在画布android上旋转矩形

Question

我创建了一个将另一个活动设置为视图的活动，在这个活动中我创建了画布（onDraw）并在一个矩形内，现在我想旋转它，我尝试了canvas.rotate()，但似乎什么也没发生。这是我的代码：

public class DrawView extends View {
Paint paint = new Paint();
private Rect rec1;

public DrawView(Context context) {
    super(context);
}

protected void onDraw(Canvas canvas) {
    Paint paint = new Paint();
    paint.setStyle(Paint.Style.STROKE);
    DisplayMetrics metrics = new DisplayMetrics();
    ((Activity)    getContext()).getWindowManager().getDefaultDisplay().getMetrics(metrics);
    int y = metrics.heightPixels;
    int x = metrics.widthPixels;
    rec1 = new Rect(x / 2 - 25, 0, x / 2 + 25, y);
    paint.setColor(Color.BLACK);
    paint.setStrokeWidth(3);
    canvas.drawRect(rec1, paint);
    for (int j = 1; j <= 200; j++) {
        canvas.rotate(5);
    }
}

谁知道问题出在哪里？我还检查了问题是否出在 for 中，所以我删除了它并添加了一行 canvas.rotate(45) ，但什么也没有。

如果需要，这里是 MainActivity

import android.app.Activity;
    import android.graphics.Color;
    import android.os.Bundle;

public class MainActivity extends Activity {
DrawView drawView;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    drawView = new DrawView(this);
    drawView.setBackgroundColor(Color.WHITE);
    setContentView(drawView);

      }
 }

谢谢大家:)

Answer 1

动画/rotate.xml

<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
    android:repeatMode="restart"
    android:repeatCount="infinite"
    android:interpolator="@android:anim/linear_interpolator"
    android:fromDegrees="0"
    android:toDegrees="360"
    android:pivotX="50%"
    android:pivotY="50%"
    android:duration="1500" />

---

<View
    android:layout_width="match_parent"
    android:layout_height="200dp"
    android:background="#f90"
    android:id="@+id/rect"/>

---

View rect = findViewById(R.id.rect);
Animation rotate = AnimationUtils.loadAnimation(this, R.anim.rotate);
rect.startAnimation(rotate);

Answer 2

绘制前需要旋转：

canvas.rotate(45);
canvas.drawRect(rec1, paint);