制作水波载入动画

本来想写写有点意思的东西的，哈哈。上篇文章说的。以后再写吧。今天先介绍一下一个水波载入动画，效果图例如以下：

做的比較简单。真机效果比这个好非常多，这个截图做的gif，有点蛋疼。

说说思路吧：

1. 首先画正弦曲线。这里取的是正弦周期的前3/4个周期。这样看起来比其它的周期变化非常好点；

2. 画了正弦曲线以后，就要让正弦曲线动起来，怎么动起来？乍一看认为非常困难的样子。事实上我们想想移动正弦曲线，只是是某个位置的Y轴值变化了，那么我们仅仅要给sin(x)中加入一个变量即可。即sin(x + offset)。offset的值按时间规律来变化。那么最后表现出来的效果就有移动的感觉。

3. 关于正弦曲线振幅不能设置的太高，由于我们的屏幕本来就非常小，假设振幅非常大就表现的非常不真实。我这里取的是30，看起来效果还不错。

4. 最后就是y轴方向的改变了。

要不停的提升。这里写死了，假设想用。就直接写个方法。去设置即可，比方你要设置百分比之类的。

最后上代码：

package com.zdl.wavedemo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by zhoudailiang on 2015/7/14.
 */
public class WaveView extends View {

    private Paint paint;
    private Path mPath;
    private float offset = 0.0f; // 控制正弦曲线的变化
    private MyThread thread;
    private final float amplidute = 30; // 振幅
    private float gradualY; // Y方向的渐变量
    private float gradualX; // X方向的渐变量
    private boolean isMoving = true; // 能够移动

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


    public WaveView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        // 初始化画笔
        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setColor(Color.BLUE);
        paint.setStrokeWidth(2);

        // 初始化变量
        gradualX = 0.02f;

        // 初始化路径
        mPath = new Path();

        // 初始化线程
        thread = new MyThread();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        gradualY = getMeasuredHeight();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int width = getMeasuredWidth();
        int height = getMeasuredHeight();

        mPath.reset();
        for (float i = 0; i < width; i += 0.5) {
            float tmp = (float) (1.5 * Math.PI * i / width);
            float y = amplidute * (float)Math.sin(tmp + offset) + gradualY;
            if (i == 0) {
                mPath.moveTo(0f, y);
            } else {
                mPath.lineTo(i, y);
            }
        }
        mPath.lineTo(width, height);
        mPath.lineTo(0, height);
        mPath.close();
        canvas.drawPath(mPath, paint);
        // 启动线程開始更新
        if (!thread.isAlive() && isMoving) {
            thread.start();
        }
    }

    class MyThread extends Thread {
        public void run() {
            while (isMoving) {
                offset =  offset + gradualX > 2 * Math.PI ? 0 : offset + gradualX;
                gradualY -= 0.5;
                if (gradualY < -amplidute) {
                    isMoving = false;
                    break;
                }
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                postInvalidate();
            }
        }
    }
}

代码如上，非常easy。事实上这里还能够通过还有一种方式实现。下篇文章进行介绍。

2015-7-15补充：

使用贝塞尔曲线，代码例如以下：

package com.zdl.wavedemo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by Administrator on 2015/7/14.
 */
public class WaveBesselView extends View{
    private Paint paint;
    private Path mPath;
    private float offset = 0.0f; // 控制正弦曲线的变化
    private MyThread thread;
    private final float amplidute = 100; // 振幅
    private float gradualY; // Y方向的渐变量
    private float gradualX; // X方向的渐变量
    private boolean isMoving = true; //
    private int width, height;

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

    public WaveBesselView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        // 初始化画笔
        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setColor(Color.BLUE);
        paint.setStrokeWidth(2);

        // 初始化变量
        gradualX = 0.0f;

        // 初始化路径
        mPath = new Path();

        // 初始化线程
        thread = new MyThread();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        gradualY = getMeasuredHeight() - amplidute;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        width = getMeasuredWidth();
        height = getMeasuredHeight();
        int ave = width / 4;

        mPath.reset();
        mPath.moveTo(gradualX, gradualY);
        mPath.cubicTo(gradualX + 1.73f * ave, gradualY - amplidute, gradualX + width - 1.73f * ave, gradualY + amplidute, gradualX + width, gradualY);
        mPath.cubicTo(gradualX + 1.73f * ave + width, gradualY - amplidute, gradualX + 2 * width - 1.73f * ave, gradualY + amplidute, gradualX + 3 * width, gradualY);
        mPath.lineTo(width, height);
        mPath.lineTo(0, height);
        mPath.close();
        canvas.drawPath(mPath, paint);
        // 启动线程開始更新
        if (!thread.isAlive() && isMoving) {
            thread.start();
        }
    }

    class MyThread extends Thread {
        public void run() {
            while (isMoving) {
                gradualX = gradualX - 1f > -width ? gradualX - 1f : gradualX - 1f + width;
                gradualY -= 0.2;
                if (gradualY < -amplidute) {
                    isMoving = false;
                    break;
                }
                try {
                    Thread.sleep(5);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                postInvalidate();
            }
        }
    }

}