Android如何实现购物车加减功能

public class adderView extends LinearLayout implements View.OnClickListener, TextWatcher {
 private int amount = 0; //购买数量
 private int goods_storage = Integer.MAX_VALUE; //商品库存
 private OnAmountChangeListener mListener;
 private EditText etAmount;
 private Button btnDecrease;
 private Button btnIncrease;
 public adderView(Context context) {
  this(context, null);
 }
 public adderView(Context context, AttributeSet attrs) {
  super(context, attrs);
  LayoutInflater.from(context).inflate(R.layout.number_adder, this);
  etAmount = (EditText) findViewById(R.id.etAmount);
  btnDecrease = (Button) findViewById(R.id.btnDecrease);
  btnIncrease = (Button) findViewById(R.id.btnIncrease);
  btnDecrease.setOnClickListener(this);
  btnIncrease.setOnClickListener(this);
  etAmount.addTextChangedListener(this);
  TypedArray obtainStyledAttributes = getContext().obtainStyledAttributes(attrs, R.styleable.AmountView);
  int btnWidth = obtainStyledAttributes.getDimensionPixelSize(R.styleable.AmountView_btnWidth, 100);
  int tvWidth = obtainStyledAttributes.getDimensionPixelSize(R.styleable.AmountView_tvWidth, 200);
  int tvTextSize = obtainStyledAttributes.getDimensionPixelSize(R.styleable.AmountView_tvTextSize, 0);
  int btnTextSize = obtainStyledAttributes.getDimensionPixelSize(R.styleable.AmountView_btnTextSize, 0);
  obtainStyledAttributes.recycle();
  LayoutParams btnParams = new LayoutParams(btnWidth, LayoutParams.MATCH_PARENT);
  btnDecrease.setLayoutParams(btnParams);
  btnIncrease.setLayoutParams(btnParams);
  if (btnTextSize != 0) {
   btnDecrease.setTextSize(TypedValue.COMPLEX_UNIT_PX, btnTextSize);
   btnIncrease.setTextSize(TypedValue.COMPLEX_UNIT_PX, btnTextSize);
  }
  LayoutParams textParams = new LayoutParams(tvWidth, LayoutParams.MATCH_PARENT);
  etAmount.setLayoutParams(textParams);
  if (tvTextSize != 0) {
   etAmount.setTextSize(tvTextSize);
  }
 }
 public void setOnAmountChangeListener(OnAmountChangeListener onAmountChangeListener) {
  this.mListener = onAmountChangeListener;
 }
 public void setGoods_storage(int goods_storage) {
  this.goods_storage = goods_storage;
 }
 public void setTextCount(int count){
  this.amount = count;
  this.etAmount.setText(amount+"");
 }
 @Override
 public void onClick(View v) {
  int i = v.getId();
  if (i == R.id.btnDecrease) {
   if (amount > 0) {
    amount--;
    etAmount.setText(amount + "");
   }
  } else if (i == R.id.btnIncrease) {
   if (amount < goods_storage) {
    amount++;
    etAmount.setText(amount + "");
   }
  }
  etAmount.clearFocus();
  if (mListener != null) {
   mListener.onAmountChange(this, amount);
  }
 }
 @Override
 public void beforeTextChanged(CharSequence s, int start, int count, int after) {
 }
 @Override
 public void onTextChanged(CharSequence s, int start, int before, int count) {
 }
 @Override
 public void afterTextChanged(Editable s) {
  if (s.toString().isEmpty())
   return;
  amount = Integer.valueOf(s.toString());
  if (amount > goods_storage) {
   etAmount.setText(goods_storage + "");
   return;
  }
  if (amount == 0){
//   btnDecrease.setBackgroundResource(R.drawable.jian);
  }
  if (amount > 0){
//   btnDecrease.setBackgroundResource(R.drawable.lvjian);
  }
  if (mListener != null) {
   mListener.onAmountChange(this, amount);
  }
 }
 public interface OnAmountChangeListener {
  void onAmountChange(View view, int amount);
 }

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<com.zhy.autolayout.AutoLinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="90px"
 android:focusable="true"
 android:divider="@drawable/divder"
 android:background="@drawable/bg_amout_layout"
 android:showDividers="middle"
 android:orientation="horizontal">
 <Button
  android:id="@+id/btnDecrease"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_weight="1"
  android:gravity="center"
  android:background="@drawable/jian"/>
 <EditText
  android:id="@+id/etAmount"
  android:layout_width="200px"
  android:layout_height="match_parent"
  android:minWidth="150px"
  android:layout_weight="2"
  android:background="@null"
  android:inputType="number"
  android:textSize="13sp"
  android:text="0"
  android:gravity="center"/>
 <Button
  android:id="@+id/btnIncrease"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_weight="1"
  android:gravity="center"
  android:background="@drawable/jia"/>
</com.zhy.autolayout.AutoLinearLayout>