购物车自定义加减器

1.自定义view

2.在xml中写入控件

3.写入一个布局 (+,- 数字)

第一步:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="#a19999"
    android:orientation="horizontal">

    <TextView
        android:id="@+id/jia_jian"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp"
        android:gravity="center"
        android:text="-"
        android:textColor="#fff"
        android:textSize="20sp" />

    <TextView
        android:id="@+id/jia"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:gravity="center"
        android:text="1"
        android:textColor="#fff"
        android:textSize="20sp" />

    <TextView
        android:id="@+id/jia_jia"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="5dp"
        android:gravity="center"
        android:text="+"
        android:textColor="#fff"
        android:textSize="20sp" />
</LinearLayout>

第二步:

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

public AddView(Context context, AttributeSet attrs) {
    this(context, attrs, -1);
}

public AddView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    //找控件
    initView(context);
    //监听
    initListener();
}


private void initView(Context context) {
    rootView = View.inflate(context, R.layout.jia_jian, this);
    jia_jian = rootView.findViewById(R.id.jia_jian);
    jia_jia = rootView.findViewById(R.id.jia_jia);
    jia = rootView.findViewById(R.id.jia);
   // jia.setText("1");
}

private void initListener() {
    //加
    jia_jia.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            add();
        }
    });
    //减
    jia_jian.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            jian();
        }
    });

}

private void add() {
    String s = jia.getText().toString();
    int i = Integer.parseInt(s);
    i++;
    setCurrentCount(i);
}

private void jian() {
    String s = jia.getText().toString();
    int i = Integer.parseInt(s);
    if (i > 1) {
        i--;
        setCurrentCount(i);
    } else {
        Toast.makeText(getContext(), "不能再减少了", Toast.LENGTH_SHORT).show();
    }

}

public void setCurrentCount(int i) {
    jia.setText(""+i);
    if (onNumChangeListener != null) {
        onNumChangeListener.onNumChanged(this, i);
    }
}

//接口
private OnNumChangeListener onNumChangeListener;

public void setOnNumChangeListener(OnNumChangeListener onNumChangeListener) {
    this.onNumChangeListener = onNumChangeListener;
}

public interface OnNumChangeListener {
    void onNumChanged(View view, int curNum);
}

第三步:

把控件写入布局