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Android自定义View之旅(二)继承View实现自定义

继承View是实现自定义View的重要方式,通过自定义属性以实现xml中的便捷使用,通过重写onMeasure和onDraw方法自定义View的绘制过程,通过拦截事件响应完成特定的行为,让想法变为现实。

上一篇文章Android自定义View之旅(一)自定义View的几种方式

本文将通过实战来讲述如何通过继承View实现自定义,先仔细看看需求,一个声音波形控件,持续动画效果,单靠上面的简单实现是不可能的了,需要的效果如下:
在这里插入图片描述

1、继承View实现自定义View

在上一篇文章中,我们详细介绍了简单的“自定义”如何实现,继承了安卓系统的原生控件,再在此基础上完成附加的功能样式或者更改原有的功能样式,可以迅速达到想要的效果,缺点是会受到父类的限制、无法完成复杂的需求。

对于这次需要实现的声音波形控件,我们需要新建一个类VoiceLineView,继承自View

/**
 * 自定义声音振动曲线view
 */
public class VoiceLineView extends View {

    public VoiceLineView(Context context) {
        super(context);
    }

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

    public VoiceLineView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

}

2、提供一些自定义的属性

通过自定义属性以实现xml中的便捷使用,就像我们在使用TextView的时候,设置android:text="Hello World!"

首先,需要在src/main/res/values文件夹下的attrs.xml文件(如不存在此文件新建一个即可)中新增如下代码:

<?xml version="1.0" encoding="utf-8"?>
<resources>
	······
	<!--name为获取属性时使用,不可与其他控件的自定义属性重复-->
    <declare-styleable name="voiceView">
        <!--中间线的颜色,就是波形的时候,大家可以看到,中间有一条直线,就是那个-->
        <attr name="middleLine" format="color" />
        <!--中间线的高度,中间线的宽度是充满的无需设定-->
        <attr name="middleLineHeight" format="dimension" />
        <!--波动的线的颜色-->
        <attr name="voiceLine" format="color" />
        <!--波动线的横向移动速度,线的速度的反比,即这个值越小,线横向移动越快,越大线移动越慢,默认90-->
        <attr name="lineSpeed" format="integer" />
        <!--所输入音量的最大值,默认是100-->
        <attr name="maxVolume" format="float" />
        <!--灵敏度,默认值是4-->
        <attr name="sensibility">
            <enum name="one" value="1" />
            <enum name="two" value="2" />
            <enum name="three" value="3" />
            <enum name="four" value="4" />
            <enum name="five" value="5" />
        </attr>
        <!--精细度,绘制曲线的时候,每几个像素绘制一次,默认是1,一般,这个值越小,曲线越顺滑,但在一些旧手机上,会出现帧率过低的情况,可以把这个值调大一点,在图片的顺滑度与帧率之间做一个取舍-->
        <attr name="fineness">
            <enum name="one" value="1" />
            <enum name="two" value="2" />
            <enum name="three" value="3" />
        </attr>
    </declare-styleable>
    ······
</resources>

新增一个declare-styleable标签声明一个属性集,根据需要,在declare-styleable标签中增加多个attr标签声明属性,attr标签根据控件的可设置属性进行配置。关于attr自定义属性的类型可以看文章Android中attr属性的类型

随后在VoiceLineView类中修改代码如下:

public class VoiceLineView extends View {

    private int middleLineColor = Color.BLACK;
    private int voiceLineColor = Color.BLACK;
    private float middleLineHeight = 4;
    private int sensibility = 4;
    private float maxVolume = 100;
    private int fineness = 1;
    private int lineSpeed = 90;

    public VoiceLineView(Context context) {
        super(context);
    }

    public VoiceLineView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initAtts(context, attrs);
    }

    public VoiceLineView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initAtts(context, attrs);
    }

    private void initAtts(Context context, AttributeSet attrs) {
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.voiceView);
        voiceLineColor = typedArray.getColor(R.styleable.voiceView_voiceLine, Color.BLACK);
        maxVolume = typedArray.getFloat(R.styleable.voiceView_maxVolume, 100);
        sensibility = typedArray.getInt(R.styleable.voiceView_sensibility, 4);
        middleLineColor = typedArray.getColor(R.styleable.voiceView_middleLine, Color.BLACK);
        middleLineHeight = typedArray.getDimension(R.styleable.voiceView_middleLineHeight, 4);
        lineSpeed = typedArray.getInt(R.styleable.voiceView_lineSpeed, 90);
        fineness = typedArray.getInt(R.styleable.voiceView_fineness, 1);
        typedArray.recycle();
    }

}

在布局中使用如下:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <VoiceLineView
        android:id="@+id/voice_line"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        app:middleLine="@color/colorPrimary"
        app:middleLineHeight="1dp"
        app:voiceLine="@color/colorPrimary"
        app:lineSpeed="90"
        app:maxVolume="100"
        app:sensibility="four"
        app:fineness="one" />

</LinearLayout>

3、重写onDraw方法,持续绘制声波

话不多说,直接上代码:

public class VoiceLineView extends View {
	······

    private Paint paint;
    private Paint paintVoicLine;
    private float translateX = 0;
    private boolean isSet = false;
    private float amplitude = 1;
    private float volume = 10;
    private long lastTime = 0;
    private int lineSpeed = 90;
    List<Path> paths = null;

	······

    public void setVolume(int volume) {
        if (volume > maxVolume * sensibility / 25) {
            isSet = true;
            this.targetVolume = getHeight() * volume / 2 / maxVolume;
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        drawMiddleLine(canvas);
        drawVoiceLine(canvas);
        run();
    }

    private void drawMiddleLine(Canvas canvas) {
        if (paint == null) {
            paint = new Paint();
            paint.setColor(middleLineColor);
            paint.setAntiAlias(true);
        }
        canvas.save();
        canvas.drawRect(0, getHeight() / 2 - middleLineHeight / 2, getWidth(), getHeight() / 2 + middleLineHeight / 2, paint);
        canvas.restore();
    }

    private void drawVoiceLine(Canvas canvas) {
        lineChange();
        if (paintVoicLine == null) {
            paintVoicLine = new Paint();
            paintVoicLine.setColor(voiceLineColor);
            paintVoicLine.setAntiAlias(true);
            paintVoicLine.setStyle(Paint.Style.STROKE);
            paintVoicLine.setStrokeWidth(2);
        }
        canvas.save();
        if (paths == null) {
            paths = new ArrayList<>(20);
            for (int i = 0; i < 20; i++) {
                paths.add(new Path());
            }
        }
        int moveY = getHeight() / 2;
        for (int i = 0; i < paths.size(); i++) {
            paths.get(i).reset();
            paths.get(i).moveTo(getWidth(), getHeight() / 2);
        }
        for (float i = getWidth() - 1; i >= 0; i -= fineness) {
            amplitude = 4 * volume * i / getWidth() - 4 * volume * i * i / getWidth() / getWidth();
            for (int n = 1; n <= paths.size(); n++) {
                float sin = amplitude * (float) Math.sin((i - Math.pow(1.22, n)) * Math.PI / 180 - translateX);
                paths.get(n - 1).lineTo(i, (2 * n * sin / paths.size() - 15 * sin / paths.size() + moveY));
            }
        }
        for (int n = 0; n < paths.size(); n++) {
            if (n == paths.size() - 1) {
                paintVoicLine.setAlpha(255);
            } else {
                paintVoicLine.setAlpha(n * 130 / paths.size());
            }
            if (paintVoicLine.getAlpha() > 0) {
                canvas.drawPath(paths.get(n), paintVoicLine);
            }
        }
        canvas.restore();
    }

    private void lineChange() {
        if (lastTime == 0) {
            lastTime = System.currentTimeMillis();
            translateX += 1.5;
        } else {
            if (System.currentTimeMillis() - lastTime > lineSpeed) {
                lastTime = System.currentTimeMillis();
                translateX += 1.5;
            } else {
                return;
            }
        }
        if (volume < targetVolume && isSet) {
            volume += getHeight() / 30;
        } else {
            isSet = false;
            if (volume <= 10) {
                volume = 10;
            } else {
                if (volume < getHeight() / 30) {
                    volume -= getHeight() / 60;
                } else {
                    volume -= getHeight() / 30;
                }
            }
        }
    }

    public void run() {
        invalidate();
    }

}

到此,需求就已经完成啦,使用时按第2点加入布局,代码中使用:

VoiceLineView voiceLine = findViewById(R.id.voice_line);

// 循环设置音量即可绘制声波图
voiceLine.setVolume(volume);

版权声明
本文为[coder-ice]所创,转载请带上原文链接,感谢
https://www.cnblogs.com/hwb04160011/p/13960621.html

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