写在前面

因为有这样的一个场景，需要实现竖直方向的多色进度条，然后在网上也找了下，没看到符合需要的，于是自定义了一个，效果如下：

具体实现

本来想定义水平的，然后旋转一下，后来发现还不如直接定义竖直方向来的直接，就直接在竖直方向画了下。
首先讲一下思路，就是通过继承View，然后通过onDraw()方法进行绘制。具体绘制的时候，需要处理一些小细节。比如，我们需要画一个圆形的滑动块，那么我们的背景色带就不能把整个宽度占满，要不然，小圆块只能和色带一样宽了，效果不是很好看，所以在绘制的时候应该把背景画的宽度小于View的实际宽度。
接下来我要贴代码了：

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int h = getMeasuredHeight();
        int w = getMeasuredWidth();
        mRadius = (float) w/2;
        sLeft = w * 0.25f; // 背景左边缘坐标
        sRight = w * 0.75f;// 背景右边缘坐标
        sTop = 0;
        sBottom = h; 
        sWidth = sRight - sLeft; // 背景宽度
        sHeight = sBottom - sTop; // 背景高度
        x = (float) w/2;//圆心的x坐标
        y = (float) (1-0.01*progress)*sHeight;//圆心y坐标
        drawBackground(canvas);
        drawCircle(canvas);
        paint.reset();
    }

再看下画背景：

private void drawBackground(Canvas canvas){
        RectF rectBlackBg = new RectF(sLeft, sTop, sRight, sBottom);
        linearGradient=new LinearGradient(sLeft,sTop,sWidth,sHeight,colorArray,null, Shader.TileMode.MIRROR);
        paint.setAntiAlias(true);
        paint.setStyle(Paint.Style.FILL);
        //设置渲染器
        paint.setShader(linearGradient);
        canvas.drawRoundRect(rectBlackBg, sWidth/2, sWidth/2, paint);
}

这里使用LinearGradient实现多种颜色渐变，默认初始化定义如下:

    private int endColor=Color.WHITE;
    private int thumbColor=Color.BLACK;
    private int thumbBorderColor=Color.WHITE;
    private int colorArray[]={startColor, middleColor, endColor};

然后看下画圆的操作：

    private void drawCircle(Canvas canvas){
        Paint thumbPaint = new Paint();
        y = y < mRadius ? mRadius : y;//判断thumb边界
        y = y > sHeight-mRadius ? sHeight-mRadius : y;
        thumbPaint.setAntiAlias(true);
        thumbPaint.setStyle(Paint.Style.FILL);
        thumbPaint.setColor(thumbColor);
        canvas.drawCircle(x, y, mRadius, thumbPaint);
        thumbPaint.setStyle(Paint.Style.STROKE);
        thumbPaint.setColor(thumbBorderColor);
        thumbPaint.setStrokeWidth(2);
        canvas.drawCircle(x, y, mRadius, thumbPaint);
    }

这里通过画布画了一个圆形，内部填充和外边沿。
上面的过程已经可以使效果展示出来了，但是无法操作，我们还需要给它加上事件才行：

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        this.y = event.getY();
        progress= (sHeight-y)/sHeight*100;
        switch(event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                break;
            case MotionEvent.ACTION_UP:
                if (onStateChangeListener!=null){
                    onStateChangeListener.onStopTrackingTouch(this, progress);
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if (onStateChangeListener!=null){
                    onStateChangeListener.OnStateChangeListener(this, progress);
                }
                setProgress(progress);
                this.invalidate();
                break;
        }

        return true;
    }
    public interface OnStateChangeListener{
        void OnStateChangeListener(View view, float progress);
        void onStopTrackingTouch(View view, float progress);
    }

    public void setOnStateChangeListener(OnStateChangeListener onStateChangeListener){
        this.onStateChangeListener=onStateChangeListener;
    }

这里写了个回调接口，然后我们在Activity中就可以接收到相应的滑动进度，进而进行操作，当然，这里我们还得再加一个方法，以便改变seekbar的状态：

    public void setProgress(float progress) {
        this.progress = progress;
        invalidate();
    }

到这里，功能基本就OK了，然后我们可以在Activity中去使用它了,下面是布局中的引用：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:background="@color/bgColor"
    >
    <include layout="@layout/bar_simple_title" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        android:gravity="center"
        >

        <RelativeLayout
            android:layout_marginTop="20dp"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_marginRight="35dp"
            >
            <TextView
                android:id="@+id/tv_inner_temper"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/inner_temperature"
                android:layout_centerHorizontal="true"
                />

            <com.tfxiaozi.widget.VerticalColorSeekBar
                android:id="@+id/vpb_inner_temper"
                android:layout_width="20dp"
                android:layout_height="300dp"
                android:layout_centerHorizontal="true"
                android:layout_marginTop="30dp"/>

            <TextView
                android:id="@+id/tv_current_temper"
                android:layout_below="@id/vpb_inner_temper"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/current_temperature"
                />
        </RelativeLayout>
        <RelativeLayout
            android:layout_marginLeft="35dp"
            android:layout_marginTop="20dp"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            >
            <TextView
                android:id="@+id/tv_brightness"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/brightness"
                android:layout_centerHorizontal="true"
                />

            <com.tfxiaozi.widget.VerticalColorSeekBar
                android:id="@+id/vpb_brightness"
                android:layout_width="20dp"
                android:layout_height="300dp"
                android:layout_centerHorizontal="true"
                android:layout_marginTop="30dp"/>

            <TextView
                android:id="@+id/tv_current_brightness"
                android:layout_below="@id/vpb_brightness"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerHorizontal="true"
                android:text="0"
                />
        </RelativeLayout>
    </LinearLayout>
</LinearLayout>

怎么使用就很简单了：

package com.tfxiaozi.activity.setting;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import com.tfxiaozi.R;
import com.tfxiaozi.activity.BaseActivity;
import com.tfxiaozi.utils.ToastUtils;
import com.tfxiaozi.widget.VerticalColorSeekBar;

/**
 * Created by dongqiang on 2016/10/16.
 */
public class ManualSettingActivity extends BaseActivity implements View.OnClickListener, VerticalColorSeekBar.OnStateChangeListener {

    private TextView tvCurrentTemper, tvCurrentBrightness, tvMainTitle;
    private ImageView ivBack;
    private VerticalColorSeekBar vpbInnerTemper;
    private VerticalColorSeekBar vpbBrightness;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_manual_setting);
        initViews();
        initEvents();
        initData();
    }

    private void initViews() {
        tvMainTitle = (TextView) findViewById(R.id.title_main_text);
        tvMainTitle.setText(getString(R.string.manual_setting));
        tvMainTitle.setVisibility(View.VISIBLE);
        ivBack = (ImageView) findViewById(R.id.title_back);
        ivBack.setVisibility(View.VISIBLE);

        tvCurrentTemper = (TextView) findViewById(R.id.tv_current_temper);
        tvCurrentBrightness = (TextView) findViewById(R.id.tv_current_brightness);
        vpbInnerTemper = (VerticalColorSeekBar)findViewById(R.id.vpb_inner_temper);
        vpbBrightness = (VerticalColorSeekBar) findViewById(R.id.vpb_brightness);
        vpbInnerTemper.setColor(Color.RED, Color.YELLOW, Color.GREEN, Color.BLUE, Color.TRANSPARENT);
        vpbBrightness.setColor(Color.BLUE, Color.WHITE, Color.YELLOW, Color.BLUE, Color.TRANSPARENT);
    }

    private void initEvents() {
        ivBack.setOnClickListener(this);
        vpbInnerTemper.setOnStateChangeListener(this);
        vpbBrightness.setOnStateChangeListener(this);
    }

    private void initData() {
        vpbInnerTemper.setProgress(50);
        vpbBrightness.setProgress(70);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.title_back:
                finish();
                break;
        }
    }

    @Override
    public void OnStateChangeListener(View view, float progress) {

    }

    @Override
    public void onStopTrackingTouch(View view, float progress) {
        int viewId = view.getId();
        switch (viewId) {
            case R.id.vpb_inner_temper:
                if (progress < 0) {
                    progress = 0;
                }
                if(progress > 100) {
                    progress = 100;
                }
                ToastUtils.showShort(this, "progress= " + progress);
                break;

            case R.id.vpb_brightness:
                if (progress < 0) {
                    progress = 0;
                }
                if(progress > 100) {
                    progress = 100;
                }
                ToastUtils.showShort(this, "progress1= " + progress);
                break;
        }

    }
}

到这里就结束了，最后还是附上自定义View的整个代码吧：

package com.tfxiaozi.widget;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

/**
 * Created by dongqiang on 2016/10/21.
 */
public class VerticalColorSeekBar extends View{

    private static final String TAG = VerticalColorSeekBar.class.getSimpleName();
    private int startColor= Color.BLACK;
    private int middleColor = Color.GRAY;
    private int endColor=Color.WHITE;
    private int thumbColor=Color.BLACK;
    private int thumbBorderColor=Color.WHITE;
    private int colorArray[]={startColor, middleColor, endColor};
    private float x,y;
    private float mRadius;
    private float progress;
    private float maxCount = 100f;
    private float sLeft, sTop, sRight, sBottom;
    private float sWidth,sHeight;
    private LinearGradient linearGradient;
    private Paint paint = new Paint();
    protected OnStateChangeListener onStateChangeListener;

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

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

    @Override
    protected synchronized void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        setMeasuredDimension(getMeasuredWidth(), getMeasuredHeight());
    }

    public void setColor(int startColor,int middleColor, int endColor,int thumbColor,int thumbBorderColor){
        this.startColor= startColor;
        this.middleColor = middleColor;
        this.endColor= endColor;
        this.thumbColor= thumbColor;
        this.thumbBorderColor= thumbBorderColor;
        colorArray[0] = startColor;
        colorArray[1] = middleColor;
        colorArray[2] = endColor;
    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int h = getMeasuredHeight();
        int w = getMeasuredWidth();
        mRadius = (float) w/2;
        sLeft = w * 0.25f; // 背景左边缘坐标
        sRight = w * 0.75f;// 背景右边缘坐标
        sTop = 0; 
        sBottom = h;  
        sWidth = sRight - sLeft; // 背景宽度
        sHeight = sBottom - sTop; // 背景高度
        x = (float) w/2;//圆心的x坐标
        y = (float) (1-0.01*progress)*sHeight;//圆心y坐标
        drawBackground(canvas);
        drawCircle(canvas);
        paint.reset();
    }

    private void drawBackground(Canvas canvas){
        RectF rectBlackBg = new RectF(sLeft, sTop, sRight, sBottom);
        linearGradient=new LinearGradient(sLeft,sTop,sWidth,sHeight,colorArray,null, Shader.TileMode.MIRROR);
        paint.setAntiAlias(true);
        paint.setStyle(Paint.Style.FILL);
        //设置渲染器
        paint.setShader(linearGradient);
        canvas.drawRoundRect(rectBlackBg, sWidth/2, sWidth/2, paint);
    }

    private void drawCircle(Canvas canvas){
        Paint thumbPaint = new Paint();
        y = y < mRadius ? mRadius : y;//判断thumb边界
        y = y > sHeight-mRadius ? sHeight-mRadius : y;
        thumbPaint.setAntiAlias(true);
        thumbPaint.setStyle(Paint.Style.FILL);
        thumbPaint.setColor(thumbColor);
        canvas.drawCircle(x, y, mRadius, thumbPaint);
        thumbPaint.setStyle(Paint.Style.STROKE);
        thumbPaint.setColor(thumbBorderColor);
        thumbPaint.setStrokeWidth(2);
        canvas.drawCircle(x, y, mRadius, thumbPaint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        this.y = event.getY();
        progress= (sHeight-y)/sHeight*100;
        switch(event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                break;
            case MotionEvent.ACTION_UP:
                if (onStateChangeListener!=null){
                    onStateChangeListener.onStopTrackingTouch(this, progress);
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if (onStateChangeListener!=null){
                    onStateChangeListener.OnStateChangeListener(this, progress);
                }
                setProgress(progress);
                this.invalidate();
                break;
        }

        return true;
    }


    public interface OnStateChangeListener{
        void OnStateChangeListener(View view, float progress);
        void onStopTrackingTouch(View view, float progress);
    }

    public void setOnStateChangeListener(OnStateChangeListener onStateChangeListener){
        this.onStateChangeListener=onStateChangeListener;
    }

    public void setProgress(float progress) {
        this.progress = progress;
        invalidate();
    }
}

结束

到这里就真的结束啦，就当记录一下吧，然后也希望帮到有需要的人。有更好的实现也可以告诉我哈~