实现一个彩虹色进度条功能，不说明具体用途大家应该能猜到。想找别人造的轮子，但是没有合适的，所以决定自己实现一个。
相关知识
android 自定义view
LinearGradient 线性渐变
实现步骤
自定义view
自定义一个TmcView类继承View
重写两个构造方法。构造方法一共有4个，这里边重写两个
重写ongSizeChanged方法，用来获取控件宽、高，来计算内部组件尺寸。
重写onDraw方法，里边要描画背景drawBackground，分段数据drawSection，和seekbar图片drawImage。
import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.View;
import androidx.annotation.Nullable;
import java.util.List;
public class TmcView extends View {
public TmcView(Context context) {
super(context);
}
public TmcView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
drawBackground(canvas);
drawSection(canvas);
drawImage(canvas);
}
/**
* 画背景
* @param canvas 画布
*/
private void drawBackground(Canvas canvas) {
}
/**
* 画分段数据
* @param canvas 画布
*/
private void drawSection(Canvas canvas) {
}
/**
* 画图片
* @param canvas 画布
*/
private void drawImage(Canvas canvas) {
}
/**
* 更新view
* @param total 总长度
* @param rest 剩余长度
* @param sections 分段数据
*/
public void updateView(int total, int rest, List<SectionData> sections){
}实现几个重构方法
标注：
整体宽度为图片宽度44px
背景条宽度30px，外边距7px，圆角15px
带颜色的条宽度20xp，外边距5px，圆角15px
自定义view的坐标轴是以view的左上角位置为原点，向右为x轴正方向，向下为y轴正方向
在视图中用RectF创建背景，和颜色条，并在onSizeChanged中设置尺寸
public class TmcView extends View {
private final RectF backgroundRectF = new RectF();
private final RectF colorRectF = new RectF();
public TmcView(Context context) {
super(context);
}
public TmcView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//设置矩形 left top right bottom 左上右下点的值 按照标注计算得出
backgroundRectF.set(7, 0, 37, h);
colorRectF.set(12, 5, 32, h-5);
}
...
}绘制背景条
实现drawBackground方法，画背景需要一根画笔Paint 为了避免重复创建，声明为成员变量
public class TmcView extends View {
/*背景画笔*/
private final Paint backPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final RectF backgroundRectF = new RectF();
private final RectF colorRectF = new RectF();
public TmcView(Context context) {
super(context);
}
public TmcView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//设置矩形 left top right bottom 左上右下点的值 按照标注计算得出
backgroundRectF.set(7, 0, 37, h);
colorRectF.set(12, 5, 32, h-5);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
drawBackground(canvas);
drawSection(canvas);
drawImage(canvas);
}
/**
* 画背景
* @param canvas 画布
*/
private void drawBackground(Canvas canvas) {
backPaint.setStyle(Paint.Style.FILL);
backPaint.setAntiAlias(true); //抗锯齿
backPaint.setColor(Color.parseColor("#FFFFFF"));
//画圆角矩形，15为圆角的角度
canvas.drawRoundRect(backgroundRectF, 15, 15, backPaint);
}
...
}
布局中加入TmcView
<com.bigxuan.tesapp.view.TmcView
android:id="@+id/tmc"
android:layout_width="44px"
android:layout_height="690px"
android:layout_marginEnd="1230px"
android:layout_marginBottom="100px"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
/>绘制颜色条
实现drawSection方法，这里要用到线性渐变LinearGradient
LinearGradient 简单说，指定每一段的颜色和位置百分比，就能实现每一段显示不同颜色。
但它默认是渐变色，要想不变就在每一段的开始和结束位置都设置相同的颜色。
再创建一个画笔 Paint，画颜色条
public class TmcView extends View {
private final Paint backPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final Paint colorPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final RectF backgroundRectF = new RectF();
private final RectF colorRectF = new RectF();
public TmcView(Context context) {
super(context);
}
public TmcView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//设置矩形 left top right bottom 左上右下点的值 按照标注计算得出
backgroundRectF.set(7, 0, 37, h);
colorRectF.set(12, 5, 32, h-5);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
drawBackground(canvas);
drawSection(canvas);
drawImage(canvas);
}
/**
* 画背景
* @param canvas 画布
*/
private void drawBackground(Canvas canvas) {
backPaint.setStyle(Paint.Style.FILL);
backPaint.setAntiAlias(true); //抗锯齿
backPaint.setColor(Color.parseColor("#FFFFFF"));
//画圆角矩形，15为圆角的角度
canvas.drawRoundRect(backgroundRectF, 15, 15, backPaint);
}
/**
* 画分段数据
* @param canvas 画布
*/
private void drawSection(Canvas canvas) {
int[] colorArray = {
Color.parseColor("#FF0000"), Color.parseColor("#FF0000"),
Color.parseColor("#00FF00"), Color.parseColor("#00FF00"),
Color.parseColor("#0000FF"), Color.parseColor("#0000FF")
};
float[] positionArray = {
0f, 0.2f,
0.2f, 0.6f,
0.6f, 1f
};
colorPaint.setStyle(Paint.Style.FILL);
colorPaint.setAntiAlias(true);
//指定渐变色方向x轴方向不变，沿y方向渐变，渐变范围为 颜色条高度
colorPaint.setShader(new LinearGradient(0, 0, 0, colorRectF.bottom, colorArray, positionArray, Shader.TileMode.REPEAT));
canvas.drawRoundRect(colorRectF,15, 15, colorPaint);
}
...
}绘制进度图片
app加入图片资源，根据资源id获取bitmap对象，绘制。
需要注意的是，坐标轴的顶点在左上角，绘制图片时也是以图片左上顶点位置做定位，图片位置是view的高度减掉图片的高度，才能显示在正确位置。
public class TmcView extends View {
private Context context;
private final Paint backPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final Paint colorPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final RectF backgroundRectF = new RectF();
private final RectF colorRectF = new RectF();
/*图片资源id*/
private int imgResId;
/*图片位置*/
private int imgPos;
public TmcView(Context context) {
super(context);
}
public TmcView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
this.context = context;
this.imgResId = R.drawable.icon_seekbar_day;
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//设置矩形 left top right bottom 左上右下点的值 按照标注计算得出
backgroundRectF.set(7, 0, 37, h);
colorRectF.set(12, 5, 32, h-5);
imgPos = h - 44; // 设置一个初始位置
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
drawBackground(canvas);
drawSection(canvas);
drawImage(canvas);
}
/**
* 画背景
* @param canvas 画布
*/
private void drawBackground(Canvas canvas) {
backPaint.setStyle(Paint.Style.FILL);
backPaint.setAntiAlias(true); //抗锯齿
backPaint.setColor(Color.parseColor("#FFFFFF"));
//画圆角矩形，15为圆角的角度
canvas.drawRoundRect(backgroundRectF, 15, 15, backPaint);
}
/**
* 画分段数据
* @param canvas 画布
*/
private void drawSection(Canvas canvas) {
int[] colorArray = {
Color.parseColor("#FF0000"), Color.parseColor("#FF0000"),
Color.parseColor("#00FF00"), Color.parseColor("#00FF00"),
Color.parseColor("#0000FF"), Color.parseColor("#0000FF")
};
float[] positionArray = {
0f, 0.2f,
0.2f, 0.6f,
0.6f, 1f
};
colorPaint.setStyle(Paint.Style.FILL);
colorPaint.setAntiAlias(true);
//指定渐变色方向x轴方向不变，沿y方向渐变，渐变范围为 颜色条高度
colorPaint.setShader(new LinearGradient(0, 0, 0, colorRectF.bottom, colorArray, positionArray, Shader.TileMode.REPEAT));
canvas.drawRoundRect(colorRectF,15, 15, colorPaint);
}
/**
* 画图片
* @param canvas 画布
*/
private void drawImage(Canvas canvas) {
Bitmap bitmap = initBitmap(imgResId);
canvas.save();
canvas.translate(0, 0);
canvas.drawBitmap(bitmap, 0, imgPos, null);
canvas.restore();
}
/**
* 通过资源id 创建bitmap
* @param resId 资源id
* @return
*/
private Bitmap initBitmap(int resId) {
Bitmap originalBmp = BitmapFactory.decodeResource(context.getResources(), resId);
return Bitmap.createScaledBitmap(originalBmp, 44, 44, true);
}
...
}公共方法
暴露方法用来更新进度updateView
定义一个图片有效的运动距离为view高度减掉图片高度，函数参数为总距离和剩余距离，计算百分比后乘以有效运动距离得出图片描画位置。最后调用invalidate方法刷新view
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
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.view.View;
import androidx.annotation.Nullable;
import com.navinfo.tesapp.R;
import java.util.List;
public class TmcView extends View {
private Context context;
private final Paint backPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final Paint colorPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final RectF backgroundRectF = new RectF();
private final RectF colorRectF = new RectF();
/*图片资源id*/
private int imgResId;
/*图片位置*/
private int imgPos;
/*图片有效的运动距离*/
private int imgValidHeight;
public TmcView(Context context) {
super(context);
}
public TmcView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
this.context = context;
this.imgResId = R.drawable.icon_seekbar_day;
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//设置矩形 left top right bottom 左上右下点的值 按照标注计算得出
backgroundRectF.set(7, 0, 37, h);
colorRectF.set(12, 5, 32, h-5);
imgValidHeight = h - 44;
imgPos = h - 44; // 设置一个初始位置
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
drawBackground(canvas);
drawSection(canvas);
drawImage(canvas);
}
/**
* 画背景
* @param canvas 画布
*/
private void drawBackground(Canvas canvas) {
backPaint.setStyle(Paint.Style.FILL);
backPaint.setAntiAlias(true); //抗锯齿
backPaint.setColor(Color.parseColor("#FFFFFF"));
//画圆角矩形，15为圆角的角度
canvas.drawRoundRect(backgroundRectF, 15, 15, backPaint);
}
/**
* 画分段数据
* @param canvas 画布
*/
private void drawSection(Canvas canvas) {
int[] colorArray = {
Color.parseColor("#FF0000"), Color.parseColor("#FF0000"),
Color.parseColor("#00FF00"), Color.parseColor("#00FF00"),
Color.parseColor("#0000FF"), Color.parseColor("#0000FF")
};
float[] positionArray = {
0f, 0.2f,
0.2f, 0.6f,
0.6f, 1f
};
colorPaint.setStyle(Paint.Style.FILL);
colorPaint.setAntiAlias(true);
//指定渐变色方向x轴方向不变，沿y方向渐变，渐变范围为 颜色条高度
colorPaint.setShader(new LinearGradient(0, 0, 0, colorRectF.bottom, colorArray, positionArray, Shader.TileMode.REPEAT));
canvas.drawRoundRect(colorRectF,15, 15, colorPaint);
}
/**
* 画图片
* @param canvas 画布
*/
private void drawImage(Canvas canvas) {
Bitmap bitmap = initBitmap(imgResId);
canvas.save();
canvas.translate(0, 0);
canvas.drawBitmap(bitmap, 0, imgPos, null);
canvas.restore();
}
/**
*
* @param resId
* @return
*/
private Bitmap initBitmap(int resId) {
Bitmap originalBmp = BitmapFactory.decodeResource(context.getResources(), resId);
return Bitmap.createScaledBitmap(originalBmp, 44, 44, true);
}
/**
* 更新view
* @param total 总长度
* @param rest 剩余长度
* @param sections 分段数据
*/
public void updateView(int total, int rest, List<SectionData> sections){
float percent = (1f * rest) / total;
//防止溢出
if(percent < 0){
return;
}
imgPos = (int)(percent * imgValidHeight);
invalidate();
}
}updateView方法还有第三个参数，是用来传出颜色条不同段的颜色和百分比数据的。根据此数据来更新颜色条。这里需要根据业务不同自己实现，我这里就不写了。
总结
大家可能看出来了，这个视图是用来展示导航中不同路段交通情况和当前车辆进度用的。自定义view中可以在构造方法中获取一些自定义属性，像背景条和颜色条的边距、圆角这些都可以定义到xml中，因为只适配一种屏幕尺寸所以也没有做多尺寸适配。以前也没有做过，这次记录下来。
