Android实现仿淘宝购物车增加和减少商品数量功能demo示例

package jczb.shoping.ui;
import android.R.string;
import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class ShoppingCartItemActivity extends Activity {
  private Button btAdd, btReduce;
  private EditText edtNumber;
  int num=0; //数量
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_shoppingcart_item);
    btAdd=(Button)findViewById(R.id.cart_pro_reduce);
    btReduce=(Button) findViewById(R.id.cart_pro_add);
    edtNumber=(EditText) findViewById(R.id.cart_pro_count);
    btAdd.setTag("+");
    btReduce.setTag("-");
    //设置输入类型为数字
    edtNumber.setInputType(android.text.InputType.TYPE_CLASS_NUMBER);
    edtNumber.setText(String.valueOf(num));
    SetViewListener();
  }
  /**
   * 设置文本变化相关监听事件
   */
  private void SetViewListener()
  {
    btAdd.setOnClickListener(new OnButtonClickListener());
    btReduce.setOnClickListener(new OnButtonClickListener());
    edtNumber.addTextChangedListener(new OnTextChangeListener());
  }
  /**
   * 加减按钮事件监听器
   *
   *
   */
  class OnButtonClickListener implements OnClickListener
  {
    @Override
    public void onClick(View v)
    {
      String numString = edtNumber.getText().toString();
      if (numString == null || numString.equals(""))
      {
        num = 0;
        edtNumber.setText("0");
      } else
      {
        if (v.getTag().equals("-"))
        {
          if (++num <0) //先加，再判断
          {
            num--;
            Toast.makeText(ShoppingCartItemActivity.this, "请输入一个大于0的数字",
                Toast.LENGTH_SHORT).show();
          } else
          {
            edtNumber.setText(String.valueOf(num));
          }
        } else if (v.getTag().equals("+"))
        {
          if (--num <0) //先减，再判断
          {
            num++;
            Toast.makeText(ShoppingCartItemActivity.this, "请输入一个大于0的数字",
                Toast.LENGTH_SHORT).show();
          } else
          {
            edtNumber.setText(String.valueOf(num));
          }
        }
      }
    }
  }
  /**
   * EditText输入变化事件监听器
   */
  class OnTextChangeListener implements TextWatcher
  {
    @Override
    public void afterTextChanged(Editable s)
    {
      String numString = s.toString();
      if(numString == null || numString.equals(""))
      {
        num = 0;
      }
      else {
        int numInt = Integer.parseInt(numString);
        if (numInt <0)
        {
          Toast.makeText(ShoppingCartItemActivity.this, "请输入一个大于0的数字",
              Toast.LENGTH_SHORT).show();
        } else
        {
          //设置EditText光标位置 为文本末端
          edtNumber.setSelection(edtNumber.getText().toString().length());
          num = numInt;
        }
      }
    }
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count,
        int after)
    {
    }
    @Override
    public void onTextChanged(CharSequence s, int start, int before,
        int count)
    {
    }
  }
}