Android widget - 实现雷达扫描特效，以百分比的方式显示探测到的物体距离，距离越近，点的位置越靠近中心。
软件架构
Android 雷达扫描特效, 两种实现，纯canvas绘制， 或者绘制点图片（以便硬件加速用， 默认）
1. XML里添加布局
<org.tcshare.widgets.RadarView
android:id="@+id/radarView"
android:layout_width="300dp"
android:layout_height="300dp"/>
2. 代码里启动扫描，并添加雷达反射点的距离，用百分比表示距离。
radarView.setSearching(true); // 开启扫描模式，扫描线会转动
radarView.addPoint(RandomUtils.getRandomFloat(1)); // 传入一个百分比，用来指示点距离中心点的百分比点击开始按钮，循环添加搜索到的点，这里随机数值演示。
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tcradar_main);
radarView = findViewById(R.id.radarView);
radarView.setSearching(true);
addPoint();
}
private void addPoint(){
radarView.postDelayed(new Runnable() {
@Override
public void run() {
radarView.addPoint(RandomUtils.getRandomFloat(1));
addPoint();
}
}, 50);
}RadarView.java 源代码：
package org.tcshare.widgets;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BlurMaskFilter;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.MaskFilter;
import android.graphics.Paint;
import android.graphics.PointF;
import android.graphics.Shader;
import android.graphics.SweepGradient;
import android.util.AttributeSet;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import org.tcshare.androidutils.R;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class RadarView extends View {
private Bitmap pointImg;
// 参数调整>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
private final boolean usePointBitmap = true;
private final float pointRadius = 10f; // 扫描点的半径
private final int MAX_POINT_SHOW = 100;// 最多显示100个点
private final MaskFilter outLightFilter = new BlurMaskFilter(pointRadius, BlurMaskFilter.Blur.SOLID); // 外发光
private final int showPointAngel = 300; // 最大显示范围, 最大360度
private final int bgColor = -0x472304; // 背景颜色
private final int bgRadar = -0xcd874c; // 雷达区域背景色
private final int colorCircle = -0xce360e; // 内部园环及分割线的颜色
private final int radarColor = Color.parseColor("#AA0000FF"); // 扫描扇形的颜色
private final int mNumCicle = 4; // 多少个园环
private final int mNumLines = 4; // 对角线的个数
// 参数调整<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
private SweepGradient sweepGradient = null;
private boolean isSearching = false;
private final Paint mPaint = new Paint();
private int mCurrentAngel = 0;
private final List<MyPoint> mPointArray = new ArrayList<MyPoint>();
private int mWidth = 0;
private int mHeight = 0;
private int mOutWidth = 0; // 外圆宽度(w/4/5*2=w/10)
private int mCx = 0; // x、y轴中心点
private int mCy = 0;
private int mOutsideRadius = 0;// 外、内圆半径
private int mInsideRadius = 0;
public RadarView(Context context) {
super(context);
init(context);
}
public RadarView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init(context);
}
public RadarView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context);
}
public RadarView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init(context);
}
private void init(Context context) {
if (usePointBitmap) {
pointImg = BitmapFactory.decodeResource(getResources(), R.mipmap.point); // xxhdpi
// 默认硬件加速
setLayerType(View.LAYER_TYPE_HARDWARE, (Paint) null);
} else {
setLayerType(View.LAYER_TYPE_SOFTWARE, (Paint) null);
}
}
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
// 获取控件区域宽高
if (mWidth == 0 || mHeight == 0) {
int minimumWidth = getSuggestedMinimumWidth();
int minimumHeight = getSuggestedMinimumHeight();
mWidth = resolveMeasured(widthMeasureSpec, minimumWidth);
mHeight = resolveMeasured(heightMeasureSpec, minimumHeight);
// 获取x/y轴中心点
mCx = mWidth / 2;
mCy = mHeight / 2;
// 获取外圆宽度
mOutWidth = mWidth / 10;
// 计算内、外半径
mOutsideRadius = mWidth / 2;// 外圆的半径
mInsideRadius = (mWidth - mOutWidth) / mNumCicle / 2;// 内圆的半径,除最外层,其它圆的半径=层数*insideRadius
sweepGradient = new SweepGradient((float) mCx, (float) mCy, 0, radarColor);
}
}
@Override
protected void onDraw(@NonNull Canvas canvas) {
super.onDraw(canvas);
// 1. 绘制圆形背景
mPaint.setAntiAlias(true);
mPaint.setStyle(Paint.Style.FILL);
mPaint.setColor(bgColor);
mPaint.setShader(null);
mPaint.setAlpha(255);
canvas.drawCircle((float) mCx, (float) mCy, (float) mOutsideRadius, mPaint);
// 2. 绘制雷达区域背景
mPaint.setColor(bgRadar);
canvas.drawCircle((float) mCx, (float) mCy, (float) mInsideRadius * (float) mNumCicle, mPaint);
// 3. 绘制园环
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setColor(colorCircle);
for (int num = mNumCicle; num >= 1; --num) {
canvas.drawCircle((float) mCx, (float) mCy, (float) mInsideRadius * (float) num, mPaint);
}
// 4. 绘制对角线
double angle = (double) (180 / mNumLines);
int lineRadius = mInsideRadius * mNumCicle;
for (int num = 0; num < mNumLines; ++num) {
double radianS = Math.toRadians(num * angle); // 将角度转换为弧度
double radianE = Math.toRadians(num * angle + 180);
canvas.drawLine(
(float) (mCx + lineRadius * Math.cos(radianS)),
(float) (mCy + lineRadius * Math.sin(radianS)),
(float) (mCx + lineRadius * Math.cos(radianE)),
(float) (mCy + lineRadius * Math.sin(radianE)),
mPaint
);
}
// 5.绘制扫描扇形图
if (isSearching) {// 判断是否处于扫描
canvas.save();
canvas.rotate(
mCurrentAngel,
mCx,
mCy
);
mPaint.setStyle(Paint.Style.FILL);
mPaint.setShader(sweepGradient);
mCurrentAngel += 3;
canvas.drawCircle(
mCx,
mCy,
mInsideRadius * mNumCicle,
mPaint
);
canvas.restore();
// 6.开始绘制动态点
mPaint.setColor(Color.WHITE);
mPaint.setStyle(Paint.Style.FILL);
mPaint.setShader(null);
if (!usePointBitmap) mPaint.setMaskFilter(outLightFilter); // 绘制圆的外发光, 需要关闭硬件加速
for (int i = mPointArray.size() - 1; i >= 0; i--) { // 倒序，先画最新的，然后更改不透明度
MyPoint p = mPointArray.get(i);
if (mCurrentAngel >= showPointAngel && mCurrentAngel - showPointAngel > p.angel) {
mPointArray.remove(i); //倒序移除
} else {
int sAngel = (mCurrentAngel - p.angel - 1) % showPointAngel; // 这里减一，是因为浮点型导致最后一个又正常显示了
if (sAngel == 0) {
mPaint.setAlpha(255);
} else {
mPaint.setAlpha((int) (255 - (float) sAngel / showPointAngel * 255));
}
if (usePointBitmap) {
canvas.drawBitmap(
pointImg,
p.pos.x - pointImg.getWidth() / 2f,
p.pos.y - pointImg.getHeight() / 2f,
mPaint
);
} else {
canvas.drawCircle(
p.pos.x,
p.pos.y,
pointRadius,
mPaint
);
}
}
}
this.invalidate();
}
}
public final void setSearching(boolean status) {
isSearching = status;
if (!isSearching) {
mPointArray.clear();
}
invalidate();
}
public final boolean isSearching() {
return isSearching;
}
public final void addPoint(float percent) {
if (!isSearching) return;
double radian = Math.toRadians(mCurrentAngel);
float lineRadius = mInsideRadius * mNumCicle * percent;
float pX = (float) (mCx + lineRadius * Math.cos(radian));
float pY = (float) (mCy + lineRadius * Math.sin(radian));
MyPoint point = new MyPoint(percent, new PointF(pX, pY), mCurrentAngel);
mPointArray.add(point);
if (mPointArray.size() > MAX_POINT_SHOW) { // 超过允许的点个数，移除最开始的一个
mPointArray.remove(0); //TODO 测试是否存在重新分配数组的问题
}
this.invalidate();
}
private int resolveMeasured(int measureSpec, int desired) {
int specSize = MeasureSpec.getSize(measureSpec);
int result;
switch (MeasureSpec.getMode(measureSpec)) {
case MeasureSpec.UNSPECIFIED:
result = desired;
break;
case MeasureSpec.AT_MOST:
result = Math.max(specSize, desired);
break;
case MeasureSpec.EXACTLY:
result = specSize;
break;
default:
result = specSize;
break;
}
return result;
}
public static final class MyPoint {
float percent;
PointF pos;
int angel;
public String toString() {
return "MyPoint(percent=" + percent + ", pos=" + pos + "， mOffsetArgs=" + angel + ",)";
}
public MyPoint(float percent, @NonNull PointF pos, int angel) {
super();
this.percent = percent;
this.pos = pos;
this.angel = angel;
}
}
}