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.
 * 女神面部掃描
 */

public class ShaderView3 extends View {

  /**
   * 繪制掃描圈的筆
   */
  private Paint mSweepPaint;
  /**
   * 繪制女神bitmap的筆
   */
  private Paint mBitmapPaint;
  /**
   * 這個自定義View的寬度，就是你在xml布局里面設(shè)置的寬度（目前不支持）
   */
  private int mWidth;
  /**
   * 女神圖片
   */
  private Bitmap mBitmap;
  /**
   * 雷達掃描旋轉(zhuǎn)角度
   */
  private int degrees = 0;
  /**
   * 用于控制掃描圈的矩陣
   */
  Matrix mSweepMatrix = new Matrix();
  /**
   * 用于控制女神Bitmap的矩陣
   */
  Matrix mBitmapMatrix = new Matrix();
  /**
   * 著色器---生成掃描圈
   */
  private SweepGradient mSweepGradient;
  /**
   * 圖片著色器
   */
  private BitmapShader mBitmapShader;
  private float mScale;

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

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

  /**
   * 屬性動畫，必須有setXxx方法，才可以針對這個屬性實現(xiàn)動畫
   *
   * @param degrees
   */
  public void setDegrees(int degrees) {
    this.degrees = degrees;
    postInvalidate();//在主線程里執(zhí)行OnDraw
  }

  private void init() {
//    1.準備好畫筆
    mSweepPaint = new Paint();
    mBitmapPaint = new Paint();
//    2.圖片著色器
    mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ccc);
    mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
//    3.將圖片著色器設(shè)置給畫筆
    mBitmapPaint.setShader(mBitmapShader);
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
//    獲取這個自定義view的寬高，注意在onMeasure里獲取，在構(gòu)造函數(shù)里得到的是0
    mWidth = getMeasuredWidth();
//    根據(jù)你所設(shè)置的view的尺寸和bitmap的尺寸計算一個縮放比例，否則的話，得到的圖片是一個局部，而不是一整張圖片
    mScale = (float) mWidth / (float) mBitmap.getWidth();
//    4.梯度掃描著色器
    mSweepGradient = new SweepGradient(mWidth / 2, mWidth / 2, new int[]{Color.argb(200, 200, 0, 0), Color.argb(10, 30, 0, 0)}, null);
//    5.將梯度掃描著色器設(shè)置給另外一支畫筆
    mSweepPaint.setShader(mSweepGradient);


  }

  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
//    迫不得已的時候，才在onDraw方法寫代碼，能提前準備的要在之前去準備，
//    不要寫在onDraw里面，因為onDraw會不停地刷新繪制，寫的代碼越多，越影響效率


//    將圖片縮放至你指定的自定義View的寬高
    mBitmapMatrix.setScale(mScale, mScale);
    mBitmapShader.setLocalMatrix(mBitmapMatrix);

//   設(shè)置掃描圈旋轉(zhuǎn)角度
    mSweepMatrix.setRotate(degrees, mWidth / 2, mWidth / 2);
    mSweepGradient.setLocalMatrix(mSweepMatrix);

//    5. 使用設(shè)置好圖片著色器的畫筆，畫圓，先畫出下層的女神圖片，在畫出上層的掃描圖片
    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>