這次主要是練習一下Android的自定義view和path的相關使用，所以做了一個簡單的demo：自定義一個view，並用path在上面畫一個可以動態改變圓角大小的長方形。

自定義相關屬性

自定義view首先需要在values資料夾下建一個attrs檔案，並在其中定義view的相關屬性，如下：

<resources>
  <declare-styleable name="CustomView">
    <attr name="round_position">
      <flag name="left-top" value="0x1"></flag>
      <flag name="right-top" value="0x4"></flag>
      <flag name="left-bottom" value="0x2"></flag>
      <flag name="right-bottom" value="0x8"></flag>
    </attr>
    <attr name="round_radius" format="dimension"></attr>
  </declare-styleable>
</resources>

其中round_position指的是圓角的位置，這裡屬性型別定為flag（位或運算）這樣就可以在佈局中同時使用多個屬性了，類似於EditText中定義文字樣式：android:textStyle="bold|italic";round_radius指圓角大小，型別為dimension。

自定義view類

新建一個類繼承View，如下：

public class CustomView extends View {
  private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
  private Path path;
  private int color = Color.GREEN;
  private final int LEFT_TOP = 0x1;
  private final int LEFT_BOTTOM = 0x2;
  private final int RIGHT_TOP = 0x4;
  private final int RIGHT_BOTTOM = 0x8;
  private boolean drawLeftTop;
  private boolean drawLeftBottom;
  private boolean drawRightTop;
  private boolean drawRightBottom;
  private float radius;

  public CustomView(Context context) {
    super(context);
    initDraw();
  }

  public CustomView(Context context,@Nullable AttributeSet attrs) {
    super(context,attrs);
    TypedArray typedArray = context.obtainStyledAttributes(attrs,R.styleable.CustomView);
    int position = typedArray.getInt(R.styleable.CustomView_round_position,0);
    radius = typedArray.getDimension(R.styleable.CustomView_round_radius,0);
    drawLeftTop = (position & LEFT_TOP) == LEFT_TOP;
    drawLeftBottom = (position & LEFT_BOTTOM) == LEFT_BOTTOM;
    drawRightTop = (position & RIGHT_TOP) == RIGHT_TOP;
    drawRightBottom = (position & RIGHT_BOTTOM) == RIGHT_BOTTOM;
    typedArray.recycle();
    initDraw();
  }

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

  private void initDraw() {
    path = new Path();
    paint.setColor(Color.GREEN);
    paint.setAntiAlias(true);
    paint.setStrokeWidth((float) 5);
    paint.setStyle(Paint.Style.STROKE);
  }

  @Override
  protected void onDraw(Canvas canvas) {
    path.reset();//這裡很重要，如果不寫這一行，則每次重繪view後先前繪製的還會存在
    path.moveTo(radius,0);
    if (drawRightTop) {
      path.lineTo(getWidth() - radius,0);
//      path.cubicTo(radius + getWidth() / 3,radius + getWidth() / 3 * 2,getWidth() - radius,0);
      path.cubicTo(getWidth() - radius / 2,getWidth(),radius / 2,radius);
    } else {
      path.lineTo(getWidth(),0);
    }
    path.lineTo(getWidth(),getHeight() - radius);
//    path.cubicTo(getWidth(),radius + getHeight() / 3,radius + getHeight() / 3 * 2,getHeight() - radius);
    if (drawRightBottom) {
      path.cubicTo(getWidth(),getHeight() - radius / 2,getWidth() - radius / 2,getHeight(),getHeight());
    } else {
      path.lineTo(getWidth(),getHeight());
    }
    path.lineTo(radius,getHeight());
    if (drawLeftBottom) {
      path.cubicTo(radius / 2,getHeight() - radius);
    } else {
      path.lineTo(0,getHeight());
    }
    path.lineTo(0,radius);
    if (drawLeftTop) {
      path.cubicTo(0,radius,0);
    } else {
      path.lineTo(0,0);
      path.lineTo(radius,0);
    }
    canvas.drawPath(path,paint);
    super.onDraw(canvas);
  }

  public void setRadius(float radius) {
    this.radius = radius;
  }

  public void refreshView() {
    invalidate();
  }
}

這裡使用了path和貝塞爾曲線的繪製方法來繪製可動態調整圓角大小的長方形，注意每次重繪時要先呼叫path.reset()清除之前繪製的path，然後再繪製新的path，不然舊的path還會一直存在。

佈局中使用自定義view

<wjc.myrecyclerview.CustomView
    android:id="@+id/custom_view"
    android:layout_width="200dp"
    android:layout_height="200dp"
    android:layout_margin="100dp"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:round_position="left-bottom|right-bottom|right-top|left-top" />

這樣就完成了一個簡單的自定義可調整圓角的長方形，在MainActivity中進行動態控制：

view.setRadius(progress);
view.refreshView();

實現的最終效果

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支援我們。