自定开关——SwitchButton

<?xml version="1.0" encoding="utf-8"?>
<resources>
    
    <declare-styleable name="SwitchButton">
        <attr name="android:layout_width"/>
        <attr name="android:layout_height"/>
        <attr name="mask" format="reference"/>
        <attr name="android:track"/>
        <attr name="android:thumb"/>
    </declare-styleable>
    
</resources>

package com.kale.switchbutton;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;

/**
 * @author:swust_chenpeng 
 * 本文转自：http://blog.csdn.net/swust_chenpeng/article/details/19967501
 * @tips : 白色圆点:switch_btn_pressed; 
 *     左白右红的长条:switch_bottom; 
 *     无色长条:switch_frame;
 *     黑色长条:switch_mask.
 * @date :2014-7-20
 */
public class SwitchButton extends View implements OnClickListener {
    private Bitmap mSwitchTrack, mSwitchThumb, mSwitchMask;
    private float mCurrentX = 0;// 当前的x坐标
    private boolean mSwitchOn = true;// 开关默认是开着的
    private int mMoveLength;// 最大移动距离
    private float mLastX = 0;// 第一次按下的有效区域

    private Rect mDest = null;// 绘制的目标区域大小
    private Rect mSrc = null;// 截取源图片的大小
    private int mDeltX = 0;// 移动的偏移量

    private int width, height;

    private Paint mPaint = null;
    private OnCheckedChangeListener mListener = null;
    private boolean mFlag = false;
    
    private float scaleWidth,scaleHeight;//图片缩放的比例

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

    public SwitchButton(Context context, AttributeSet attrs) {
        this(context, attrs, 0);

    }

    public SwitchButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context, attrs);
    }

    /**
     * 初始化相关资源
     */
    private void init(Context context, AttributeSet attrs) {
        TypedArray mTypedArray = context.obtainStyledAttributes(attrs,
                R.styleable.SwitchButton);

        width = (int) mTypedArray.getDimension(
                R.styleable.SwitchButton_android_layout_width, 100);
        height = (int) mTypedArray.getDimension(
                R.styleable.SwitchButton_android_layout_height,43);
        
        // 遮罩
        mSwitchMask = getSrcBitmap(mTypedArray, R.styleable.SwitchButton_mask);
        // 背景(轨道的背景)
        mSwitchTrack = getSrcBitmap(mTypedArray, R.styleable.SwitchButton_android_track);
        // 滑块
        mSwitchThumb = getSrcBitmap(mTypedArray, R.styleable.SwitchButton_android_thumb);
        
        // 计算缩放的比例
        scaleWidth = ((float) width / mSwitchMask.getWidth());
        scaleHeight = ((float) height / mSwitchMask.getHeight());
        
        mSwitchMask = getScaleBitmap(mSwitchMask);
        mSwitchTrack = getScaleBitmap(mSwitchTrack);
        mSwitchThumb = getScaleBitmap(mSwitchThumb);    

        setOnClickListener(this);
        setOnTouchListener(new OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                return false;
            }
        });
        // 可以移动的长度
        mMoveLength = mSwitchTrack.getWidth() - mSwitchMask.getWidth();
        // 创建一个矩形对象(目标区域的大小)，通过使用四个整数来初始化矩形左上角的横坐标、纵坐标以及矩形的高度、宽度
        mDest = new Rect(0, 0, mSwitchMask.getWidth(),mSwitchMask.getHeight());
        // 创建一个矩形对象，矩形左上角的横坐标、纵坐标以及矩形的宽度、高度均为零。这是默认的构造函数
        mSrc = new Rect();
        mPaint = new Paint();
        mPaint.setAntiAlias(true);// 消除锯齿
        mPaint.setAlpha(255);// 设置透明度
        mPaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
    }
    
    // 从资源中获取图片对象
    private Bitmap getSrcBitmap(TypedArray mTypedArray,int index) {
        BitmapDrawable tempBit;
        tempBit = (BitmapDrawable)mTypedArray.getDrawable(index);
        return tempBit.getBitmap();
    }
    
    // 将原图，按照布局文件中的控件长度来缩放
    private Bitmap getScaleBitmap(Bitmap bitmap) {
        Matrix matrix = new Matrix();
        if (isInEditMode()) {
            return bitmap;
        }
        matrix.postScale(scaleWidth, scaleHeight);
            bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
                    bitmap.getHeight(), matrix, true);
        return bitmap;
    }

    // 该方法指定该控件在屏幕上的大小,这里要计算一下控件的实际大小，然后调用setMeasuredDimension来设置
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        setMeasuredDimension(width, height);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (mDeltX > 0 || mDeltX == 0 && mSwitchOn) {
            if (mSrc != null) {
                mSrc.set(mMoveLength - mDeltX, 0,
                        mSwitchTrack.getWidth() - mDeltX, mSwitchMask.getHeight());
            }
        } 
        else if (mDeltX < 0 || mDeltX == 0 && !mSwitchOn) {
            if (mSrc != null) {
                mSrc.set(-mDeltX, 0, mSwitchMask.getWidth() - mDeltX,
                        mSwitchMask.getHeight());
            }
        }

        // 这儿是离屏缓冲，自己感觉类似双缓冲机制吧
        int count = canvas.saveLayer(new RectF(mDest), null,
                Canvas.MATRIX_SAVE_FLAG 
                | Canvas.CLIP_SAVE_FLAG
                | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
                | Canvas.FULL_COLOR_LAYER_SAVE_FLAG
                | Canvas.CLIP_TO_LAYER_SAVE_FLAG);

        canvas.drawBitmap(mSwitchTrack, mSrc, mDest, null);
        canvas.drawBitmap(mSwitchTrack, mSrc, mDest, null);
        canvas.drawBitmap(mSwitchMask, 0, 0, mPaint);
        canvas.drawBitmap(mSwitchThumb, mSrc, mDest, null);
        //这个判断，用来让这个控件可以在布局文件中预览
        if (isInEditMode()) {
            return ;
        }
        canvas.restoreToCount(count);
        
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            mLastX = event.getX();
            break;
        case MotionEvent.ACTION_MOVE:
            mCurrentX = event.getX();
            mDeltX = (int) (mCurrentX - mLastX);
            // 如果开关开着向左滑动，或者开关关着向右滑动（这时候是不需要处理的）
            if ((mSwitchOn && mDeltX < 0) || (!mSwitchOn && mDeltX > 0)) {
                mFlag = true;
                mDeltX = 0;
            }

            if (Math.abs(mDeltX) > mMoveLength) {
                mDeltX = mDeltX > 0 ? mMoveLength : -mMoveLength;
            }
            invalidate();
            return true;
        case MotionEvent.ACTION_UP:
            if (Math.abs(mDeltX) > 0 && Math.abs(mDeltX) < mMoveLength / 2) {
                mDeltX = 0;
                invalidate();
                return true;
            } else if (Math.abs(mDeltX) > mMoveLength / 2
                    && Math.abs(mDeltX) <= mMoveLength) {
                mDeltX = mDeltX > 0 ? mMoveLength : -mMoveLength;
                mSwitchOn = !mSwitchOn;
                if (mListener != null) {
                    mListener.onCheckedChanged(this, mSwitchOn);
                }
                invalidate();
                mDeltX = 0;
                return true;
            } else if (mDeltX == 0 && mFlag) {
                // 这时候得到的是不需要进行处理的，因为已经move过了
                mDeltX = 0;
                mFlag = false;
                return true;
            }
            return super.onTouchEvent(event);
        default:
            break;
        }
        invalidate();
        return super.onTouchEvent(event);
    }

    public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {
        mListener = listener;
    }

    public interface OnCheckedChangeListener {
        public void onCheckedChanged(SwitchButton button, boolean isChecked);
    }

    @Override
    public void onClick(View v) {
        mDeltX = mSwitchOn ? mMoveLength : -mMoveLength;
        mSwitchOn = !mSwitchOn;
        if (mListener != null) {
            mListener.onCheckedChanged(this, mSwitchOn);
        }
        invalidate();// 重绘
        mDeltX = 0;
    }
    
    public Boolean isChecked() {
        return mSwitchOn;
    }
    
    public void setChecked(Boolean checked) {
        mSwitchOn = checked;
        invalidate();
    }
    
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:pv="http://schemas.android.com/apk/res/com.kale.switchbutton"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <com.kale.switchbutton.SwitchButton
        android:id="@+id/switch_id"
        android:layout_width="80dp"
        android:layout_height="34dp"
        android:layout_marginTop="20dp"
        android:layout_gravity="center_horizontal"
        android:thumb="@drawable/switch_thumb"
        android:track="@drawable/switch_bottom"
        pv:mask="@drawable/switch_mask" />
    
        <Switch
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:layout_gravity="center_horizontal"
            android:switchMinWidth="40dp"
            android:switchPadding="30dp"
            android:padding="5dp"
            android:text="自定义风格"
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:textOff=" "
            android:textOn="  "
            android:thumb="@drawable/tt_button"
            android:track="@drawable/tt_path" />

    <Switch
        android:id="@+id/switch1"
        android:layout_marginTop="20dp"
        android:layout_gravity="center_horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>


</LinearLayout>