Android自定义View-------IOS风格的滑动开关
源码和测试例子已经放到github https://github.com/Leaking/SlideSwitch，欢迎star欢迎fork欢迎提issue
项目开发中，经常会有一些关于用户个性化的设置，此时经常需要一个开关控件，周末将之前写的自定义开关控件优化了一下，效果图如下。先说说大概思路：按钮绘制了三个图层，最下面是覆盖整个View的灰色，第二个是覆盖整个View的自定义的颜色，它可以改变透明度。第三个是白色。当白色部分移动时，修改第二个图层的透明度，即可作出如图滑动过程中颜色渐变的效果。
大概记录一下重写一个组件的实现过程。
1，定义属性
2,，在Java代码中的构造器获取属性的值
3，重写onMeasure()
4，重写onDraw()
5，如果需要，重写onTouch监听
6，在自己项目的布局文件中，定义一个命名空间，使用属性
1，定义属性
新建一个项目，命名为SlieSwitch，并新建属性文件SlideSwitch\res\values\attrs.xml
[html] <?xml version="1.0" encoding="utf-8"?> <resources> <declare-styleable name="slideswitch"> <attr name="themeColor" format="color" /> <attr name="isOpen" format="boolean" /> <attr name="shape"> <enum name="rect" value="1" /> <enum name="circle" value="2" /> </attr> </declare-styleable> </resources>
其中定义了三个属性，一个是按钮的颜色，一个是按钮的打开状态，一个是枚举类型，它用来描述按钮的形状，关于这些的属性以及其它几个类型的属性的使用，可以容易百度谷歌到相关知识，这里暂不作记录。
2,，在Java代码中的构造器获取属性的值
在SlieSwitch中新建一个包com.leaking.slideswitch，然后再包里面新建一个文件文件SlieSwitch.java。自定义组件首先得继承View类，然后再构造器中获取自定义属性，如下艾玛片段：
[java]
public class SlideSwitch extends View {
//,,,,,,,省略,,,,,,,,,,
public SlideSwitch(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
listener = null;
paint = new Paint();
paint.setAntiAlias(true);
TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.slideswitch);
color_theme = a.getColor(R.styleable.slideswitch_themeColor,
COLOR_THEME);
isOpen = a.getBoolean(R.styleable.slideswitch_isOpen, false);
shape = a.getInt(R.styleable.slideswitch_shape, SHAPE_RECT);
a.recycle();
}
public SlideSwitch(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public SlideSwitch(Context context) {
this(context, null);
}
//,,,,,,,省略,,,,,,,,,,
}
一般View有三个构造器，我习惯让只有一个参数的构造方法调用有两个参数的构造方法，然后两个的调用三个的，在有三个参数的构造方法里使用TypeArray读取自定义属性，然后调用TypeArray的recycle()方法回收资源。
3，重写onMeasure()
上网稍微搜索一下，很快能只奥怎么重写onMeasure()方法，但是为什么需要重写onMeasure()方法这一点，倒是不好搜索到。这个问题我记录在另一篇文章。
android自定义View-------为什么重写onMeasure()以及怎么重写
我们在onMeasure()中此处主要做了两件事，第一是计算View的大小，也就是它的长和宽，第二是记录了白色色块的起始位置，以及绘制按钮的一些其他参数。需要注意的是，当你调用view的invalidate()方法进行重绘时，系统只会去调用onDraw()方法，但是如果有关于其他组件的大小、内容（比如TextView的setText()）发生修改，都会触发onMeasure()，所以在onMeasure()中计算的位置变量，要避免受到重新调用onMeasure()的影响。编码过程遇到的一个bug就是因为这个原因。
4，重写onDraw()
onDraw()部分比较容易，只需按照onMeasure()中计算出来的参数绘制三个图层即可。
5，如果需要，重写onTouch监听
该部分也是比较容易，就是分别按照down,move,up三个事件计算位置，修改第二个图层颜色的透明度，然后调用invaliate重绘View。在up事件中启动一个线程，让按钮的滑动自动进行到结束。
6，在自己项目的布局文件中，定义一个命名空间，使用属性
[html] <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" xmlns:slideswitch="http://schemas.android.com/apk/res/com.example.testlibs" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#ffffffff" android:gravity="center_horizontal" android:orientation="vertical" android:padding="10dip" tools:context="com.example.testlibs.MainActivity" > <com.leaking.slideswitch.SlideSwitch android:id="@+id/swit" android:layout_width="150dip" android:layout_height="60dip" slideswitch:isOpen="true" slideswitch:shape="rect" slideswitch:themeColor="#ffee3a00" > </com.leaking.slideswitch.SlideSwitch> </LinearLayout>
需要注意的是，上述代码片段的第二行，它引入了一个命名空间，其格式如下
[html] xmlns:随便起名字="http://schemas.android.com/apk/res/你的应用的包名"
注意最后一部分，是你使用这个自定义VIew的那个项目的应用包名。
接下来，在Java代码中设置开关的监听以及状态的设置，如下代码
[java]
public class MainActivity extends Activity implements SlideListener {
TextView txt;
SlideSwitch slide;
SlideSwitch slide2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
slide = (SlideSwitch) findViewById(R.id.swit);
slide2 = (SlideSwitch) findViewById(R.id.swit2);
slide.setState(false);
txt = (TextView) findViewById(R.id.txt);
slide.setSlideListener(this);
}
@Override
public void open() {
// TODO Auto-generated method stub
txt.setText(" is opend ");
}
@Override
public void close() {
// TODO Auto-generated method stub
txt.setText(" is close ");
}
}
SlideSwitch.java完整代码
完整代码和测试例子都放到github了，https://github.com/Leaking/SlideSwitch
[java] view plaincopy
package com.leaking.slideswitch;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.support.v4.view.MotionEventCompat;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import com.example.slideswitch.R;
public class SlideSwitch extends View {
public static final int SHAPE_RECT = 1;
public static final int SHAPE_CIRCLE = 2;
private static final int RIM_SIZE = 6;
private static final int COLOR_THEME = Color.parseColor("#ff00ee00");
// 3 attributes
private int color_theme;
private boolean isOpen;
private int shape;
// varials of drawing
private Paint paint;
private Rect backRect;
private Rect frontRect;
private int alpha;
private int max_left;
private int min_left;
private int frontRect_left;
private int frontRect_left_begin = RIM_SIZE;
private int eventStartX;
private int eventLastX;
private int diffX = 0;
private SlideListener listener;
public interface SlideListener {
public void open();
public void close();
}
public SlideSwitch(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
listener = null;
paint = new Paint();
paint.setAntiAlias(true);
TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.slideswitch);
color_theme = a.getColor(R.styleable.slideswitch_themeColor,
COLOR_THEME);
isOpen = a.getBoolean(R.styleable.slideswitch_isOpen, false);
shape = a.getInt(R.styleable.slideswitch_shape, SHAPE_RECT);
a.recycle();
}
public SlideSwitch(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public SlideSwitch(Context context) {
this(context, null);
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int width = measureDimension(280, widthMeasureSpec);
int height = measureDimension(140, heightMeasureSpec);
if (shape == SHAPE_CIRCLE) {
if (width < height)
width = height * 2;
}
setMeasuredDimension(width, height);
initDrawingVal();
}
public void initDrawingVal(){
int width = getMeasuredWidth();
int height = getMeasuredHeight();
backRect = new Rect(0, 0, width, height);
min_left = RIM_SIZE;
if (shape == SHAPE_RECT)
max_left = width / 2;
else
max_left = width - (height - 2 * RIM_SIZE) - RIM_SIZE;
if (isOpen) {
frontRect_left = max_left;
alpha = 255;
} else {
frontRect_left = RIM_SIZE;
alpha = 0;
}
frontRect_left_begin = frontRect_left;
}
public int measureDimension(int defaultSize, int measureSpec) {
int result;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
if (specMode == MeasureSpec.EXACTLY) {
result = specSize;
} else {
result = defaultSize; // UNSPECIFIED
if (specMode == MeasureSpec.AT_MOST) {
result = Math.min(result, specSize);
}
}
return result;
}
@Override
protected void onDraw(Canvas canvas) {
if (shape == SHAPE_RECT) {
paint.setColor(Color.GRAY);
canvas.drawRect(backRect, paint);
paint.setColor(color_theme);
paint.setAlpha(alpha);
canvas.drawRect(backRect, paint);
frontRect = new Rect(frontRect_left, RIM_SIZE, frontRect_left
+ getMeasuredWidth() / 2 - RIM_SIZE, getMeasuredHeight()
- RIM_SIZE);
paint.setColor(Color.WHITE);
canvas.drawRect(frontRect, paint);
} else {
// 画圆形
int radius;
radius = backRect.height() / 2 - RIM_SIZE;
paint.setColor(Color.GRAY);
canvas.drawRoundRect(new RectF(backRect), radius, radius, paint);
paint.setColor(color_theme);
paint.setAlpha(alpha);
canvas.drawRoundRect(new RectF(backRect), radius, radius, paint);
frontRect = new Rect(frontRect_left, RIM_SIZE, frontRect_left
+ backRect.height() - 2 * RIM_SIZE, backRect.height()
- RIM_SIZE);
paint.setColor(Color.WHITE);
canvas.drawRoundRect(new RectF(frontRect), radius, radius, paint);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
int action = MotionEventCompat.getActionMasked(event);
switch (action) {
case MotionEvent.ACTION_DOWN:
eventStartX = (int) event.getRawX();
break;
case MotionEvent.ACTION_MOVE:
eventLastX = (int) event.getRawX();
diffX = eventLastX - eventStartX;
int tempX = diffX + frontRect_left_begin;
tempX = (tempX > max_left ? max_left : tempX);
tempX = (tempX < min_left ? min_left : tempX);
if (tempX >= min_left && tempX <= max_left) {
frontRect_left = tempX;
alpha = (int) (255 * (float) tempX / (float) max_left);
invalidateView();
}
break;
case MotionEvent.ACTION_UP:
int wholeX = (int) (event.getRawX() - eventStartX);
frontRect_left_begin = frontRect_left;
boolean toRight;
toRight = (frontRect_left_begin > max_left / 2 ? true : false);
if (Math.abs(wholeX) < 3) {
toRight = !toRight;
}
moveToDest(toRight);
break;
default:
break;
}
return true;
}
/**
* draw again
*/
private void invalidateView() {
if (Looper.getMainLooper() == Looper.myLooper()) {
invalidate();
} else {
postInvalidate();
}
}
public void setSlideListener(SlideListener listener) {
this.listener = listener;
}
public void moveToDest(final boolean toRight) {
final Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
if (msg.what == 1) {
listener.open();
} else {
listener.close();
}
}
};
new Thread(new Runnable() {
@Override
public void run() {
if (toRight) {
while (frontRect_left <= max_left) {
alpha = (int) (255 * (float) frontRect_left / (float) max_left);
invalidateView();
frontRect_left += 3;
try {
Thread.sleep(3);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
alpha = 255;
frontRect_left = max_left;
isOpen = true;
if (listener != null)
handler.sendEmptyMessage(1);
frontRect_left_begin = max_left;
} else {
while (frontRect_left >= min_left) {
alpha = (int) (255 * (float) frontRect_left / (float) max_left);
invalidateView();
frontRect_left -= 3;
try {
Thread.sleep(3);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
alpha = 0;
frontRect_left = min_left;
isOpen = false;
if (listener != null)
handler.sendEmptyMessage(0);
frontRect_left_begin = min_left;
}
}
}).start();
}
public void setState(boolean isOpen) {
this.isOpen = isOpen;
initDrawingVal();
invalidateView();
if(listener != null)
if(isOpen == true){
listener.open();
}else{
listener.close();
}
}
public void setShapeType(int shapeType) {
this.shape = shapeType;
}
}