Android 雷达扫描效果、动画SweepGradient

摘要：

      今天群里（QQ群64026923）的同学在讨论雷达的效果怎么实现，机智的小伙伴们马上想到让美工切图，然后再给图片做动画不就行了吗？？？确实这个方法也不错，那么还有没有其他的方法呢？先来看看效果图：。

API分析

      SweepGradient扫描/梯度渲染, 

public SweepGradient(float cx, float cy, int[] colors, float[] positions)

Parameters:

cx	渲染中心点x 坐标
cy	渲染中心y 点坐标
colors	围绕中心渲染的颜色数组，至少要有两种颜色值
positions	相对位置的颜色数组,可为null,  若为null,可为null,颜色沿渐变线均匀分布

public SweepGradient(float cx, float cy, int color0, int color1)

Parameters:

cx	渲染中心点x 坐标
cy	渲染中心点y 坐标
color0	起始渲染颜色
color1	结束渲染颜色

效果实现：

import java.util.ArrayList;
import java.util.Random;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Shader;
import android.graphics.SweepGradient;
import android.util.AttributeSet;
import android.view.View;
import android.widget.FrameLayout;

/**
 * SweepGradient扫描/梯度渲染
 * @author mick
 *
 */
public class RadaView extends FrameLayout {
private int viewSize = 800;
private Paint mPaintLine;
private Paint mPaintSector;  // 扫描效果的画笔
public boolean isstart = false;
private ScanThread mThread;  // 扫描的线程
private int start = 0;
private Matrix matrix;

public RadaView(Context context, AttributeSet attrs) {
super(context, attrs);
initPaint();
mThread = new ScanThread(this);
setBackgroundColor(Color.TRANSPARENT);
}

public RadaView(Context context) {
this(context, null);
}

/**
 * 画笔的基本设置
 */
private void initPaint() {
mPaintLine = new Paint();
mPaintLine.setStrokeWidth(10);
mPaintLine.setAntiAlias(true);
mPaintLine.setStyle(Style.STROKE); 
mPaintLine.setColor(0xff000000);
mPaintSector = new Paint();
mPaintSector.setColor(0x9D00ff00);
mPaintSector.setAntiAlias(true);
}

public void setViewSize(int size) {
this.viewSize = size;
setMeasuredDimension(viewSize, viewSize);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(viewSize, viewSize);
}

/**
 * 开始扫描
 */
public void startScann() {
mThread.start();
isstart = true;
}

/**
 * 暂停扫描
 */
public void stopScann() {
if (isstart) {
Thread.interrupted();
isstart = false;
}
}

public void setList(ArrayList<View> list) {
for (int i = 0; i < list.size(); i++) {
int xy[] = getRamdomXY();
list.get(i).setX(xy[0]);
list.get(i).setY(xy[1]);
addView(list.get(i));
}
}

private int[] getRamdomXY() {
Random rand = new Random();
int x = rand.nextInt(900);
int y = rand.nextInt(900);
int r = (int) ((float) viewSize / 2);
if ((x >= r - 350 || x <= r + 350) && (y >= r - 350 || y <= r + 350)) {
int xy[] = new int[2];
xy[0] = x;
xy[1] = y;
return xy;
} else {
return getRamdomXY();
}
}

@Override
protected void onDraw(Canvas canvas) {
canvas.drawCircle(viewSize / 2, viewSize / 2, 175, mPaintLine);
canvas.drawCircle(viewSize / 2, viewSize / 2, 350, mPaintLine);
canvas.drawLine(viewSize / 2, 0, viewSize / 2, viewSize, mPaintLine);
canvas.drawLine(0, viewSize / 2, viewSize, viewSize / 2, mPaintLine); //
/**
 * SweepGradient扫描/梯度渲染
 * SweepGradient(float cx, float cy, int color0, int color1)
 * cx渲染中心点x 坐标
         * cy渲染中心点y 坐标
         * color0起始渲染颜色
         * color1结束渲染颜色
 * 
 */
Shader mShader = new SweepGradient(viewSize / 2, viewSize / 2, Color.TRANSPARENT, Color.GREEN);
mPaintSector.setShader(mShader);
canvas.concat(matrix);
canvas.drawCircle(viewSize / 2, viewSize / 2, 350, mPaintSector);
super.onDraw(canvas);
}



protected class ScanThread extends Thread {
private RadaView view;

public ScanThread(RadaView view) {
this.view = view;
}

@Override
public void run() {
while (true) {
if (isstart) {
view.post(new Runnable() {
public void run() {
start = start + 1;
matrix = new Matrix();
matrix.postRotate(start, viewSize / 2, viewSize / 2);
view.invalidate();
}
});
try {
Thread.sleep(10);  // 设置扫描的停止时间 
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
}

大功告成。谢谢阅读.

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