Android Shader应用开发之雷达扫描效果

package com.example.apple.shaderdemo;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Shader;
import android.graphics.SweepGradient;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by apple on 2017/5/23.
 * 女神面部扫描
 */

public class ShaderView3 extends View {

  /**
   * 绘制扫描圈的笔
   */
  private Paint mSweepPaint;
  /**
   * 绘制女神bitmap的笔
   */
  private Paint mBitmapPaint;
  /**
   * 这个自定义View的宽度，就是你在xml布局里面设置的宽度（目前不支持）
   */
  private int mWidth;
  /**
   * 女神图片
   */
  private Bitmap mBitmap;
  /**
   * 雷达扫描旋转角度
   */
  private int degrees = 0;
  /**
   * 用于控制扫描圈的矩阵
   */
  Matrix mSweepMatrix = new Matrix();
  /**
   * 用于控制女神Bitmap的矩阵
   */
  Matrix mBitmapMatrix = new Matrix();
  /**
   * 着色器---生成扫描圈
   */
  private SweepGradient mSweepGradient;
  /**
   * 图片着色器
   */
  private BitmapShader mBitmapShader;
  private float mScale;

  public ShaderView3(Context context) {
    super(context);
    init();
  }

  public ShaderView3(Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
    init();
  }

  /**
   * 属性动画，必须有setXxx方法，才可以针对这个属性实现动画
   *
   * @param degrees
   */
  public void setDegrees(int degrees) {
    this.degrees = degrees;
    postInvalidate();//在主线程里执行OnDraw
  }

  private void init() {
//    1.准备好画笔
    mSweepPaint = new Paint();
    mBitmapPaint = new Paint();
//    2.图片着色器
    mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ccc);
    mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
//    3.将图片着色器设置给画笔
    mBitmapPaint.setShader(mBitmapShader);
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
//    获取这个自定义view的宽高，注意在onMeasure里获取，在构造函数里得到的是0
    mWidth = getMeasuredWidth();
//    根据你所设置的view的尺寸和bitmap的尺寸计算一个缩放比例，否则的话，得到的图片是一个局部，而不是一整张图片
    mScale = (float) mWidth / (float) mBitmap.getWidth();
//    4.梯度扫描着色器
    mSweepGradient = new SweepGradient(mWidth / 2, mWidth / 2, new int[]{Color.argb(200, 200, 0, 0), Color.argb(10, 30, 0, 0)}, null);
//    5.将梯度扫描着色器设置给另外一支画笔
    mSweepPaint.setShader(mSweepGradient);


  }

  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
//    迫不得已的时候，才在onDraw方法写代码，能提前准备的要在之前去准备，
//    不要写在onDraw里面，因为onDraw会不停地刷新绘制，写的代码越多，越影响效率


//    将图片缩放至你指定的自定义View的宽高
    mBitmapMatrix.setScale(mScale, mScale);
    mBitmapShader.setLocalMatrix(mBitmapMatrix);

//   设置扫描圈旋转角度
    mSweepMatrix.setRotate(degrees, mWidth / 2, mWidth / 2);
    mSweepGradient.setLocalMatrix(mSweepMatrix);

//    5. 使用设置好图片着色器的画笔，画圆，先画出下层的女神图片，在画出上层的扫描图片
    canvas.drawCircle(mWidth / 2, mWidth / 2, mWidth / 2, mBitmapPaint);
    canvas.drawCircle(mWidth / 2, mWidth / 2, mWidth / 2, mSweepPaint);


  }
}

package com.example.apple.shaderdemo;

import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.animation.LinearInterpolator;

public class MainActivity extends AppCompatActivity {

  private ShaderView3 mShaderView;
  int degrees = 0;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mShaderView = (ShaderView3) findViewById(R.id.sv);

    mShaderView.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        ObjectAnimator degrees = ObjectAnimator.ofInt(mShaderView, "degrees", 0, 360);
        degrees.setInterpolator(new LinearInterpolator());
        degrees.setDuration(10000);
        degrees.setRepeatCount(ValueAnimator.INFINITE);
        degrees.start();
        /* new Thread(new Runnable() {
          @Override
          public void run() {
            while (degrees <= 360) {
              degrees += 1;
              mShaderView.setDegrees(degrees);

              try {
                Thread.sleep(30);
              } catch (InterruptedException e) {
                e.printStackTrace();
              }
            }


          }
        }).start();

        degrees = 0;
        mShaderView.setDegrees(degrees);*/


      }
    });
  }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context="com.example.apple.shaderdemo.MainActivity">

  <com.example.apple.shaderdemo.ShaderView3
    android:id="@+id/sv"
    android:layout_width="300dp"
    android:layout_height="300dp"
    />

</LinearLayout>