Android学习札记2：滑动开关的实现

package com.qing;

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 MySlipSwitch extends View implements OnTouchListener {

//开关开启时的背景，关闭时的背景，滑动按钮
private Bitmap switch_on_Bkg, switch_off_Bkg, slip_Btn;
private Rect on_Rect, off_Rect;

//是否正在滑动
private boolean isSlipping = false;
//当前开关状态，true为开启，false为关闭
private boolean isSwitchOn = false;

//手指按下时的水平坐标X，当前的水平坐标X
private float previousX, currentX;

//开关监听器
private OnSwitchListener onSwitchListener;
//是否设置了开关监听器
private boolean isSwitchListenerOn = false;

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

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

private void init() {
setOnTouchListener(this);
}

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);

//右半边Rect，即滑动按钮在右半边时表示开关开启
on_Rect = new Rect(switch_off_Bkg.getWidth() - slip_Btn.getWidth(), 0, switch_off_Bkg.getWidth(), slip_Btn.getHeight());
//左半边Rect，即滑动按钮在左半边时表示开关关闭
off_Rect = new Rect(0, 0, slip_Btn.getWidth(), slip_Btn.getHeight());
}

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

protected boolean getSwitchState() {
return isSwitchOn;
}

protected void updateSwitchState(boolean switchState) {
isSwitchOn = switchState;
invalidate();
}

@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);

Matrix matrix = new Matrix();
Paint paint = new Paint();
//滑动按钮的左边坐标
float left_SlipBtn;

//手指滑动到左半边的时候表示开关为关闭状态，滑动到右半边的时候表示开关为开启状态
if(currentX < (switch_on_Bkg.getWidth() / 2)) {
canvas.drawBitmap(switch_off_Bkg, matrix, paint);
} else {
canvas.drawBitmap(switch_on_Bkg, matrix, paint);
}

//判断当前是否正在滑动
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 {
//根据当前的开关状态设置滑动按钮的位置
if(isSwitchOn) {
left_SlipBtn = on_Rect.left;
} else {
left_SlipBtn = off_Rect.left;
}
}

//对滑动按钮的位置进行异常判断
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) {
// TODO Auto-generated method stub
setMeasuredDimension(switch_on_Bkg.getWidth(), switch_on_Bkg.getHeight());
}

@Override
public boolean onTouch(View v, MotionEvent event) {
// TODO Auto-generated method stub
switch(event.getAction()) {
//滑动
case MotionEvent.ACTION_MOVE:
currentX = event.getX();
break;

//按下
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;

//松开
case MotionEvent.ACTION_UP:
isSlipping = false;
//松开前开关的状态
boolean previousSwitchState  = isSwitchOn;

if(event.getX() >= (switch_on_Bkg.getWidth() / 2)) {
isSwitchOn = true;
} else {
isSwitchOn = false;
}

//如果设置了监听器，则调用此方法
if(isSwitchListenerOn && (previousSwitchState != isSwitchOn)) {
onSwitchListener.onSwitched(isSwitchOn);
}
break;

default:
break;
}

//重新绘制控件
invalidate();
return true;
}

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

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

package com.qing;

import com.qing.MySlipSwitch.OnSwitchListener;

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 Button switch_Btn;
private MySlipSwitch slipswitch_MSL;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

slipswitch_MSL = (MySlipSwitch)findViewById(R.id.main_myslipswitch);
slipswitch_MSL.setImageResource(R.drawable.bkg_switch, R.drawable.bkg_switch, R.drawable.btn_slip);
slipswitch_MSL.setSwitchState(true);
slipswitch_MSL.setOnSwitchListener(new OnSwitchListener() {

@Override
public void onSwitched(boolean isSwitchOn) {
// TODO Auto-generated method stub
if(isSwitchOn) {
Toast.makeText(MainActivity.this, "开关已经开启", 300).show();
} else {
Toast.makeText(MainActivity.this, "开关已经关闭", 300).show();
}
}
});

switch_Btn = (Button)findViewById(R.id.main_button_switch);
switch_Btn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
slipswitch_MSL.updateSwitchState(!slipswitch_MSL.getSwitchState());

if(slipswitch_MSL.getSwitchState()) {
Toast.makeText(MainActivity.this, "开关已经开启", 300).show();
} else {
Toast.makeText(MainActivity.this, "开关已经关闭", 300).show();
}
}
});
}
}