android 自定义SwitchButton 开关状态

//自定义类继承View

 "font-size:18px;">public class SwitchButton extends View {

     private Bitmap back;
     private Bitmap slide;
     private int currentX;//处理事件
     private boolean isTouch;//判断是否在触摸状态
     private boolean state;//开关的状态
     private OnStateChangeListener onStateChangeListener;//监听对象 接口对象
     //new的时候调用
     public SwitchButton(Context context) {
         this(context,null);
     }
     //使用style的使用调用
     public SwitchButton(Context context, @Nullable AttributeSet attrs) {
         this(context, attrs,0);
     }
     //写在布局文件里面的时候调用
     public SwitchButton(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
         super(context, attrs, defStyleAttr);
         //初始化两张图片
         //将资源 文件转成Bitmap对象
         //getResources() 包含图片资源的资源对象
         //R.drawable.background 图片资源的id
         back = BitmapFactory.decodeResource(getResources(), R.drawable.background);
         slide = BitmapFactory.decodeResource(getResources(), R.drawable.slide);

     }
     //将图片绘制到控件上面

     @Override
     protected void onDraw(Canvas canvas) {
         super.onDraw(canvas);
         //绘制
         //参数1.图片对象
         //参数2.x轴的开始位置
         //参数3.y轴的开始位置
         //参数4.画笔
         canvas.drawBitmap(back,0,0,null);
         int left = 0;
             if(isTouch){
                 //滑块和手指一起移动
                 //判断是否在触摸状态
                 left = currentX;//修正位置
                 left = currentX - slide.getWidth() / 2;
                 //处理边界问题
                 if(left<0){
                     left=0;
                 }
                 if(left>back.getWidth()-slide.getWidth()){
                     left=back.getWidth()-slide.getWidth();
                 }
                 canvas.drawBitmap(slide, left, 0, null);//滑块儿
             }else{
                 //根据开关的状态绘制滑块
                 if(state){
                     //getWidth()---背景的宽度
                     left=back.getWidth()-slide.getWidth();
                 }else{
                     left=0;
                 }
                 canvas.drawBitmap(slide, left, 0, null); //滑块儿
             }

     }

     @Override
     public boolean onTouchEvent(MotionEvent event) {
          super.onTouchEvent(event);
         switch (event.getAction()){
             case MotionEvent.ACTION_DOWN:
                 currentX = (int) event.getX();
                 isTouch=true;
                 break;
             case MotionEvent.ACTION_MOVE:
                 currentX = (int) event.getX();
                 isTouch=true;
                 break;
             case MotionEvent.ACTION_UP:
                 isTouch=false;
                 currentX = (int) event.getX();
                 //当手指抬起的时候，应该判断一下滑块儿的位置，然后设置开关的状态
                 //currentX 在中间位置的那边
                 int centerX = back.getWidth()/2;//获取图片的宽度
                 //如果抬起时的位置大于图片宽度的一半
                 if(currentX>centerX){
                     state = true;
                 }else{
                     state=false;
                 }
                 //调用接口里的方法
                 onStateChangeListener.onStateChange(state);
                break;
         }
         //重新绘制
         invalidate();
         return true;
     }

     //将控件的尺寸重新设置一下

     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
         //根据背景图设置控件的宽高
         setMeasuredDimension(back.getWidth(),back.getHeight());//将需要的宽高设置进去
     }


     //接口回调
     public interface OnStateChangeListener{
         void onStateChange(boolean state);
     }
     //提供一个外部访问的方法
     public void setOnStateChange(OnStateChangeListener onStateChangeListener){
         this.onStateChangeListener = onStateChangeListener;
     }

     //给外部提供一个设置开关的方法
     public void setState(boolean state) {
         this.state = state;
     }
     public boolean getState(){
         return state;
     };
 }

2.MainActivity

 "font-size:18px;">public class MainActivity extends AppCompatActivity {

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         SwitchButton sb=findViewById(R.id.sb);
         //在外部设置监听
         sb.setOnStateChange(new SwitchButton.OnStateChangeListener() {
             @Override
             public void onStateChange(boolean state) {
                 Toast.makeText(MainActivity.this,"当前状态---"+state, Toast.LENGTH_SHORT).show();
             }
         });
     }
 }

3.布局文件

 "font-size:18px;">"1.0" encoding="utf-8"?>
 "http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context="com.bwie.day04_switchbutton.MainActivity">


        android:id="@+id/sb"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />