自定義view和簡述介面回撥

    自定義WiperSwitch類實現可拖動的開關按鈕

    用到的3張圖片

/**
 * Created by 撩個小媳婦 on 2018/5/11.
 */

public class WiperSwitch extends View implements View.OnTouchListener {
    private Bitmap bg_on, bg_off, slipper_btn;
    /**
     * 按下時的x和當前的x
     */
    private float downX, nowX;

    /**
     * 記錄使用者是否在滑動
     */
    private boolean onSlip = false;

    /**
     * 當前的狀態
     */
    private boolean nowStatus = false;

    /**
     * 監聽介面
     */
    private OnChangedListener listener;


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

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

    public void init(){
        //載入圖片資源
        bg_on = BitmapFactory.decodeResource(getResources(), R.drawable.kai);
        bg_off = BitmapFactory.decodeResource(getResources(), R.drawable.guan);
        slipper_btn = BitmapFactory.decodeResource(getResources(), R.drawable.dian);

        setOnTouchListener(this);
    }

    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Matrix matrix = new Matrix();
        Paint paint = new Paint();
        float x = 0;

        //根據nowX設定背景，開或者關狀態
        if (nowX < (bg_on.getWidth()/2)){
            canvas.drawBitmap(bg_off, matrix, paint);//畫出關閉時的背景
        }else{
            canvas.drawBitmap(bg_on, matrix, paint);//畫出開啟時的背景
        }

        if (onSlip) {//是否是在滑動狀態,
            if(nowX >= bg_on.getWidth())//是否劃出指定範圍,不能讓滑塊跑到外頭,必須做這個判斷
                x = bg_on.getWidth() - slipper_btn.getWidth()/2;//減去滑塊1/2的長度
            else
                x = nowX - slipper_btn.getWidth()/2;
        }else {
            if(nowStatus){//根據當前的狀態設定滑塊的x值
                x = bg_on.getWidth() - slipper_btn.getWidth();
            }else{
                x = 0;
            }
        }

        //對滑塊滑動進行異常處理，不能讓滑塊出界
        if (x < 0 ){
            x = 0;
        }
        else if(x > bg_on.getWidth() - slipper_btn.getWidth()){
            x = bg_on.getWidth() - slipper_btn.getWidth();
        }

        //畫出滑塊
        canvas.drawBitmap(slipper_btn, x , 0, paint);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        switch(event.getAction()){
            case MotionEvent.ACTION_DOWN:{
                if (event.getX() > bg_off.getWidth() || event.getY() > bg_off.getHeight()){
                    return false;
                }else{
                    onSlip = true;
                    downX = event.getX();
                    nowX = downX;
                }
                break;
            }
            case MotionEvent.ACTION_MOVE:{
                nowX = event.getX();
                break;
            }
            case MotionEvent.ACTION_UP:{
                onSlip = false;
                if(event.getX() >= (bg_on.getWidth()/2)){
                    nowStatus = true;
                    nowX = bg_on.getWidth() - slipper_btn.getWidth();
                }else{
                    nowStatus = false;
                    nowX = 0;
                }

                if(listener != null){
                    listener.OnChanged(WiperSwitch.this, nowStatus);
                }
                break;
            }
        }
        //重新整理介面
        invalidate();
        return true;
    }



    /**
     * 為WiperSwitch設定一個監聽，供外部呼叫的方法
     */
    public void setOnChangedListener(OnChangedListener listener){
        this.listener = listener;
    }


    /**
     * 設定滑動開關的初始狀態，供外部呼叫
     */
    public void setChecked(boolean checked){
        if(checked){
            nowX = bg_off.getWidth();
        }else{
            nowX = 0;
        }
        nowStatus = checked;
    }


    /**
     * 回撥介面
     *
     */
    public interface OnChangedListener {
        public void OnChanged(WiperSwitch wiperSwitch, boolean checkState);
    }
}
 

接下來是MainActivity.java

public class MainActivity extends Activity implements WiperSwitch.OnChangedListener {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //例項化WiperSwitch
        WiperSwitch wiperSwitch = (WiperSwitch)findViewById(R.id.wiperSwitch1);

        //設定初始狀態為false
        wiperSwitch.setChecked(false);

        //設定監聽
        wiperSwitch.setOnChangedListener(this);
    }


    @Override
    public void OnChanged(WiperSwitch wiperSwitch, boolean checkState) {
        if (checkState){
            Toast.makeText(MainActivity.this,"開關開啟了",Toast.LENGTH_SHORT).show();
        }else if (!checkState){
            Toast.makeText(MainActivity.this,"開關關閉了",Toast.LENGTH_SHORT).show();
        }
    }

}