尝试调用虚拟方法'android.text.Editable android.widget.EditText.getText()

Question

当我在输入输入后单击“添加”按钮或任何其他按钮时应用程序停止

 public class MainActivity extends AppCompatActivity implements View.OnClickListener {
      // Buttons and Text  Fields
    private Button btnAdd,btnSub,btnDiv,btnMul;
    private EditText etFirst,etSecond;
    private TextView tvresult;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
    }
    private void init()
    {
    // Button Id's
    btnAdd=(Button)findViewById(R.id.btnAdd);  
    btnSub=(Button)findViewById(R.id.btnSub);  
    btnMul=(Button)findViewById(R.id.btnMulti);  
    btnDiv=(Button)findViewById(R.id.btnDivide);  
    btnAdd.setOnClickListener(this);
    btnSub.setOnClickListener(this);
    btnDiv.setOnClickListener(this);
    btnMul.setOnClickListener(this);
    }
    @Override
    public void onClick(View v) {
        //Operations
        String num1=etFirst.getText().toString();
        String num2=etSecond.getText().toString();
        switch(v.getId())
        {
            case R.id.btnAdd:
                int addition=Integer.parseInt(num1)+Integer.parseInt(num2);
                tvresult.setText(String.valueOf(addition));
                break;
            case R.id.btnSub:
                int sub=Integer.parseInt(num1)-Integer.parseInt(num2);
                tvresult.setText(String.valueOf(sub));
                break;
            case R.id.btnMulti:
                int multiply=Integer.parseInt(num1)* Integer.parseInt(num2);
                tvresult.setText(String.valueOf(multiply));
                break;
            case R.id.btnDivide:

                    int div = Integer.parseInt(num1) / Integer.parseInt(num2);
                    tvresult.setText(String.valueOf(div));
                    break;
        }
    }
    }

Answer 1

你还没有初始化 etFirst & etSecond 。 将此添加到您的 init() 方法中：

etFirst = (EditText) findViewById(R.id.etFirst);
etSecond = (EditText) findViewById(R.id.etSecond);