b1.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {

        if (e1.getText().toString().isEmpty()||e2.getText().toString().isEmpty()) {
            Toast.makeText(MainActivity.this, "空", Toast.LENGTH_SHORT).show();
        }
        else if (r1.isChecked()) {
            Double wb1 = Double.parseDouble(e1.getText().toString());
            Double wb2 = Double.parseDouble(e2.getText().toString());
            Double result = wb1 +wb2;
            t1.setText(result.toString());
        } else if (r2.isChecked()) {
            Double wb1 = Double.parseDouble(e1.getText().toString());
            Double wb2 = Double.parseDouble(e2.getText().toString());
            Double result = wb1 - wb2;
            t1.setText(result.toString());
        } else {
            AlertDialog.Builder dlg = new AlertDialog.Builder(MainActivity.this);
            dlg.setTitle("错误error");
            dlg.setMessage("请检查控件或文本框有没有被输入和选中");
            dlg.setPositiveButton("确定", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {

                }
            });
            dlg.show();
        }