Question

我想创建一个应用程序，其中我有2个按钮和1个edittext。按钮是+和 - 。当我点击+按钮时，我应该在edittext中获得计数器++，当我点击 - 按钮时，计数器 - 发生并在编辑文本中写入。现在当我点击计数器 - 当编辑文本中的默认数字为0时，它会像-1，-2，-3等...但我不想把数字小于0。那么应该添加什么以下代码。

代码。

public class MainActivity extends Activity implements OnClickListener
{
     int counter=0;
     EditText et1;
     Button btnminus,btnplus;
     protected void onCreate(Bundle savedInstanceState) 
     {
         // TODO Auto-generated method stub
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         et1 = (EditText) findViewById(R.id.et_number);
         btnminus = (Button) findViewById(R.id.btn_minus);
         btnplus = (Button) findViewById(R.id.btn_plus);

         btnminus.setOnClickListener(this);
         btnplus.setOnClickListener(this);
     }

     public void onClick(View v)
     {
         if(v == btnminus)
         {
             counter--;
             et1.setText(Integer.toString(counter));
         }

         if(v == btnplus)
         {
             counter++;
             et1.setText(Integer.toString(counter));
         }
     }
}

Answer 1

if(v == btnminus && counter!=0)
     {
         counter--;
         et1.setText(Integer.toString(counter));
     }

Answer 2

protected void onCreate(Bundle savedInstanceState) 
 {
     // TODO Auto-generated method stub
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_main);
     et1 = (EditText) findViewById(R.id.et_number);
     btnminus = (Button) findViewById(R.id.btn_minus);
     btnplus = (Button) findViewById(R.id.btn_plus);

     et1.setText(Integer.toString(counter));
     btnminus.setOnClickListener(this);
     btnplus.setOnClickListener(this);
 }    

 public void onClick(View v)
 {
     if(v == btnminus)
     {
       int check=Integer.valueOf(et1.getText().toString);
       if(check!=0){            
         counter--;
         et1.setText(Integer.toString(counter));
       }
     }

     if(v == btnplus)
     {
         counter++;
         et1.setText(Integer.toString(counter));
     }
 }

Answer 3

if(v == btnminus && counter>0) // if counter at least ==1 it could be decremented
     et1.setText(String.valueOf(--counter)); //prefix decrement

else if(v == btnplus) // else if wont be checked if v == btnminus but counter is 0
     et1.setText(String.valueOf(++counter)); // prefix inscrement

Counter ++和Counter--在android中的例子

3 个答案: