
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(new MsView(MainActivity.this));
       }
   }

   这里先调用了 translate(500，500) 将 canvas 的坐标原点移向了 (500,500)，再进行绘制

   绘制的结果可以完整的在画布上显示出来，假如我们设置 canvsd.rotate(10,200,200) 则会是这样