Android之实现滑动开关组件

    由于Android并未提供滑动开关之类的组件，所以我们需要自己去实现一个自定义的视图组件来实现滑动开关效果。

    这里有一个示例代码，它包括三个类：开关组件视图、状态监听接口、MainActivity

    我们先来看看整个demo的效果图：

   我们先来看看视图组件的完整代码，代码都已经注释：

package com.bear.swtichbuttondemo;

import java.util.ArrayList;

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;

/**
 * 自定义滑动开关
 */
public class MySwitchButton extends View implements OnTouchListener {

	private Bitmap switchOnBkg; // 开关开启时的背景
	private Bitmap switchOffBkg; // 开关关闭时的背景
	private Bitmap slipSwitchButton; // 滑动开关的图片

	private boolean isSlipping = false; // 是否正在滑动
	private boolean isSwitchOn = false; // 当前开关的状态，true表示开启，flase表示关闭
	private float previousX; // 手指按下时的水平坐标x
	private float currentX; // 当前的水平坐标X

	private ArrayList<OnSwitchListener> onSwitchListenerList; // 开关监听器列表

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

	private void init() {
		this.setOnTouchListener(this); // 设置触摸监听器
		onSwitchListenerList = new ArrayList<OnSwitchListener>();
	}

	public void setImageResource(int switchBkg, int slipBtn) {
		switchOnBkg = BitmapFactory.decodeResource(this.getResources(),
				switchBkg);
		switchOffBkg = BitmapFactory.decodeResource(this.getResources(),
				switchBkg);
		slipSwitchButton = BitmapFactory.decodeResource(this.getResources(),
				slipBtn);

	}

	public void setSwitchState(boolean switchState) {
		this.isSwitchOn = switchState;
		this.invalidate();
	}

	public boolean getSwitchState() {
		return this.isSwitchOn;
	}
	
	public void setOnSwitchStateListener(OnSwitchListener listener){
		onSwitchListenerList.add(listener);
	}

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);

		Matrix matrix = new Matrix();
		Paint paint = new Paint();

		float leftSlipBtnX; // 滑动按钮的左边坐标
		
		//画开关的背景图片
		canvas.drawBitmap(switchOnBkg, matrix, paint);

		if (isSlipping) {
			// 如果正在滑动
			if (currentX > switchOnBkg.getWidth()) {
				leftSlipBtnX = switchOnBkg.getWidth()
						- slipSwitchButton.getWidth();
			} else {
				leftSlipBtnX = currentX - slipSwitchButton.getWidth();
			}
		} else {
			//如果没有滑动
			if (isSwitchOn) {
				leftSlipBtnX = switchOnBkg.getWidth()
						- slipSwitchButton.getWidth();
			} else {
				leftSlipBtnX = 0;
			}
		}
		
		//如果手指滑出了开关的范围，应当这样处理
		if (leftSlipBtnX < 0) {
			leftSlipBtnX = 0;
		} else if (leftSlipBtnX > switchOnBkg.getWidth()
				- slipSwitchButton.getWidth()) {
			leftSlipBtnX = switchOnBkg.getWidth() - slipSwitchButton.getWidth();
		}
		
		//在画布上画开关图片
		canvas.drawBitmap(slipSwitchButton, leftSlipBtnX, 0, paint);

	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		setMeasuredDimension(switchOnBkg.getWidth(), switchOnBkg.getHeight());
	}

	@Override
	public boolean onTouch(View v, MotionEvent event) {
		//获取触摸动作类型
		int action = event.getAction();
		switch (action) {
		case MotionEvent.ACTION_MOVE:
			//如果现在处于手指一动状态
			currentX = event.getX();
			break;
		case MotionEvent.ACTION_DOWN:
			//如果现在手指刚刚按上屏幕状态
			isSlipping = true;
			break;
		case MotionEvent.ACTION_UP:
			//如果现在手指刚刚离开屏幕状态
			isSlipping = false;
			boolean previousState = isSwitchOn;
			if (event.getX() > (switchOnBkg.getWidth() / 2)) {
				isSwitchOn = true;
			} else {
				isSwitchOn = false;
			}
			
			//调用接口回调方法，将开关状态通知给监听对象
			if(previousState != isSwitchOn){
				if(onSwitchListenerList.size() > 0){
					for(OnSwitchListener listener : onSwitchListenerList){
						listener.onSwitched(isSwitchOn);
					}
				}
			}
			break;

		default:
			break;
		}

		this.invalidate();
		return true;
	}

}

package com.bear.swtichbuttondemo;

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

package com.bear.swtichbuttondemo;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {

	private MySwitchButton mySwitchButton;
	private Button myBtn;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		setupViews();
	}

	private void setupViews() {
		mySwitchButton = (MySwitchButton) findViewById(R.id.my_switch_button);
		//传图片给自定义组件
		mySwitchButton.setImageResource(R.drawable.switch_bkg_switch,
				R.drawable.switch_btn_slip);
		myBtn = (Button) findViewById(R.id.button);
		
		//设置开关状态监听
		mySwitchButton.setOnSwitchStateListener(new OnSwitchListener() {

			@Override
			public void onSwitched(boolean isSwitchOn) {
				if (isSwitchOn) {
					Toast.makeText(MainActivity.this, "开关开启",
							Toast.LENGTH_SHORT).show();
				} else {
					Toast.makeText(MainActivity.this, "开关关闭",
							Toast.LENGTH_SHORT).show();
				}

			}
		});
		
		myBtn.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				boolean isOn = mySwitchButton.getSwitchState();
				mySwitchButton.setSwitchState(!isOn);
			}
		});
	}

}

Android之实现滑动开关组件