Android 自定义实现switch开关按钮

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 stub
		init();
	}

	/**
	 * 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() {
			
			@Override
			public boolean onTouch(View v, MotionEvent event) {
				// TODO Auto-generated method stub
				return 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));
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		// TODO Auto-generated method stub
		setMeasuredDimension(mSwitchFrame.getWidth(), mSwitchFrame.getHeight());
	}

	@Override
	protected void onDraw(Canvas canvas) {
		// TODO Auto-generated method stub
		super.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);
	}
	
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		// TODO Auto-generated method stub
		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.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);
	}

	@Override
	public void onClick(View v) {
		// TODO Auto-generated method stub
		mDeltX = 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 {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		SwitchButton sb = (SwitchButton) findViewById(R.id.wiperSwitch1);
		sb.setOnChangeListener(new OnChangeListener() {
			
			@Override
			public void onChange(SwitchButton sb, boolean state) {
				// TODO Auto-generated method stub
				Log.d("switchButton", state ? "开":"关");
				Toast.makeText(MainActivity.this, state ? "开":"关", Toast.LENGTH_SHORT).show();
			}
		});
	}

	@Override
	public 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="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/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" >

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <com.example.switchbutton.SwitchButton
        android: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：http://stackoverflow.com/questions/11838022/how-to-paint-with-alpha

            http://blog.csdn.net/zenip/article/details/8766263