//佈局加減器三個textview

<TextView
    android:background="#ffffff"
    android:layout_weight="1"
    android:id="@+id/sub_tv"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:gravity="center"
    android:text="-"
    android:textSize="16sp" />

<TextView
    android:text="1"
    android:layout_marginLeft="2dp"
    android:background="#ffffff"
    android:layout_weight="1"
    android:id="@+id/product_number_tv"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:gravity="center"
    />

<TextView
    android:layout_marginLeft="2dp"
    android:background="#ffffff"
    android:layout_weight="1"
    android:id="@+id/add_tv"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:gravity="center"
    android:text="+"
    android:textSize="16sp" />
 

//利用組合式自定義控制元件實現加減器的操作

public class MyAddSubView extends LinearLayout implements View.OnClickListener {
private int number = 1;
private TextView sub_tv;
private TextView product_number_tv;
private TextView add_tv;

public MyAddSubView(Context context) {
    this(context, null);
}

public MyAddSubView(Context context, @Nullable AttributeSet attrs) {
    this(context, attrs, 0);
}

public MyAddSubView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    View view = inflate(context, R.layout.add_remove_view_layout, this);

    sub_tv = view.findViewById(R.id.sub_tv);
    product_number_tv = view.findViewById(R.id.product_number_tv);
    add_tv = view.findViewById(R.id.add_tv);


    sub_tv.setOnClickListener(this);
    add_tv.setOnClickListener(this);
}


@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.sub_tv:
            if (number > 1) {
                --number;
                product_number_tv.setText(number + "");
                if (onNumberChangeListener != null) {
                    onNumberChangeListener.onNumberChange(number);
                }
            } else {
                Toast.makeText(getContext(), "不能再少了", Toast.LENGTH_SHORT).show();
            }
            break;


        case R.id.add_tv:
            ++number;
            product_number_tv.setText(number + "");
            if (onNumberChangeListener != null) {
                onNumberChangeListener.onNumberChange(number);
            }
            break;
    }
}


public int getNumber() {
    return number;
}

public void setNumber(int number) {
    this.number = number;
    product_number_tv.setText(number + "");
}

OnNumberChangeListener onNumberChangeListener;

public void setOnNumberChangeListener(OnNumberChangeListener onNumberChangeListener) {
    this.onNumberChangeListener = onNumberChangeListener;
}

public interface OnNumberChangeListener {
    void onNumberChange(int num);
}
 

}