前几天在看蘑菇街上有个开关按钮：
就在想是怎样实现的，于是反编译了它的源码，但是这时得到了下面的几张图片：
图片对应的名称：
无色长条:switch_frame;
白色圆点:switch_btn_pressed;左白右红的长条:switch_bottom;黑色长条:switch_mask.
那我们就用这几张图片来实现类似的效果吧。
代码：
SwitchButton类：
package com.example.switchbutton;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.PorterDuff.Mode;import android.graphics.PorterDuffXfermode;import android.graphics.Rect;import android.graphics.RectF;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;public class SwitchButton extends View implements android.view.View.OnClickListener{private Bitmap mSwitchBottom, mSwitchThumb, mSwitchFrame, mSwitchMask;private float mCurrentX = 0;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 Paint mPaint = null;private OnChangeListener mListener = null;private boolean mFlag = false;public SwitchButton(Context context) {this(context, null);// TODO Auto-generated constructor stub}public SwitchButton(Context context, AttributeSet attrs) {this(context, attrs, 0);// TODO Auto-generated constructor stub}public SwitchButton(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);// TODO Auto-generated constructor stubinit();}/** * 初始化相关资源 */public void init() {mSwitchBottom = BitmapFactory.decodeResource(getResources(),R.drawable.switch_bottom);mSwitchThumb = BitmapFactory.decodeResource(getResources(),R.drawable.switch_btn_pressed);mSwitchFrame = BitmapFactory.decodeResource(getResources(),R.drawable.switch_frame);mSwitchMask = BitmapFactory.decodeResource(getResources(),R.drawable.switch_mask);setOnClickListener(this);setOnTouchListener(new OnTouchListener() {@Overridepublic boolean onTouch(View v, MotionEvent event) {// TODO Auto-generated method stubreturn false;}});mMoveLength = mSwitchBottom.getWidth() – mSwitchFrame.getWidth();mDest = new Rect(0, 0, mSwitchFrame.getWidth(), mSwitchFrame.getHeight());mSrc = new Rect();mPaint = new Paint();mPaint.setAntiAlias(true);mPaint.setAlpha(255);mPaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {// TODO Auto-generated method stubsetMeasuredDimension(mSwitchFrame.getWidth(), mSwitchFrame.getHeight());}@Overrideprotected void onDraw(Canvas canvas) {// TODO Auto-generated method stubsuper.onDraw(canvas);if (mDeltX > 0 || mDeltX == 0 && mSwitchOn) {if(mSrc != null) {mSrc.set(mMoveLength – mDeltX, 0, mSwitchBottom.getWidth()- mDeltX, mSwitchFrame.getHeight());} } else if(mDeltX < 0 || mDeltX == 0 && !mSwitchOn){if(mSrc != null) {mSrc.set(-mDeltX, 0, mSwitchFrame.getWidth() – mDeltX,mSwitchFrame.getHeight());}} <span style="white-space:pre"></span>//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(mSwitchBottom, mSrc, mDest, null);canvas.drawBitmap(mSwitchThumb, mSrc, mDest, null);canvas.drawBitmap(mSwitchFrame, 0, 0, null);canvas.drawBitmap(mSwitchMask, 0, 0, mPaint);canvas.restoreToCount(count);}@Overridepublic boolean onTouchEvent(MotionEvent event) {// TODO Auto-generated method stubswitch (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.onChange(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 setOnChangeListener(OnChangeListener listener) {mListener = listener;}public interface OnChangeListener {public void onChange(SwitchButton sb, boolean state);}@Overridepublic void onClick(View v) {// TODO Auto-generated method stubmDeltX = mSwitchOn ? mMoveLength : -mMoveLength;mSwitchOn = !mSwitchOn;if(mListener != null) {mListener.onChange(this, mSwitchOn);}invalidate();mDeltX = 0;}}MainActivity：package com.example.switchbutton;import com.example.switchbutton.SwitchButton.OnChangeListener;import android.app.Activity;import android.os.Bundle;import android.util.Log;import android.view.Menu;import android.widget.Toast;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);SwitchButton sb = (SwitchButton) findViewById(R.id.wiperSwitch1);sb.setOnChangeListener(new OnChangeListener() {@Overridepublic void onChange(SwitchButton sb, boolean state) {// TODO Auto-generated method stubLog.d("switchButton", state ? "开":"关");Toast.makeText(MainActivity.this, state ? "开":"关", Toast.LENGTH_SHORT).show();}});}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}}activity_main.xml:<LinearLayout xmlns:android=""xmlns:tools=""android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"android:paddingBottom="@dimen/activity_vertical_margin"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin" ><ImageViewandroid:id="@+id/imageView"android:layout_width="wrap_content"android:layout_height="wrap_content" /><com.example.switchbutton.SwitchButtonandroid:id="@+id/wiperSwitch1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginLeft="100dip" /></LinearLayout>主要的代码在switchbutton类中，，代码有什么不足还希望大家多提提意见，自己很少写。
参考：
而只有在充满了艰辛的人生旅途中，
