仿iphone的左右开关

package com.ejoy.customcontrol;

import com.ejoy.android.R;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class FwpUiSwitch extends View implements OnTouchListener {
	private Bitmap switch_on_Bkg, switch_off_Bkg, slip_Btn;
	private Rect on_Rect, off_Rect;

	private boolean isSlipping = false;
	private boolean isSwitchOn = false;

	private float previousX, currentX;

	private OnSwitchListener onSwitchListener;

	private boolean isSwitchListenerOn = false;

	public FwpUiSwitch(Context context) {
		super(context);
		init();
	}

	public FwpUiSwitch(Context context, AttributeSet attrs) {
		super(context, attrs);
		init();
	}

	private void init() {
		setOnTouchListener(this);
		setImageResource(R.drawable.switchbg, R.drawable.switchbg,
				R.drawable.switchskip);
		setSwitchState(true);
	}

	protected void setImageResource(int switchOnBkg, int switchOffBkg,
			int slipBtn) {
		switch_on_Bkg = BitmapFactory.decodeResource(getResources(),
				switchOnBkg);
		switch_off_Bkg = BitmapFactory.decodeResource(getResources(),
				switchOffBkg);
		slip_Btn = BitmapFactory.decodeResource(getResources(), slipBtn);
		on_Rect = new Rect(switch_off_Bkg.getWidth() - slip_Btn.getWidth(), 0,
				switch_off_Bkg.getWidth(), slip_Btn.getHeight());
		off_Rect = new Rect(0, 0, slip_Btn.getWidth(), slip_Btn.getHeight());
	}

	protected void setSwitchState(boolean switchState) {
		isSwitchOn = switchState;
	}

	public boolean getSwitchState() {
		return isSwitchOn;
	}

	public void updateSwitchState(boolean switchState) {
		setSwitchState(switchState);
		invalidate();
	}

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		if (switch_off_Bkg != null && switch_on_Bkg != null) {
			Matrix matrix = new Matrix();
			Paint paint = new Paint();
			float left_SlipBtn;

			if (currentX < (switch_on_Bkg.getWidth() / 2)) {
				canvas.drawBitmap(switch_off_Bkg, matrix, paint);
			} else {
				canvas.drawBitmap(switch_on_Bkg, matrix, paint);
			}

			if (isSlipping) {
				if (currentX > switch_on_Bkg.getWidth()) {
					left_SlipBtn = switch_on_Bkg.getWidth()
							- slip_Btn.getWidth();
				} else {
					left_SlipBtn = currentX - slip_Btn.getWidth() / 2;
				}
			} else {
				if (isSwitchOn) {
					left_SlipBtn = on_Rect.left;
				} else {
					left_SlipBtn = off_Rect.left;
				}
			}

			if (left_SlipBtn < 0) {
				left_SlipBtn = 0;
			} else if (left_SlipBtn > switch_on_Bkg.getWidth()
					- slip_Btn.getWidth()) {
				left_SlipBtn = switch_on_Bkg.getWidth() - slip_Btn.getWidth();
			}
			canvas.drawBitmap(slip_Btn, left_SlipBtn, 0, paint);
		}
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		if (switch_on_Bkg != null && switch_on_Bkg != null) {
			setMeasuredDimension(switch_on_Bkg.getWidth(),
					switch_on_Bkg.getHeight());
		} else {
			super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		}
	}

	public boolean onTouch(View v, MotionEvent event) {
		switch (event.getAction()) {

		case MotionEvent.ACTION_MOVE:
			currentX = event.getX();
			break;

		case MotionEvent.ACTION_DOWN:
			if (event.getX() > switch_on_Bkg.getWidth()
					|| event.getY() > switch_on_Bkg.getHeight()) {
				return false;
			}

			isSlipping = true;
			previousX = event.getX();
			currentX = previousX;
			break;
		case MotionEvent.ACTION_UP:
			isSlipping = false;
			boolean previousSwitchState = isSwitchOn;

			if (event.getX() >= (switch_on_Bkg.getWidth() / 2)) {
				isSwitchOn = true;
			} else {
				isSwitchOn = false;
			}
			if (isSwitchListenerOn && (previousSwitchState != isSwitchOn)) {
				onSwitchListener.onSwitched(isSwitchOn);
			}
			break;

		default:
			break;
		}
		invalidate();
		return true;
	}

	public void setOnSwitchListener(OnSwitchListener listener) {
		if (listener != null) {
			onSwitchListener = listener;
			isSwitchListenerOn = true;
		}
	}

	public interface OnSwitchListener {
		abstract void onSwitched(boolean isSwitchOn);
	}
}