Shader应用---雷达扫描效果

效果图

知识点提要

1. Shader
2. 矩阵matrix
3. 属性动画

ShaderView3

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);


    }
}

外部调用

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布局

<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>