Android自定义view 实现圆的扩散(简单实用一步到位)

自定义View的实现水波纹

一:
实现效果

MainActivity.xml

MainActivity中的点击事件

public class MainActivity extends AppCompatActivity {
    private Button button;
    private Button button2;
    private DiffuseView diffuseView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button =   findViewById(R.id.button);
        button2 =   findViewById(R.id.button2);
        diffuseView = findViewById(R.id.diffuseView);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                diffuseView.start();
            }
        });

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                diffuseView.stop();
            }
        });
    }
}

自定义view类

public class DiffuseView extends View {

    /** 扩散圆圈颜色 */
    private int mColor = getResources().getColor(R.color.colorAccent);
    /** 圆圈中心颜色 */
    private int mCoreColor = getResources().getColor(R.color.colorPrimary);
    /** 中心圆半径 */
    private float mCoreRadius = 150;
    /** 扩散圆宽度 */
    private int mDiffuseWidth = 3;
    /** 最大宽度 */
    private Integer mMaxWidth = 255;
    /** 扩散速度 */
    private int mDiffuseSpeed = 5;
    /** 是否正在扩散中 */
    private boolean mIsDiffuse = false;
    // 透明度集合
    private List mAlphas = new ArrayList<>();
    // 扩散圆半径集合
    private List mWidths = new ArrayList<>();
    private Paint mPaint;

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

    public DiffuseView(Context context, AttributeSet attrs) {
        this(context, attrs, -1);
    }

    public DiffuseView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.DiffuseView, defStyleAttr, 0);
        mColor = a.getColor(R.styleable.DiffuseView_diffuse_color, mColor);
        mCoreColor = a.getColor(R.styleable.DiffuseView_diffuse_coreColor, mCoreColor);
        mCoreRadius = a.getFloat(R.styleable.DiffuseView_diffuse_coreRadius, mCoreRadius);
        mDiffuseWidth = a.getInt(R.styleable.DiffuseView_diffuse_width, mDiffuseWidth);
        mMaxWidth = a.getInt(R.styleable.DiffuseView_diffuse_maxWidth, mMaxWidth);
        mDiffuseSpeed = a.getInt(R.styleable.DiffuseView_diffuse_speed, mDiffuseSpeed);
        a.recycle();
    }

    private void init() {
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mAlphas.add(255);
        mWidths.add(0);
    }

    @Override
    public void invalidate() {
        if(hasWindowFocus()){
            super.invalidate();
        }
    }

    @Override
    public void onWindowFocusChanged(boolean hasWindowFocus) {
        super.onWindowFocusChanged(hasWindowFocus);
        if(hasWindowFocus){
            invalidate();
        }
    }

    @Override
    public void onDraw(Canvas canvas) {
        // 绘制扩散圆
        mPaint.setColor(mColor);
        for (int i = 0; i < mAlphas.size(); i ++) {
            // 设置透明度
            Integer alpha = mAlphas.get(i);
            mPaint.setAlpha(alpha);
            // 绘制扩散圆
            Integer width = mWidths.get(i);
            canvas.drawCircle(getWidth() / 2, getHeight() / 2, mCoreRadius + width, mPaint);

            if(alpha > 0 && width < mMaxWidth){
                mAlphas.set(i, alpha - mDiffuseSpeed > 0 ? alpha - mDiffuseSpeed : 1);
                mWidths.set(i, width + mDiffuseSpeed);
            }
        }
        // 判断当扩散圆扩散到指定宽度时添加新扩散圆
        if (mWidths.get(mWidths.size() - 1) >= mMaxWidth / mDiffuseWidth) {
            mAlphas.add(255);
            mWidths.add(0);
        }
        // 超过10个扩散圆，删除最外层
        if(mWidths.size() >= 10){
            mWidths.remove(0);
            mAlphas.remove(0);
        }

        // 绘制中心圆
        mPaint.setAlpha(255);
        mPaint.setColor(mCoreColor);
        canvas.drawCircle(getWidth() / 2, getHeight() / 2, mCoreRadius, mPaint);

        if(mIsDiffuse){
            invalidate();
        }
    }

    /**
     * 开始扩散
     */
    public void start() {
        mIsDiffuse = true;
        invalidate();
    }

    /**
     * 停止扩散
     */
    public void stop() {
        mIsDiffuse = false;
        mWidths.clear();
        mAlphas.clear();
        mAlphas.add(255);
        mWidths.add(0);
        invalidate();
    }

    /**
     * 是否扩散中
     */
    public boolean isDiffuse(){
        return mIsDiffuse;
    }

    /**
     * 设置扩散圆颜色
     */
    public void setColor(int colorId){
        mColor = colorId;
    }

    /**
     * 设置中心圆颜色
     */
    public void setCoreColor(int colorId){
        mCoreColor = colorId;
    }

    /**
     * 设置中心圆半径
     */
    public void setCoreRadius(int radius){
        mCoreRadius = radius;
    }

    /**
     * 设置扩散圆宽度(值越小宽度越大)
     */
    public void setDiffuseWidth(int width){
        mDiffuseWidth = width;
    }

    /**
     * 设置最大宽度
     */
    public void setMaxWidth(int maxWidth){
        mMaxWidth = maxWidth;
    }

    /**
     * 设置扩散速度，值越大速度越快
     */
    public void setDiffuseSpeed(int speed){
        mDiffuseSpeed = speed;
    }
}

自己添加的attrs.xml(创建在Values包底下,切勿倒错)

这样就搞定了.绝对简单…