Android 自定义SeekBar (一)
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一、前言
巩固自定义view基础用，本次尝试构建一个拖动条组件。代码参考于 https://github.com/woxingxiao/BubbleSeekBar ，精简其中高度可重用的部分，仅保留基本的拖拽功能，由于代码很巧妙，以后可以再深入探究学习。
本文在前面自定义view的基础上，增加了测量(onMeasure) 以及 触碰屏幕事件(onTouchEvent)。相信可以一步步踏实巩固，学会自定义view的知识。由于本拖动条仍是一个view，不需要涉及到布局(onLayout) 。以后学习自定义viewGroup时再另行探究。老规矩第一章先放效果图和全部代码。
二、效果图
三、代码
values/attr.xml
<?
xml version="1.0" encoding="utf-8"
?>
<
resources
>
<
declare-styleable
name
="MySeekBar"
>
<
attr
name
="progress_max"
format
="float|reference"
/>
<!--
进度条最大值
-->
<
attr
name
="progress_min"
format
="float|reference"
/>
<!--
进度条最小值
-->
<
attr
name
="progress_default"
format
="float|reference"
/>
<!--
进度条默认值
-->
<
attr
name
="track_left_height"
format
="dimension|reference"
/>
<!--
进度条左边高度
-->
<
attr
name
="track_right_height"
format
="dimension|reference"
/>
<!--
进度条右边高度
-->
<
attr
name
="track_left_color"
format
="color|reference"
/>
<!--
进度条左边颜色
-->
<
attr
name
="track_right_color"
format
="color|reference"
/>
<!--
进度条右边颜色
-->
<
attr
name
="thumb_color_default"
format
="color|reference"
/>
<!--
拖动滑块默认颜色
-->
<
attr
name
="thumb_radius_default"
format
="dimension|reference"
/>
<!--
拖动滑块半径
-->
<
attr
name
="thumb_color_on_dragging"
format
="color|reference"
/>
<!--
拖动滑块拖动中颜色
-->
<
attr
name
="thumb_radius_on_dragging"
format
="dimension|reference"
/>
<!--
拖动滑块拖动中半径
-->
</
declare-styleable
>
</
resources
>
MySeekBar.java
package
com.kms.myseekbar;
/*
* Created by kwy on 2020/5/22
*/
import
android.animation.ValueAnimator;
import
android.content.Context;
import
android.content.res.TypedArray;
import
android.graphics.Canvas;
import
android.graphics.Color;
import
android.graphics.Paint;
import
android.util.AttributeSet;
import
android.view.MotionEvent;
import
android.view.View;
import
android.view.animation.LinearInterpolator;
import
com.kms.myseekbar.util.DimensionUtil;
import
androidx.annotation.Nullable;
public
class MySeekBar extends View {
/********************** 参数 **********************/privatefloat progress_max; // 进度条最大值privatefloat progress_min; // 进度条最小值privatefloat progress_default; // 进度条默认值privateint track_left_height; // 进度条左边高度privateint track_right_height; // 进度条右边高度privateint track_left_color; // 进度条左边颜色privateint track_right_color; // 进度条右边颜色privateint thumb_color_default; // 拖动滑块默认颜色privateint thumb_radius_default; // 拖动滑块半径privateint thumb_color_on_dragging; // 拖动滑块拖动中颜色privateint thumb_radius_on_dragging; // 拖动滑块拖动中半径/********************** 绘制相关 **********************/private Paint paint; // 画笔privateint xLeft; // 实际的绘图区域按距离父布局左边 padding 算起privateint xRight; // 到距离父布局右边的的 padding 结束privateint yCenter; // 确定绘制进度条Y轴意义上的中点privateint thumb_radius; // 滑动滑块半径/********************** 构造函数 **********************/public MySeekBar(Context context) {
this(context, null);
}
public MySeekBar(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public MySeekBar(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.MySeekBar, defStyleAttr, 0);
this.progress_max = typedArray.getFloat(R.styleable.MySeekBar_progress_max, 100);
this.progress_min = typedArray.getFloat(R.styleable.MySeekBar_progress_min, 0);
this.progress_default = typedArray.getFloat(R.styleable.MySeekBar_progress_default, progress_min);
this.track_left_height = typedArray.getDimensionPixelSize(R.styleable.MySeekBar_track_left_height, DimensionUtil.dp2px(8));
this.track_right_height = typedArray.getDimensionPixelSize(R.styleable.MySeekBar_track_right_height, track_left_height - DimensionUtil.dp2px(2));
this.track_left_color = typedArray.getColor(R.styleable.MySeekBar_track_left_color, Color.BLUE);
this.track_right_color = typedArray.getColor(R.styleable.MySeekBar_track_right_color, Color.LTGRAY);
this.thumb_color_default = typedArray.getColor(R.styleable.MySeekBar_thumb_color_default, track_left_color);
this.thumb_radius_default = typedArray.getDimensionPixelSize(R.styleable.MySeekBar_thumb_radius_default, track_left_height + DimensionUtil.dp2px(2));
this.thumb_color_on_dragging = typedArray.getColor(R.styleable.MySeekBar_thumb_color_on_dragging, thumb_color_default);
this.thumb_radius_on_dragging = typedArray.getDimensionPixelSize(R.styleable.MySeekBar_thumb_radius_on_dragging, thumb_radius_default + DimensionUtil.dp2px(2));
typedArray.recycle();
thumb_radius = thumb_radius_default;
initPaint(); // 初始化画笔 }
/********************** Getter and Setter **********************/publicfloat getProgressMax() {
return progress_max;
}
public MySeekBar setProgressMax(float progressMax) {
this.progress_max = progressMax;
returnthis;
}
publicfloat getProgressMin() {
return progress_min;
}
public MySeekBar setProgressMin(float progressMin) {
this.progress_min = progressMin;
returnthis;
}
publicfloat getProgressDefault() {
return progress_default;
}
public MySeekBar setProgressDefault(float progressDefault) {
this.progress_default = progressDefault;
returnthis;
}
publicint getTrackLeftHeight() {
return track_left_height;
}
public MySeekBar setTrackLeftHeight(int trackLeftHeight) {
this.track_left_height = trackLeftHeight;
returnthis;
}
publicint getTrackRightHeight() {
return track_right_height;
}
public MySeekBar setTrackRightHeight(int trackRightHeight) {
this.track_right_height = trackRightHeight;
returnthis;
}
publicint getTrackLeftColor() {
return track_left_color;
}
public MySeekBar setTrackLeftColor(int trackLeftColor) {
this.track_left_color = trackLeftColor;
returnthis;
}
publicint getTrackRightColor() {
return track_right_color;
}
public MySeekBar setTrackRightColor(int trackRightColor) {
this.track_right_color = trackRightColor;
returnthis;
}
publicint getThumbColorDefault() {
return thumb_color_default;
}
public MySeekBar setThumbColorDefault(int thumbColorDefault) {
this.thumb_color_default = thumbColorDefault;
returnthis;
}
publicint getThumbRadiusDefault() {
return thumb_radius_default;
}
public MySeekBar setThumbRadiusDefault(int thumbRadiusDefault) {
this.thumb_radius_default = thumbRadiusDefault;
returnthis;
}
publicint getThumbColorOnDragging() {
return thumb_color_on_dragging;
}
public MySeekBar setThumbColorOnDragging(int thumbColorOnDragging) {
this.thumb_color_on_dragging = thumbColorOnDragging;
returnthis;
}
publicint getThumbRadiusOnDragging() {
return thumb_radius_on_dragging;
}
public MySeekBar setThumbRadiusOnDragging(int thumbRadiusOnDragging) {
this.thumb_radius_on_dragging = thumbRadiusOnDragging;
returnthis;
}
/********************** 绘制相关 **********************/privatevoid initPaint(){
paint = new Paint();
paint.setAntiAlias(true);
paint.setStrokeCap(Paint.Cap.ROUND);
}
@Override
protectedvoid onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
// 仅当 android_layout_width = wrap_content 或未指定时生效，若测出来的size大于你所指定的size (譬如这里是180dp)，则使用所指定的sizeint width = resolveSize(DimensionUtil.dp2px(180), widthMeasureSpec);
int height = thumb_radius_on_dragging * 2; // 控件高度按拖动时的滑块直径
setMeasuredDimension(width, height); // 强制指定控件大小
xLeft = getPaddingLeft() + thumb_radius_on_dragging; // 实际的绘图区域按距离父布局左边 padding 算起
xRight = getMeasuredWidth() - getPaddingRight() - thumb_radius_on_dragging; // 到距离父布局右边的的 padding 结束
yCenter = getPaddingTop() + thumb_radius_on_dragging; // 确定绘制进度条Y轴意义上的中点 }
@Override
protectedvoid onDraw(Canvas canvas) {
super.onDraw(canvas);
int currentProgress = (int) (progress_default / progress_max * (xRight-xLeft));
drawRightTrack(canvas, currentProgress);
drawLeftTrack(canvas, currentProgress);
drawThumb(canvas, currentProgress);
}
/**
* 绘制进度条左边
*/privatevoid drawLeftTrack(Canvas canvas, int currentProgress){
paint.setColor(track_left_color);
paint.setStrokeWidth(track_left_height);
canvas.drawLine(xLeft, yCenter, xLeft + currentProgress, yCenter, paint);
}
/**
* 绘制拖动滑块
*/privatevoid drawThumb(Canvas canvas, int currentProgress){
paint.setColor(thumb_color_default);
canvas.drawCircle(xLeft + currentProgress, yCenter, thumb_radius, paint);
}
/**
* 绘制进度条右边
*/privatevoid drawRightTrack(Canvas canvas, int currentProgress){
paint.setColor(track_right_color);
paint.setStrokeWidth(track_right_height);
canvas.drawLine(xLeft + currentProgress, yCenter, xRight, yCenter, paint);
}
publicvoid startAnim(){
final ValueAnimator animator = ValueAnimator.ofInt(0,100);
animator.setDuration(100*500);
animator.setRepeatCount(ValueAnimator.INFINITE);
animator.setRepeatMode(ValueAnimator.RESTART);
animator.setInterpolator(new LinearInterpolator());
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
publicvoid onAnimationUpdate(ValueAnimator animation) {
progress_default = (int) animation.getAnimatedValue();
invalidate();
}
});
animator.start();
}
@Override
publicboolean onTouchEvent(MotionEvent event) {
switch (event.getActionMasked()){
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
performClick(); // 若 SeekBar设置了 OnClickListener，可以在此处唤醒监听器
getParent().requestDisallowInterceptTouchEvent(true); // 不允许父组件拦截触摸事件
thumb_radius = thumb_radius_on_dragging;
progress_default = calculateDraggingX(event.getX());
break;
default:
thumb_radius = thumb_radius_default;
}
invalidate();
returntrue;
}
/**
* 计算拖动值
*
* @param x 屏幕上的event.getX()
* @return 经转换后对应拖动条的进度值
*/privatefloat calculateDraggingX(float x){
if(x < xLeft){
return progress_min;
}
if(x > xRight){
return progress_max;
}
return x / getMeasuredWidth() * progress_max;
}
}
layout/activity_main.xml
<?
xml version="1.0" encoding="utf-8"
?>
<
androidx.constraintlayout.widget.ConstraintLayout
xmlns:android
="http://schemas.android.com/apk/res/android"
xmlns:app
="http://schemas.android.com/apk/res-auto"
xmlns:tools
="http://schemas.android.com/tools"
android:layout_width
="match_parent"
android:layout_height
="match_parent"
tools:context
=".MainActivity"
android:padding
="10dp"
>
<
com.kms.myseekbar.MySeekBar
android:id
="@+id/my_seek_bar"
android:layout_width
="match_parent"
android:layout_height
="20dp"
app:layout_constraintBottom_toBottomOf
="parent"
app:layout_constraintLeft_toLeftOf
="parent"
app:layout_constraintRight_toRightOf
="parent"
app:layout_constraintTop_toTopOf
="parent"
/>
</
androidx.constraintlayout.widget.ConstraintLayout
>
MainActivity.java
package
com.kms.myseekbar;
import
android.graphics.Color;
import
android.os.Bundle;
import
androidx.appcompat.app.AppCompatActivity;
public
class MainActivity extends AppCompatActivity {
MySeekBar mySeekBar;
@Override
protectedvoid onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mySeekBar = findViewById(R.id.my_seek_bar);
mySeekBar.setThumbColorDefault(Color.BLUE).setProgressDefault(50);
// mySeekBar.startAnim(); }
}
完！下一节将讲解下基本思路
原文：https://www.cnblogs.com/qq1094417747/p/12938516.html
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